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This study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management. Plain Language Summary: This paper is centered around the simulation of the dynamic rupture of the 1819 M 7.7 Kachchh earthquake in India. We have successfully replicated the earthquake's behavior using a three‐dimensional simulation method. The study's results demonstrate the significant influence of the local tectonic setting and non‐planar fault structure on earthquake generation and rupture progression. Although slight discrepancies exist between the simulation results and actual observations, the simulations capture significant trends and reproduce macroscopic rupture patterns. The estimated magnitude of the earthquake aligns well with previous studies. The study highlights the role of fault bending and its impact on surface deformation, contributing to a better understanding of seismic hazards and providing insights for seismic hazard assessments and earthquake source characterization. This work is valuable for comprehending earthquake sources, particularly from earthquake perspectives in the SCR region and other areas. Key Points: Dynamic rupture simulations of the 1819 Kachchh M 7.7 earthquake replicate co‐seismic fault slip, enhance our knowledge of the earthquake sourceWeak barrier characteristics observed at the bending part of the fault enabled further rupturing, influenced by SH and the nucleation pointContributes to understanding earthquake hazards, enhancing seismic assessment, engineering, and disaster management strategies [ABSTRACT FROM AUTHOR]

We use a combination of near-field simulated and observational data to constrain the rise time, rupture velocity, and high frequency stress parameter for the 2010 M7.8 Mentawai tsunami earthquake. Tsunami earthquakes, which are shallow-rupturing events generating exceptionally large seafloor displacements, are challenging for current tsunami early warning systems. A combination of near-field high-rate GNSS and seismic data can be used for early-discrimination, but the dearth of data from these events limits testing of such an implementation in a real-time scenario. In lieu of near-field data, models with realistic rupture physics can be leveraged to improve local tsunami warning. We develop recommendations for such parameters based on observations of near-field data from the 2010 M7.8 Mentawai earthquake. We find that rise time and rupture velocity covary, and that rise time–rupture velocity combinations ranging from 5.4 s–1.23 km/s to 12 s–1.6 km/s adequately model the long duration of the Mentawai event. We find that a stress parameter of 1.43 MPa best models the high frequency deficiency. We present equations which can be used to determine reasonable parameter values for simulating tsunami earthquakes, and we find that simulated data generated with the recommended parameters capture defining characteristics of tsunami earthquakes.

Summary: This study shows how GPU performance of the ADER discontinuous Galerkin method in SeisSol (an earthquake simulation software) can be further improved while preserving its original design that ensures high CPU performance. We introduce a new code generator ("ChainForge") that fuses subsequent batched matrix multiplications ("GEMMs") into a single GPU kernel, holding intermediate results in shared memory as long as necessary. The generator operates as an external module linked against SeisSol's domain specific language YATeTo and, as a result, the original SeisSol source code remains mainly unchanged. In this paper, we discuss several challenges related to automatic fusion of GPU kernels and provide solutions to them. By and large, we gain ≈$$ \approx $$60% in performance of SeisSol's wave propagation solver using Fused‐GEMMs compared to the original GPU implementation. We demonstrated this on benchmarks as well as on a real production scenario simulating the Northridge 1994 earthquake. [ABSTRACT FROM AUTHOR]

Effective relief reduces damages and protects people during natural disasters, such as earthquakes. This research proposes a data-driven model based on sustainability, taking into account the pre and post-crisis simultaneously. Real data was used to validate the model in various earthquake scenarios. The study addresses questions regarding the amount and allocation of relief goods during earthquakes. This research is carried out in two phases: simulation and modeling. The purpose of the simulation phase is to estimate the number of relief goods in different scenarios. Additionally, in the modeling phase, a data-based multi-objective model is presented, considering sustainability, to minimize the lack of relief goods, the number of untreated wounded, and supply chain costs. Using the dynamic simulation system, and after designing the structure of the earthquake effects on urban infrastructure, the actions and effects of the earthquake on vital arteries are investigated in different scenarios, and scenarios with a higher degree of risk are identified. The results showed that the highest and lowest demands for relief goods were related to the "Mosha-day fault" and "North Tehran-night fault" scenarios, respectively. [ABSTRACT FROM AUTHOR]

Fault‐damage zones comprise multiscale fracture networks that may slip dynamically and interact with the main fault during earthquake rupture. Using 3D dynamic rupture simulations and scale‐dependent fracture energy, we examine dynamic interactions of more than 800 intersecting multiscale fractures surrounding a listric fault, emulating a major listric fault and its damage zone. We investigate 10 distinct orientations of maximum horizontal stress, probing the conditions necessary for sustained slip within the fracture network or activating the main fault. Additionally, we assess the feasibility of nucleating dynamic rupture earthquake cascades from a distant fracture and investigate the sensitivity of fracture network cascading rupture to the effective normal stress level. We model either pure cascades or main fault rupture with limited off‐fault slip. We find that cascading ruptures within the fracture network are dynamically feasible under certain conditions, including: (a) the fracture energy scales with fracture and fault size, (b) favorable relative pre‐stress of fractures within the ambient stress field, and (c) close proximity of fractures. We find that cascading rupture within the fracture network discourages rupture on the main fault. Our simulations suggest that fractures with favorable relative pre‐stress, embedded within a fault damage zone, may lead to cascading earthquake rupture that shadows main fault slip. We find that such off‐fault events may reach moment magnitudes up to Mw ≈ 5.5, comparable to magnitudes that can be otherwise hosted by the main fault. Our findings offer insights into physical processes governing cascading earthquake dynamic rupture within multiscale fracture networks. Plain Language Summary: Large geological faults are surrounded by many small fractures of different sizes and orientations, forming a fracture network around the main fault. The characteristics of an earthquake and its size may depend on the orientation of the main fault (and surrounding fractures) within the ambient stress field. Can a small (initial) rupture within a fracture network start a domino‐like (cascading) earthquake across the entire fault network? How does the compounded earthquake process depend on fracture orientation, local stress, and rupture starting point? To address these questions, we study earthquake rupture physics in a complex fault‐zone model comprising over 800 multiscale fracture planes surrounding a main fault. Using 3D dynamic rupture simulations and supercomputing, we explore how different ambient stress orientations, earthquake hypocenters, and levels of fault loading affect earthquake dynamics in fracture networks. The simulations demonstrate that cascading rupture in a fault zone is possible under certain conditions. Our results provide important insights into the physics of cascading earthquakes in multiscale fracture systems and hence are useful for advancing seismic hazard assessment for both natural and induced earthquakes. Key Points: We perform 3D dynamic rupture simulations in a network of >800 fractures and a listric main fault, assuming scale‐dependent fracture energyCascading rupture is possible under high fracture connectivity if a subset of fractures is favorable with respect to the ambient stressWe demonstrate the feasibility of dynamic rupture cascade irrespective of hypocenter locations within the fracture network [ABSTRACT FROM AUTHOR]

Abstract This study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management.

Reported test results suggest reinforcement grade can have an important effect on the seismic displacement demands of reinforced concrete (RC) structures. Two one‐story one‐bay RC frames (Specimens C1 and H1) were mounted in parallel on the NCREE‐Taiwan shake table and simultaneously subjected to 16 base motions, each representing a horizontal component of recorded earthquakes. The dynamic tests were followed by quasi‐static large‐amplitude cyclic testing. The specimens had the same nominal dimensions and base shear strengths with longitudinal reinforcement that was Grade 60 (60 ksi [420 MPa]) in C1 and Grade 100 (100 ksi [690 MPa]) in H1. Maximum drifts of H1 were 1.3 to 2.3 times larger than for C1. The lateral stiffness of H1 was consistently lower than C1, with stiffness ratios (H1 to C1) ranging from 0.78 after Run 1 to 0.45 after Run 16. Drift estimates using stiffness values based on gross‐section properties provided a reasonable upper bound for C1 but were unconservative for H1. Drift estimates based on the secant‐to‐yield stiffnesses, which were inversely proportional to reinforcement grade, provided an upper bound for both specimens. Preliminary recommendations are made for accounting for these effects in design. [ABSTRACT FROM AUTHOR]

Earthquake-induced ground shaking near rupturing faults is highly sensitive to the rupture characteristics, seismic wave propagation patterns and site conditions, and field recordings of near-fault shaking are relatively sparse. These challenges complicate the assessment of the seismic performance of near-fault structures. A common approach to representing near-fault ground motion in engineering analysis is to explicitly consider and select records with strong directivity pulses (pulse records). We use three-dimensional high-resolution physics-based earthquake simulations to test this approach in the context of scenario-based ground motion record selection, and to study the important characteristics of near-fault ground shaking. We highlight the deficiencies associated with classifying near-fault simulated records as "pulse" or "non-pulse," based on the presence of a single dominating pulse in the velocity time history. We show that this approach is inadequate for characterizing near-fault shaking on soft soils which can be dominated by both forward rupture directivity and basin amplification effects. We conduct ground motion selection experiments for the analysis of near-fault structures with and without explicit classification of the pulse features in the records, and evaluate the bias in the predicted structural demands. We find that the maximum interstory drift demands on building structures imposed by unscaled site-specific simulated ground motion records selected based on relevant spectral shape features are not sensitive to the classification of records as pulse/non-pulse. Therefore, with regard to predicting the maximum interstory drifts in near-fault buildings, we do not find justification for the binary pulse classification of near-fault records. [ABSTRACT FROM AUTHOR]

Zagros is very active in terms of seismicity and is the most seismic region of Iran. In the book on the history of earthquakes in Iran, two major earthquakes have been reported on 1st January 958 Mw 6.3, and 1st April 1150 Mw 6.1 (Ambraseys & Melville, 1982). It is well-known that the historical earthquakes consist of valuable information for identifying the hazard of earthquakes, completing the earthquake catalogs, better understanding the Zagros area, and better preparing for this natural phenomenon; on 12th November 2017, an earthquake with a magnitude of 7.3 occurred at a distance of 10 km from the Ezgleh and about 37 km northwest of Sarpolzahab city in Kermanshah province, located at the Iran-Iraq border. The earthquake location was close to historical earthquakes. In this regard, we used the empirical Green's function method to simulate the historical earthquake. Empirical Green's function evaluates parameters of strong ground motion such as time history, frequency content, effective duration, P and S wave arrival time, the Earth response spectrum, and the maximum acceleration of the earth that occurred during the earthquake. Empirical Green's function method is one of the most common and simple simulation methods for generating strong ground motion with geological heterogeneity effects, which is used to model ground motions using foreshocks and aftershocks. In this study, the simulation of one of the Sarpolzahab earthquake aftershocks was conducted by small aftershocks recorded in the Ezgeleh region, using the empirical function method. The temporary network data of the International Institute of Seismology and Earthquake Engineering was used for this study. The simulation results show that there is a good similarity between the waveforms, the Fourier amplitude spectra, and the simulated response spectra observed at the existing stations and that the errors are acceptable. The parameters of the acquired model consist of rupture velocity of 2.6 to 3.5 km/sec equivalent to 0.8 to 0.9 times the S-wave speed and healing velocity equal to 0.95 times the rupture velocity. The dimensions of the fault grids were 0.05x0.05 and the scalar seismic moment of the aftershock was 1.04x1023 Nm. In the simulation, asperities were not considered. The source time function was Kostrov-ramp and fault roughness was taken into account. Furthermore, the waveforms, Fourier amplitude spectra, and response spectra for the mentioned historical earthquakes were constructed with the results obtained from the reference earthquake for simulation. The results are reasonable; however, some errors are unavoidable. [ABSTRACT FROM AUTHOR]

With HPC (high performance computing) evolving into the exascale era, improvements in computing performance and power efficiency have become increasingly more important. Based on our previous work on enabling earthquake simulations on a large scale on Sunway TaihuLight, we further explore other possibilities to improve the application through a fully-customized hardware design on reconfigurable FPGA (field programmable gate array) devices. We investigate the feasibility and the potential benefits of a complete fixed-point design. We first perform a coarse-resolution-based simulation to analyze the representation range and precision needed to capture both the total energy and the energy distribution of variables over space and time. We then derive a complete fixed-point design that identifies the suitable bitwidth for major categories of variables and dynamically represents the range through a dynamic scaling scheme. Finally, we use the optimized fixed-point design to run a case of the Wenchuan earthquake to demonstrate the potential of supporting large-scale scientific simulations on FPGA devices. The results demonstrate that an 18-bit fixed-point design already provides an almost identical description of the seismic events in the Wenchuan scenario down to a single-precision floating-point version and provides sustainable performance equivalent to 13.1 Intel Xeon Gold 6154 18-core CPUs or 2.10 Sunway 260-core processors, with performance per watt (power efficiency) improved by 15.3 and 3.72 times compared with the Intel Xeon Gold 6154 18-core CPUs and the Sunway 260-core processors, respectively. [ABSTRACT FROM AUTHOR]

Dynamics of lithospheric plates resulting in localisation of tectonic stresses and their release in large earthquakes provides important information for seismic hazard assessments. Numerical modelling of the dynamics and earthquake simulations have been changing our view about occurrences of large earthquakes in a system of major regional faults and about the recurrence time of the earthquakes. Here, we overview quantitative models of tectonic stress generation and stress transfer, models of dynamic systems reproducing basic features of seismicity, and fault dynamics models. Then, we review the thirty-year efforts in the modelling of lithospheric block-and-fault dynamics, which allowed us to better understand how the blocks react to the plate motion, how stresses are localised and released in earthquakes, how rheological properties of fault zones exert influence on the earthquake dynamics, where large seismic events occur, and what is the recurrence time of these events. A few key factors influencing the earthquake sequences, clustering, and magnitude are identified including lithospheric plate driving forces, the geometry of fault zones, and their physical properties. We illustrate the effects of the key factors by analysing the block-and-fault dynamics models applied to several earthquake-prone regions, such as Carpathians, Caucasus, Tibet-Himalaya, and the Sunda arc, as well as to the global tectonic plate dynamics. [ABSTRACT FROM AUTHOR]

The Asia-Pacific Economic Cooperation for Earthquake Science（ACES）is one of the eight scientific and technological cooperation projects under the branch of Policy Partnership on Science，Technology and Innovation of APEC. The major participating economies are Australia，China，Japan，the United States，Canada，New Zealand，Chinese Taipei and Korea. Since the proposal was approved in 1997，the project has been running for more than 20 years，and has obtained a lot of scientific and technological achievements. This paper summarizes the origin，operation，cooperation form，cooperation fields，main cooperation achievements and future prospects of the ACES project.

The prediction of the seismic response of critical structures is highly sensitive to many aspects, among which the earthquake source and the geological setting are prominent. The related uncertainty issues must be taken into account in seismic risk mitigation studies, for example through the evaluation of several realizations of a future earthquake scenario. This aspect is crucial when addressing vulnerability studies at a regional scale. When opting for physical-based numerical simulations (PBS), however, the computational burden increases along with the expected degree of fidelity, making it difficult to evaluate more than a few dozens of alternatives. To cope with this disadvantage, in this work an alternative method is proposed, which exploits a rather low number of synthetic earthquake simulations and combines them with the empirical Green function (EGF) method, to finally generate thousands of alternative yet realistic seismic response of the site of interest. This hybrid strong motion predictions benefit of both (i) PBS high fidelity and (ii) data assimilation of strong ground motion records in the seismic area of interest, via EGF method, producing broadband synthetics at a relative cheap computational price. The power of the hybrid method is tested on a real case scenario, embodied by the ground-shaking prediction at the nuclear site of Cadarache, in the surroundings of the fault of Middle Durance, in South-Eastern France. Thousands of broadband (0–15 Hz) hybrid synthetic seismic response are generated, associated with different fault parameters (EGF method) and based upon a few key physics-based simulations, accurate up to 5 Hz. [ABSTRACT FROM AUTHOR]

According to the IAEA and USNRC (United State Nuclear Regulatory Commision) regulations, calculating a strong ground motion during an earthquake is of great importance for the design of nuclear facilities, especially nuclear power plants. In the absence of precise seismic studies and in case of severe earthquakes, many radioactive contaminants are released into the environment, with irreparable physical and financial losses, hazarding the nuclear facilities, people and the environment. In this research, in order to develop the earthquake attenuation relationships for Boushehr, an important region, simulation of the ground motion was used along with the stochastic finite fault method. The results obtained from the simulation have been compared with the results obtained from the valid world relations for the Zagros region. Evidently, they show good consistency. The proposed model is a theory-empirical relationship of the Bushehr susceptible region, which can be used to assess the safety of the existing nuclear power plant in Boushehr and to design new nuclear power plants in the future.

On 24 August 2016, a Mw 6.0 earthquake started a damaging seismic sequence in central Italy. The historical center of Amatrice village reached the XI degree (MCS scale) but the high vulnerability alone could not explain the heavy damage. Unfortunately, at the time of the earthquake only AMT station, 200 m away from the downtown, recorded the mainshock, whereas tens of temporary stations were installed afterwards. We propose a method to simulate the ground motion affecting Amatrice, using the FFT amplitude recorded at AMT, which has been modified by the standard spectral ratio (SSR) computed at 14 seismic stations in downtown. We tested the procedure by comparing simulations and recordings of two later mainshocks (Mw 5.9 and Mw 6.5), underlining advantages and limits of the technique. The strong motion variability of simulations was related to the proximity of the seismic source, accounted for by the ground motion at AMT, and to the peculiar site effects, described by the transfer function at the sites. The largest amplification characterized the stations close to the NE hill edge and produced simulated values of intensity measures clearly above one standard deviation of the GMM expected for Italy, up to 1.6 g for PGA.

Experimental setup for studying the behavior of structures are large and require high investment costs. However, comparing theoretical results to the dynamic behavior of structures using scaled structure models is a preferred research method in civil engineering. Therefore, a low-cost shake table named SARSAR with Arduino microcontroller boards has been developed for earthquake simulations. The horizontal components of the acceleration records obtained from past earthquakes are scaled and transferred to the shake table by developing software programs using an Arduino DUE board. For verification, the response of the table is measured by a data acquisition unit based on an Arduino MEGA board. The seismic ground motion along the horizontal axis is transferred to the shake table via a linear actuator system built with a ball screw assembly, linear bearings and a stepper motor. [ABSTRACT FROM AUTHOR]

Four reinforced concrete portal frames were tested on an earthquake simulator. Columns in two frames had conventional steel longitudinal reinforcement. Columns in the other two frames had smaller-diameter, ultra-high-strength steel longitudinal reinforcement (fy >120 ksi [830 MPa]). Test results suggested that peak drift was driven by the initial period of the frames (based on uncracked sections). To examine this observation in more detail, a database was used to evaluate an equation in which peak drift is expressed in terms of initial period and peak ground velocity (PGV), neither of which are sensitive to reinforcement ratio, yield stress, or displacement history. This database includes results from more than 160 laboratory tests and the measured responses of three buildings to earthquakes. For motions representative of what has been observed in the field and in the ranges considered, this expression provided a reasonable upper-bound estimate of drift for tests in the database. [ABSTRACT FROM AUTHOR]

Abstract The scope of this paper is to give an insight into the advantages of a new, all-embracing, modeling approach of a strong ground motion scenario, by carrying out a source-to-structure analysis at regional scale, accounting explicitly for the uncertainties related to the databases and the models. To this end, a suitable case-study is represented by the 2007 Mw6.6 Niigata-Ken Chūetsu-Oki seismic sequence (west Japan), that damaged the Kashiwazaki Kariwa Nuclear Power Plant. This study describes the effect of the wave propagation path within the Earth's crust on the seismic response of nuclear reactor buildings located nearby a seismogenic source. The multiscale problem is de-coupled into three steps: (1) a parallel simulation of seismic-wave propagation throughout the Earth's crust at regional scale (≈ 60 km wide, major 3-D geological interfaces found below the nuclear site), reliable up to 5.0 Hz; (2) a mid hybridization step consisting in enriching the synthetic wave-field at high frequency (up to 30 Hz), employing an Artificial Neural Network to predict the short-period (SP) spectral ordinates; (3) a high-resolution structural dynamic analysis, introducing the hybrid broad-band synthetics as input wave-motion. A simplified stress-test is performed, by simulating two small point-wise aftershocks at different source-site position. The impact of the underground 3-D geology on the structural components is finally quantified, by injecting the obtained broad-band time-histories in a Soil-Structure Interaction (SSI) model of the nuclear reactor building. The good fit obtained in terms of amplification factor at different recording stations assures the high-fidelity of the holistic philosophy endorsed. Highlights • Source-to-structure simulation of nuclear power plant seismic response. • 3D physics-based earthquake simulation (PBS) at regional scale (60 km) up to f max = 5 Hz. • Realistic simulation of ground motion spatial variability due to 3D folding geology. • Hybrid broad-band wave-motion by coupling PBS with Artificial Neural Networks (ANN). • SSI analysis of reactor building injecting broad-band synthetics (PBS + ANN). [ABSTRACT FROM AUTHOR]

Ground motion simulations solve wave equations in space and time, thus producing detailed estimates of the shaking time series. This is essentially uncharted territory for geomorphologists, for we have yet to understand which ground motion (synthetic or not) parameter, or combination of parameters, is more suitable to explain the coseismic landslide distribution. To address this gap, we developed a method to select the best ground motion simulation using a combination of Synthetic Aperture Radar Interferometry (InSAR) and strong motion data. Upon selecting the best simulation, we further developed a method to extract a suite of intensity parameters, which we used to analyse coseismic landslide occurrences taking the Gorkha earthquake (M7.8, 25 th April 2015) as a reference. Our results show that beyond the virtually unanimous use of peak ground acceleration, velocity, or displacement in the literature, different shaking parameters could play a more relevant role in landslide occurrences. These parameters are not necessarily the product of peak ground motion but are linked to the total displacement, frequency content, and shaking duration; elements too often neglected in geomorphological analyses. This, in turn, implies that we have yet to fully acknowledge the complexity of the interactions between full waveforms and hillslope responses. • Review of existing ground motion and landslide simulation techniques • Review and tests of available fault rupture models for Gorkha earthquake • Use of synthetic full waveforms to explain co-seismic landslide occurrences • Novel geo-spatial analyses to examine slope responses to seismic shaking [ABSTRACT FROM AUTHOR]

For time history analysis of structures, appropriate records are needed. Due to the lack of strong-motion records from large earthquakes in some parts of Iran (e.g. Tehran region), earthquake simulation is a useful tool for studying strong-motion characteristics. In this study, a hybrid method has been used for obtaining source parameters of the 1990 Rudbar-Manjil earthquake (Mw7.3). In this simulation we assume fault plane, slip distribution and etc., then each parameter optimized after comparing simulated results with observed ones. In this hybrid method low frequency component of record obtained by the wave-number scheme that is a deterministic method and high frequency component obtained by the stochastic simulation method of Boore (2003), extended to the case of finite faults. Records from the stochastic method filtered with a high pass filter (fc=1.5 Hz) and results from the deterministic method filtered with low pass filter (fc=1.5 Hz), then the time-histories have been combined/added in the time domain. Final results have been compared with observed PSA and PSV in specified strong-motion stations. After comparing, optimized parameters have found, then based on this optimized parameters intensity contour has drawn; simulated intensity contours show good match with and observed ones. Best parameters are 2500 m/s for rupture velocity and 3 seconds for ramp function (i.e. rise time) and 36.82° N and 49.40° for earthquake epicenter. The results are important for the assessment of hazards in other seismically active parts of Alborz mountains (e.g. Greater Tehran area).

Abstract: Sheared granular layers undergoing stick‐slip behavior are broadly employed to study the physics and dynamics of earthquakes. Here a two‐dimensional implementation of the combined finite‐discrete element method (FDEM), which merges the finite element method (FEM) and the discrete element method (DEM), is used to explicitly simulate a sheared granular fault system including both gouge and plate, and to investigate the influence of different normal loads on seismic moment, macroscopic friction coefficient, kinetic energy, gouge layer thickness, and recurrence time between slips. In the FDEM model, the deformation of plates and particles is simulated using the FEM formulation while particle‐particle and particle‐plate interactions are modeled using DEM‐derived techniques. The simulated seismic moment distributions are generally consistent with those obtained from the laboratory experiments. In addition, the simulation results demonstrate that with increasing normal load, (i) the kinetic energy of the granular fault system increases, (ii) the gouge layer thickness shows a decreasing trend, and (iii) the macroscopic friction coefficient does not experience much change. Analyses of the slip events reveal that, as the normal load increases, more slip events with large kinetic energy release and longer recurrence time occur, and the magnitude of gouge layer thickness decrease also tends to be larger; while the macroscopic friction coefficient drop decreases. The simulations not only reveal the influence of normal loads on the dynamics of sheared granular fault gouge but also demonstrate the capabilities of FDEM for studying stick‐slip dynamic behavior of granular fault systems. [ABSTRACT FROM AUTHOR]

Abstract: It is well established that subsurface injection of fluids increases pore fluid pressures that may lead to shear failure along a preexisting fault surface. Concern among oil and gas, geothermal, and carbon storage operators has risen dramatically over the past decade due to the increase in the number and magnitude of induced earthquakes. Efforts to mitigate the risk associated with injection‐induced earthquakes include modeling of the interaction between fluids and earthquake faults. Here we investigate this relationship with simulations that couple a geomechanical reservoir model and RSQSim, a physics‐based earthquake simulator. RSQSim employs rate‐ and state‐dependent friction (RSF) that enables the investigation of the time‐dependent nature of earthquake sequences. We explore the effect of two RSF parameters and normal stress on the spatiotemporal characteristics of injection‐induced seismicity. We perform >200 simulations to systematically investigate the effect of these model components on the evolution of induced seismicity sequences and compare the spatiotemporal characteristics of our synthetic catalogs to observations of induced earthquakes. We find that the RSF parameters control the ability of seismicity to migrate away from the injection well, the total number and maximum magnitude of induced events. Additionally, the RSF parameters control the occurrence/absence of premonitory events. Lastly, we find that earthquake stress drops can be modulated by the normal stress and/or the RSF parameters. Insight gained from this study can aid in further development of models that address best practice protocols for injection operations, site‐specific models of injection‐induced earthquakes, and probabilistic hazard and risk assessments. [ABSTRACT FROM AUTHOR]

Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current (DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density (10−7–10−8 A/m2) generated by the pulsed power systems at the epicenter depth (5–10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory “earthquake” triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory “earthquake” (sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98–0.99 of its critical value. The threshold of electric triggering action is about 20 A/m2 that is 7–8 orders of magnitude higher than estimated electric current density for Bishkek test site (Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties. [ABSTRACT FROM AUTHOR]

We developed a large-scale three-dimensional ground analysis method aimed at improving the estimation of dynamic ground strain during earthquakes. Using the developed ground modeling and analysis method, a 40 billion degrees-of-freedom unstructured finite element ground model of a 3.25km × 3.25km area of Tokyo was generated with 0.66m sized elements, and its strain time history for ground motion of the 1995 Kobe wave was computed using the full K computer system with 82,944 compute nodes. The obtained strain response showed a complex distribution reflecting the input wave characteristics, surface topography, and underlying ground structure. We also showed the seismic response of 41,675 buildings in the target area computed using the wave at surface as an input. Such a method is expected to be useful for the improvement of seismic design and mitigation of pipelines against anticipated earthquakes. [ABSTRACT FROM AUTHOR]