Articles de revues : « Earthquake source and dynamics »

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VEITCH, STEPHEN A., et MEREDITH NETTLES. « Assessment of glacial-earthquake source parameters ». Journal of Glaciology 63, n^o 241 (octobre 2017) : 867–76. http://dx.doi.org/10.1017/jog.2017.52.

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ABSTRACTGlacial earthquakes are slow earthquakes of magnitude M~5 associated with major calving events at near-grounded marine-terminating glaciers. These globally detectable earthquakes provide information on the grounding state of outlet glaciers and the timing of large calving events. Seismic source modeling of glacial earthquakes provides information on the size and orientation of forces associated with calving events. We compare force orientations estimated using a centroid-single-force technique with the calving-front orientations of the source glaciers at or near the time of earthquake occurrence. We consider earthquakes recorded at four glaciers in Greenland – Kangerdlugssuaq Glacier, Helheim Glacier, Kong Oscar Glacier, and Jakobshavn Isbræ – between 1999 and 2010. We find that the estimated earthquake force orientations accurately represent the orientation of the calving front at the time of the earthquake, and that seismogenic calving events are produced by a preferred section of the calving front, which may change with time. We also find that estimated earthquake locations vary in a manner consistent with changes in calving-front position, though with large scatter. We conclude that changes in glacial-earthquake source parameters reflect true changes in the geometry of the source glaciers, providing a means for identifying changes in glacier geometry and dynamics that complements traditional remote-sensing techniques.

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Yin, Jiuxun, Zefeng Li et Marine A. Denolle. « Source Time Function Clustering Reveals Patterns in Earthquake Dynamics ». Seismological Research Letters 92, n^o 4 (31 mars 2021) : 2343–53. http://dx.doi.org/10.1785/0220200403.

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Abstract We cluster a global database of 3529 Mw>5.5 earthquakes in 1995–2018 based on a dynamic time warping distance between earthquake source time functions (STFs). The clustering exhibits different degrees of complexity of the STF shapes and suggests an association between STF complexity and earthquake source parameters. Most of the thrust events have simple STF shapes across all depths. In contrast, earthquakes with complex STF shapes tend to be located at shallow depths in complicated tectonic regions, exhibit long source duration compared with others of similar magnitude, and tend to have strike-slip mechanisms. With 2D dynamic modeling of dynamic ruptures on heterogeneous fault properties, we find a systematic variation of the simulated STF complexity with frictional properties. Comparison between the observed and synthetic clustering distributions provides useful constraints on frictional properties. In particular, the characteristic slip-weakening distance could be constrained to be short (<0.1 m) and depth dependent if stress drop is in general constant.

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Badea, Lori, Ioan R. Ionescu et Sylvie Wolf. « Schwarz method for earthquake source dynamics ». Journal of Computational Physics 227, n^o 8 (avril 2008) : 3824–48. http://dx.doi.org/10.1016/j.jcp.2007.11.044.

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Madden, E. H., M. Bader, J. Behrens, Y. van Dinther, A.-A. Gabriel, L. Rannabauer, T. Ulrich, C. Uphoff, S. Vater et I. van Zelst. « Linked 3-D modelling of megathrust earthquake-tsunami events : from subduction to tsunami run up ». Geophysical Journal International 224, n^o 1 (10 octobre 2020) : 487–516. http://dx.doi.org/10.1093/gji/ggaa484.

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SUMMARY How does megathrust earthquake rupture govern tsunami behaviour? Recent modelling advances permit evaluation of the influence of 3-D earthquake dynamics on tsunami genesis, propagation, and coastal inundation. Here, we present and explore a virtual laboratory in which the tsunami source arises from 3-D coseismic seafloor displacements generated by a dynamic earthquake rupture model. This is achieved by linking open-source earthquake and tsunami computational models that follow discontinuous Galerkin schemes and are facilitated by highly optimized parallel algorithms and software. We present three scenarios demonstrating the flexibility and capabilities of linked modelling. In the first two scenarios, we use a dynamic earthquake source including time-dependent spontaneous failure along a 3-D planar fault surrounded by homogeneous rock and depth-dependent, near-lithostatic stresses. We investigate how slip to the trench influences tsunami behaviour by simulating one blind and one surface-breaching rupture. The blind rupture scenario exhibits distinct earthquake characteristics (lower slip, shorter rupture duration, lower stress drop, lower rupture speed), but the tsunami is similar to that from the surface-breaching rupture in run-up and length of impacted coastline. The higher tsunami-generating efficiency of the blind rupture may explain how there are differences in earthquake characteristics between the scenarios, but similarities in tsunami inundation patterns. However, the lower seafloor displacements in the blind rupture result in a smaller displaced volume of water leading to a narrower inundation corridor inland from the coast and a 15 per cent smaller inundation area overall. In the third scenario, the 3-D earthquake model is initialized using a seismo-thermo-mechanical geodynamic model simulating both subduction dynamics and seismic cycles. This ensures that the curved fault geometry, heterogeneous stresses and strength and material structure are consistent with each other and with millions of years of modelled deformation in the subduction channel. These conditions lead to a realistic rupture in terms of velocity and stress drop that is blind, but efficiently generates a tsunami. In all scenarios, comparison with the tsunamis sourced by the time-dependent seafloor displacements, using only the time-independent displacements alters tsunami temporal behaviour, resulting in later tsunami arrival at the coast, but faster coastal inundation. In the scenarios with the surface-breaching and subduction-initialized earthquakes, using the time-independent displacements also overpredicts run-up. In the future, the here presented scenarios may be useful for comparison of alternative dynamic earthquake-tsunami modelling approaches or linking choices, and can be readily developed into more complex applications to study how earthquake source dynamics influence tsunami genesis, propagation and inundation.

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Abercrombie, Rachel E. « Resolution and uncertainties in estimates of earthquake stress drop and energy release ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 379, n^o 2196 (15 mars 2021) : 20200131. http://dx.doi.org/10.1098/rsta.2020.0131.

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Our models and understanding of the dynamics of earthquake rupture are based largely on estimates of earthquake source parameters, such as stress drop and radiated seismic energy. Unfortunately, the measurements, especially those of small and moderate-sized earthquakes (magnitude less than about 5 or 6), are not well resolved, containing significant random and potentially systematic uncertainties. The aim of this review is to provide a context in which to understand the challenges involved in estimating these measurements, and to assess the quality and reliability of reported measurements of earthquake source parameters. I also discuss some of the ways progress is being made towards more reliable parameter measurements. At present, whether the earthquake source is entirely self-similar, or not, and which factors and processes control the physics of the rupture remains, at least in the author's opinion, largely unconstrained. Detailed analysis of the best recorded earthquakes, using the increasing quantity and quality of data available, and methods less dependent on simplistic source models is one approach that may help provide better constraints. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

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Nakanishi, Hiizu. « Complex Behavior in Earthquake Dynamics ». International Journal of Modern Physics B 12, n^o 03 (30 janvier 1998) : 273–84. http://dx.doi.org/10.1142/s0217979298000211.

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Recent progresses in understanding earthquake dynamics with the aid of a simple spring-block system is reviewed from a physicists' point of view. Dynamical instability due to negative dynamical friction amplifies any perturbation and leads to a chaotic behavior for almost any initial configurations. It is also pointed out that static friction gives another source of the complex behavior which is characteristic to a threshold element system.

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Tinti, E. « A Kinematic Source-Time Function Compatible with Earthquake Dynamics ». Bulletin of the Seismological Society of America 95, n^o 4 (1 août 2005) : 1211–23. http://dx.doi.org/10.1785/0120040177.

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Cao, Zelin, Xiaxin Tao, Zhengru Tao et Aiping Tang. « Kinematic Source Modeling for the Synthesis of Broadband Ground Motion Using the f‐k Approach ». Bulletin of the Seismological Society of America 109, n^o 5 (23 juillet 2019) : 1738–57. http://dx.doi.org/10.1785/0120180294.

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Abstract A procedure for building a kinematic source model is proposed in this article for the synthesis of broadband ground motion based on the frequency–wavenumber Green’s function. The spatial distribution of slip on the rupture plane is generated by combining asperity slip with random slip. A set of scaling laws recently updated for the global and local parameters of seismic sources is adopted. To characterize the temporal evolution of slip on the rupture plane, different rupture velocities, and rise times are first generated by considering the correlation with slip, and a source time function obtained by rupture dynamics is selected for each subsource. Then, the entire rupture process is set as the object to jointly determine the rise time and rupture velocity for a given slip distribution under the selection criterion that the entire rupture process should radiate the closest seismic energy to the expected energy. To reduce uncertainty, 30 spatiotemporal rupture processes for an earthquake scenario are realized to select a mean source model. To demonstrate the feasibility of the proposed source modeling approach, two California earthquakes, the Whittier Narrows earthquake and the Loma Prieta earthquake, are chosen as case studies. The performance of the obtained source models shows that our modeling approach is advantageous for estimating the size of the rupture plane, emphasizing the effect of asperity, and considering the correlation between temporal rupture parameters and slip. The bias values between the observed and synthetic pseudospectral accelerations are relatively small compared to those for the methods on the Southern California Earthquake Center broadband platform. The synthetics are further compared with the estimates from regional ground‐motion prediction equations for four scenario earthquakes with moment magnitudes of 6.0, 6.5, 7.0, and 7.5. Finally, the sensitivity of the synthetic motion to various rupture parameters is analyzed.

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Uchida, Naoki, et Roland Bürgmann. « Repeating Earthquakes ». Annual Review of Earth and Planetary Sciences 47, n^o 1 (30 mai 2019) : 305–32. http://dx.doi.org/10.1146/annurev-earth-053018-060119.

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Repeating earthquakes, or repeaters, are identical in location and geometry but occur at different times. They appear to represent recurring seismic energy release from distinct structures such as slip on a fault patch. Repeaters are most commonly found on creeping plate boundary faults, where seismic patches are loaded by surrounding slow slip, and they can be used to track fault creep at depth. Their hosting environments also include volcanoes, subducted slabs, mining-induced fault structures, glaciers, and landslides. While true repeaters should have identical seismic waveforms, small differences in their seismograms can be used to examine subtle changes in source properties or in material properties of the rocks through which the waves propagate. Source studies have documented the presence of smaller slip patches within the rupture areas of larger repeaters, illuminated earthquake triggering mechanisms, and revealed systematic changes in rupture characteristics as a function of loading rate. ▪ Repeating earthquakes are observed in diverse tectonic and nontectonic settings. ▪ Their occurrence patterns provide quantitative information about fault creep, earthquake cycle dynamics, triggering, and predictability. ▪ Their seismic waveform characteristics provide important insights on earthquake source variability and temporal Earth structure changes.

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Sobolev, G. A. « Seismicity dynamics and earthquake predictability ». Natural Hazards and Earth System Sciences 11, n^o 2 (14 février 2011) : 445–58. http://dx.doi.org/10.5194/nhess-11-445-2011.

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Abstract. Many factors complicate earthquake sequences, including the heterogeneity and self-similarity of the geological medium, the hierarchical structure of faults and stresses, and small-scale variations in the stresses from different sources. A seismic process is a type of nonlinear dissipative system demonstrating opposing trends towards order and chaos. Transitions from equilibrium to unstable equilibrium and local dynamic instability appear when there is an inflow of energy; reverse transitions appear when energy is dissipating. Several metastable areas of a different scale exist in the seismically active region before an earthquake. Some earthquakes are preceded by precursory phenomena of a different scale in space and time. These include long-term activation, seismic quiescence, foreshocks in the broad and narrow sense, hidden periodical vibrations, effects of the synchronization of seismic activity, and others. Such phenomena indicate that the dynamic system of lithosphere is moving to a new state – catastrophe. A number of examples of medium-term and short-term precursors is shown in this paper. However, no precursors identified to date are clear and unambiguous: the percentage of missed targets and false alarms is high. The weak fluctuations from outer and internal sources play a great role on the eve of an earthquake and the occurrence time of the future event depends on the collective behavior of triggers. The main task is to improve the methods of metastable zone detection and probabilistic forecasting.

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Elbanna, Ahmed, Mohamed Abdelmeguid, Xiao Ma, Faisal Amlani, Harsha S. Bhat, Costas Synolakis et Ares J. Rosakis. « Anatomy of strike-slip fault tsunami genesis ». Proceedings of the National Academy of Sciences 118, n^o 19 (3 mai 2021) : e2025632118. http://dx.doi.org/10.1073/pnas.2025632118.

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Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated.

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Du, Xue-Bin, Zhi-De Yan et Ming-Wu Zou. « Process of source dynamics of the Jingtai earthquake (M=6.2) ». Acta Seismologica Sinica 7, n^o 3 (août 1994) : 379–88. http://dx.doi.org/10.1007/bf02650675.

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Pustovitenko, B., et E. Eredzhepov. « SPECTRAL and SOURCE PARAMETERS of CRIMEAN-BLACK SEA EARTHQUAKES ». Earthquakes in Northern Eurasia, n^o 23 (15 décembre 2020) : 250–62. http://dx.doi.org/10.35540/1818-6254.2020.23.25.

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The spectral and dynamic source parameters (М0, r0, , , ησ, , ū, Eu and Mw) of 13 Crimean earthquakes with КП = 7.2–11.2 (Mw=2.6–4.1), restored by 123 amplitude spectra of longitudinal and transverse seismic waves recorded by digital regional seismic stations is shown. Approximation of the spectra and the source dynamic parameters calculation based on their parameters is performed in the framework of the Brune dislocation model. Four to seven station definitions participated in the averaging of focal parameters, which ensured a small standard deviation, the scattering degree index of the individual estimates. The best convergence of the station definitions is obtained for the radius of a circular dislocation. The highest values of dynamic para-meters have been obtained for the perceptible earthquake on March 2 with КП=11.2, and the lowest values have been obtained for its weak aftershock on April 6 with КП = 7.2. Within the total range of energies the value of the stress drop does not exceed = 106Pa(10 bar), and the apparent stress drop does not exceed ησ<3∙105Pa (3 bar). The average values of seismic moments and circular dislocation radius within the errors of their deter-mination match the average long-term correlations of the parameters on the earthquake energy level obtained by the analog recording.For the strongest earthquakes on March 2 with Mwreg=4.1 and October 18 with Mwreg=3.8 solutions of the focal mechanisms were obtained. The March 2 earthquake occurred in the central part of the region near the South Coast of Crimea under the action of horizontal tensile forces oriented near the latitude. The type of movement in the focus is a obligue slip with predominance of a normal component over a strike-slip. The earthquake on October 18 occurred in the central part of the Black Sea basin in condition of sublatitudinal compression and submeridional extension. Type of movement in the source is a pure strike-slip. For the main shock on March 2 and its six aftershocks, energy spectra according to the data of Alushta station and their main parameters are given. The analysis of obtained results is given.

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Tang, Chenxiao, Hakan Tanyas, Cees J. van Westen, Chuan Tang, Xuanmei Fan et Victor G. Jetten. « Analysing post-earthquake mass movement volume dynamics with multi-source DEMs ». Engineering Geology 248 (janvier 2019) : 89–101. http://dx.doi.org/10.1016/j.enggeo.2018.11.010.

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Panas, N. M., et B. A. Assinovskaya. « Dynamic parameters of weak earthquakes on the southeastern slope of the Baltic Shield ». Russian Journal of Seismology 4, n^o 4 (20 décembre 2022) : 65–78. http://dx.doi.org/10.35540/2686-7907.2022.4.05.

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The dynamic parameters of earthquake sources characterize the features of the process of destruction of the seismogenic medium. These parameters are defined in the world for earthquakes of different magnitudes and different genesis. For the seismically weakly active region of Fennoscandia, the source characteristics of earthquakes were characterized in the 1990s from analog records. In this paper, we obtained a summary of the indicated valuesfor weak earthquakes with ML=1-2 that took place on the southeastern slope of the Fennoscandian shield in 2009-2019 for two earthquake swarms of different origins - tectonic Kouvola and technogenic Erkilia. The work was carried out according to the data of the St. Petersburg digital seismic network. In the process of research, using seismograms of the network, the spectra of direct waves Sg were constructed, the values of the seismic moment, corner frequency, source radius and stress drop for 15 earthquakes of a tectonic and technogenic nature were calculated. The results obtained, although they have a spread in values, do not differ much from the world averages. However, it turned out that the seismic moment and stress drop significantly depend on the genesis of events.

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Badreldin, Hazem, Hamada Saadalla, Ahmed Abu El-Ata, Abd el-aziz Khairy Abd el-aal et Amir Mahr Lala. « Dynamic Source Parameters of Significant Earthquakes in the Gulf of Aqaba, Egypt ». Iraqi Geological Journal 55, n^o 2C (30 septembre 2022) : 187–97. http://dx.doi.org/10.46717/igj.55.2c.14ms-2022-08-27.

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Several seismological and paloseismolgical studies and historical reports have indicated that Gulf of Aqaba is characterized by higher seismicity than any other seismogenic sources around Egypt. Accordingly, surrounding areas have been impacted by several destructive earthquakes (AD 1068, AD 1212, AD 1229, AD 1458, and AD 1995). Cities situated around the Gulf of Aqaba have experienced different damage levels due to historical and instrumental earthquakes resulting in considerable fatalities. The Aqaba earthquake which occurred on November 22, 1995 (Moment magnitude (Mw) = 7.3) was the largest recorded earthquake along with the Dead Sea Fault System, strongly felt at Eastern Mediterranean region. Many seismic sequences have ocuuerd in the Gulf of Aqaba in the last decades and some of them continued for almost two years. This paper applies a spectral decomposition method based on a reference site to correct the source spectra from the path and site effects by employing Iterative Least Square analysis. The obtained displacement source spectra are modulated with Brune’s omega square type spectrum. The dynamic earthquakes parameters are computed using the S-wave window for the significant Gulf of Aqaba earthquakes. 50 earthquakes have been used in this study with Ml 3.0 to 6. The calculated seismic moments range spans from 1.48E+19 to 2.193E+22 dyne-cm, and the corner frequency range spans from 4.1 to 8.5 Hz. The source radii span which range from 84.3 m to 173.4 meters. The observed stress drops vary from 0.3 to 371.7 megapascal (Mpa).

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Lee, Jaeseok, Jung-Hun Song, Seongryong Kim, Junkee Rhie et Seok Goo Song. « Three-Dimensional Seismic-Wave Propagation Simulations in the Southern Korean Peninsula Using Pseudodynamic Rupture Models ». Bulletin of the Seismological Society of America 112, n^o 2 (14 décembre 2021) : 939–60. http://dx.doi.org/10.1785/0120210172.

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ABSTRACT Accurate and practical ground-motion predictions for potential large earthquakes are crucial for seismic hazard analysis of areas with insufficient instrumental data. Studies on historical earthquake records of the Korean Peninsula suggest that damaging earthquakes are possible in the southeastern region. Yet classical ground-motion prediction methods are limited in considering the physical rupture process and its effects on ground motion in complex velocity structures. In this study, we performed ground-motion simulations based on rigorous physics through pseudodynamic source modeling and wave propagation simulations in a 3D seismic velocity model. Ensembles of earthquake scenarios were generated by emulating the one- and two-point statistics of earthquake source parameters derived from a series of dynamic rupture models. The synthetic seismograms and the distributions of simulated peak ground velocities (PGVs) were compared with the observations of the 2016 Mw 5.4 Gyeongju earthquake in the Korean Peninsula. The effects of surface-wave radiation, rupture directivity, and both local and regional amplifications from the 3D wave propagation were reproduced accurately in the spatial distribution of simulated PGVs, in agreement with the observations from dense seismic networks by mean log residuals of −0.28 and standard deviations of 0.78. Amplifications in ground motions were found in regions having low crustal velocities and in regions of constructive interference from the crustal shear-wave phases associated with postcritical reflections from the Moho discontinuity. We extended the established approach to earthquake scenarios of Mw 6.0, 6.5, and 7.0, at the same location, to provide the distribution of ground motions from potential large earthquakes in the area. Although we demonstrate the value of these simulations, improvements in the accuracy of the 3D seismic velocity model and the scaling relationship of the source models would be necessary for a more accurate estimation of near-source ground motions.

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Islam, A. B. M. Saiful, Syed Ishtiaq Ahmad, Mohd Zamin Jumaat, Raja Rizwan Hussain, Muhammad Ashiqur Rahman et Kh Mahfuz ud Darain. « EFFICIENT DESIGN IN BUILDING CONSTRUCTION WITH RUBBER BEARING IN MEDIUM RISK SEISMICITY : CASE STUDY AND ASSESSMENT ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 20, n^o 5 (20 octobre 2014) : 621–31. http://dx.doi.org/10.3846/13923730.2013.801910.

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Earthquakes pose tremendous threats to life, property and a country's economy, not least due to their capability of destroying buildings and causing enormous structural damage. The hazard from ground excitations should be properly assessed to mitigate their action on building structures. This study is concerned with medium risk seismic regions. Specifically, the heavily populated capital city Dhaka in Bangladesh has been considered. Recent earthquakes that occurred inside and very close to the city have manifested the city's earthquake sources and vulnerability. Micro-seismicity data supports the existence of at least four earthquake source points in and around Dhaka. The effects of the earthquakes on buildings are studied for this region. Rubber base isolation is selected as an innovative option to lessen seismic loads on buildings. Case studies have been carried out for fixed and isolated based multi-storey buildings. Lead rubber bearing and high damping rubber bearing have been designed and incorporated in building bases. Structural response behaviours have been evaluated through static and dynamic analyses. For the probable severe earthquake, rubber bearing isolation can be a suitable alternative as it mitigates seismic effects, reduces structural responses and provides structural and economic benefits.

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Pustovitenko, B., et E. Eredzhepov. « SOURCE PARAMETERS of CRIMEAN-BLACK SEA EARTHQUAKES in 2015 ». Earthquakes in Northern Eurasia, n^o 24 (14 décembre 2021) : 226–36. http://dx.doi.org/10.35540/1818-6254.2021.24.22.

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The spectral and dynamic source parameters (М0, r0, , , ησ, , u, Eu and Mw) of 16 Crimean earthquakes with КП=6.5–10.8, restored by amplitude spectra of compression and shear seismic waves recorded by digital regional seismic stations are analyzed. Approximation of the spectra and source parameters calculation is performed in the framework of the Brune dislocation model. The highest values of dynamic parameters (М0, r0, , , ησ, u, EU и Mw) are obtained for the earthquakes on June 13 and August 16 with h=11 km, h=7 km respectively and КП=10.8, which occurred in the Azov-Kuban and Kerch-Anapa areas. The radiation friction r for all earthquakes had a negative value, pointing to a complex slide of the rupture in the source. Within the whole energy range, the average value of the released stress did not exceed Δσ=8∙105 PA (8 bar) and apparent stress ησ <11∙105 PA (11 bar). For most 2015 earthquakes, the average M0 и r0 values were within the confidence intervals of long-term dependencies M0(КП), r0(КП). The values of r0 were evenly distributed concerning the regression r0(КП) and М0 is mostly located below the average according to М0 (КП). The maximum deviations of M0 from the long-term М0(КП) dependence were obtained for the most strong earthquakes on June 13 and August 16 with КП=10.8. These deviations can be associated with participation in average M0 of the "Sevastopol" station data which give low values of М0 and possible errors in determining the focal depths influencing the choice of environment velocity models to calculate М0. For the most strong earthquake of August 16 with Мw=3.8, which occurred in the Kerch-Anapa region, a solution of focal mechanism was obtained. The earthquake occurred under the action of horizontal latitudinal tensile forces. The type of movement in the source is an oblique normal fault. Both nodal planes have near-meridional (STKNP1=167°) and near-diagonal (STKNP2=336°) strike.

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Chepkunas, L., et L. Malyanova. « SOURCE PARAMETERS of STRONG EARTHQUAKES of the EARTH ». Earthquakes in Northern Eurasia, n^o 23 (15 décembre 2020) : 244–49. http://dx.doi.org/10.35540/1818-6254.2020.23.24.

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For nine strongest earthquakes in Russia and the World, dynamic parameters were determined. They were calculated from the P-wave spectra recorded by IRIS-IDA digital equipmentat Obninsk (OBN), Talaya (TLY) and Arti (ARU) stations at the epicentral distances =30–80°.The following parameters are given: seismic moment, rupture length, stress drop and apparent stress, average displacement during rupture of earthquake. The moment magnitude Mw obtained from seismic moment M0 at Obninsk, Talaya, and Arti stations was calculate by the formula of H. Kanamori.A comparison of the obtained parameters M0 and Mw with the data of the GCMT international center showed their proximity.

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Носов, Михаил Александрович, Сергей Владимирович Колесов, Гульназ Нуровна Нурисламова, Анна Владимировна Большакова, Кирилл Александрович Семенцов et Вячеслав Александрович Карпов. « The role of Coriolis force in the dynamics of the waves excited in the ocean by deep-focal earthquakes ». Вычислительные технологии, n^o 1(24) (19 mars 2019) : 73–85. http://dx.doi.org/10.25743/ict.2019.24.1.006.

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На примере сейсмического события, обладающего магнитудой и механизмом глубокофокусного землетрясения у берегов Фиджи 19.08.2018, теоретически исследована связь параметров источника цунами с глубиной землетрясения. Показано, что сильные глубокофокусные землетрясения способны создавать обширные области косейсмических деформаций дна, размер которых сопоставим с баротропным радиусом деформации Россби. Волны цунами, формируемые такими источниками, обладают необычайно большой длиной и поэтому подвержены влиянию силы Кориолиса. Это влияние может варьироваться от существенного в высоких широтах до малозначительного в приэкваториальных районах. Методом численного моделирования исследовано влияние силы Кориолиса на слабые волны цунами, вызванные Фиджийским землетрясением 2018 г. Using the example of a seismic event with the same magnitude and mechanism as for the 2018 Fiji deep-focus earthquake the relationship between the parameters of a tsunami source and the depth of an earthquake was theoretically investigated. It is shown that strong deep-focus earthquakes are capable of creating extensive areas of co-seismic deformations for the ocean bottom, the size of which is comparable to the barotropic Rossby deformation radius. Tsunami waves generated by such sources have an unusually large length, and therefore they are subject to the influence of the Coriolis force. The influence of the Coriolis force on the weak tsunami waves caused by the 2018 Fiji earthquake has been studied by numerical simulation. It was found that for a virtual sea-level station located to the south of the source at latitude of 40S, the amplitude of the leading tsunami wave under the influence of the Coriolis force decreased by ≈ 30%. For virtual stations located at the equator or at latitude of 20S, taking into account the Coriolis force changes the amplitude of the waves by no more than 10%. For stations located in the equatorial zone, the effect of delaying of the manifestation of differences in sea-level fluctuations, calculated with and without Coriolis force, as compared with the entry of the leading tsunami wave was discovered. A physical interpretation of the observed delay effect is proposed.

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Носов, Михаил Александрович, Сергей Владимирович Колесов, Гульназ Нуровна Нурисламова, Анна Владимировна Большакова, Кирилл Александрович Семенцов et Вячеслав Александрович Карпов. « The role of Coriolis force in the dynamics of the waves excited in the ocean by deep-focal earthquakes ». Вычислительные технологии, n^o 1(24) (19 mars 2019) : 73–85. http://dx.doi.org/10.25743/ict.2019.24.1.006.

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На примере сейсмического события, обладающего магнитудой и механизмом глубокофокусного землетрясения у берегов Фиджи 19.08.2018, теоретически исследована связь параметров источника цунами с глубиной землетрясения. Показано, что сильные глубокофокусные землетрясения способны создавать обширные области косейсмических деформаций дна, размер которых сопоставим с баротропным радиусом деформации Россби. Волны цунами, формируемые такими источниками, обладают необычайно большой длиной и поэтому подвержены влиянию силы Кориолиса. Это влияние может варьироваться от существенного в высоких широтах до малозначительного в приэкваториальных районах. Методом численного моделирования исследовано влияние силы Кориолиса на слабые волны цунами, вызванные Фиджийским землетрясением 2018 г. Using the example of a seismic event with the same magnitude and mechanism as for the 2018 Fiji deep-focus earthquake the relationship between the parameters of a tsunami source and the depth of an earthquake was theoretically investigated. It is shown that strong deep-focus earthquakes are capable of creating extensive areas of co-seismic deformations for the ocean bottom, the size of which is comparable to the barotropic Rossby deformation radius. Tsunami waves generated by such sources have an unusually large length, and therefore they are subject to the influence of the Coriolis force. The influence of the Coriolis force on the weak tsunami waves caused by the 2018 Fiji earthquake has been studied by numerical simulation. It was found that for a virtual sea-level station located to the south of the source at latitude of 40S, the amplitude of the leading tsunami wave under the influence of the Coriolis force decreased by ≈ 30%. For virtual stations located at the equator or at latitude of 20S, taking into account the Coriolis force changes the amplitude of the waves by no more than 10%. For stations located in the equatorial zone, the effect of delaying of the manifestation of differences in sea-level fluctuations, calculated with and without Coriolis force, as compared with the entry of the leading tsunami wave was discovered. A physical interpretation of the observed delay effect is proposed.

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Ma, Xiaona, Weitao Wang, Shanhui Xu, Wei Yang, Yunpeng Zhang et Chuanjie Dong. « Imaging the Fault Zone Structure of the Pearl River Estuary Fault in Guangzhou, China, from Waveform Inversion with an Active Source and Dense Linear Array ». Remote Sensing 15, n^o 1 (1 janvier 2023) : 254. http://dx.doi.org/10.3390/rs15010254.

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Since high-resolution structure imaging of active faults within urban areas is vital for earthquake hazard mitigation, we perform a seismic survey line crossing the Pearl River Estuary Fault (PREF) in Guangzhou, China. First, ten shots of a new and environmentally friendly gas explosion source are excited with about 1 km spacing and recorded by 241 nodal short-period seismometers with an average spacing of 60 m. Then, based on these acquisition data, we adopt waveform inversion to explore the kinematic and dynamic information of early arrival wavefields to recover the subsurface structures. The inversion results indicate that while the low-velocity zone (LVZ) in depth surrounding the PREF is 2.5 km in width and extended to 0.7 km, another LVZ of 1.5 km in width and extended to 0.7 km in depth is surrounded by the Beiting–Nancun fault. We observe that the analysis of evolution and activities of the fault systems reveal no historical earthquakes in our study area; we interpret that the two LVZs controlled by the faults are probably attributed to the fluid dynamics, sediment source, and fault motion at different geological times, rather than fault-related damage zones. The results can provide significant basis for earthquake prevention and hazard assessment in Guangzhou. The finding also shows that the waveform inversion can effectively explore the fine structure of active faults in urban area with dense linear array and spare active source excitations.

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Kikuchi, Masayuki, et Mizuho Ishida. « Source retrieval for deep local earthquakes with broadband records ». Bulletin of the Seismological Society of America 83, n^o 6 (1 décembre 1993) : 1855–70. http://dx.doi.org/10.1785/bssa0830061855.

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Abstract Body wave data recorded at a small network of broadband seismograph stations are analyzed to investigate local events with focal depths deeper than about 50 km. For these events the initial portion of P-wave displacement represents well the source time function with a scaler correction for the seismic moment. The magnitudes of the analyzed earthquakes range from MW = 3.1 to 6.5. It is shown that the seismic moment M0 and the pulse width τ are well correlated as M0/τ3 = constant, indicating that the stress drop is largely constant. This dynamic similarity seems to be valid for a vast range of earthquake sizes: MW = 1 ∼ 8. It is also shown that source complexity such as a multiple shock nature is not a characteristic of only large earthquakes but is often observed even for small earthquakes.

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Saito, Tatsuhiko, et Tatsuya Kubota. « Tsunami Modeling for the Deep Sea and Inside Focal Areas ». Annual Review of Earth and Planetary Sciences 48, n^o 1 (30 mai 2020) : 121–45. http://dx.doi.org/10.1146/annurev-earth-071719-054845.

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This article reviews tsunami modeling and its relation to recent developments of deep-ocean observations. Unlike near-coast observations, deep-ocean observations have enabled the capture of short-wavelength dispersive tsunamis and reflected waves from the coast. By analyzing these waves, researchers can estimate tsunami sources and earthquake slip distributions more reliably with higher spatial resolution. In addition, fractional tsunami speed reduction due to the elasticity of the Earth medium is now clearly detected. Densely and widely distributed tsunami sensors make it possible to observe tsunamis inside the earthquake focal area, and understanding tsunami generation mechanisms is increasingly important. In order to describe the generation field, we should consider seismic waves overlapping tsunami signals in addition to vertical and horizontal displacements at the sea bottom. The importance of elastic dynamics, in addition to fluid dynamics, is increasing in order for researchers to fully understand tsunami phenomena using the new offshore and inside focal area observations. ▪ Deep-ocean observations have advanced tsunami propagation modeling. ▪ New deep-ocean observations in earthquake focal areas are expected to detect in situ tsunami generation caused by megathrust earthquakes. ▪ The importance of elastic dynamics, in addition to fluid dynamics, is increasing to help researchers fully understand mechanics in tsunami generation and propagation. ▪ Tsunami modeling including earthquake rupture and seismic waves contributes to mega-thrust earthquake investigation and disaster mitigation.

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Barba-Sevilla, Magali, Bridger Baird, Abbie Liel et Kristy Tiampo. « Hazard Implications of the 2016 Mw 5.0 Cushing, OK Earthquake from a Joint Analysis of Damage and InSAR Data ». Remote Sensing 10, n^o 11 (30 octobre 2018) : 1715. http://dx.doi.org/10.3390/rs10111715.

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The Cushing Hub in Oklahoma, one of the largest oil storage facilities in the world, is federally designated as critical national infrastructure. In 2014, the formerly aseismic city of Cushing experienced a Mw 4.0 and 4.3 induced earthquake sequence due to wastewater injection. Since then, an M4+ earthquake sequence has occurred annually (October 2014, September 2015, November 2016). Thus far, damage to critical infrastructure has been minimal; however, a larger earthquake could pose significant risk to the Cushing Hub. In addition to inducing earthquakes, wastewater injection also threatens the Cushing Hub through gradual surface uplift. To characterize the impact of wastewater injection on critical infrastructure, we use Differential Interferometric Synthetic Aperture Radar (DInSAR), a satellite radar technique, to observe ground surface displacement in Cushing before and during the induced Mw 5.0 event. Here, we process interferograms of Single Look Complex (SLC) radar data from the European Space Agency (ESA) Sentinel-1A satellite. The preearthquake interferograms are used to create a time series of cumulative surface displacement, while the coseismic interferograms are used to invert for earthquake source characteristics. The time series of surface displacement reveals 4–5.5 cm of uplift across Cushing over 17 months. The coseismic interferogram inversion suggests that the 2016 Mw 5.0 earthquake is shallower than estimated from seismic inversions alone. This shallower source depth should be taken into account in future hazard assessments for regional infrastructure. In addition, monitoring of surface deformation near wastewater injection wells can be used to characterize the subsurface dynamics and implement measures to mitigate damage to critical installations.

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Palgunadi, Kadek Hendrawan, Alice-Agnes Gabriel, Thomas Ulrich, José Ángel López-Comino et Paul Martin Mai. « Dynamic Fault Interaction during a Fluid-Injection-Induced Earthquake : The 2017 Mw 5.5 Pohang Event ». Bulletin of the Seismological Society of America 110, n^o 5 (4 août 2020) : 2328–49. http://dx.doi.org/10.1785/0120200106.

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ABSTRACT The 15 November 2017 Mw 5.5 Pohang, South Korea, earthquake has been linked to hydraulic stimulation and fluid injections, making it the largest induced seismic event associated with an enhanced geothermal system. To understand its source dynamics and fault interactions, we conduct the first 3D high-resolution spontaneous dynamic rupture simulations of an induced earthquake. We account for topography, off-fault plastic deformation under depth-dependent bulk cohesion, rapid velocity weakening friction, and 1D subsurface structure. A guided fault reconstruction approach that clusters spatiotemporal aftershock locations (including their uncertainties) is used to identify a main and a secondary fault plane that intersect under a shallow angle of 15°. Based on simple Mohr–Coulomb failure analysis and 180 dynamic rupture experiments in which we vary local stress loading conditions, fluid pressure, and relative fault strength, we identify a preferred two-fault-plane scenario that well reproduces observations. We find that the regional far-field tectonic stress regime promotes pure strike-slip faulting, whereas local stress conditions constrained by borehole logging generate the observed thrust-faulting component. Our preferred model is characterized by overpressurized pore fluids, nonoptimally oriented but dynamically weak faults and a close-to-critical local stress state. In our model, earthquake rupture “jumps” to the secondary fault by dynamic triggering, generating a measurable non-double-couple component. Our simulations suggest that complex dynamic fault interaction may occur during fluid-injection-induced earthquakes and that local stress perturbations dominate over regional stress conditions. Therefore, our findings have important implications for seismic hazard in active georeservoir.

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Mikheeva, Anna, et Igor Kalinnikov. « Creepex-analysis of processes in focal zones of large earthquakes by means of GIS-ENDDB ». Russian Journal of Seismology 3, n^o 4 (21 décembre 2021) : 7–17. http://dx.doi.org/10.35540/2686-7907.2021.4.01.

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The creepex (creep & explosion) parameter provides information on the relation between low- and high-frequency radiation components in the earthquake source and has become a physically meaningful tool for analyzing various aspects of seismogenesis, in particular, the diagnostics of the preparation processes and the its aftershocks activity of a strong event. This paper investigates the spatial-temporal dynamics of creepex in the focal zones of a number of the major earthquakes from the plate convergence regions, including continental Kashmir earthquake (08.10.2005, MS=7.6) and continental-oceanic Tohoku (11.03.2011, Mw=8.7). One of the goals of this work is to demonstrate the capabilities of the method in studying physically grounded patterns of focal zones development at the first hours after the main shock. Because of this study, the following regularities of the source relaxation process were revealed: the partiality of the aftershock process, positive values of the creepex at its first hours (explained by the influence of the dilatancy process), and abrupt changes in the creepex during deep transitions (explained by the thermodynamic effect and by the increase in pressure with depth).

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Sherman, S. I., et E. A. Gorbunova. « The rheology of the geological medium of interblock seismically active faults in the continental lithosphere : a key to understanding the generation of the strongest earthquakes in Central Asia ». Geodynamics & ; Tectonophysics 9, n^o 3 (9 octobre 2018) : 571–86. http://dx.doi.org/10.5800/gt-2018-9-3-0363.

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The problem of earthquake forecasting remains challenging, especially considering strong seismic events (M≥8). Strong earthquakes occur most often along the fault planes due to large-amplitude displacements of the contacting blocks. In such cases, the physical parameters of the earthquake foci generation process are estimated on the basis of the concepts describing the destruction of solids. In this paper, we present a new tectonophysical model of strong earthquake foci in the continental lithosphere. In this model, an earthquake focus is viewed as a body whose rheological properties are changing over time throughout the entire seismic period, including the moment of the seismic event initiation, its occurrence and the subsequent stress release in of the geological medium. In the period when a future earthquake source develops and grows, the physical properties of the host rocks are assumed to change substantially, and both the viscosity and the relative shear strength decreases. At the moment of time when a strong earthquake takes place, the viscosity of the rocks in its focus is at its minimum value and thus favorable for high-amplitude interblock shearing under the current regional stress and unchanged geodynamic factors. A decrease in the viscosity is facilitated by an increase in the fault length and leads to weakening of the geological medium and decreases its strength properties. When the earthquake occurs, the viscosity of the rocks in its source is assumed significantly lower than the dynamic viscosity of the lithosphere and not less than one or two orders below the viscosity of the interblock seismically active medium containing the source. It is most likely that at the moment of time when an earthquake takes place, the viscosity in its source is 1017–1019 Pa·s. In our approach, the parameter of viscosity is introduced into the physics of earthquake foci, and the time factor is taken into account when studying the process of earthquake preparation and occurrence, which can be an important step to gaining more knowledge for forecasting of the strongest seismic events (M≥8).

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Main, Ian G., et Mark Naylor. « Entropy production and self-organized (sub)criticality in earthquake dynamics ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 368, n^o 1910 (13 janvier 2010) : 131–44. http://dx.doi.org/10.1098/rsta.2009.0206.

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We derive an analytical expression for entropy production in earthquake populations based on Dewar’s formulation, including flux (tectonic forcing) and source (earthquake population) terms, and apply it to the Olami–Feder–Christensen numerical model for earthquake dynamics. Assuming the commonly observed power-law rheology between driving stress and remote strain rate, we test the hypothesis that maximum entropy production (MEP) is a thermodynamic driver for self-organized ‘criticality’ (SOC) in the model. MEP occurs when the global elastic strain is near-critical, with small relative fluctuations in macroscopic strain energy expressed by a low seismic efficiency, and broad-bandwidth power-law scaling of frequency and rupture area. These phenomena, all as observed in natural earthquake populations, are hallmarks of the broad conceptual definition of SOC (which has, to date, often included self-organizing systems in a near but strictly subcritical state). In the MEP state, the strain field retains some memory of past events, expressed as coherent ‘domains’, implying a degree of predictability, albeit strongly limited in practice by the proximity to criticality and our inability to map the natural stress field at an equivalent resolution to the numerical model.

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Lyu, Pengfei, et Yijian Geng. « Unified Mechanism of Rock Burst Induced by Coal Mine Earthquake and Its Activity and Response Characteristics ». Shock and Vibration 2023 (14 février 2023) : 1–14. http://dx.doi.org/10.1155/2023/2145765.

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The occurrence regularity of the coal mine earthquake under the influence of hard roof, fault, and mining was studied by theoretical analysis, field investigation, and monitoring data analysis for the phenomenon of rock burst induced by coal mine earthquakes. The dissipation characteristics of coal mine earthquake energy propagation considering a hypocenter scale were described, and the coal mine earthquake response characteristics were analyzed. The two principles of rock burst induced by hard rock fractured type coal mine earthquakes and the three principle of rock burst induced by fault were described. Based on this, the unified mechanism rock burst induced by different types of coal mine earthquakes was proposed. The results show that the microseismic energy increases sharply and decreases sharply when mining in the fault area. The amplitude and frequency of support resistance increased before and after the heavy coal mine earthquake occurred. The periodic characteristics of the coal mine earthquake in the 43upper 13 working face of the Dongtan coal mine show that there are 50 m small periods within 100 m large periods. The multiparameter field monitoring can make it possible for instantaneous capture of the coal mine earthquake dynamic responses. The unified rock burst mechanism induced different types of coal mine earthquake and is the difference energy between the superposition energy of the rock burst source region and the energy consumed by coal-rock instability increases suddenly under the action of coal mine earthquakes. Meanwhile, the violent rock burst accident occurs when the stiffness condition is satisfied.

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Pustovitenko, B. G., E. E. Eredzhepov et M. N. Bondar. « FOCAL PARAMETERS of CRIMEAN-BLACK SEA REGION EARTHQUAKES in 2016–2017 ». Earthquakes in Northern Eurasia, n^o 25 (20 décembre 2022) : 242–52. http://dx.doi.org/10.35540/1818-6254.2022.25.22.

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Focal parameters of twenty-one 2016–2017 earthquakes of the Crimean-Black sea region with KП=6.5–13.1 have been recovered. Solutions of focal mechanisms have been obtained for the four strongest earthquakes. The dynamic source parameters – scalar seismic moment M0, the radius of circular dislocation r0, released stress , shear deformation , apparent stress ησ, radiation friction r, average slip along fault ū, energy of dislocation formation in the source ЕU, moment magnitude Mw – have been restored for twenty-one earthquakes by 149 amplitude spectra using Brune theoretical dislocation model. The type of slip in the source of May 13, 2016, felt an earthquake, which happened near the southern coast of Crimea, is a strike-slip. The June 28, July 22 and October 15, 2016 earthquakes occurred in the Black sea basin under the action of horizontal compressive stress, the type of slip in the source is a reverse fault. In the source of the June 16, 2017 earthquake, a thrust of active rupture wing occurred under the action of horizontal compression stress of the meridional direction. This type of movement is typical for earthquakes in the eastern part of the Crimean-Black Sea region. The mechanism parameters of these earthquakes were used to determine the direction of the source radiation to the recording station to account for relevant amendments in the calculation of the seismic moment M0. In general, average values of M0 and r0 for 2016–2017 earthquakes were within the confidence intervals of long-term dependencies M0(KП), r0(KП). The best correspondence of seismic moment values to the long-term dependencies was obtained for the earthquakes of the June 28, July 22, October 15, 2016 and June 16, 2017, with known focal mechanisms because the corrections for real radiation direction Rφ were introduced in the formula for M0 calculation. For reliable estimates of the spectral and dynamic source parameters of the 2016–2017 Crimean earthquakes, only very clear records of body waves at seismic stations with reliable characteristics of recording equipment were used. The averaging of the source dynamic parameters was done by 2–10 station definitions, which provided a small value of standard deviations. In this regard, quantitative estimates of focal parameters can be classified as reliable for further use for scientific and scientific-applied problems, in particular, for the development of geodynamic models.

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Yi, Shu-jian, Chun-hao Wu, Yu-sheng Li et Chao Huang. « Source tectonic dynamics features of Jiuzhaigou Ms 7.0 earthquake in Sichuan Province, China ». Journal of Mountain Science 15, n^o 10 (octobre 2018) : 2266–75. http://dx.doi.org/10.1007/s11629-017-4703-6.

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Singh, Rashmi, Prosanta Kumar Khan et A. P. Singh. « Earthquake source dynamics and kinematics of the Eastern Indian Shield and adjoining regions ». Acta Geophysica 68, n^o 2 (13 mars 2020) : 337–55. http://dx.doi.org/10.1007/s11600-020-00418-z.

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Rogozhin, E. A. « Evolution of views on the structure of sources of strong earthquakes at the end of XX and beginning of XXI centuries ». Физика Земли, n^o 1 (27 mars 2019) : 134–48. http://dx.doi.org/10.31857/s0002-333720191134-148.

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The paper addresses the evolution of scientific views on the structure of the sources of strong earthquakes at the end of the 20th and beginning of the 21th century in Russia. The scientific concepts that emerged in the main developed countries initially typically lacked a clear and consistent understanding of the structure of sources of the strongest seismic events. In the 1950s, at the Schmidt Institute of Physics of the Earth of the USSR Academy of Sciences, G.A. Gamburtsev formulated a hypothesis of a long-term (a few hundred years) stability of seismic regime of a system of seismic sutures. The recently studied earthquakes have their sources in the regions of the large faults. The earthquakes of larger magnitudes have more extended and structurally more complex sources. Some sources in the considered cases are relatively simple to reconstruct (they encompass the fault planes of the large faults, e.g., the Spitak source, M = 6.8). Other sources are more complex; they are formed in the disjunctive nodes or encompass the crustal blocks. For example, the seismic source of the Altai earthquake (M = 7.3) has a volumetric structure and is developed along the boundaries of the large seismogenic blocks. The Wenchuan earthquake (M = 7.9) has a most complicated source which looks as a three-dimensional (3D) structure composed of a few crustal blocks framed by two extended northeast striking faults and separated by the northwesterly trending transverse fault. The structurally different sources differently manifest themselves in the pattern of seismic dislocations on the surface and in the distribution of aftershock hypocenters at depth. The anomalously low velocity “pockets” identified by local seismic tomography in the source areas of the Spitak and Altai earthquakes which accompany the main and secondary faults at depth are likely to be the zones of dynamic control of these faults. The breaked near-fault zones abundant with cracks and fractures are the severely looze inclusions in the crustal rocks hampering the propagation of seismic waves. Therefore, the P-waves in these pockets propagate at lower velocities than in the undamaged geological medium. The paleoseismological studies of seismic faults in trenches have shown that the strong earthquakes have occurred in the same sources in the past and the recurrence period of the strongest seismic events ranges from a few hundred to a few thousand years. Thus, the combined studies of the source zones of the strongest earthquakes conducted in the past decades in the different regions of Eurasia have shown that Gamburtsev’s hypothesis has remained relevant.

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Dahm, T., S. Heimann, M. Metz et M. P. Isken. « A self-similar dynamic rupture model based on the simplified wave-rupture analogy ». Geophysical Journal International 225, n^o 3 (10 mars 2021) : 1586–604. http://dx.doi.org/10.1093/gji/ggab045.

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SUMMARY The investigation of stresses, faults, structure and seismic hazards requires a good understanding and mapping of earthquake rupture and slip. Constraining the finite source of earthquakes from seismic and geodetic waveforms is challenging because the directional effects of the rupture itself are small and dynamic numerical solutions often include a large number of free parameters. The computational effort is large and therefore difficult to use in an exploratory forward modelling or inversion approach. Here, we use a simplified self-similar fracture model with only a few parameters, where the propagation of the fracture front is decoupled from the calculation of the slip. The approximative method is flexible and computationally efficient. We discuss the strengths and limitations of the model with real-case examples of well-studied earthquakes. These include the Mw 8.3 2015 Illapel, Chile, megathrust earthquake at the plate interface of a subduction zone and examples of continental intraplate strike-slip earthquakes like the Mw 7.1 2016 Kumamoto, Japan, multisegment variable slip event or the Mw 7.5 2018 Palu, Indonesia, supershear earthquake. Despite the simplicity of the model, a large number of observational features ranging from different rupture-front isochrones and slip distributions to directional waveform effects or high slip patches are easy to model. The temporal evolution of slip rate and rise time are derived from the incremental growth of the rupture and the stress drop without imposing other constraints. The new model is fast and implemented in the open-source Python seismology toolbox Pyrocko, ready to study the physics of rupture and to be used in finite source inversions.

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Miyazaki, Mitsuo. « The Next Generation of Seismic Isolation Going Beyond Seismic Design Dominated by Earthquakes ». Journal of Disaster Research 3, n^o 6 (1 décembre 2008) : 479–502. http://dx.doi.org/10.20965/jdr.2008.p0479.

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Seismic isolation can provide superior building safety and dynamic response during strong earthquakes, however, performance is only assured below the design earthquake intensity level. This paper opens with a study of observed strong, near-source ground motions and long-period earthquake waves proposed by researchers. Through the examination of a widerange of earthquake response and input energy spectra, up to a period of 100 seconds, the most suitable range of damping values and isolation periods are found. The optimal period range is further confirmed by evaluating earthquake-wave amplification features during propagation from bedrock to the ground surface. Three types of next-generation seismic isolation systems are proposed along with new parameters to evaluate the dynamic response of seismically isolated structures. By comparing the dynamic response performance of four isolation systems, including a "conventional" 4-second period system, the superior seismic performance of the three next-generation isolation systems is confirmed. The paper shows the direction for a new generation of seismically isolated structures, with periods exceeding 10 seconds, and which minimize the elastic strain energy stored in the structure. Seismically isolated structures possessing these properties will survive strong earthquake input regardless of the uncertainty inherent in earthquake ground motions.

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Carlino, Stefano, Nicola Alessandro Pino, Anna Tramelli, Vincenzo De Novellis et Vincenzo Convertito. « A common source for the destructive earthquakes in the volcanic island of Ischia (Southern Italy) : insights from historical and recent seismicity ». Natural Hazards 108, n^o 1 (15 mars 2021) : 177–201. http://dx.doi.org/10.1007/s11069-021-04675-z.

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AbstractThe island of Ischia, located in the Gulf of Naples, represents an unusual case of resurgent caldera where small-to-moderate magnitude volcano-tectonic earthquakes generate large damage and catastrophic effects, as in the case of 4 March 1881 (Imax-VIII-IXMCS) and 28 July 1883 (Imax X-XI MCS) historical earthquakes, and of the recent 21 August 2017 MW = 3.9, event. All these earthquakes struck the northern area of the island. With about 65,000 inhabitants, Ischia is a popular touristic destination for thermals baths, hosting more than 3,000,000 visitors per year, thus representing a high seismic risk area. Assessing its seismic potential appears a fundamental goal and, to this end, the estimate of the magnitude of significant historical events and the characterization of their source are crucial. We report here a reassessment of historical data of damage of 1881 and 1883 earthquakes to evaluate the main source parameters of these events (obtained with the BOXER and EXISM software) and quantitatively compare, for the first time, the results with the source characteristics, obtained from instrumental data, of the recent 2017 earthquake. The results allowed us to assess the location, as well as the possible dimension and the related maximum magnitude, of the seismogenic structure responsible for such damaging earthquakes. Our results also provide an additional framework to define the mechanisms leading to earthquakes associated with the dynamics of calderas.

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Furumura, Takashi, et Tatsuhiko Saito. « Integrated Ground Motion and Tsunami Simulation for the 1944 Tonankai Earthquake Using High-Performance Supercomputers ». Journal of Disaster Research 4, n^o 2 (1 avril 2009) : 118–26. http://dx.doi.org/10.20965/jdr.2009.p0118.

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An integrated simulation of seismic wave and tsunami has been developed for mitigation of earthquake and tsunami disasters associated with large subduction-zone earthquakes occurring in the Nankai Trough. The ground motion due to the earthquake is firstly calculated by solving equation of motions with heterogeneous source-rupture model and 3-D heterogeneous subsurface structural model. Tsunami generation and propagation in heterogeneous bathymetry is then simulated by solving the 3-D Navier-Stokes equation. Ground motion and tsunami simulations are combined through an appropriate dynamic boundary condition at the sea floor. Thanks to supercomputers and efficient parallel computing, we are reproducing strong ground motion and tsunamis caused by the M8.0 Tonankai earthquake in the Nankai Trough in 1944. The visualized seismic wavefield and tsunami derived by integrated simulation provides a direct understanding of disasters associated with Nankai Trough earthquakes with the development of long-period ground motion in highly populated basins such as Tokyo, Osaka, and Nagoya and tsunamis striking along Japan’s Pacific Ocean coast.

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Lan, Tian Wei, Hong Wei Zhang, Jian Yang Yu et Jun Han. « Study on the Correlation of Shallow Source Earthquake and Mine Dynamic Disasters in the Weast of Beijing ». Applied Mechanics and Materials 416-417 (septembre 2013) : 1942–46. http://dx.doi.org/10.4028/www.scientific.net/amm.416-417.1942.

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Mine dynamic disasters is due to a sudden release of energy by mine engineering disturbed. Shallow-focus earthquake is due to plate movement caused by sudden release of energy. In this paper, on the basis of plate tectonics, geophysical, In this paper, on the basis of plate tectonics, geophysical, through the shallow source analogy is the mechanism of dynamic disaster, earthquake and mine exploration seismic energy result in mine power. The mechanism of disaster analysis seismic energy has the possibility of mine dynamic disaster, combining shallow-focus earthquake and the mine dynamic natural disaster site scheduling, and shallow-focus earthquake and the mine dynamic disasters of space position relations. Analysis in complex geological conditions shallow-focus earthquake geological structure as the first energy transmission medium for mine power disaster role relationship, for the prediction of mine dynamic disaster and the effective prevention and control provides the basis of the production test.

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Klyuchevskii, A. V., V. I. Grebenshchikova, M. I. Kuz’min, V. I. Dem’yanovicha et A. A. Klyuchevskaya. « The Relationship between Powerful Geodynamic Impacts and an Increase in the Mercury Content of the Water of the Angara River Source (Baikal Rift Zone) ». Russian Geology and Geophysics 62, n^o 2 (1 février 2021) : 239–54. http://dx.doi.org/10.2113/rgg20194139.

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Abstract—The results of Hg content determination in the water of the Angara River source are considered in relationship with the seismic processes proceeding at different levels of the lithosphere in the Baikal Rift Zone (BRZ), the geodynamic rejuvenation of the South Baikal rifting attractor structure (RAS), and the time distribution of M ≥ 7 earthquakes which occurred at a significant distance from the water sampling station. The correlation coefficients calculated between the pairs Hg content–earthquake numbers n and Hg–logarithm of summary seismic energy lgΣES are most often low, thus indicating the absence of a statistically meaningful relationship between the remote seismic process and the dynamics of mercury release. However, the correlation coefficients in the vicinity of the Angara River source are high, thus proving the relationship of the mercury release with the deformation of this territory. The statistical validity of the «deformation–mercury release» cause-and-effect relationship is verified by the fact that strong geodynamic impacts precede all meaningful Hg release maxima. In the period 1997–1998, the South Baikal RAS produced the highest impact, being in the phase of the maximum geodynamic activity. The combined impact of the RAS and the South Baikal earthquake of 1999 resulted in a series of the maximum mercury contents within 1999–2000. The subsequent gradual relaxation of the RAS activity led to a reduction in the average annual Hg content. Remote M ≥ 7 earthquakes and close strong earthquakes of the BRZ are responsible for the significant Hg release maxima. The predicted trend of the average annual Hg contents is their considerable increase in the fields of fluid discharge of faults under the powerful geodynamic impact of the RAS or strong earthquake. We assume that in the study lithosphere area, the powerful geodynamic impact caused an opening of fault zones leading to decompression with boiling and degassing of mercury and its rapid rise to the surface.

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Afraimovich, E. L., N. P. Perevalova, A. V. Plotnikov et A. M. Uralov. « The shock-acoustic waves generated by earthquakes ». Annales Geophysicae 19, n^o 4 (30 avril 2001) : 395–409. http://dx.doi.org/10.5194/angeo-19-395-2001.

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Abstract. We investigate the form and dynamics of shock-acoustic waves generated by earthquakes. We use the method for detecting and locating the sources of ionospheric impulsive disturbances, based on using data from a global network of receivers of the GPS navigation system, and require no a priori information about the place and time of the associated effects. The practical implementation of the method is illustrated by a case study of earthquake effects in Turkey (17 August and 12 November 1999), in Southern Sumatra (4 June 2000), and off the coast of Central America (13 January 2001). It was found that in all instances the time period of the ionospheric response is 180–390 s, and the amplitude exceeds, by a factor of two as a minimum, the standard deviation of background fluctuations in total electron content in this range of periods under quiet and moderate geomagnetic conditions. The elevation of the wave vector varies through a range of 20–44°, and the phase velocity (1100–1300 m/s) approaches the sound velocity at the heights of the ionospheric F-region maximum. The calculated (by neglecting refraction corrections) location of the source roughly corresponds to the earthquake epicenter. Our data are consistent with the present views that shock-acoustic waves are caused by a piston-like movement of the Earth’s surface in the zone of an earthquake epicenter.Key words. Ionosphere (ionospheric disturbances; wave propagation) – Radio science (ionospheric propagation)

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Li, Yingping, Charles Doll et M. N. Toksöz. « Source characterization and fault plane determination for MbLg = 1.2 to 4.4 earthquakes in the Charlevoix Seismic Zone, Quebec, Canada ». Bulletin of the Seismological Society of America 85, n^o 6 (1 décembre 1995) : 1604–21. http://dx.doi.org/10.1785/bssa0850061604.

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Abstract Two earthquake doublets and two multiplets recorded by the Charlevoix Telemetered Network (CLTN) in the Charlevoix Seismic Zone (CSZ) of southern Quebec, Canada, have been analyzed using an empirical Green's function (EGF) method to derive the relative source time functions (RSTF's) of seven master events with MbLg = 1.2 to 4.4. We identified the doublets and multiplets using a waveform cross-correlation and relative event location technique to verify that each earthquake pair had similar focal mechanisms and hypocentral locations. Three-component S waveforms recorded by the high dynamic range (126 dB) instrumentation of the CLTN were used to extract the RSTF's. The RSTF's reveal that six of the seven events are simple with single-source pulses having durations of 0.05 to 0.2 sec. Another earthquake (920310-0545, M 3.3) appears to be a double event with two episodes of rupturing. Azimuthal variations of the RSTF pulse amplitudes and widths provide strong evidence for the rupture directivities of five of the earthquakes (M = 1.2 to 4.4). The azimuthal variations in the RSTF pulse amplitudes were used to estimate the rupture directions and rupture velocities. Lower-bound estimates of the rupture velocity range from 0.5 to 0.7 Vs. Estimates of the rupture direction were combined with P-wave focal mechanisms for the four largest events (M 3.3 to 4.4) to identify the fault plane for these earthquakes. Source parameters were measured for the RSTF's of the master events, including seismic moments of 3.5 × 1018 to 5.3 × 1021 dyne-cm, fault radii of 100 to 330 m, and static stress drops of 2 to 90 bars. The fault radii and stress-drop estimates for M > 3 events agree well with estimates obtained by other researchers for M ∼ 3 to 4.5 earthquakes in the CSZ. We also observed apparent scaling between the stress drop and the earthquake size, which has been reported in other studies of stress drop in northeastern North America.

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Partono, Windu. « Development of two components acceleration time histories for Semarang, Indonesia, due to Semarang fault earthquake scenarios using 30 meters soil deposit model ». MATEC Web of Conferences 159 (2018) : 01043. http://dx.doi.org/10.1051/matecconf/201815901043.

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Development of surface acceleration time histories is important for dynamic analysis of structure design and evaluation. Acceleration time histories usually developed from seismograph records due to specific earthquake event. Following the research conducted by Team for Revision of Seismic Hazard Maps of Indonesia 2010 and 2016, Lasem fault and Semarang fault are two closest and dangerous shallow crustal fault earthquake sources which must be taken into account for seismic mitigation of Semarang. This paper presents the development two components surface acceleration time histories for Semarang caused by Semarang fault earthquake scenarios, with magnitude from 6 Mw to 7 Mw and maximum epicentre distance 15 Km. This research was performed by conducting deterministic hazard analysis, response spectral matching and site response analysis to obtain a pair of modified acceleration time histories. Site response analysis was performed by conducting 30 meters soil deposit model by taking the assumption that the position of bedrock elevation is 30 meters below the surface layer. Modified acceleration time histories were developed from a pair time histories (North-South/NS and East-West/EW direction) collected from worldwide historical earthquakes. Modified time histories were developed due to limited time histories data caused by Semarang fault earthquake source.

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Petrosino, Simona, et Paola Cusano. « Low frequency seismic source investigation in volcanic environment : the Mt. Vesuvius atypical case ». Advances in Geosciences 52 (10 juin 2020) : 29–39. http://dx.doi.org/10.5194/adgeo-52-29-2020.

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Abstract. We present a detailed analysis of the low frequency seismicity occurred at Mt. Vesuvius in the time range 2003–2018. This kind of seismicity is atypical for the volcano and poorly studied, therefore we characterized it in terms of spectral analysis, waveform cross-correlation, location and polarization properties. The different decay patterns of the spectra, the existence of both earthquake families as well as single events, the relatively wide seismogenic volume inferred from the locations and polarization features, indicate that the events are caused by distinct source mechanisms: slow brittle failure in dry rocks and resonance of fluid-filled cracks. On these basis, we classified the earthquakes as Low Frequency (LF) and Long Period (LP). Despite the differences between the two classes, both the event types are ascribable to the dynamics of the deep hydrothermal reservoir which induces variations of the fluid pore pressure in the medium. The fluid amount involved in the generation process, as well as the physical-chemical properties of the surrounding rocks are the essential factors that control the occurrence of a mechanism rather than the other.

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Ma, Feng, Guangsheng Zhao, Xingyu Gao et Xiaojing Niu. « Spatial Distribution of Tsunami Hazard Posed by Earthquakes along the Manila Trench ». Journal of Marine Science and Engineering 10, n^o 10 (7 octobre 2022) : 1449. http://dx.doi.org/10.3390/jmse10101449.

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Quantitative probability has been computed for the tsunami hazard posed by earthquakes from the Manila Trench, which has been regarded as a huge threat in the South China Sea. This study provides a spatial distribution of the tsunami hazard covering the affected area with a spatial resolution of 0.1° for disaster prevention of islands and continental coasts. The quantitative probability of the tsunami hazard is computed by an efficient model, which can realize a large amount of potential tsunami scenarios analysis in order to consider the randomness and uncertainty in earthquake magnitude, source location and focal depth. In the model, for each potential tsunami scenario, the occurrence probability of the corresponding earthquake and the intensity of tsunami waves at each target location are computed. The occurrence probability of each scenario is estimated based on the historical earthquake records. Then, the subsequent tsunami caused by each scenario is computed using a new, efficient approach, instead of direct simulation using an ocean dynamics model. A total of 1,380,000 scenarios are computed in order to obtain a stable statistical result. Based on the results, the spatial distribution of the tsunami hazard is discussed and high-hazard regions along the coast have been identified.

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Eken, Tuna. « Moment magnitude estimates for central Anatolian earthquakes using coda waves ». Solid Earth 10, n^o 3 (23 mai 2019) : 713–23. http://dx.doi.org/10.5194/se-10-713-2019.

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Abstract. A proper estimate of moment magnitude, which is a physical measure of the energy released at an earthquake source, is essential for better seismic hazard assessments in tectonically active regions. Here a coda wave modeling approach that enables the source displacement spectrum modeling of the examined event was used to estimate moment magnitudes of central Anatolia earthquakes. To achieve this aim, three-component waveforms of local earthquakes with magnitudes 2.0≤ML≤5.2 recorded at 69 seismic stations, which were operated between 2013 and 2015 within the framework of the Continental Dynamics–Central Anatolian Tectonics (CD–CAT) passive seismic experiment, were utilized. An inversion on the coda wave traces of each selected single event in the database was performed in five different frequency bands between 0.75 and 12 Hz. The resultant moment magnitudes (Mw coda) exhibit a good agreement with routinely reported local magnitude (ML) estimates for the study area. Apparent move-out that is particularly significant around the scattered variation of ML–Mw coda data points for small earthquakes (ML < 3.5) can be explained by possible biases of wrong assumptions to account for anelastic attenuation and seismic recordings with a finite sampling interval. Finally, I present an empirical relation between Mw coda and ML for central Anatolian earthquakes.

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Malyanova, L., et Irina Gabsatarova. « SPECTRAL and SOURCE EARTHQUAKE PARAMETERS on NORTHERN CAUCASUS ». Zemletriaseniia Severnoi Evrazii [Earthquakes in Northern Eurasia], n^o 22 (12 novembre 2019) : 311–19. http://dx.doi.org/10.35540/1818-6254.2019.22.28.

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The dynamic parameters of of 18 earthquakes sources in the North Caucasus for 2013 with КР=10.0–12.9, determined from 64 amplitude spectra of S-waves are given. Records of three regional digital seismic sta-tions, “Anapa”, “Kislovodsk” and “Sochi” are used. They are located no more than 300 km from the sources. The records of the “Makhachkala” station were used in a test mode. For the environment near these stations, the values of the frequency-dependent Q-factor, necessary for recalculating the station spectra to the focal ones, were obtained earlier. In 2013, the largest number of studied earthquakes was located in the Eastern Caucasus. The dependence of log M0 and КР for this zone was established with use of the data ob-tained in 2010–2013. Compared to the similar equation of world average dependence (Riznichenko, 1976), our dependence is in a good agreement with it by the slope, but the free term exceeds the same in the world average dependence by almost two units.

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Lambert, Valère, et Nadia Lapusta. « Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes ». Solid Earth 11, n^o 6 (26 novembre 2020) : 2283–302. http://dx.doi.org/10.5194/se-11-2283-2020.

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Abstract. Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need to reexamine the assumption of predetermined frictional breakdown energy common in dynamic rupture modeling and to better understand the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.

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Spivak, A. A., et S. A. Riabova. « Geomagnetic effect of earthquakes ». Доклады Академии наук 488, n^o 2 (24 septembre 2019) : 197–201. http://dx.doi.org/10.31857/s0869-56524882197-201.

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Based on the results of instrumental observations carried out at a number of mid-latitude observatories of the INTERMAGNET network and at the Mikhnevo Geophysical Observatory of Institute of Geosphere Dynamics of Russian Academy of Sciences, it is shown that strong earthquakes are accompanied by increased variations of Earth’s magnetic field. In this case, the short-period stage (period ~ 0.5-0.8 min) and long-period stage (period ~ 5-20 min) of increased geomagnetic variations are clearly distinguished. The maximum amplitude of induced geomagnetic variations is 1.5-2 nT and 2- 4 nT, respectively, for short-period and long-period variations. A similar in morphology and almost synchronous nature of the induced geomagnetic disturbances at the observatories located at significantly different distances from the earthquake source is noted.

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