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Anbazhagan, P., M. Neaz Sheikh i Aditya Parihar. "Influence of Rock Depth on Seismic Site Classification for Shallow Bedrock Regions". Natural Hazards Review 14, nr 2 (maj 2013): 108–21. http://dx.doi.org/10.1061/(asce)nh.1527-6996.0000088.
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KIM, DONG-SOO, i JONG-KU YOON. "DEVELOPMENT OF NEW SITE CLASSIFICATION SYSTEM FOR THE REGIONS OF SHALLOW BEDROCK IN KOREA". Journal of Earthquake Engineering 10, nr 3 (maj 2006): 331–58. http://dx.doi.org/10.1080/13632460609350600.
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Burkart, Michael R., i Janos Feher. "Regional estimation of ground water vulnerability to nonpoint sources of agricultural chemicals". Water Science and Technology 33, nr 4-5 (1.02.1996): 241–47. http://dx.doi.org/10.2166/wst.1996.0511.
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The potential for ground water contamination by agricultural chemicals exists in many regions of the world. A collaborative effort between Hungarian and United States scientists has developed a general strategy to estimate the regional vulnerability of ground water to agricultural chemicals. The midwest U.S. and most of Hungary are major agricultural regions with similar hydrogeologic settings. Many areas where ground water provides public drinking water supplies in these regions are vulnerable to ground-water contamination. The vulnerability of shallow, unconsolidated aquifers and thinly-covered bedrock aquifers to agricultural chemicals is being investigated in an initial application of the strategy. This strategy integrates elements of overlay methods of vulnerability estimation, process-based modeling methods, and statistical methods. Strategy steps include: identifying characteristics of ground water needed to classify regional ground water resources; mapping the spatial distribution of aquifer classes (unconsolidated and bedrock) using a regional geographic information system; and estimating the occurrence of agricultural contaminants by applying leaching models to representative conditions in each aquifer class. In the U.S. project, pedologic data bases are being used for both mapping aquifer classes and model input. Estimated vulnerability will be evaluated against data from a regional survey of shallow aquifers recently completed in the Midwest. The Hungarian project is developing new maps of basic hydrogeologic characteristics with data that can be used to model vulnerability of the 1-meter root zone, the unsaturated zone, and the saturated zone.
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Jakobsen, Peter Roll. "Distribution and intensity of glaciotectonic deformation in Denmark". Bulletin of the Geological Society of Denmark 42 (1.02.1996): 175–85. http://dx.doi.org/10.37570/bgsd-1995-42-14.
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Glaciotectonic deformation has a large impact on the stratigraphical and lithological variability of Quaternary deposits and the shallow subsurface pre-Quaternary sediments. Mapping of the distribution of glaciotectonic deformation involving pre-Quaternary and interglacial deposits has been carried out, and the density of glaciotectonic deformation analysed, on the basis of data from the well database ZEUS, at the Geological Survey of Denmark. Glaciotectonic deformation is widespread in Denmark. It is recognised in glacial terrains within morphological well-defined glaciotectonic complexes, and in areas with no obvious glaciotectonic related morphology as well as in areas covered with postglacial deposits. The dislocated bedrock is usually not transported for long distances, although rafts of pre-Quaternary bedrock may be transported up to 50 km or more. On a large scale, regions have been located showing high intensity of glaciotectonic deformation. Some of these regions are in good agreement with records from exposures and the geomorphology, others cannot be recognised without well log information.
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Dranga, Stefana Aurora, Simon Hayles i Konrad Gajewski. "Synthesis of limnological data from lakes and ponds across Arctic and Boreal Canada". Arctic Science 4, nr 2 (1.06.2018): 167–85. http://dx.doi.org/10.1139/as-2017-0039.
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A compilation of published and new limnological data from 1489 shallow lakes and ponds in northern Canada, sampled between 1979 and 2009, revealed significant patterns that correlated with landscape features and climate. Lakes and ponds underlain by Archean or Proterozoic bedrock had lower specific conductivity and pH. Vegetation cover had a lesser influence on these parameters. Forested landscapes tended to have higher phosphorus and nitrogen, as did younger rock types. Dissolved organic carbon was higher, but dissolved inorganic carbon was lower in forested regions. Phytoplankton biomass of the surface waters, as estimated by chlorophyll a concentrations, was positively correlated with July air temperature and nutrients, and was higher in forested relative to polar desert regions. There were no significant differences in the measured limnological variables between shallow (<2 m depth) and deep lakes (>2 m); however, all water chemistry parameters were negatively correlated with depth. Despite large variability within and among regions, spatial trends in water chemistry were associated with geology, vegetation, and climate at a continental scale.
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Jarosch, A. H., C. G. Schoof i F. S. Anslow. "Restoring mass conservation to shallow ice flow models over complex terrain". Cryosphere 7, nr 1 (7.02.2013): 229–40. http://dx.doi.org/10.5194/tc-7-229-2013.
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Abstract. Numerical simulation of glacier dynamics in mountainous regions using zero-order, shallow ice models is desirable for computational efficiency so as to allow broad coverage. However, these models present several difficulties when applied to complex terrain. One such problem arises where steep terrain can spuriously lead to large ice fluxes that remove more mass from a grid cell than it originally contains, leading to mass conservation being violated. This paper describes a vertically integrated, shallow ice model using a second-order flux-limiting spatial discretization scheme that enforces mass conservation. An exact solution to ice flow over a bedrock step is derived for a given mass balance forcing as a benchmark to evaluate the model performance in such a difficult setting. This benchmark should serve as a useful test for modellers interested in simulating glaciers over complex terrain.
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Jarosch, A. H., C. G. Schoof i F. S. Anslow. "Numerical mass conservation issues in shallow ice models of mountain glaciers: the use of flux limiters and a benchmark". Cryosphere Discussions 6, nr 5 (21.09.2012): 4037–70. http://dx.doi.org/10.5194/tcd-6-4037-2012.
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Abstract. Numerical simulation of glacier dynamics in mountainous regions using low-order, shallow ice models is desirable for computational efficiency and their capability of including ice dynamics in estimates of mountain glacier wastage worldwide. However, these models present several difficulties when applied to complex topography. One such problem arises where dynamical mass flux over steep topography produces spurious mass at a grid cell flux boundary if upstream cells receive positive mass balance. This paper describes a vertically integrated, shallow ice model using a second order flux limiting spatial discretization scheme that enforces mass conservation. An exact solution to ice flow over a bedrock step is derived for a given mass balance forcing as a benchmark to evaluate the model performance in such a difficult setting. This benchmark should serve as a useful test for modellers interested in simulating glaciers over complex terrain.
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Lee, Sei-Hyun, Chang-Guk Sun, Jong-Ku Yoon i Dong-Soo Kim. "Development and Verification of a New Site Classification System and Site Coefficients for Regions of Shallow Bedrock in Korea". Journal of Earthquake Engineering 16, nr 6 (18.07.2012): 795–819. http://dx.doi.org/10.1080/13632469.2012.658491.
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Taussi, Marco, Walter Borghi, Michele Gliaschera i Alberto Renzulli. "Defining the Shallow Geothermal Heat-Exchange Potential for a Lower Fluvial Plain of the Central Apennines: The Metauro Valley (Marche Region, Italy)". Energies 14, nr 3 (1.02.2021): 768. http://dx.doi.org/10.3390/en14030768.
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In this work we assessed the shallow geothermal heat-exchange potential of a fluvial plain of the Central Apennines, the lower Metauro Valley, where about 90,000 people live. Publicly available geognostic drilling data from the Italian Seismic Microzonation studies have been exploited together with hydrogeological and thermophysical properties of the main geological formations of the area. These data have been averaged over the firsts 100 m of subsoil to define the thermal conductivity, the specific heat extraction rates of the ground and to establish the geothermal potential of the area (expressed in MWh y−1). The investigation revealed that the heat-exchange potential is mainly controlled by the bedrock lithotypes and the saturated conditions of the sedimentary infill. A general increase in thermal conductivity, specific heat extraction and geothermal potential have been mapped moving from the coast, where higher sedimentary infill thicknesses have been found, towards the inland where the carbonate bedrock approaches the surface. The geothermal potential of the investigated lower Metauro Valley is mostly between ~9.0 and ~10 MWh y−1 and the average depth to be drilled to supply a standard domestic power demand of 4.0 kW is ~96 m (ranging from 82 to 125 m all over the valley). This investigation emphasizes that the Seismic Microzonation studies represent a huge database to be exploited for the best assessment of the shallow geothermal potential throughout the Italian regions, which can be addressed by the implementation of heating and cooling through vertical closed-loop borehole heat exchanger systems coupled with geothermal heat pumps.
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Gołębiowski, Tomisław, i Elżbieta Jarosińska. "Application of GPR and ERT methods for recognizing of gypsum deposits in urban areas". Acta Geophysica 67, nr 6 (8.10.2019): 2015–30. http://dx.doi.org/10.1007/s11600-019-00370-7.
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Abstract This paper presents the selected results of GPR (ground penetrating radar) and ERT (electrical resistivity tomography) surveys carried out on the sites in Poland where shallow karst forms were found in gypsum deposits. The aim of the surveys was the noninvasive detection of karst forms as well as weathered and fractured bedrock which may threaten the stability of the surface and, consequently, may cause damage to buildings, as well as overground and underground infrastructure. The geophysical surveys were conducted at a depth of only a few meters, i.e., to the depth of buildings foundations. GPR surveys were carried out in short-offset reflection profiling mode with standard orientation of the antennae set; however, on one site, different orientations of antennae were tested. During ERT surveys, different measurement arrays were applied in order to analyze which array was optimal for the detection of karst forms as well as weathered and fractured bedrock. Complex interpretation of geophysical surveys resulted in reduced ambiguity and revealed some regions, dangerous for surface stability. Due to the fact that gypsum deposits were investigated to the depth of maximum 10 m; therefore, hydrological processes were analyzed in the paper instead of hydrogeological processes.
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Lüthi, Martin P., i Martin Funk. "Modelling heat flow in a cold, high-altitude glacier: interpretation of measurements from Colle Gnifetti, Swiss Alps". Journal of Glaciology 47, nr 157 (2001): 314–24. http://dx.doi.org/10.3189/172756501781832223.
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AbstractModelling the heat flow in small, cold high-altitude glaciers is important for the interpretation of paleoclimatic data from ice cores. Coupled glacier-flow and heat-flow models are presented that incorporate the densification, heat advection and possible phase transitions at the permafrost boundaries within the bedrock. Marked bends observed in the temperature profiles from two recent boreholes on Colle Gnifetti, Swiss Alps, are interpreted with the help of a transient heat-flow model, driven with a temperature history. The conclusion is that substantial warming of the mean firn temperature at shallow depths has taken place over the last few decades. This has not been observed before in cold-firn regions of the Alps. Modelled heat fluxes in the Monte Rosa massif are strongly influenced by the mountain topography. This leads to a spatial variability of the temperature gradient near the glacier base which has been observed in boreholes to the bedrock. In order to match the measured temperature profiles in the glacier, the vertical heat flux at great depth must be set to an extremely low value. It is shown with the help of the transient heat-flow model that this is a paleoclimatic effect, possibly enhanced by a degrading permafrost base.
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Lobkovsky, Leopold I., Alexey A. Baranov, Mukamay M. Ramazanov, Irina S. Vladimirova, Yurii V. Gabsatarov, Igor P. Semiletov i Dmitry A. Alekseev. "Trigger Mechanisms of Gas Hydrate Decomposition, Methane Emissions, and Glacier Breakups in Polar Regions as a Result of Tectonic Wave Deformation". Geosciences 12, nr 10 (8.10.2022): 372. http://dx.doi.org/10.3390/geosciences12100372.
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Trigger mechanisms are proposed for gas hydrate decomposition, methane emissions, and glacier collapse in polar regions. These mechanisms are due to tectonic deformation waves in the lithosphere–asthenosphere system, caused by large earthquakes in subduction zones, located near the polar regions: the Aleutian arc, closest to the Arctic, and the Antarctica–Chilean and Tonga–Kermadec–Macquarie subduction zones. Disturbances of the lithosphere are transmitted over long distances (of the order of 2000–3000 km and more) at a speed of about 100 km/year. Additional stresses associated with them come to the Arctic and Antarctica several decades after the occurrence of seismic events. On the Arctic shelf, additional stresses destroy the microstructure of metastable gas hydrates located in frozen rocks at shallow depths, releasing the methane trapped in them and leading to filtration and emissions. In West Antarctica, these wave stresses lead to decreases in the adhesions of the covered glaciers with underlying bedrock, sharp accelerations of their sliding into the sea, and fault occurrences, reducing pressure on the underlying rocks containing gas hydrates, which leads to their decomposition and methane emissions.
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Flinchum, Brady, Luk Peeters, Tim Munday i Kevin Cahill. "Improving the hydrogeologic conceptualization of a remote semiarid palaeovalley groundwater system using airborne electromagnetics, seismic refraction and reflection, and downhole nuclear magnetic resonance". GEOPHYSICS 86, nr 5 (1.09.2021): WB207—WB226. http://dx.doi.org/10.1190/geo2020-0614.1.
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A hydrogeologic conceptualization is critical to understand, manage, protect, and sustain groundwater resources, particularly in regions where data are sparse and accessibility is difficult. We used airborne electromagnetics (AEM), shallow seismic reflection and refraction, and downhole nuclear magnetic resonance (NMR) logs to improve our understanding of an arid groundwater system influenced by palaeovalleys. We found that there is a limited connection between the palaeovalley and fractured bedrock aquifers because they are separated by a spatially variable layer of saprolite, which is the layer of chemically altered rock on top of the fractured bedrock. The AEM data provided an estimate of the top of the saprolite but failed to effectively image the bottom. In contrast, the seismic data provided an estimate of the bottom of the saprolite but failed to image the top. This geophysical combination of electrical and seismic data allowed us to map saprolite thickness in detail along a 1.7 km long transect that runs perpendicular the main trunk of a well-defined palaeovalley. These data indicate that the palaeovalley is lined with a heterogeneous layer of saprolite (approximately 3–120 m thick) that is thickest near its edges. Despite the observed variability, only a small percentage of the fractured bedrock aquifer (8%–17%) appears to be in contact with the palaeovalley aquifer. Furthermore, the lack of an elastic boundary at the top of saprolite suggests that the porosity of the saprolite is similar to the palaeovalley sediments — an observation that is supported by the downhole NMR-derived water contents. The electrical change at the top of saprolite is caused by a combination of a decrease in total dissolved solids of the groundwater in the saprolite and a change in pore structure associated weathering in situ versus transported weathered materials. The presence of saprolite, which commonly behaves as an aquitard, may limit the groundwater exchange between the palaeovalley and bedrock aquifers, with implications for the regional groundwater resource potential.
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Yang, Haibin, Mark Quigley i Tamarah King. "Surface slip distributions and geometric complexity of intraplate reverse-faulting earthquakes". GSA Bulletin 133, nr 9-10 (13.01.2021): 1909–29. http://dx.doi.org/10.1130/b35809.1.
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Abstract Earthquake ground surface ruptures provide insights into faulting mechanics and inform seismic hazard analyses. We analyze surface ruptures for 11 historical (1968–2018) moment magnitude (Mw) 4.7–6.6 reverse earthquakes in Australia using statistical techniques and compare their characteristics with magnetic, gravity, and stress trajectory data sets. Of the total combined (summative) length of all surface ruptures (∼148 km), 133 km (90%) to 145 km (98%) align with the geophysical structure in the host basement rocks. Surface rupture length (SRL), maximum displacement (MD), and probability of surface rupture at a specified Mw are high compared with equivalent Mw earthquakes globally. This is attributed to (1) a steep cratonic crustal strength gradient at shallow depths, promoting shallow hypocenters (∼1–6 km) and limiting downdip rupture widths (∼1–8.5 km), and (2) favorably aligned crustal anisotropies (e.g., bedrock foliations, faults, fault intersections) that enhanced lateral rupture propagation and/or surface displacements. Combined (modeled and observed) MDs are in the middle third of the SRL with 68% probability and either the ≤33rd or ≥66th percentiles of SRL with 16% probability. MD occurs proximate to or directly within zones of enhanced fault geometric complexity (as evidenced from surface ruptures) in 8 of 11 earthquakes (73%). MD is approximated by 3.3 ± 1.6 (1σ) × AD (average displacement). S-transform analyses indicates that high-frequency slip maxima also coincide with fault geometric complexities, consistent with stress amplifications and enhanced slip variability due to geometric and kinematic interactions with neighboring faults. Rupture slip taper angles exhibit large variations (−90% to +380% with respect to the mean value) toward rupture termini and are steepest where ruptures terminate at obliquely oriented magnetic lineaments and/or lithology changes. Incremental slip approximates AD between the 10th and 90th percentiles of the SRL. The average static stress drop of the studied earthquakes is 4.8 ± 2.8 MPa. A surface rupture classification scheme for cratonic stable regions is presented to describe the prevailing characteristics of intraplate earthquakes across diverse crustal structural-geophysical settings. New scaling relationships and suggestions for logic tree weights are provided to enhance probabilistic fault displacement hazard analyses for bedrock-dominated intraplate continental regions.
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Ianniruberto, Marco, José E. G. Campos i Vitto C. M. Araújo. "Application of shallow seismic profiling to study riverbed architectural facies: a case study of the Tocantins river (Pará - Brazil)". Anais da Academia Brasileira de Ciências 84, nr 3 (wrzesień 2012): 645–54. http://dx.doi.org/10.1590/s0001-37652012000300007.
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To date, the vast majority of river sedimentology study has relied on two main categories of observation: direct observation of shallow trenches, cut faces and cores or geophysical survey on dry and shallow regions of braid bars. In this study, a sub-bottom profiler was used to investigate the stratigraphy of the lower course of the Tocantins River in the Amazon region, between the city of Tucuruì and the village of Nazaré dos Patos. The interest in this specific region lies on the possible variation of the fluvial regime due to the installation of the dam of the Tucuruì hydroelectric plant and the perspective that such river would become navigable as soon as the canal lock will be completed. Collected data show a detailed variety and complexity of architectural elements, as well as internal structure of sandy macroforms. Furthermore, the results allowed the identification of three main environments linked to channel sedimentation processes: by-pass, transition and deposition environments, whose distribution is linked to channel dynamics and bedrock topography. The application of the study is manifold, once it provides not only an insight into sedimentary structure of alluvial forms and sedimentation history, but also elements demanded to plan eventual engineering works for river navigability.
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Siegert, M. J., i W. Fjeldskaar. "Isostatic uplift in the late Weichselian Barents Sea: implications for ice-sheet growth". Annals of Glaciology 23 (1996): 352–58. http://dx.doi.org/10.3189/s026030550001363x.
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Results from a recent time-dependent ice-sheet modelling study of the late Weichselian Svalbard—Barents Sea ice sheet suggest that, under environmental conditions representative of those during the late Weichselian, ice derived solely from Svalbard may have occupied only the relatively shallow (<300 m water depth) northwestern Barents Sea, with other deeper regions remaining free of grounded ice (Siegert and Dowdeswell, 1995a). However, late Weichselian geological information from the 400 m deep Bjørnøyrenna (southern Barents Sea) indicates that grounded ice was present in an area modelled by Siegert and Dowdeswell (1995a) as free of ice (e.g. Laberg and Vorren, in press a). Isostatic uplift of the central Barents Sea may have reduced the relative sea level and hence provided a mechanism by which grounded ice could have migrated from relatively shallow regions of the Barents Sea into, previous to uplift, deeper water. We have used an isostatic Earth model to determine the geometry of an isostatic forebulge within the late Weichselian Barents Sea, caused by ice loads over Svalbard, Franz Josef Land, Novaya Zemlya and Fennoscandia. These data were then used as input to a time-dependent glaciological model, in order to predict further information about the magnitude of bedrock uplift required to allow grounded ice to flow from Svalbard into the central and southern Barents Sea. Our experiments suggest that grounded ice, originating from Svalbard, is able to form over Sentralbanken, providing that at least 60 m of uplift is achieved in the central Barents Sea. Grounded ice within Bjørnøyrenna was only predicted when the amplitude of the local forebulge exceeded 250 m.
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Siegert, M. J., i W. Fjeldskaar. "Isostatic uplift in the late Weichselian Barents Sea: implications for ice-sheet growth". Annals of Glaciology 23 (1996): 352–58. http://dx.doi.org/10.1017/s026030550001363x.
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Results from a recent time-dependent ice-sheet modelling study of the late Weichselian Svalbard—Barents Sea ice sheet suggest that, under environmental conditions representative of those during the late Weichselian, ice derived solely from Svalbard may have occupied only the relatively shallow (<300 m water depth) northwestern Barents Sea, with other deeper regions remaining free of grounded ice (Siegert and Dowdeswell, 1995a). However, late Weichselian geological information from the 400 m deep Bjørnøyrenna (southern Barents Sea) indicates that grounded ice was present in an area modelled by Siegert and Dowdeswell (1995a) as free of ice (e.g. Laberg and Vorren, in press a). Isostatic uplift of the central Barents Sea may have reduced the relative sea level and hence provided a mechanism by which grounded ice could have migrated from relatively shallow regions of the Barents Sea into, previous to uplift, deeper water. We have used an isostatic Earth model to determine the geometry of an isostatic forebulge within the late Weichselian Barents Sea, caused by ice loads over Svalbard, Franz Josef Land, Novaya Zemlya and Fennoscandia. These data were then used as input to a time-dependent glaciological model, in order to predict further information about the magnitude of bedrock uplift required to allow grounded ice to flow from Svalbard into the central and southern Barents Sea. Our experiments suggest that grounded ice, originating from Svalbard, is able to form over Sentralbanken, providing that at least 60 m of uplift is achieved in the central Barents Sea. Grounded ice within Bjørnøyrenna was only predicted when the amplitude of the local forebulge exceeded 250 m.
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Gülerce, Zeynep, Ronnie Kamai, Norman A. Abrahamson i Walter J. Silva. "Ground Motion Prediction Equations for the Vertical Ground Motion Component Based on the NGA-W2 Database". Earthquake Spectra 33, nr 2 (maj 2017): 499–528. http://dx.doi.org/10.1193/121814eqs213m.
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Empirical ground motion models for the vertical component from shallow crustal earthquakes in active tectonic regions are derived using the PEER NGA-West2 database. The model is applicable to magnitudes 3.0–8.0, distances of 0–300 km, and spectral periods of 0–10 s. The model input parameters are the same as used by Abrahamson et al. (2014) except that the nonlinear site response and depth to bedrock effects are evaluated but found to be insignificant. Regional differences in large distance attenuation and site amplification scaling between California, Japan, China, Taiwan, Italy, and the Middle East are included. Scaling for the hanging-wall effect is incorporated using the constraints from numerical simulations by Donahue and Abrahamson (2014) . The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations at short periods but smaller standard deviations at long periods. The vertical ground motion model developed in this study can be paired with the horizontal component model proposed by Abrahamson et al. (2014) to produce a V/H ratio. For applications where the horizontal spectrum is derived from the weighted average of several horizontal ground motion models, a V/H model derived directly from the V/H data (such as Gülerce and Abrahamson 2011 ) should be preferred.
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Parnell, John, i Sean McMahon. "Physical and chemical controls on habitats for life in the deep subsurface beneath continents and ice". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, nr 2059 (28.01.2016): 20140293. http://dx.doi.org/10.1098/rsta.2014.0293.
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The distribution of life in the continental subsurface is likely controlled by a range of physical and chemical factors. The fundamental requirements are for space to live, carbon for biomass and energy for metabolic activity. These are inter-related, such that adequate permeability is required to maintain a supply of nutrients, and facies interfaces invite colonization by juxtaposing porous habitats with nutrient-rich mudrocks. Viable communities extend to several kilometres depth, diminishing downwards with decreasing porosity. Carbon is contributed by recycling of organic matter originally fixed by photosynthesis, and chemoautotrophy using crustal carbon dioxide and methane. In the shallow crust, the recycled component predominates, as processed kerogen or hydrocarbons, but abiotic carbon sources may be significant in deeper, metamorphosed crust. Hydrogen to fuel chemosynthesis is available from radiolysis, mechanical deformation and mineral alteration. Activity in the subcontinental deep biosphere can be traced through the geological record back to the Precambrian. Before the colonization of the Earth's surface by land plants, a geologically recent event, subsurface life probably dominated the planet's biomass. In regions of thick ice sheets the base of the ice sheet, where liquid water is stable and a sediment layer is created by glacial erosion, can be regarded as a deep biosphere habitat. This environment may be rich in dissolved organic carbon and nutrients accumulated from dissolving ice, and from weathering of the bedrock and the sediment layer.
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de Caritat, Patrice, Anthony Dosseto i Florian Dux. "A strontium isoscape of northern Australia". Earth System Science Data 15, nr 4 (14.04.2023): 1655–73. http://dx.doi.org/10.5194/essd-15-1655-2023.
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Abstract. Strontium isotopes (87Sr/86Sr) are useful to trace processes in the Earth sciences as well as in forensic, archaeological, palaeontological, and ecological sciences. As very few large-scale Sr isoscapes exist in Australia, we have identified an opportunity to determine 87Sr/86Sr ratios on archived fluvial sediment samples from the low-density National Geochemical Survey of Australia. The present study targeted the northern parts of Western Australia, the Northern Territory, and Queensland, north of 21.5∘ S. The samples were taken mostly from a depth of ∼60–80 cm in floodplain deposits at or near the outlet of large catchments (drainage basins). A coarse (<2 mm) grain-size fraction was air-dried, sieved, milled, and digested (hydrofluoric acid + nitric acid followed by aqua regia) to release total Sr. The Sr was then separated by chromatography, and the 87Sr/86Sr ratio was determined by multicollector inductively coupled plasma mass spectrometry. The results demonstrate a wide range of Sr isotopic values (0.7048 to 1.0330) over the survey area, reflecting a large diversity of source rock lithologies, geological processes, and bedrock ages. The spatial distribution of 87Sr/86Sr shows coherent (multi-point anomalies and smooth gradients), large-scale (>100 km) patterns that appear to be broadly consistent with surface geology, regolith/soil type, and/or nearby outcropping bedrock. For instance, the extensive black clay soils of the Barkly Tableland define a >500 km long northwest–southeast-trending unradiogenic anomaly (87Sr/86Sr <0.7182). Where sedimentary carbonate or mafic/ultramafic igneous rocks dominate, low to moderate 87Sr/86Sr values are generally recorded (medians of 0.7387 and 0.7422, respectively). Conversely, In proximity to the outcropping Proterozoic metamorphic basement of the Tennant, McArthur, Murphy, and Mount Isa geological regions, radiogenic 87Sr/86Sr values (>0.7655) are observed. A potential correlation between mineralization and elevated 87Sr/86Sr values in these regions needs to be investigated in greater detail. Our results to date indicate that incorporating soil/regolith Sr isotopes in regional, exploratory geoscience investigations can help identify basement rock types under (shallow) cover, constrain surface processes (e.g. weathering and dispersion), and, potentially, recognize components of mineral systems. Furthermore, the resulting Sr isoscape and future models derived therefrom can also be utilized in forensic, archaeological, palaeontological, and ecological studies that aim to investigate, for example, past and modern animal (including humans) dietary habits and migrations. The new spatial Sr isotope dataset for the northern Australia region is publicly available (de Caritat et al., 2022a; https://doi.org/10.26186/147473).
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Clark, Dan J., Sarah Brennand, Gregory Brenn, Matthew C. Garthwaite, Jesse Dimech, Trevor I. Allen i Sean Standen. "Surface deformation relating to the 2018 Lake Muir earthquake sequence, southwest Western Australia: new insight into stable continental region earthquakes". Solid Earth 11, nr 2 (30.04.2020): 691–717. http://dx.doi.org/10.5194/se-11-691-2020.
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Abstract. A shallow Mw 5.3 earthquake near Lake Muir in the stable continental region (SCR) crust of southwest Western Australia on the 16 September 2018 was followed on the 8 November by a proximal Mw 5.2 event. Focal mechanisms produced for the events suggest reverse and strike-slip rupture, respectively. Field mapping, guided by Sentinel-1 InSAR data, reveals that the first event produced an approximately 3 km long and up to 0.4–0.6 m high west-facing surface rupture, consistent with reverse slip on a moderately east-dipping fault. The InSAR data also show that the surface scarp relates to a subsurface rupture ∼ 5 km long, bound at its northern and southern extremities by bedrock structures. The November event produced a surface deformation envelope that is spatially coincident with that of the September event but did not result in discrete surface rupture. Almost 900 aftershocks were recorded by a temporary seismometer deployment. Hypocentre locations correlate poorly with the rupture plane of their respective mainshocks but correlate well with regions of increased Coulomb stress. The spatial and temporal relationships between the Mw>5.0 events and their aftershocks reveals dependencies with implications for how other less well-documented SCR earthquake sequences could be interpreted. Furthermore, the September Mw 5.3 Lake Muir earthquake was the ninth event documented to have produced surface rupture in Australia in historical times. These nine ruptures are located exclusively in the Precambrian non-extended SCR rocks of central and western Australia, and none could have been identified and mapped using topographic signature prior to the historical event. Consistent, though fragmentary, evidence exists from analogous regions worldwide. Our analysis of the Lake Muir earthquake sequence therefore provides constraint on models describing mechanisms for strain accumulation and localized release as earthquakes in non-extended SRC crust.
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Kuzina, Z. Ya, N. N. Nevedrova i А. M. Sanchaa. "Structural features of the upper part of the section of the Gorniy Altai Uimon depression according to electrotomography data using 3D software". Vestnik MGTU 26, nr 2 (30.06.2023): 160–69. http://dx.doi.org/10.21443/1560-9278-2023-26-2-160-169.
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Determining the structure of intermountain depressions in seismically active regions at different depths is important for understanding the stages of neotectonic formation of the region and seismic hazard assessment. On the territory of the Uimon depression of the Altai Mountains in different years, measurements were carried out by deep methods of electrical exploration, such as sounding by the formation of the field and vertical electrical soundings. However, to clarify the structure of the upper part of the section, where bedrock outcrops are observed on the day surface, it is necessary to use shallow methods, for example, electrical tomography (ET). The paper discusses the results of ET data interpretation using 2D and 3D inversion when studying basement outcrops in the western part of the basin. Taking into account a priori information and the obtained models, the geological structure of the object of study has been refined. Based on the results of the interpretation of the data of electrotomography using programs of two- and three-dimensional inversion, the geoelectric structure of one of the outcrops of the basement rocks on the day surface has been determined. The immersion of the studied object in the western direction towards the adjacent outcrop of rocks of the Baratal Formation of smaller sizes located in the immediate vicinity has been established. It can be assumed that these two exits are connected at a depth of 15–20 m and, most likely, are one structure.
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Steiner, Matthias, Florian M. Wagner, Theresa Maierhofer, Wolfgang Schöner i Adrián Flores Orozco. "Improved estimation of ice and water contents in alpine permafrost through constrained petrophysical joint inversion: The Hoher Sonnblick case study". GEOPHYSICS 86, nr 5 (17.06.2021): WB119—WB133. http://dx.doi.org/10.1190/geo2020-0592.1.
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Quantitative estimation of subsurface water and ice content values is critical for the understanding and modeling of permafrost evolution in alpine regions. Geophysical methods permit the assessment of subsurface conditions in a noninvasive and quasicontinuous manner; in particular, the combination of seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) through a petrophysical model can quantitatively estimate ground water and ice content values. For the Hoher Sonnblick study area (3106 m.a.s.l., Austrian Alps), we have investigated the improved estimation of water and ice content values based on SRT, ERT, and ground-penetrating radar data collected in June and October 2019. We solve for the water and ice content values following different approaches, namely, (1) the independent inversion and subsequent transformation of the imaging results to the target parameters through a petrophysical model and (2) the petrophysical joint inversion (PJI) of the data sets. Supported by a synthetic study, we determine that the incorporation of structural and porosity constraints in the PJI allows for an improved quantitative characterization of subsurface conditions. For our measurements at Hoher Sonnblick, the constrained PJI resolves a shallow debris layer characterized by high air content and porosity, on top of a layer with lower porosity corresponding to fractured gneiss, and the bedrock layer with the lowest porosity. For both time steps, we find high water content at the lower end of the investigated area. Substantial variations in the subsurface ice content resolved between June and October 2019 indicate a correlation between the high water content and the meltwater discharge within the debris layer. Our results demonstrate that the constrained PJI permits an improved characterization of subsurface hydrologic parameters in alpine permafrost environments.
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Milly, P. C. D., Sergey L. Malyshev, Elena Shevliakova, Krista A. Dunne, Kirsten L. Findell, Tom Gleeson, Zhi Liang, Peter Phillipps, Ronald J. Stouffer i Sean Swenson. "An Enhanced Model of Land Water and Energy for Global Hydrologic and Earth-System Studies". Journal of Hydrometeorology 15, nr 5 (25.09.2014): 1739–61. http://dx.doi.org/10.1175/jhm-d-13-0162.1.
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Abstract LM3 is a new model of terrestrial water, energy, and carbon, intended for use in global hydrologic analyses and as a component of earth-system and physical-climate models. It is designed to improve upon the performance and to extend the scope of the predecessor Land Dynamics (LaD) and LM3V models by better quantifying the physical controls of climate and biogeochemistry and by relating more directly to components of the global water system that touch human concerns. LM3 includes multilayer representations of temperature, liquid water content, and ice content of both snowpack and macroporous soil–bedrock; topography-based description of saturated area and groundwater discharge; and transport of runoff to the ocean via a global river and lake network. Sensible heat transport by water mass is accounted throughout for a complete energy balance. Carbon and vegetation dynamics and biophysics are represented as in LM3V. In numerical experiments, LM3 avoids some of the limitations of the LaD model and provides qualitatively (though not always quantitatively) reasonable estimates, from a global perspective, of observed spatial and/or temporal variations of vegetation density, albedo, streamflow, water-table depth, permafrost, and lake levels. Amplitude and phase of annual cycle of total water storage are simulated well. Realism of modeled lake levels varies widely. The water table tends to be consistently too shallow in humid regions. Biophysical properties have an artificial stepwise spatial structure, and equilibrium vegetation is sensitive to initial conditions. Explicit resolution of thick (>100 m) unsaturated zones and permafrost is possible, but only at the cost of long (≫300 yr) model spinup times.
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Zelt, B. C., i R. M. Ellis. "Receiver-function studies in the Trans-Hudson Orogen, Saskatchewan". Canadian Journal of Earth Sciences 36, nr 4 (7.04.1999): 585–603. http://dx.doi.org/10.1139/e98-109.
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Teleseismic events were recorded on an array of three-component broadband and short-period seismographs in the Trans-Hudson Orogen over a period of almost 3 years. Receiver functions calculated from these data were used in a forward-modelling study to derive the local shear-wave velocity structure beneath 20 stations. Station FFC (Flin Flon), located within the Flin Flon belt, was one of two stations situated on bedrock and produced the highest quality receiver functions. The FFC velocity model correlates well with an interpretation of nearby reflection data and features a distinct lower crust interpreted as Archean basement which cores the entire Reindeer Zone. Both radial and tangential receiver functions at FFC show strong evidence for a northeasterly dipping shallow boundary within rocks of the Flin Flon belt with a dip angle of 20°. Total crustal thickness is 37 km. Eighteen stations are situated on Phanerozoic sedimentary cover ranging in thickness from 0.4 km to greater than 2 km. Receiver functions at these stations display prominent high-amplitude, low-frequency reverberations that obscure more subtle phases associated with deeper structure. Because of this, only the gross crustal velocity structure can be constrained by modelling. Depth to Moho, which is 40-43 km at most stations, is the most strongly constrained feature. Stations with relatively thick crust within the Glennie domain suggest a connection between two regions of thick crust previously inferred from reflection and refraction data. This crustal root, presumably associated with a structural culmination imaged by reflection data and cored by Archean basement, is confined to the southwestern Glennie domain. One-dimensional modelling results show that the reverberations can be explained by a thin layer (<0.7 km) at the top of the sediments with a very high Poisson's ratio (0.4-0.48). The degree to which later arrivals are affected by reverberations is directly related to the parameters of this uppermost layer. We present the results of synthetic studies that demonstrate the sensitivity of receiver functions to this type of feature.
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Zima, Lukáš, Jozef Kollár i Ivana Vykouková. "Impact of the Former Vineyard Land Use on the Productivity of Secondary Forest Herb Layer in the Little Carpathians (SW Slovakia)". Ekológia (Bratislava) 35, nr 3 (1.09.2016): 253–62. http://dx.doi.org/10.1515/eko-2016-0020.
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AbstractThe Little Carpathians Mountains include a vineyard region with long tradition that dates back up to the Roman Empire period (and according to some opinions, even earlier). In the late 19th century, it was strongly impacted by the phylloxera epidemic, and the vineyard area has significantly reduced here. Large areas of the former vineyards are covered by forests, which mostly have formed spontaneously, but some of them were also planted. This contribution is focused on the impact of the former vineyard land use on the productivity (aboveground, belowground, and total biomass) of such forest herb layer. Research included also the forests, which occupy rocky mounds formed by rock gathering and their placement on the vineyard borders. There were sampled by following four stands, mostly differed by tree composition, origin, age, and succession stage: (i) up to 100 years old spontaneously formed thermophilous acidophilous oak forest on the former vineyard on the granite substrate, (ii) up to 100 years old spontaneously formed oak-dominated forest on the rocky (granite) mounds (borders between the former vineyards formed by rock gathering), (iii) 40–60 years old planted ash stands on the gneiss bedrock, and (iv) 40–60 years old planted ash-dominated stands on the rocky (gneiss) mounds. According to our results, the former land use modified original relief, where the former vineyards have modified soil profile and new relief forms rocky mounds were created. These mounds with no or just shallow soils are usually much less covered by vegetation, thus production of herb layer biomass is lower here than in the adjacent former vineyards. Moreover, rocky mounds show a higher ratio of synanthropic species and apophytes than the adjacent former vineyards, and same as for ratio of therophytes. The younger the stands on the former vineyards, the higher is the ratio of synanthropic species, apophytes, and therophytes. On the other hand, when estimating the production quantity, the values of herb layer production on the former vineyards are similar to those in natural oak-hornbeam forests found in the Little Carpathians Mts. and the adjacent regions, except for the rocky mounds covered by old oak forests, which are less productive. In other words, the former vineyard land use affects the herb layer production quality rather than quantity.
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Luino, Fabio, Jerome De Graff, Marcella Biddoccu, Francesco Faccini, Michele Freppaz, Anna Roccati, Fabrizio Ungaro, Michele D’Amico i Laura Turconi. "The Role of Soil Type in Triggering Shallow Landslides in the Alps (Lombardy, Northern Italy)". Land 11, nr 8 (22.07.2022): 1125. http://dx.doi.org/10.3390/land11081125.
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Shallow landslides due to the soil saturation induced by intense rainfall events are very common in northern Italy, particularly in the Alps and Prealps. They are usually triggered during heavy rainstorms, causing severe damage to property, and sometimes causing casualties. A historical study and analysis of shallow landslides and mud-debris flows triggered by rainfall events in Lombardy was carried out for the period of 1911–2010, over an area of 14,019 km2. In this study, intensity–duration rainfall thresholds have been defined using the frequentist approach, considering some pedological characteristics available in regional soil-related databases, such as the soil region, the textural class, and the dominant soil typological units (STU). The soil-based empirical rainfall thresholds obtained considering the soil regions of the study area were significantly different, with a lower threshold for landslide occurrence in the soil region M1 (Alps), where soils developed over siliceous parent material, with respect to the whole study area and the soil region M2 (Prealps), where soils developed over calcareous bedrocks. Furthermore, by considering textural classes, the curves were differentiated, with coarse-textured soils found more likely to triggerlandslides than fine soils. Finally, considering both texture and main soil groups, given the same rainfall duration, the rainfall amount and intensity needed to initiate a landslide increased in the following order: “coarse-skeletal” Cambisols < Umbrisols < Podzols < “fine” Cambisols. The results of this study highlighted the relevant role of pedological conditioning factors in differentiating the activation of rainfall-induced shallow landslides in a definite region. The information on soils can be used to define more precise rainfall–pedological thresholds than empirical thresholds based solely on meteorological conditions, even when they are locally defined. This knowledge is crucial for forecasting and preventing geo-hydrological processes and in developing better warning strategies to mitigate risks and to reduce socio-economic damage.
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Petrella, E., A. Bucci, K. Ogata, A. Zanini, G. Naclerio, A. Chelli, R. Francese, T. Boschetti, D. Pittalis i F. Celico. "Hydrodynamics in Evaporate-Bearing Fine-Grained Successions Investigated through an Interdisciplinary Approach: A Test Study in Southern Italy—Hydrogeological Behaviour of Heterogeneous Low-Permeability Media". Geofluids 2018 (2018): 1–15. http://dx.doi.org/10.1155/2018/5978597.
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Messinian evaporates are widely distributed in the Mediterranean Sea as outcropping sediments in small marginal basins and in marine cores. Progressive filling of subbasins led to the formation of complex aquifer systems in different regions where hypersaline and fresh water coexist and interact in different manner. It also generates a significant diversification of groundwater hydrochemical signature and different microbial communities. In the case study, the hydrogeology and hydrochemistry of the whole system are influenced by good hydraulic connection between the shallower pyroclastic horizon and the underlying evaporate-bearing fine-grained Messinian succession. This is demonstrated by the merge of hydrogeological, chemical, isotopic, and microbiological data. No mixing with deep ascending waters has been observed. As shown by geophysical, hydraulic, and microbiological investigations, the hydraulic heterogeneity of the Messinian bedrock, mainly due to karstified evaporitic interstrata/lenses, causes the hydraulic head to significantly vary with depth. Somewhere, the head increases with the depth’s increase and artesian flow conditions are locally observed. Moreover, the metagenomic investigations demonstrated the existence of a poor hydraulic connection within the evaporate-bearing fine-grained succession at metric and decametric scales, therefore leading to a patchwork of geochemical (and microbiological) subenvironments.
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Sadiq, Hamza Maina, i Alhaji Adam Zarma. "Depth to Magnetic Sources Using Spectral Analysis of High Resolution Aeromagnetic Data Over Machina and Environs, Northeastern Nigeria". Journal of Geography and Geology 11, nr 1 (28.02.2019): 70. http://dx.doi.org/10.5539/jgg.v11n1p70.
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Analysis of high resolution aeromagnetic data over Machina and its environment shows areas of low total magnetic intensity contour values are hosts to thicker overburden sediments and near surface intrusive rock bodies reside over high total magnetic intensity contour regions. Positive and negative residual anomaly values depict the presence of basic and acid rock units; however, the acid rocks dominate over the basic components. Major linear features of the residual anomaly are oriented along the NE – SW direction. Some linear features however, cross cut the major lineaments along the NW – SE, N –S, and E – W directions. A NW – SE cross section of the residual anomaly shows irregularity of the bedrock floor. The negative residual anomalies are underlain by granite rocks, while the positive values are within the domain of basic intrusive. Determination of the magnetic source depth revealed depths to the top of the deeper and the shallower sources ranging from 0.6 – 2.0 km and from 0.4 - 0.9 km respectively. Thicker sedimentary covers are underlain by basement rocks while; shallower magnetic horizons are composed of intrusive igneous bodies. Maximum sedimentary thickness of 2.0 km in the study area might not be adequate enough for hydrocarbon maturation and accumulation. Segment directional histogram data shown on rose diagram exhibits strike directions along the E – W, NE – SW, NW – SE, NNE – SSW and NNE – SSW. Most of the fracture lines dip at angles lower than 10 degrees. The north dipping direction group of lineaments is prevalent. Orientations of the structural elements are in conformity with the dominant regional structural grain of the country. Cross- cutting of the lineaments may be related to the geothermal energy in the area as higher interconnected lineaments are associated with higher geothermal energy. Rugged terrain reliefs might have resulted from the effects of tectonic and structural evolution in the area. Variability of the dip angles is associated with non-uniform framework of the forces of deformation on the rocks and/or differential responses of the rocks to the stress imposed on them.
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Chandler, A. M., J. W. Pappin i A. W. Coburn. "Vulnerability and seismic risk assessment of buildings following the 1989 Newcastle, Australia earthquake". Bulletin of the New Zealand Society for Earthquake Engineering 24, nr 2 (30.06.1991): 116–38. http://dx.doi.org/10.5459/bnzsee.24.2.116-138.
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Ten days after the Newcastle, Australia earthquake of 28 December, 1989, the UK-based Earthquake Engineering Field Investigation Team (EEFIT) mounted a five day mission to the affected area. This paper presents the findings of the EEFIT investigation and subsequent follow up studies in relation to the extent of building damage and its distribution within the City of Newcastle and the surrounding urban area. Results are based on both detailed street surveys and general damage surveys, the former carried out in two areas, namely the heavily damaged suburban district of Hamilton (3km west of the city centre) and the Newcastle central business district. The findings of these surveys have provided valuable information on the vulnerability of building stock of types common to other parts of Australia, the UK and elsewhere, and hence form an important database for the accurate assessment of seismic risk to buildings in regions of low seismicity. This information will assist the development of realistic, economical seismic code provisions for building design and construction in low-risk areas. An important feature arising from the surveys and subsequent analytical studies of site response in the heavily damaged districts within the Hunter River alluvial basin is that, contrary to reports published by the Institution of Engineers, Australia amongst others, the areas of deep alluvial soil and fill do not correlate strongly with the more heavily damaged districts determined from post-earthquake assessments. Hence, suggestions that this form of site soil amplification effect played a major part in the distribution and extent of heavy damage in this earthquake are somewhat misleading for the future development of planning and design regulations. Furthermore, the results of site response analyses show that it is more likely to be the shallower soils near the border of the alluvial basin which tend to amplify bedrock ground motions generated by this type of earthquake.
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Mo, Tao, i Januka Attanayake. "Modulation of Seismic Radiation by Fault-Scale Geology of the 2016 Mw 6.0 Shallow Petermann Ranges Earthquake (PRE) in Central Australia". Bulletin of the Seismological Society of America, 10.01.2023. http://dx.doi.org/10.1785/0120220137.
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ABSTRACT Understanding the modulatory influence of fault-scale geology on seismic behavior of earthquake faults is central to determining the physics of faulting and seismic hazard analysis. Although laboratory experiments predict that seismic parameters can be modulated by fault-scale geology, there is scant empirical evidence of this process at field scale due largely to a lack of shallow earthquakes of which causative faults can be mapped to known bedrock structure. The 20 May 2016 Mw 6 Petermann Ranges earthquake (PRE) is the best-recorded continental event in Australia to date, and it is an excellent candidate to investigate the possible link between seismic parameters and fault-scale geology as its causative fault has previously been linked to known bedrock structure using distributions of aftershocks, surface observations, and geophysical mapping. In this study, we analyze strain energy partitioning of PRE by determining seismic radiation efficiency (0.31) and apparent stress (0.34 MPa) together with previously estimated stress drop (2.2 MPa) and find that the combination of these macroseismic parameters deviates from that expected of a shallow immature fault in intraplate continental regions typically characterized by large recurrence intervals. It instead appears to have mimicked a mature fault, which we attribute to the characteristics of the causative fault confined to mechanically weaker, phyllosilicate-rich foliations of the bedrock that have anomalously lower fracture energy. Therefore, PRE rupture suggests the presence of a spectrum of shallow (<20 km) fault slip behavior modulated by fault-scale geology.
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Zhu, Xinrong, Hongyan Liu, Lu Wu, Boyi Liang, Feng Liu i Wengqi He. "Impact of bedrock geochemistry on vegetation productivity depends on climate dryness in the Guizhou karst of China". Progress in Physical Geography: Earth and Environment, 8.07.2020, 030913332093608. http://dx.doi.org/10.1177/0309133320936085.
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The Guizhou karst area is one of the largest continuous areas of karst in the humid climate zone and is representative of karst landforms in China. Large portions of the karst system are characterized by extremely shallow soils underlain by weathered bedrock and water deficits are common. Although the distribution of ecosystem productivity is largely related to variations in the temperature and precipitation, the influence of the substrate in karst areas requires further exploration. We explored the relative importance of the bedrock geochemistry (characterized by the concentrations of Ca, Mg and Si) and climatic factors (temperature and precipitation) to explain the spatial variability in gross primary productivity (GPP) with various degrees of water deficit during the time period 2001–2015. Our results show that the impact of bedrock geochemistry is an important parameter in changing the original relationship between climate and the GPP. The bedrock geochemistry functioned as a “regulator” of the relation between climate and the GPP, which strengthened with decreasing climate favourability. The variations in GPP and surface water storage were significantly different when different elements (Ca, Mg or Si) were dominant. The Mg-rich regions showed the greatest annual variations in the GPP, whereas the Si-rich regions had the strongest surface water storage potential to support vegetation growth. The results of our study are important for systematically evaluating the effects of climate on vegetation productivity and provide a benchmark for global vegetation modelling predictions.
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Sun, Jikai, Hiroshi Kawase, Kiyoshi Fukutake, Fumiaki Nagashima i Shinichi Matsushima. "Simulation of soil liquefaction distribution in downtown Mashiki during 2016 Kumamoto earthquake using nonlinear site response". Bulletin of Earthquake Engineering, 14.06.2022. http://dx.doi.org/10.1007/s10518-022-01426-8.
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AbstractSeveral sites located between Road No.28 and Akitsu River in downtown Mashiki were liquefied during the mainshock of the 2016 Kumamoto earthquake. According to the building damage survey results, only a few buildings were damaged in areas proximate to the Akitsu River, where liquefaction occurred, however, serious building damage occurred in neighboring regions. Therefore, the effect of soil liquefaction on strong ground motions in Mashiki should be ascertained. Moreover, the distribution of visible and invisible liquefaction is required to be estimated as well. In this study, the distribution of depth of groundwater level in Mashiki was studied, which decreased from 14 to 0 m from northeast to southwest. Thereafter, the nonlinearities of the shallow layers at four borehole drilling sites were identified from the experimental data using the Ramberg–Osgood relationship. Subsequently, the dynamic nonlinear effective stress analysis of the one-dimensional soil column was performed to 592 sites in Mashiki between the seismological bedrock and ground surface to estimate the distribution of strong ground motions during the mainshock. First, the ground motions estimated by the nonlinear analysis corresponded to the ground motions observed at the Kik-net KMMH16. Second, the soil nonlinearity of shallow layers was considerably strong in the entire target area especially in the southern Mashiki, and the PGV distribution was similar to the building damage distribution after the mainshock. Furthermore, the estimated distribution of the soil liquefaction site was similar to the observed results, whereas certain invisible-liquefaction sites were estimated in the north and middle of the target area.
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D, Ankhtsetseg, Odonbaatar Ch, Mоngоnsuren D, Bayarsaikhan E i Dembereldulam M. "Probabilistic seismic hazard assessment for Bayankhongor aimag of Mongolia". Proceedings of the Mongolian Academy of Sciences, 26.04.2019, 43–56. http://dx.doi.org/10.5564/pmas.v59i1.1137.
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Central Asia is one of the seismically most active regions in the world. Its complex seismicity is due to the collision of the Eurasian and Indian plates, which has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events.The GSHAP project, aiming at hazard assessment on a global scale, indicates that the territory of Bayankhongor aimag, Mongolia, in Central Asia is characterized by maximum bedrock peak ground accelerations for 10% probability of exceedance in 50 years as medium as in range of 80 to 160cm/s2. In this study, which has been carried out within the framework of the project “Seismic microzoning map of center of 12 aimags, Mongolia”, the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment for the Mongolia. The seismic hazard is assessed considering shallow (depth <50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalogue for the region. The hazard maps, shown in terms of 10% probability of exceedance in 50 years, are derived by using the Open Deterministic and Probabilistic Seismic Hazard Assessment (ODPSHA), which is based on the Cornell methodology. The maximum hazard observed in the region reaches 93-98 cm/s2 , which in intensity corresponds to VII in MSK64 scale in the centre of Bayankhongor aimag for 475 years mean return period.
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Sethanant, Israporn, Edwin Nissen, Léa Pousse-Beltran, Eric Bergman i Ian Pierce. "The 2020 Mw 6.5 Monte Cristo Range, Nevada, Earthquake: Anatomy of a Crossing-Fault Rupture through a Region of Highly Distributed Deformation". Bulletin of the Seismological Society of America, 8.03.2023. http://dx.doi.org/10.1785/0120220166.
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ABSTRACT The 15 May 2020 Mw 6.5 Monte Cristo Range earthquake (MCRE) in Nevada, United States, is the largest instrumental event in the Mina deflection—a zone of east-trending left-lateral faults accommodating a right step between northwest-trending right-lateral faults of the Walker Lane. The MCRE ruptured a highly distributed faulting area with muted geomorphic expressions, motivating us to characterize the behavior of an earthquake on a structurally immature fault system. Inverse modeling of Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS) displacements reveals left-lateral slip on an east-striking, eastern fault and left-lateral–normal slip on an east-northeast-striking, western fault. Unusually, the two faults cross one another and ruptured together in the mainshock. The maximum slip of 1 m occurs at 8–10 km depth, but less than 0.1 m of slip reaches the surficial model fault patches, yielding a pronounced shallow slip deficit (SSD) of 91%. Relocated hypocenters indicate that the mainshock initiated at 9 km depth and that aftershocks span depths of 1–11 km, constraining the local seismogenic thickness. Our new field observations of fracturing and pebble-clearing in the western MCRE characterize a third, shorter, northern fault that is at the resolution limit of the InSAR–GNSS modeling. The segmented and intersecting fault geometry, off-fault aftershocks with variable mechanisms, distributed surface fractures, limited long-term geomorphic offsets, and a 600–700 m (cumulative) bedrock offset are all characteristic of a structurally immature fault system. However, the large SSD is not unusual for an earthquake of this magnitude, and a larger compilation of InSAR models (28 Mw≥6.4 strike-slip events) shows that SSDs correlate with magnitude rather than structural maturity. This study demonstrates the importance of integrating geodesy, seismology, and field observations to capture the full complexity of large earthquakes, and further suggests that seismic hazard assessments in shattered crustal regions consider the potential for multi- and cross-fault rupture.