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1
KIKUCHI, Masayuki. "Complexity of Earthquake Source Processes." Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 44, Supplement (1991): 301–14. http://dx.doi.org/10.4294/zisin1948.44.supplement_301.
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Yin, Jiuxun, Zefeng Li, and Marine A. Denolle. "Source Time Function Clustering Reveals Patterns in Earthquake Dynamics." Seismological Research Letters 92, no. 4 (March 31, 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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Vallianatos, F., G. Michas, G. Papadakis, and A. Tzanis. "Evidence of non-extensivity in the seismicity observed during the 2011–2012 unrest at the Santorini volcanic complex, Greece." Natural Hazards and Earth System Sciences 13, no. 1 (January 28, 2013): 177–85. http://dx.doi.org/10.5194/nhess-13-177-2013.
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Abstract. During the period of October 2011–January 2012, an increase of earthquake activity has been observed in the volcanic complex of Santorini Island, Greece. Herein, the magnitude distribution of earthquakes as well as the temporal distribution of seismicity are studied. The statistics of both parameters exhibit complexity that is evident in the frequency-magnitude distribution and the inter-event time distribution, respectively. Because of this, we have used the analysis framework of non-extensive statistical physics (NESP), which seems suitable for studying complex systems. The observed inter-event time distribution for the swarm-like earthquake events, as well as the energy and the inter-event earthquake energy distributions for the observed seismicity can be successfully described with NESP, indicating the inherent complexity of the Santorini volcanic seismicity along with the applicability of the NESP concept to volcanic earthquake activity, where complex correlations exist.
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Erickson, Brittany A., Junle Jiang, Michael Barall, Nadia Lapusta, Eric M. Dunham, Ruth Harris, Lauren S. Abrahams, et al. "The Community Code Verification Exercise for Simulating Sequences of Earthquakes and Aseismic Slip (SEAS)." Seismological Research Letters 91, no. 2A (January 29, 2020): 874–90. http://dx.doi.org/10.1785/0220190248.
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Abstract Numerical simulations of sequences of earthquakes and aseismic slip (SEAS) have made great progress over past decades to address important questions in earthquake physics. However, significant challenges in SEAS modeling remain in resolving multiscale interactions between earthquake nucleation, dynamic rupture, and aseismic slip, and understanding physical factors controlling observables such as seismicity and ground deformation. The increasing complexity of SEAS modeling calls for extensive efforts to verify codes and advance these simulations with rigor, reproducibility, and broadened impact. In 2018, we initiated a community code-verification exercise for SEAS simulations, supported by the Southern California Earthquake Center. Here, we report the findings from our first two benchmark problems (BP1 and BP2), designed to verify different computational methods in solving a mathematically well-defined, basic faulting problem. We consider a 2D antiplane problem, with a 1D planar vertical strike-slip fault obeying rate-and-state friction, embedded in a 2D homogeneous, linear elastic half-space. Sequences of quasi-dynamic earthquakes with periodic occurrences (BP1) or bimodal sizes (BP2) and their interactions with aseismic slip are simulated. The comparison of results from 11 groups using different numerical methods show excellent agreements in long-term and coseismic fault behavior. In BP1, we found that truncated domain boundaries influence interseismic stressing, earthquake recurrence, and coseismic rupture, and that model agreement is only achieved with sufficiently large domain sizes. In BP2, we found that complexity of fault behavior depends on how well physical length scales related to spontaneous nucleation and rupture propagation are resolved. Poor numerical resolution can result in artificial complexity, impacting simulation results that are of potential interest for characterizing seismic hazard such as earthquake size distributions, moment release, and recurrence times. These results inform the development of more advanced SEAS models, contributing to our further understanding of earthquake system dynamics.
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Ando, R., and T. Yamashita. "Fault Zone Complexity and Earthquake Ruptures." Scientific Drilling SpecialIssue (November 1, 2007): 27–28. http://dx.doi.org/10.5194/sd-specialissue-27-2007.
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Rice, J. R., and Y. Ben-Zion. "Slip complexity in earthquake fault models." Proceedings of the National Academy of Sciences 93, no. 9 (April 30, 1996): 3811–18. http://dx.doi.org/10.1073/pnas.93.9.3811.
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Barnhart, William D., Gavin P. Hayes, and David J. Wald. "Global Earthquake Response with Imaging Geodesy: Recent Examples from the USGS NEIC." Remote Sensing 11, no. 11 (June 6, 2019): 1357. http://dx.doi.org/10.3390/rs11111357.
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The U.S. Geological Survey National Earthquake Information Center leads real-time efforts to provide rapid and accurate assessments of the impacts of global earthquakes, including estimates of ground shaking, ground failure, and the resulting human impacts. These efforts primarily rely on analysis of the seismic wavefield to characterize the source of the earthquake, which in turn informs a suite of disaster response products such as ShakeMap and PAGER. In recent years, the proliferation of rapidly acquired and openly available in-situ and remotely sensed geodetic observations has opened new avenues for responding to earthquakes around the world in the days following significant events. Geodetic observations, particularly from interferometric synthetic aperture radar (InSAR) and satellite optical imagery, provide a means to robustly constrain the dimensions and spatial complexity of earthquakes beyond what is typically possible with seismic observations alone. Here, we document recent cases where geodetic observations contributed important information to earthquake response efforts—from informing and validating seismically-derived source models to independently constraining earthquake impact products—and the conditions under which geodetic observations improve earthquake response products. We use examples from the 2013 Mw7.7 Baluchistan, Pakistan, 2014 Mw6.0 Napa, California, 2015 Mw7.8 Gorkha, Nepal, and 2018 Mw7.5 Palu, Indonesia earthquakes to highlight the varying ways geodetic observations have contributed to earthquake response efforts at the NEIC. We additionally provide a synopsis of the workflows implemented for geodetic earthquake response. As remote sensing geodetic observations become increasingly available and the frequency of satellite acquisitions continues to increase, operational earthquake geodetic imaging stands to make critical contributions to natural disaster response efforts around the world.
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Zhang, J., F. Gao, H. Yu, and X. Zhao. "Use of an orthogonal parallel robot with redundant actuation as an earthquake simulator and its experiments." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, no. 1 (October 3, 2011): 257–72. http://dx.doi.org/10.1177/0954406211413050.
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In this article, an orthogonal 6-degree-of-freedom (DOF) parallel robot with redundant actuation is studied as an earthquake motion simulator. Taking the practical simulation of earthquake waves into consideration, the general characteristics of natural earthquakes are analysed and complexity and variety of seismic waves, three-dimensional and multi-DOF movement, and strong devastating force are regarded as the three obvious features in this article. Based on the characteristics of this orthogonal 6-DOF parallel robot with redundant actuation and the features of earthquakes, the feasibility of using this parallel robot as an earthquake motion simulator is analysed from three aspects: orthogonal 6-DOF structure, decoupling feature, and redundant actuation module. In order to simulate an earthquake motion using this parallel robot, its inverse kinematics and dynamics models are derived. The control system of this earthquake simulator is developed based on the PXIbus development platform. The computed-torque control algorithm based on the inverse dynamics is used in the controller of this equipment. A typical three-directional earthquake motion, the El Centro earthquake, is simulated on the end-effector of this parallel robot by means of its mathematical models and control system. Three main motion parameters of simulated seismic waves, displacements, velocities, and accelerations, are measured, respectively, by laser tracker and acceleration sensors. The experimental results show this equipment is appropriate to be used as an earthquake simulator.
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BHATTACHARYA, S. N., K. C. SINHA RAY, and H. N. SRIVASTAVA. "Large fractal dimension of chaotic at tractor for earthquake sequence near Nurek reservoir." MAUSAM 46, no. 2 (January 1, 2022): 187–92. http://dx.doi.org/10.54302/mausam.v46i2.3227.
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Fractal dimension of the chaotic attractor for earthquake sequence in Nurek dam based on 22.000 earthquakes detected during the period 1976-87 has been studied for this total period of observations as well as for the period from December 1977 to December 1987. The second period excluded increased seismic activity during second stage of filling the reservoir. Large fractal dimensions of the chaotic at tractor of 8.3 and 7.3 were found for the respective period which suggests the complexity of earthquake .dynamics in this region as compared to Koyna reservoir.
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Quintanar, Luis, J. Yamamoto, and Z. Jiménez. "Source mechanism of two 1994 intermediate-depth-focus earthquakes in Guerrero, Mexico." Bulletin of the Seismological Society of America 89, no. 4 (August 1, 1999): 1004–18. http://dx.doi.org/10.1785/bssa0890041004.
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Abstract In May and December 1994, two medium-size, intermediate-depth-focus earthquakes occurred in Guerrero, Mexico, eastward of the rupture area of the great Michoacan earthquake of September 19, 1985. Even though these are not major earthquakes (∼6.4 Mw), they were widely felt through central and southern Mexico, with minor damage at Zihuatanejo and Acapulco, located along the Pacific coast, and Mexico City. Both earthquakes, separated by ∼100 km, have similar focal depths and magnitudes, however, their focal mechanisms, based upon the polarities of first arrivals, show some differences. The May earthquake shows a clear normal faulting mechanism (φ = 307°, δ = 55°, λ = −108°), whereas the December earthquake mechanism solution suggests an initial thrust faulting (φ = 313°, δ = 62°, λ = 98°) process. Although previous analysis, including local and teleseismic stations, reported a normal faulting for the December earthquake, we find that modeling using the CMT focal mechanism solution fails to reproduce the first 5 sec of the observed P-wave signal at the nearest broadband station (Δ = 168 km) and the S-wave polarity at two strong ground-motion local stations (Δ = 32, 53 km); in fact, the best fit for these stations is obtained using the thrust focal mechanism calculated from the first-motion method. Seismic moment value and rupture duration time deduced from the teleseismic spectral analysis are: 2.0 × 1018 N-m and 6.9 sec for the May event; 2.8 × 1018 N-m and 7.1 sec for the December earthquake. From the inferred seismic moment, an average Δσ of ∼15 bars for both earthquakes is obtained. Inversion of teleseismic P-wave data indicates a better fit using the CMT focal mechanism solution (normal faulting) than the first-motion mechanism for both earthquakes, although the adjustment's differences are small for the May event; for this earthquake, the rupture consisted of two sources separated by ∼7 sec, starting at a depth of ∼40 km and then propagating downdip, reaching a depth of ∼60 km. The December earthquake however, released, all its energy at a depth of 50 km in two main sources separated by ∼10 sec. The non-double-couple components values are −0.004 and −0.01 for the May and December events, respectively, indicating that the December shock has a small contribution of non-double-couple radiation that could be the result of a changing mechanism. This result agrees with the hypothesis that a slab subducting at a shallower angle (our case) is associated with the existence of random subfaults with different fault orientations. From a tectonic point of view, the complexity of the December earthquake could be the result of the observed complexity of the stress distribution around 101°W and the existence of compressional events beneath the normal faulting earthquakes near the coastline. This feature permits the flexural stresses associated to the slab bending upward to become subhorizontal at the Guerrero region. We conclude that the May earthquake corresponds to a pure normal faulting, whereas the December shock is a complex event with a variable fault geometry.
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Chochlaki, Kalliopi, Georgios Michas, and Filippos Vallianatos. "Complexity of the Yellowstone Park Volcanic Field Seismicity in Terms of Tsallis Entropy." Entropy 20, no. 10 (September 20, 2018): 721. http://dx.doi.org/10.3390/e20100721.
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The Yellowstone Park volcanic field is one of the most active volcanic systems in the world, presenting intense seismic activity that is characterized by several earthquake swarms over the last decades. In the present work, we focused on the spatiotemporal properties of the recent earthquake swarms that occurred on December–January 2008–2009 and the 2010 Madison Plateau swarm, using the approach of Non Extensive Statistical Physics (NESP). Our approach is based on Tsallis entropy, and is used in order to describe the behavior of complex systems where fracturing and strong correlations exist, such as in tectonic and volcanic environments. This framework is based on the maximization of the non-additive Tsallis entropy Sq, introducing the q-exponential function and the entropic parameter q that expresses the degree of non-extentivity of the system. The estimation of the q-parameters could be used as a correlation degree among the events in the spatiotemporal evolution of seismicity. Using the seismic data provided by University of Utah Seismological Stations (UUSS), we analyzed the inter-event time (T) and distance (r) distribution of successive earthquakes that occurred during the two swarms, fitting the observed data with the q-exponential function, resulting in the estimation of the Tsallis entropic parameters qT, qr for the inter-event time and distance distributions, respectively. Furthermore, we studied the magnitude-frequency distribution of the released earthquake energies E as formulated in the frame of NESP, which results in the estimation of the qE parameter. Our analysis provides the triplet (qE, qT, qr) that describes the magnitude-frequency distribution and the spatiotemporal scaling properties of each of the studied earthquake swarms. In addition, the spatial variability of qE throughout the Yellowstone park volcanic area is presented and correlated with the existence of the regional hydrothermal features.
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Liu, Ching-Yi, Yeeping Chia, Po-Yu Chung, Tsai-Ping Lee, and Yung-Chia Chiu. "Temporal Variation and Spatial Distribution of Groundwater Level Changes Induced by Large Earthquakes." Water 15, no. 2 (January 15, 2023): 357. http://dx.doi.org/10.3390/w15020357.
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Sustained coseismic changes in groundwater level due to static strain during earthquakes could be considered as an indicator of crustal deformation. These changes usually occur abruptly but recover slowly after earthquakes. High-frequency data indicate a time lag between the coseismic change of well water levels and that of the groundwater levels in the aquifer. Abnormal post-seismic changes in groundwater level were observed, possibly caused by cross-formation flow, fracturing, or strain relief. Although sustained changes are generally induced by a local earthquake, they could also be triggered by a distant large earthquake that has occurred at the same tectonic plate. The magnitude and polarity of coseismic changes may vary in wells of different depths at multiple-well stations, revealing additional information about the complexity of crustal deformation in the subsurface. Coseismic falls dominated near the ruptured seismogenic fault during the 1999 M7.6 earthquake, which implied crustal extension adjacent to the thrust fault. However, coseismic rises prevail in most areas, suggesting that crustal compression caused by plate convergence plays a major role on the island of Taiwan during earthquakes.
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Efstathiou, A., A. Tzanis, and F. Vallianatos. "ON THE NATURE AND DYNAMICS OF THE SEISMOGENETIC SYSTEM OF SOUTH CALIFORNIA, USA: AN ANALYSIS BASED ON NON-EXTENSIVE STATISTICAL PHYSICS." Bulletin of the Geological Society of Greece 50, no. 3 (July 27, 2017): 1329. http://dx.doi.org/10.12681/bgsg.11839.
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We examine the nature of the seismogenetic system in South California, USA, by searching for evidence of non-extensivity in the earthquake record. We attempt to determine whether earthquakes are generated by a self-excited Poisson process, in which case they obey Boltzmann-Gibbs thermodynamics, or by a Critical process, in which long-range interactions in non-equilibrium statesare expected (correlation) and the thermodynamics deviate from the Boltzmann-Gibbs formalism. Emphasis is given to background earthquakes since it is generally agreed that aftershock sequences comprise correlated sets. Accordingly, the analysis is based on the accurate earthquake catalogue compiled of the South California Earthquake Data Center, in which aftershocks are either included or have been removed with a stochastic declustering procedure. We examine multivariate cumulative frequency distributions of earthquake magnitudes, interevent time and interevent distance, in the context of Non-Extensive Statistical Physics, which is a generalization of extensive Boltzmann-Gibbs thermodynamics to non-equilibrating (non-extensive) systems. The results indicate a persistent subextensive seismogenetic system exhibiting long-range, moderate to high correlation. Criticality appears to be a plausible causative mechanism although conclusions cannot be drawn until alternative complexity mechanisms can be ruled out.
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Ide, Satoshi, and Hideo Aochi. "Modeling Earthquakes Using Fractal Circular Patch Models with Lessons from the 2011 Tohoku-Oki Earthquake." Journal of Disaster Research 9, no. 3 (June 1, 2014): 264–71. http://dx.doi.org/10.20965/jdr.2014.p0264.
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Earthquakes occur in a complex hierarchical fault system, meaning that a realistic mechanically-consistent model is required to describe heterogeneity simply and over a wide scale. We developed a simple conceptual mechanical model using fractal circular patches associated with fracture energy on a fault plane. This model explains the complexity and scaling relation in the dynamic rupture process. We also show that such a fractal patch model is useful in simulating longterm seismicity in a hierarchal fault system by using external loading. In these studies, an earthquake of any magnitude appears as a completely random cascade growing from a small patch to larger patches. This model is thus potentially useful as a benchmarking scenario for evaluating probabilistic gain in probabilistic earthquake forecasts. The model is applied to the real case of the 2011 Tohoku-Oki earthquake based on prior information from a seismicity catalog to reproduce the complex rupture process of this very large earthquake and its resulting ground motion. Provided that a high-quality seismicity catalog is available for other regions, similar approach using this conceptual model may provide scenarios for other potential large earthquakes.
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Ochoa Gutierrez, Luis Hernán, Luis Fernando Niño Vasquez, and Carlos Alberto Vargas Jimenez. "Fast Determination of Earthquake Depth Using Seismic Records of a Single Station, Implementing Machine Learning Techniques." Ingeniería e Investigación 38, no. 2 (May 1, 2018): 91–103. http://dx.doi.org/10.15446/ing.investig.v38n2.68407.
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The purpose of this research is to apply a new approach to make a fast determination of earthquake depth using seismic records of the “El Rosal” station, near to the city of Bogota – Colombia, by applying support vector machine regression (SVMR). The algorithm was trained with descriptors obtained from time signals of 863 seismic events acquired between January 1998 and October 2008; only earthquakes with magnitude ≥ 2 were contemplated, filtering its signals to remove diverse kind of noises not related to earth tremors. During training stages of SVMR several combinations of kernel function exponent and complexity factor were considered for time signals of 5, 10 and 15 seconds along with earthquake magnitudes of 2.0, 2.5, 3.0 and 3.5 (Ml). The best classification of SVMR was obtained using time signals of 15 seconds and earthquake magnitudes of 3.5 with kernel exponent of 10 and complexity factor of 2, showing accuracy of 0.6 ± 16.5 kilometers, which is good enough to be used in an early warning system for the city of Bogota. It is recommended to provide this model with a previous phase of deep-shallow classification.
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Croissant, Thomas, Robert G. Hilton, Gen K. Li, Jamie Howarth, Jin Wang, Erin L. Harvey, Philippe Steer, and Alexander L. Densmore. "Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model." Earth Surface Dynamics 9, no. 4 (August 2, 2021): 823–44. http://dx.doi.org/10.5194/esurf-9-823-2021.
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Abstract. In mountain ranges, earthquakes can trigger widespread landsliding and mobilize large amounts of organic carbon by eroding soil and vegetation from hillslopes. Following a major earthquake, the landslide-mobilized organic carbon can be exported from river catchments by physical sediment transport processes or stored within the landscape where it may be degraded by heterotrophic respiration. The competition between these physical and biogeochemical processes governs a net transfer of carbon between the atmosphere and sedimentary organic matter, yet their relative importance following a large landslide-triggering earthquake remains poorly constrained. Here, we propose a model framework to quantify the post-seismic redistribution of soil-derived organic carbon. The approach combines predictions based on empirical observations of co-seismic sediment mobilization with a description of the physical and biogeochemical processes involved after an earthquake. Earthquake-triggered landslide populations are generated by randomly sampling a landslide area distribution, a proportion of which is initially connected to the fluvial network. Initially disconnected landslide deposits are transported downslope and connected to rivers at a constant velocity in the post-seismic period. Disconnected landslide deposits lose organic carbon by heterotrophic oxidation, while connected deposits lose organic carbon synchronously by both oxidation and river export. The modeling approach is numerically efficient and allows us to explore a large range of parameter values that exert a control on the fate of organic carbon in the upland erosional system. We explore the role of the climatic context (in terms of mean annual runoff and runoff variability) and rates of organic matter degradation using single pool and multi-pool models. Our results highlight the fact that the redistribution of organic carbon is strongly controlled by the annual runoff and the extent of landslide connection, but less so by the choice of organic matter degradation model. In the context of mountain ranges typical of the southwestern Pacific region, we find that model configurations allow more than 90 % of the landslide-mobilized carbon to be exported from mountain catchments. A simulation of earthquake cycles suggests efficient transfer of organic carbon out of a mountain range during the first decade of the post-seismic period. Pulsed erosion of organic matter by earthquake-triggered landslides is therefore an effective process to promote carbon sequestration in sedimentary deposits over thousands of years.
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PRAKASH, RAJESH, S. K. SRIVASTAV, H. V. GUPTA, and H. N. SRIVASTAVA. "Spatio temporal seismicity variation in earthquakes of Uttaranchal region." MAUSAM 55, no. 4 (January 19, 2022): 681–90. http://dx.doi.org/10.54302/mausam.v55i4.1402.
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The spatio temporal variations of seismicity preceding Uttarkashi, 1991 and Chamoli, 1999 earthquakes were studied based on the data during the period 1981 to 2000 using the catalogues of earthquakes prepared by the India Meteorological Department. Two scenarios were examined. In one case the epicentral distance from the respective impending earthquakes were worked out for all the earthquakes recorded during a ten years period prior to the earthquake of Uttarkashi and Chamoli respectively. In the other case, the epicenter near latitude 30.2° N and longitude 80.2° E near India Nepal border (where earthquakes of 1966 and 1980 occurred) were considered to compute the epicentral distance. The second case was included because it is a seismically active region where Dharachulla earthquake of 1916 (magnitude 7.5) occurred. The earthquakes of 1999, 1991 and 1980 in Uttaranchal were characterised by six phases of seismic activity namely (i) first quiescence or gap, (ii) swarm, (iii) second quiescence or gap, (iv) foreshocks, (v) main shock and (vi) aftershocks. Some differences among these phases could however, be noticed which were explained through source mechanism, isoseismals, ‘b’ (Gutenberg Richter’s relationship), ‘h’ values (Omori’s law ) and fractal dimension. It is interesting to point out that prior to the occurrence of earthquake swarms (second phase) the seismic pattern exhibits the development of a seismic gap (first phase) after the decay of the aftershock activity associated with a previous large earthquake of magnitude greater than or equal to M: 6.0 in this region. We infer that this second ‘gap’ (third phase) is a characteristic of the complexity of the tectonics in the Uttaranchal. Thus, the simple Kanamori’s asperity model could be modified to consist of six phases of seismic activity in the complex tectonic zone of Garhwal Himalaya. Detailed difference in the seismicity patterns prior to the earthquake were explained by the fractal dimensions estimated from the ‘b’values.
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Gledhill, Ken, John Ristau, Martin Reyners, Bill Fry, and Caroline Holden. "The Darfield (Canterbury) earthquake of September 2010." Bulletin of the New Zealand Society for Earthquake Engineering 43, no. 4 (December 31, 2010): 215–21. http://dx.doi.org/10.5459/bnzsee.43.4.215-221.
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The Darfield moment magnitude (Mw) 7.1 earthquake of September 2010 is the first heavily damaging earthquake to strike New Zealand since the surface wave magnitude (MS) 7.8 Hawkes Bay earthquake in 1931. Although the earthquake has a clear strike-slip surface expression characterised by the Greendale Fault, seismological evidence suggests it is a complex event beginning as a reverse faulting earthquake. Evidence for complexity of the mainshock includes a well constrained epicentre north of the surface fault trace, high near-source vertical accelerations, first-motion and regional moment tensor focal mechanisms which differ from teleseismic solutions, and a complex aftershock pattern. The earthquake and aftershock sequence were very well recorded by the GeoNet sensor networks in the region, and provide an exceptional dataset for understanding the earthquake rupture process and reducing damage from future earthquakes. This was the most significant test of GeoNet since its inception in 2001, and the first such New Zealand event in the “internet age”. GeoNet data proved important for the response and the interaction with emergency management, media and the public. The GeoNet website sustained continued heavy load over the weeks and months following the earthquake but continued to deliver timely information because of significant improvements carried out as the aftershock sequence continued.
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Shaw, Bruce E. "Frictional weakening and slip complexity in earthquake faults." Journal of Geophysical Research: Solid Earth 100, B9 (September 10, 1995): 18239–51. http://dx.doi.org/10.1029/95jb01306.
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Langer, J. S., J. M. Carlson, C. R. Myers, and B. E. Shaw. "Slip complexity in dynamic models of earthquake faults." Proceedings of the National Academy of Sciences 93, no. 9 (April 30, 1996): 3825–29. http://dx.doi.org/10.1073/pnas.93.9.3825.
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Sato, K., and J. Mori. "Relationship between rupture process complexity and earthquake size." Journal of Geophysical Research: Solid Earth 111, B5 (May 2006): n/a. http://dx.doi.org/10.1029/2005jb003614.
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Sornette, A., D. Sornette, and P. Evesque. "Frustration and disorder in granular media and tectonic blocks: implications for earthquake complexity." Nonlinear Processes in Geophysics 1, no. 4 (December 31, 1994): 209–18. http://dx.doi.org/10.5194/npg-1-209-1994.
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Abstract. We present exploratory analogies and speculations on the mechanisms underlying the organization of faulting and earthquake in the earth crust. The mechanical properties of the brittle lithosphere at scales of the order or larger than a few kilometers are proposed to be analogous to those of non-cohesive granular media, since both systems present stress amplitudes controlled by gravity, and shear band (faulting) localization is determined by a type of friction Mohr-Coulomb rupture criterion. here, we explore the implications of this correspondence with respect to the origin of tectonic and earthquake complexity, on the basis of the existing experimental data on granular media available in the mechanical literature. An important observation is that motions and deformations of non-cohesive granular media are characterized by important fluctuations both in time (sudden breaks, avalanches, which are analogous to earthquakes) and space (strain localizations, yield surfaces forming sometimes complex patterns). This is in apparent contradiction with the conventional wisdom in mechanics, based on the standard tendency to homogenize, which has led to dismiss fluctuations as experimental noise. On the basis of a second analogy with spinglasses and neural networks, based on the existence of block and grain packing disorder and block rotation "frustration", we suggest that these fluctuations observed both at large scales and at the block scale constitute an intrinsic signature of the mechanics of granular media. The space-time complexity observed in faulting and earthquake phenomenology is thus proposed to result form the special properties of the mechanics of granular media, dominated by the "frustration" of the kinematic deformations of its constitutive blocks.
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McBrearty, Ian W., Joan Gomberg, Andrew A. Delorey, and Paul A. Johnson. "Earthquake Arrival Association with Backprojection and Graph Theory." Bulletin of the Seismological Society of America 109, no. 6 (October 8, 2019): 2510–31. http://dx.doi.org/10.1785/0120190081.
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Abstract The association of seismic‐wave arrivals with causative earthquakes becomes progressively more challenging as arrival detection methods become more sensitive, and particularly when earthquake rates are high. For instance, seismic waves arriving across a monitoring network from several sources may overlap in time, false arrivals may be detected, and some arrivals may be of unknown phase (e.g., P or S waves). We propose an automated method to associate arrivals with earthquake sources and obtain source locations applicable to such situations. To do so, we use a pattern detection metric based on the principle of backprojection to reveal candidate sources followed by graph‐theory‐based clustering and an integer linear optimization routine to associate arrivals with the minimum number of sources necessary to explain the data. This method solves for all sources and phase assignments simultaneously, rather than in a sequential greedy procedure as is common in other association routines. We demonstrate our method on both synthetic and real data from the Integrated Plate Boundary Observatory Chile seismic network of northern Chile. For the synthetic tests, we report results for cases with varying complexity, including rates of 500 earthquakes/day and 500 false arrivals/station/day, for which we measure true positive detection accuracy of >95%. For the real data, we develop a new catalog between 1 January 2010 and 31 December 2017 containing 817,548 earthquakes, with detection rates on average 279 earthquakes/day and a magnitude‐of‐completion of M∼1.8. A subset of detections are identified as sources related to quarry and industrial site activity, and we also detect thousands of foreshocks and aftershocks of the 1 April 2014 Mw 8.2 Iquique earthquake. During the highest rate of aftershock activity, >600 earthquakes/day are detected in the vicinity of the Iquique earthquake rupture zone.
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Haris, Muhammad, Abdur Rehman Cheema, and Chamila Subasinghe. "Why lessons learnt are lost." Disaster Prevention and Management: An International Journal 28, no. 5 (October 7, 2019): 677–90. http://dx.doi.org/10.1108/dpm-04-2019-0103.
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Purpose The purpose of this paper is to reduce the gap in understanding the complexity of barriers, their modifiers and how these barriers and their modifiers result in malpractices and missed good practices in post-earthquake reconstruction contexts. This paper provides insights to the often asked question: why the lessons learnt from one earthquake event are not actually learnt and many of the mistakes around housing reconstruction are repeated? Design/methodology/approach The paper is based on the review of the literature of the top deadliest earthquakes in the developing countries and the two case studies of the 2005 Kashmir and 2015 earthquake in Pakistan. Findings Multifarious barriers, their modifiers, malpractices and missed good practices are deeply interwoven, and endemic and include weak financial standing, lack of technical know-how, vulnerable location, social and cultural preference, affordability and availability of materials, over-emphasis on technical restrictions, inefficient policies, lack of clarity in institutional roles, monitoring and training. Research limitations/implications The study is desk based. Practical implications A better understanding of barriers can help disaster-related organisations to improve the planning and implementation of post-earthquake housing reconstruction. Social implications The study contributes to the understanding concerning various social and cultural preferences that negotiate the Build Back Better (BBB) process. Originality/value The study offers a distinctive perspective synthesising the literature and the two case studies to sharpen the understanding of the complexity of barriers to BBB.
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Hoover, Greg A., and Frederick L. Bates. "The Impact of a Natural Disaster on the Division of Labor in Twelve Guatemalan Communities: A Study of Social Change in a Developing Country." International Journal of Mass Emergencies & Disasters 3, no. 3 (November 1985): 7–26. http://dx.doi.org/10.1177/028072708500300302.
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It has been hypothesized that disasters are a type of “intervention” which affect rates of social change and provide unique opportunities to observe this process by “compressing” it into a shorter time span. This paper utilizes an interrupted time series analysis to determine the effects of an earthquake on the rate and direction of change in the division of labor in twelve Guatemalan communities. The general trend for these communities (both control and experimental) is increasing complexity before the earthquake followed by accelerated growth in complexity after the earthquake. Differences between the experimental and control communities are discussed. It is suggested that the level of complexity may be important as an underlying influence on the response of a population to a disaster. In addition, changes in complexity (which were shown to occur) also warrant further study as possible influences upon these responses.
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Vallianatos, Filippos, Giorgos Papadakis, and Georgios Michas. "Generalized statistical mechanics approaches to earthquakes and tectonics." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2196 (December 2016): 20160497. http://dx.doi.org/10.1098/rspa.2016.0497.
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Despite the extreme complexity that characterizes the mechanism of the earthquake generation process, simple empirical scaling relations apply to the collective properties of earthquakes and faults in a variety of tectonic environments and scales. The physical characterization of those properties and the scaling relations that describe them attract a wide scientific interest and are incorporated in the probabilistic forecasting of seismicity in local, regional and planetary scales. Considerable progress has been made in the analysis of the statistical mechanics of earthquakes, which, based on the principle of entropy, can provide a physical rationale to the macroscopic properties frequently observed. The scale-invariant properties, the (multi) fractal structures and the long-range interactions that have been found to characterize fault and earthquake populations have recently led to the consideration of non-extensive statistical mechanics (NESM) as a consistent statistical mechanics framework for the description of seismicity. The consistency between NESM and observations has been demonstrated in a series of publications on seismicity, faulting, rock physics and other fields of geosciences. The aim of this review is to present in a concise manner the fundamental macroscopic properties of earthquakes and faulting and how these can be derived by using the notions of statistical mechanics and NESM, providing further insights into earthquake physics and fault growth processes.
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Matcharashvili, Teimuraz, Takahiro Hatano, Tamaz Chelidze, and Natalia Zhukova. "Simple statistics for complex Earthquake time distributions." Nonlinear Processes in Geophysics 25, no. 3 (July 10, 2018): 497–510. http://dx.doi.org/10.5194/npg-25-497-2018.
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Abstract. Here we investigated a statistical feature of earthquake time distributions in the southern California earthquake catalog. As a main data analysis tool, we used a simple statistical approach based on the calculation of integral deviation times (IDT) from the time distribution of regular markers. The research objective is to define whether and when the process of earthquake time distribution approaches to randomness. Effectiveness of the IDT calculation method was tested on the set of simulated color noise data sets with the different extent of regularity, as well as for Poisson process data sets. Standard methods of complex data analysis have also been used, such as power spectrum regression, Lempel and Ziv complexity, and recurrence quantification analysis, as well as multiscale entropy calculations. After testing the IDT calculation method for simulated model data sets, we have analyzed the variation in the extent of regularity in the southern California earthquake catalog. Analysis was carried out for different periods and at different magnitude thresholds. It was found that the extent of the order in earthquake time distributions is fluctuating over the catalog. Particularly, we show that in most cases, the process of earthquake time distributions is less random in periods of strong earthquake occurrence compared to periods with relatively decreased local seismic activity. Also, we noticed that the strongest earthquakes occur in periods when IDT values increase.
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Newman, W. I., and D. L. Turcotte. "A simple model for the earthquake cycle combining self-organized complexity with critical point behavior." Nonlinear Processes in Geophysics 9, no. 5/6 (December 31, 2002): 453–61. http://dx.doi.org/10.5194/npg-9-453-2002.
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Abstract. We have studied a hybrid model combining the forest-fire model with the site-percolation model in order to better understand the earthquake cycle. We consider a square array of sites. At each time step, a "tree" is dropped on a randomly chosen site and is planted if the site is unoccupied. When a cluster of "trees" spans the site (a percolating cluster), all the trees in the cluster are removed ("burned") in a "fire." The removal of the cluster is analogous to a characteristic earthquake and planting "trees" is analogous to increasing the regional stress. The clusters are analogous to the metastable regions of a fault over which an earthquake rupture can propagate once triggered. We find that the frequency-area statistics of the metastable regions are power-law with a negative exponent of two (as in the forest-fire model). This is analogous to the Gutenberg-Richter distribution of seismicity. This "self-organized critical behavior" can be explained in terms of an inverse cascade of clusters. Small clusters of "trees" coalesce to form larger clusters. Individual trees move from small to larger clusters until they are destroyed. This inverse cascade of clusters is self-similar and the power-law distribution of cluster sizes has been shown to have an exponent of two. We have quantified the forecasting of the spanning fires using error diagrams. The assumption that "fires" (earthquakes) are quasi-periodic has moderate predictability. The density of trees gives an improved degree of predictability, while the size of the largest cluster of trees provides a substantial improvement in forecasting a "fire."
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MEI, Shirong. "THE PRECURSORY COMPLEXITY AND REGULARITY OF THE TANGSHAN EARTHQUAKE." Journal of Physics of the Earth 34, Supplement (1986): S193—S212. http://dx.doi.org/10.4294/jpe1952.34.supplement_s193.
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Sawada, Masahiro, Shu Higuchi, and Bunpei Nakade. "Study on the Complexity of Evacuation against Chuetsu Earthquake." Journal of the City Planning Institute of Japan 40.3 (2005): 715–20. http://dx.doi.org/10.11361/journalcpij.40.3.715.
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Sawada, Masahiro, Shu Higuchi, and Bunpei Nakade. "Study on the Complexity of Evacuation against Chuetsu Earthquake." Journal of the City Planning Institute of Japan 40 (2005): 120. http://dx.doi.org/10.11361/cpij1.40.0.120.0.
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Chen, Yu, Lingsen Meng, Ailin Zhang, and Lianxing Wen. "Source Complexity of the 2015 Mw 7.9 Bonin Earthquake." Geochemistry, Geophysics, Geosystems 19, no. 7 (July 2018): 2109–20. http://dx.doi.org/10.1029/2018gc007489.
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Guoming, Zhang, Zhang Yongxian, and Shi Yaolin. "Numerical simulation of complexity of earthquake precursors (in Chinese)." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 31, no. 6 (December 1994): 269–70. http://dx.doi.org/10.1016/0148-9062(94)90067-1.
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Olsen-Kettle, L. M., and H. B. Mühlhaus. "Mesh dependence and slip complexity in earthquake fault models." Concurrency and Computation: Practice and Experience 22, no. 12 (October 22, 2009): 1653–64. http://dx.doi.org/10.1002/cpe.1521.
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Vasudevan, K., M. Cavers, and A. Ware. "Earthquake sequencing: Chimera states with Kuramoto model dynamics on directed graphs." Nonlinear Processes in Geophysics Discussions 2, no. 1 (February 20, 2015): 361–98. http://dx.doi.org/10.5194/npgd-2-361-2015.
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Abstract. Earthquake sequencing studies allow us to investigate empirical relationships among spatio-temporal parameters describing the complexity of earthquake properties. We have recently studied the relevance of Markov chain models to draw information from global earthquake catalogues. In these studies, we considered directed graphs as graph theoretic representations of the Markov chain model, and analyzed their properties. Here, we look at earthquake sequencing itself as a directed graph. In general, earthquakes are occurrences resulting from significant stress-interactions among faults. As a result, stress-field fluctuations evolve continuously. We propose that they are akin to the dynamics of the collective behaviour of weakly-coupled non-linear oscillators. Since mapping of global stress-field fluctuations in real time at all scales is an impossible task, we consider an earthquake zone as a proxy for a collection of weakly-coupled oscillators, the dynamics of which would be appropriate for the ubiquitous Kuramoto model. In the present work, we apply the Kuramoto model to the non-linear dynamics on a directed graph of a sequence of earthquakes. For directed graphs with certain properties, the Kuramoto model yields synchronization, and inclusion of non-local effects evokes the occurrence of chimera states or the co-existence of synchronous and asynchronous behaviour of oscillators. In this paper, we show how we build the directed graphs derived from global seismicity data. Then, we present conditions under which chimera states could occur and subsequently, point out the role of Kuramoto model in understanding the evolution of synchronous and asynchronous regions.
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Zhang, Yingfeng, Xinjian Shan, Guohong Zhang, Meijiao Zhong, Youjia Zhao, Shaoyan Wen, Chunyan Qu, and Dezheng Zhao. "The 2016 Mw 5.9 Menyuan Earthquake in the Qilian Orogen, China: A Potentially Delayed Depth-Segmented Rupture Following from the 1986 Mw 6.0 Menyuan Earthquake." Seismological Research Letters 91, no. 2A (January 8, 2020): 758–69. http://dx.doi.org/10.1785/0220190168.
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Abstract An Mw 5.9 thrust earthquake occurred on 21 January 2016 in the northeastern Tibetan plateau, where another similar earthquake had ruptured in 1986. Because of the complexity and close proximity of multiple faults in this area, the exact causative fault sources for these two events have not previously been determined. We determined the seismogenic fault structural geometry of the 2016 event by analyzing the coseismic deformation from Sentinel-1A images, aftershock relocations, and geological data. Furthermore, field investigations and the relocated aftershocks for the 1986 event were used to investigate its seismogenic fault and relation with the 2016 Menyuan earthquake. The results indicate that the reverse slip of both events was distributed on the southwest-dipping Minyue-Damaying fault, where the 2016 event ruptured the deep segment and the 1986 event ruptured the shallow segment. We envision that the depth segmentation played an important role in the occurrence of two moderate earthquakes rupturing the same active fault but separated by almost 30 yr, which is thought much shorter than the average earthquake recurrence cycle. Our study indicates that seismic risks could be underestimated if depth segmentation is not considered.
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YANG, DIXIONG, PIXIN YANG, and CHANGGENG ZHANG. "CHAOTIC CHARACTERISTIC ANALYSIS OF STRONG EARTHQUAKE GROUND MOTIONS." International Journal of Bifurcation and Chaos 22, no. 03 (March 2012): 1250045. http://dx.doi.org/10.1142/s0218127412500459.
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This paper aims to analyze and understand the irregularity and complexity of earthquake ground motions from the perspective of nonlinear dynamics. Chaotic dynamics theory and chaotic time series analysis are suggested to examine the nonlinear dynamical characteristic of strong earthquake ground motions. Based on the power spectral analysis, principal component analysis and modified false nearest neighbors method, it is illustrated qualitatively that the acceleration time series of earthquake ground motions exhibit chaotic property. Next, the chaotic time series analysis is proposed to calculate quantitatively the nonlinear characteristic parameters of acceleration time histories of near-fault ground motions. Numerical results show that the correlation dimension of these ground motions is fractal dimension. Their Kolmogorov entropy is a limited positive value, and their maximal Lyapunov exponent is larger than 0. It is demonstrated that the strong earthquake ground motions present the chaotic property rather than the pure random signals, and the severe irregularity and complexity of ground motions are the reflection of high nonlinearity of earthquake physical process.
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Courboulex, F., N. Deichmann, and J. C. Gariel. "Rupture complexity of a moderate intraplate earthquake in the Alps: the 1996M5 Epagny-Annecy earthquake." Geophysical Journal International 139, no. 1 (October 1, 1999): 152–60. http://dx.doi.org/10.1046/j.1365-246x.1999.00931.x.
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Vasudevan, K., M. Cavers, and A. Ware. "Earthquake sequencing: chimera states with Kuramoto model dynamics on directed graphs." Nonlinear Processes in Geophysics 22, no. 5 (September 8, 2015): 499–512. http://dx.doi.org/10.5194/npg-22-499-2015.
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Abstract. Earthquake sequencing studies allow us to investigate empirical relationships among spatio-temporal parameters describing the complexity of earthquake properties. We have recently studied the relevance of Markov chain models to draw information from global earthquake catalogues. In these studies, we considered directed graphs as graph theoretic representations of the Markov chain model and analyzed their properties. Here, we look at earthquake sequencing itself as a directed graph. In general, earthquakes are occurrences resulting from significant stress interactions among faults. As a result, stress-field fluctuations evolve continuously. We propose that they are akin to the dynamics of the collective behavior of weakly coupled non-linear oscillators. Since mapping of global stress-field fluctuations in real time at all scales is an impossible task, we consider an earthquake zone as a proxy for a collection of weakly coupled oscillators, the dynamics of which would be appropriate for the ubiquitous Kuramoto model. In the present work, we apply the Kuramoto model with phase lag to the non-linear dynamics on a directed graph of a sequence of earthquakes. For directed graphs with certain properties, the Kuramoto model yields synchronization, and inclusion of non-local effects evokes the occurrence of chimera states or the co-existence of synchronous and asynchronous behavior of oscillators. In this paper, we show how we build the directed graphs derived from global seismicity data. Then, we present conditions under which chimera states could occur and, subsequently, point out the role of the Kuramoto model in understanding the evolution of synchronous and asynchronous regions. We surmise that one implication of the emergence of chimera states will lead to investigation of the present and other mathematical models in detail to generate global chimera-state maps similar to global seismicity maps for earthquake forecasting studies.
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Neely, J. S., Y. Huang, and W. Fan. "Earthquake rupture characteristics along a developing transform boundary." Geophysical Journal International 219, no. 2 (August 5, 2019): 1237–52. http://dx.doi.org/10.1093/gji/ggz357.
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SUMMARY The 280-km-long San Cristobal Trough (SCT), created by the tearing of the Australia plate as it subducts under the Pacific Plate near the Solomon and Vanuatu subduction zones, has hosted strike-slip earthquake sequences in 1993 and 2015. Both sequences, which likely represent a complete seismic cycle, began along the oldest section of the SCT—the portion farthest from the tear that has experienced the most cumulative displacement—and migrated to the younger sections closer to the tear. The SCT's abundant seismicity allows us to study transform boundary development—a process rarely observed along a single fault system—through observations of earthquake rupture properties. Using the spectral ratio method based on empirical Green's functions (EGFs), we calculate the corner frequencies of three Mw ∼7 2015 earthquakes and colocated smaller earthquakes. We utilize two different spectral ratio stacking methods and fit both Brune and Boatwright models to the stacked spectral ratios. Regardless of stacking methods and spectral models, we find that the corner frequencies of the 2015 Mw ∼7 earthquakes decrease slightly with distance from the tear. Assuming a constant rupture velocity and an omega-square spectral model, this corner frequency decrease may be due to an increase in rupture length with distance from the tear. The spectrum of the 2015 earthquake farthest from the tear also deviates from the omega-square model, which may indicate rupture complexity. Stress drop estimates from the corner frequencies of the 2015 Mw ∼7 earthquakes range between 1 and 7 MPa, whereas stress drop estimates of their EGFs range from ∼0.05 to 10 MPa with most values between 0.1 and 1 MPa. Independent evidence from a second moments analysis of the 2015 earthquake sequence also indicates a possible increase in rupture length with distance from the tear, confirming the results from the spectral ratio analysis. We also observe an increase in normalized centroid time-delay values, a first-order proxy for rupture behaviour, with distance from the tear for the 2015 sequence. A similar trend for the 1993 sequence suggests that earthquake rupture varies systematically along the SCT. Since distance from the tear corresponds to cumulative fault displacement, these along-strike rupture variations may be due to a displacement-driven fault maturation process.
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Varotsos, Panayiotis, Nicholas Sarlis, and Efthimios Skordas. "Tsallis Entropy Index q and the Complexity Measure of Seismicity in Natural Time under Time Reversal before the M9 Tohoku Earthquake in 2011." Entropy 20, no. 10 (October 2, 2018): 757. http://dx.doi.org/10.3390/e20100757.
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The observed earthquake scaling laws indicate the existence of phenomena closely associated with the proximity of the system to a critical point. Taking this view that earthquakes are critical phenomena (dynamic phase transitions), here we investigate whether in this case the Lifshitz–Slyozov–Wagner (LSW) theory for phase transitions showing that the characteristic size of the minority phase droplets grows with time as t 1 / 3 is applicable. To achieve this goal, we analyzed the Japanese seismic data in a new time domain termed natural time and find that an LSW behavior is actually obeyed by a precursory change of seismicity and in particular by the fluctuations of the entropy change of seismicity under time reversal before the Tohoku earthquake of magnitude 9.0 that occurred on 11 March 2011 in Japan. Furthermore, the Tsallis entropic index q is found to exhibit a precursory increase.
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Lin, Jiun-Ting, Wu-Lung Chang, Diego Melgar, Amanda Thomas, and Chi-Yu Chiu. "Quick determination of earthquake source parameters from GPS measurements: a study of suitability for Taiwan." Geophysical Journal International 219, no. 2 (August 5, 2019): 1148–62. http://dx.doi.org/10.1093/gji/ggz359.
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SUMMARY We test the feasibility of GPS-based rapid centroid moment tensor (GPS CMT) methods for Taiwan, one of the most earthquake prone areas in the world. In recent years, Taiwan has become a leading developer of seismometer-based earthquake early warning systems, which have successfully been applied to several large events. The rapid determination of earthquake magnitude and focal mechanism, important for a number of rapid response applications, including tsunami warning, is still challenging because of the limitations of near-field inertial recordings. This instrumental issue can be solved by an entirely different observation system: a GPS network. Taiwan is well posed to take advantage of GPS because in the last decade it has developed a very dense network. Thus, in this research, we explore the suitability of the GPS CMT inversion for Taiwan. We retrospectively investigate six moderate to large (Mw6.0 ∼ 7.0) earthquakes and propose a resolution test for our model, we find that the minimum resolvable earthquake magnitude of this system is ∼Mw5.5 (at 5 km depth). Our tests also suggest that the finite fault complexity, often challenging for the near-field methodology, can be ignored under such good station coverage and thus, can provide a fast and robust solution for large earthquake directly from the near field. Our findings help to understand and quantify how the proposed methodology could be implemented in real time and what its contributions could be to the overall earthquake monitoring system.
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Papageorgiou, Apostolos S. "On two characteristic frequencies of acceleration spectra: Patch corner frequency and fmax." Bulletin of the Seismological Society of America 78, no. 2 (April 1, 1988): 509–29. http://dx.doi.org/10.1785/bssa0780020509.
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Abstract We examine two issues related to the radiation of tectonic earthquake sources: (i) the complexity of the shape of observed source spectra, and (ii) the effect of recording site characteristics on the cut-off frequency fmax of acceleration spectra beyond which spectral amplitudes diminish sharply. We compute the far-field spectra of the 1979 Imperial Valley and the 1984 Morgan Hill earthquakes from the slip functions that were inferred from detailed inversion studies of strong motion and teleseismic data of these two California strike-slip events. These spectra, along with data from the 1983 Central Japan Sea earthquake sequence (main shock and aftershocks), demonstrate the existence of the so-called patch corner frequency, which is related to the scale-length of heterogeneities of the fault plane. Such a frequency is a distinct feature of the source spectrum of the specific barrier model of Papageorgiou and Aki. By analyzing accelerograms of the San Fernando earthquake of 1971, we found that fmax determined from records at soil stations is nearly the same as that determined from records at hard rock stations.
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Tan, Yen Joe, Felix Waldhauser, William L. Ellsworth, Miao Zhang, Weiqiang Zhu, Maddalena Michele, Lauro Chiaraluce, Gregory C. Beroza, and Margarita Segou. "Machine-Learning-Based High-Resolution Earthquake Catalog Reveals How Complex Fault Structures Were Activated during the 2016–2017 Central Italy Sequence." Seismic Record 1, no. 1 (April 1, 2021): 11–19. http://dx.doi.org/10.1785/0320210001.
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Abstract The 2016–2017 central Italy seismic sequence occurred on an 80 km long normal-fault system. The sequence initiated with the Mw 6.0 Amatrice event on 24 August 2016, followed by the Mw 5.9 Visso event on 26 October and the Mw 6.5 Norcia event on 30 October. We analyze continuous data from a dense network of 139 seismic stations to build a high-precision catalog of ∼900,000 earthquakes spanning a 1 yr period, based on arrival times derived using a deep-neural-network-based picker. Our catalog contains an order of magnitude more events than the catalog routinely produced by the local earthquake monitoring agency. Aftershock activity reveals the geometry of complex fault structures activated during the earthquake sequence and provides additional insights into the potential factors controlling the development of the largest events. Activated fault structures in the northern and southern regions appear complementary to faults activated during the 1997 Colfiorito and 2009 L’Aquila sequences, suggesting that earthquake triggering primarily occurs on critically stressed faults. Delineated major fault zones are relatively thick compared to estimated earthquake location uncertainties, and a large number of kilometer-long faults and diffuse seismicity were activated during the sequence. These properties might be related to fault age, roughness, and the complexity of inherited structures. The rich details resolvable in this catalog will facilitate continued investigation of this energetic and well-recorded earthquake sequence.
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Anderson, John, Roberto Quaas, Quigbin Chen, David Almora, Ricardo Vázquez, Juan Velasco, Citlali Pérez, and Gerardo Castro. "CHARACTERISTICS OF EARTHQUAKES IN THE MEXICAN SUBDUCTION ZONE ON STRONG MOTION ACCELEROGRAMS." Revista de Ingeniería Sísmica, no. 54 (December 19, 1996): 17. http://dx.doi.org/10.18867/ris.54.234.
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Aceelerograms recorded on the Guerrero, Mexico, strong motion accelerograph network illustrate the dependence of strong ground motion on the magnitude and the hypocenter distance. These data suppport the hipothesis that complexity in accelerograms at short distances arises from complexity at the source. The duration of strong shaking is controlled by the source dimension at short distances, and extended by wave porpagation effects as distance increases. Peak amplitudes (peak acceleration, velocity) saturate at different magnitudes at different distances. This change in shape of attenuation curves as magnitude increases can be explained by the trnasition of Green's functions from simple, short pulses at short distances to longer duration wave trains at large distances. Spectral amplitudes demonstrate scalin relations in which loe frequency amplitudes are proportional to seismic moment but high frecuencies increase much less rapidly. The beginnings of large earthquakes look like small earthquakes, consistent with a cascade model for the growth of large events. The mostrecent large earthquake, on sept. 14,995 (Mw=7.4) shows surprisingly weak peak accelerations.
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Chu, Jinlong, Qiang Zhang, Ai Wang, and Haoran Yu. "A Hybrid Intelligent Model for Urban Seismic Risk Assessment from the Perspective of Possibility and Vulnerability Based on Particle Swarm Optimization." Scientific Programming 2021 (December 7, 2021): 1–16. http://dx.doi.org/10.1155/2021/2218044.
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Assessing seismic risk is an essential element of urban risk management and urban spatial security work. In response to the issues posed by the complexity and openness of urban systems, the nonlinearity of driving factors, and sudden changes in geological processes that affect urban seismic research, this paper is based on a variety of intelligent algorithms to develop a hybrid intelligent model that integrates probability and vulnerability to evaluate and quantify the difference in the urban spatial units distribution of earthquake risk. We applied this model to Hefei, one of the few superlarge provincial capital cities on the “Tancheng-Lujiang” fault zone, one of the four major earthquake zones in China, which suffers frequent earthquakes. Our method combined the genetic algorithm (GA), particle swarm optimization (PSO), and backpropagation neural network methods (BP) to automatically calculate rules from inputted data on known seismic events and predict the probability of seismic events in unknown areas. Then, based on the analytic hierarchy process (AHP), spatial appraisal and valuation of environment and ecosystems method (SAVEE), and EMYCIN model, an urban seismic vulnerability was evaluated from the four perspectives of buildings, risk of secondary disasters, socioeconomic conditions, and urban emergency response capabilities. In the next step, the overall urban seismic risk was obtained by standardizing and superimposing seismic probability and vulnerability. Using the hybrid intelligent model, earthquake probability, seismic vulnerability, and overall seismic risk were obtained for Hefei, and the spatial characteristics of its overall seismic risk were examined. This study concludes that areas with very high, high, low, and very low earthquake risk in Hefei account for 8.10%, 31.90%, 40.94%, and 19.06% of its total area, respectively. Areas with very high earthquake risk are concentrated in the old city, the government affairs district, Science City, and Xinzhan District. This study concludes that government authorities of Hefei should target earthquake safety measures consisting of basic earthquake mitigation measures and pre- and postearthquake emergency measures. In the face of regional disasters such as earthquakes, coordinating and governing should be strengthened between cities and regions.
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Huang, Yongming, Kun’ao Zhu, Wen Shi, Yong Lu, Gaochuan Liu, Guobao Zhang, and Yuntian Teng. "A Pre-Seismic Anomaly Detection Approach Based on Earthquake Cross Partial Multi-View Data Fusion." Magnetochemistry 9, no. 2 (February 3, 2023): 48. http://dx.doi.org/10.3390/magnetochemistry9020048.
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It is a challenge to detect pre-seismic anomalies by using only one dataset due to the complexity of earthquakes. Therefore, it is a promising direction to use multiparameteric data. The earthquake cross partial multi-view data fusion approach (EQ-CPM) is proposed in this paper. By using this method, electromagnetic data and seismicity indicators are fused. This approach tolerates the absence of data and complements the missing part in fusion. First, the effectiveness of seismicity indicators and electromagnetic data was validated through two earthquake case studies. Then, four machine learning algorithms were applied to detect pre-seismic anomalies by using the fused data and two original datasets. The results show that the fused data provided better performance than the single-modal data. In the Matthews correlation coefficient index, the results of our method showed an 8% improvement compared with the latest study.
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Hooker, J. N., and D. M. Fisher. "How cementation and fluid flow influence slip behavior at the subduction interface." Geology 49, no. 9 (May 19, 2021): 1074–78. http://dx.doi.org/10.1130/g48741.1.
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Abstract Much of the complexity of subduction-zone earthquake size and temporal patterns owes to linkages among fluid flow, stress, and fault healing. To investigate these linkages, we introduce a novel numerical model that tracks cementation and fluid flow within the framework of an earthquake simulator. In the model, there are interseismic increases in cohesion across the plate boundary and decreases in porosity and permeability caused by cementation along the interface. Seismogenic slip is sensitive to the effective stress and therefore fluid pressure; in turn, slip events increase porosity by fracturing. The model therefore accounts for positive and negative feedbacks that modify slip behavior through the seismic cycle. The model produces temporal clustering of earthquakes in the seismic record of the Aleutian margin, which has well-documented along-strike variations in locking characteristics. Model results illustrate how physical, geochemical, and hydraulic linkages can affect natural slip behavior. Specifically, coseismic drops in fluid pressure steal energy from large ruptures, suppress slip, moderate the magnitudes of large earthquakes, and lead to aftershocks.
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Wei, Shengji, Don Helmberger, Zhongwen Zhan, and Robert Graves. "Rupture complexity of the M w 8.3 sea of okhotsk earthquake: Rapid triggering of complementary earthquakes?" Geophysical Research Letters 40, no. 19 (October 3, 2013): 5034–39. http://dx.doi.org/10.1002/grl.50977.
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Han, Zhao, Donghui Ma, Benwei Hou, and Wei Wang. "Seismic Resilience Enhancement of Urban Water Distribution System Using Restoration Priority of Pipeline Damages." Sustainability 12, no. 3 (January 26, 2020): 914. http://dx.doi.org/10.3390/su12030914.
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The malfunction of the water distribution system (WDS) following severe earthquakes have significant impacts on the post-earthquake rescue. Moreover, the restoration priority of earthquake-induced pipeline damages plays an important role in improving the post-earthquake serviceability of WDS and the “seismic resilience”. Thus, to enhance the seismic resilience of WDS, this study develops a dynamic cost-benefit method and introduces three existing methods to determine the restoration priority of pipeline damages based on a quantitative resilience evaluation framework. In this resilience evaluation framework, the restoration priority is firstly determined. Then the time-varying performance of post-earthquake WDS is modeled as a discrete event dynamic system. In this model, the system state changes after the reparation of pipeline damage, and the system performance is simulated by a hydraulic model to be consistent with the system state. In this study, this method is also tested and compared with other existing methods, and the results show that the system resilience corresponding to the restoration priority obtained by this method is close to that obtained by the global optimization method with a relative difference of less than 3%, whereas the calculation complexity is about 0.4% of the optimization model. It is concluded that this proposed method is valid.