Seismic Instability Research Articles

Centrifuge modelling on seismic failure of MSW landfills with high water level

Landfill failure threatens the safety of surrounding cities and causes soil and water pollution. High water levels can usually spur landfill failure. With the presence of earthquake, landfill instability is triggered in a greater possibility. However, the dynamic response and failure mechanism of landfills with high water level subjected to earthquakes are not yet clearly understood, and relevant experimental studies are quite scarce. This study includes a series of seismic centrifuge tests to investigate the seismic response of the landfill at different water levels. An improved method is proposed to prepare synthetic municipal solid wastes (MSWs) with similar static-dynamic properties to the actual MSWs. The failure and evolution mechanism of landfills with high water levels induced by the earthquake is revealed. Significant transitions are observed in the dynamic response of deformation, acceleration, and pore-water pressure as the water level changes. With the rise of water level, the settlement at the top of the landfill decreases first and then increases, while the horizontal displacement at the toe increases slowly, followed by a sudden drop; the acceleration amplification coefficient in the middle of the landfill increases first and then decreases; the dynamic pore-water pressure gradually decreases from positive to negative, but oscillates at the moderate water level. Three failure criteria and a hydro-earthquake coupled failure limit are proposed to demonstrate the combined effect of water level and earthquake on landfill stability. The test results provide a basis to establish seismic failure standards for landfills with different water levels and guide the seismic instability design of landfills with high water level.

Brahmaputra River Bank Erosion as a Major Geo-Environmental Problem in Lower Assam, India

Abstract The concepts as well as the methodological approaches for investigating geo-environmental pattern, process and problems in a region have been continuously getting their holds since few decades past to make them firm-footed in the contemporary trend of geo-environmental studies. The lower Brahmaputra River valley of Assam, like other parts of northeast India, stands amidst complex geotectonic and physiographic set-up because, of its hills, foothills and river plain topography. The state of Assam as a whole, eventually have been experiencing natural hazards like floods including flash floods, river bank erosion, landslide, etc. Out of which bank erosion heavily affects on the life and land properties of the peoples in affected area by completely damaging it. The river Brahmaputra has a tendency to shifting southward due to various geo-tectonic and seismic instabilities of the region. It is found that during the last 50 years nearly 100 sq km of the study area is eroded in the southern part of the district of Goalpara only. The intensity of shifting is very high mostly in the lower Brahmaputra valley including western margin of the districts of Goalpara, South Salmara Mankachar and Dhubri. The data derived from 14 cross sections along the selected points of lower Brahmaputra reveals that the average annual southward shifting of the river due to bank erosion is 109.14 m/year. Hence, bank erosion has been a serious problem, which is caused mainly by the seismic instability, stream bed rise-up, continuous sedimentation; Intense rainfall, etc. And eventually the phenomenon results into the loss of large tracts of fertile agricultural lands on both the banks of the river Brahmaputra in the study area. The present paper is an attempt to analyze the cause and consequences of Brahmaputra River Bank Erosion as a major geo-environmental problem with special reference to the bank line at Goalpara district of lower Assam in India.

ИСТОЧНИКИ ГЕОЭКОЛОГИЧЕСКОГО ЗАГРЯЗНЕНИЯ ПРИ СКВАЖИННОМ СПОСОБЕ ДОБЫЧИ ПОЛЕЗНЫХ ИСКОПАЕМЫХ

To ensure geoecological safety of the Republic, it is proposed to divide all structures into groundwater (in the depth range up to 20 m) and underground ones (in the depth range over 21 m) when conducting geoecological monitoring of subsurface resources during the downhole method of field development. The improved order for scheme of the integrated subsurface exploration and carrying out geoecological monitoring was also worked out. The performed studies revealed geological and geodynamic processes, thermal pollution, as well as seismic instability, complicating the safe conditions of field development and violating the existing geoecological balance of the territory at the local and regional levels.

Rheological heterogeneities at the roots of the seismogenic zone

Although rheological heterogeneities are invoked to explain differences in fault-slip behavior, case studies where an interdisciplinary approach is adopted to capture their specific roles are still rare. In this work, we integrated geophysical, geological, and laboratory data to explain how rheological heterogeneities influence the earthquake activity at the roots of the seismogenic zone. During the 2016–2017 Central Italy sequence, following the major earthquakes, we observed a deepening of seismicity within the basement associated with a transient stress change. Part of this seismicity was organized in clusters of events, with similar sizes and waveforms. The structural study of exhumed basement rocks highlighted a heterogeneous fabric made of strong, quartz-rich lenses (up to 200 m) surrounded by a weak, interconnected phyllosilicate-rich matrix. Laboratory experiments simulating the main shock–induced increase in loading rate showed that the matrix lithology experienced an accelerating and self-decelerating aseismic creep, whereas the lens lithology showed dynamic instabilities. Our results suggest that the post–main shock loading rate increases favored accelerated creep within the matrix, which promoted, as a consequence, seismic instabilities within the lenses in the form of clustered seismicity. Our findings emphasize the strong connection between seismicity and the structural and frictional properties of the seismogenic zone.

Earthquake response and post-earthquake stability assessment of submarine clay slopes

Earthquakes are the most frequent trigger for submarine landslides; thus, seismic instability evaluation of submarine slopes has received considerable attention. Previous studies have usually regarded earthquake response and post-earthquake stability assessment of submarine slopes as two separate procedures. However, earthquake response processes significantly affect the strength degradation of the soil. Notably, relevant research on this subject is rare. Herein, a general approach is proposed to predict the earthquake response and to assess the post-earthquake stability of submarine slopes. First, an earthquake response computational method is developed for an actual submarine slope with curvilinear geometry, which utilizes the SIMPLE DSS model. The calculated results of the earthquake response are used to determine the seismic strength degradation factor. Subsequently, the position and length of the initial shear band can be determined. A modified shear band propagation (SBP) criterion is used to assess the post-earthquake slope stability after addressing the uneven strength reduction of the soil in a weak layer after an earthquake, and the slope geometry effect on stability is discussed. Finally, the proposed approach was applied in a stability risk assessment of an actual submarine slope. For geologists and engineers to evaluate the stability of submarine slopes experiencing earthquakes, this method is practical and efficient.

Settlers in Earthquake Country

This article examines how settlers in New Zealand and California responded to seismic instability throughout the late nineteenth century. By interpreting a series of moments during which the foundations of settlement were shaken by earthquakes I argue that the economic temporality of colonial boom and bust inflected contemporary understandings of natural disaster. In earthquake country, the relationships between scientists and settlers, their environmental knowledge, and the physical world existed in a dynamic equilibrium. When earthquakes struck in opportune conditions settlers were quick to resume their speculation on land, scientists were inspired by upheaval, and artists found sublimity in instability. In times of doubt earthquakes induced a latent anxiety among settlers about the prospects of the colonial project. In this context natural disasters were framed as threats to growth or harbingers of decline. Read together, responses to earthquakes offer a new way into the environmental history of settler colonialism that places a form of creative destruction at the center of the colonial project on both sides of the Pacific Rim.

Experimental Study on Seismic Instability of Pile-Supported Structure Considering Different Ground Conditions

The stability of pile-supported structures under earthquake loads involves complex dynamic soil–structure interaction (SSI). A series of large-scale shaking table experiments was performed to investigate the seismic performance and SSI of pile-supported structures considering different ground conditions. Lateral soil resistance and dynamic displacements of superstructures located in nonliquefiable and liquefiable sites as well as a rigid foundation were measured during shaking tests. The measured responses were analyzed to investigate the P-Δ effect on structural stability. It was observed that the soil lateral resistance to the pile cap at the nonliquefiable site was large and represented the main component of the lateral bearing capacity resisting structure overturning. On the other hand, the lateral resistance of liquefied soil on piles was insignificant and the lateral bearing capacity was derived primarily from soil resistance to pile cap. The analysis of the measured dynamic displacements demonstrated that the seismic instability of the structure was mainly due to the P-Δ effect caused by the rotation of the foundation, especially in liquefied sites. In addition, comparison with the results of base shears and bending moments with the rigid base assumption allows for an in-depth discussion of the effect of SSI on structural seismic design.

A Hybrid Approach for the Dynamic Instability Analysis of Single-Layer Latticed Domes with Uncertainties

Currently, there is no unified criterion to evaluate the failure of single-layer latticed domes, and an accurate nonlinear time-history analysis (NTHA) is generally required; however, this does not consider the uncertainties found in practice. The seismic instability of domes subjected to earthquake ground motions has not been thoroughly investigated. In this paper, a new approach is developed to automatically capture the instability points in the incremental dynamic analysis (IDA) of single-layer lattice domes by integrating different efficient and robust methods. First, a seismic fragility analysis with instability parameters is performed using the bootstrap calibration method for the perfect dome. Second, based on the Sobol sequence, the quasi-Monte Carlo (QMC) sampling method is used to efficiently calculate the failure probability of the dome with uncertain parameters, in which the truncated distributions of random parameters are considered. Third, the maximum entropy principle (MEP) method is used to improve the computational efficiency in the analyses of structures with uncertainties. Last, the uncertain interval of the domes is determined based on the IDA method. The proposed method has been used to investigate the instability of single-layer lattice domes with uncertain parameters. The results show that it can determine the probability of structural failure with high efficiency and reliability. Additionally, the limitations of the proposed method for parallel computation are discussed.

Seismic cumulative failure effects on a reservoir bank slope with a complex geological structure considering plastic deformation characteristics using shaking table tests

To investigate the seismic cumulative failure effect (SCFE) of a reservoir bank rock slope, the dynamic displacement response of the slope was analysed using shaking table tests. A plastic effect coefficient (PEC) is proposed to reflect the plastic deformation degree of the slope under the influence of earthquakes, and its applicability in analysing the SCFEs of slopes is verified by using the Arias intensity ( I a ) from the perspective of energy. The effects of the wave frequency components on the SCFE and local failure mechanism of the landslide are discussed based on the frequency-domain analysis. The results shows that the PEC fully considers the plastic deformation characteristics of the slope, and its physical significance is clear; thus, it can reflect the local failure of the slope better than the peak ground displacement (PGD). The analyses of the PEC and I a show that the seismic cumulative failure process of the slope includes the progressive failure effect stage, initiating effect stage, and accelerated sliding stage. In addition, according to the frequency-domain analysis, the high-frequency components of seismic waves have a great impact on the accumulation process of the local slope deformation, while the low-frequency components have a controlling effect on the overall instability of the slip mass. The seismic instability of rock slopes containing complex geological structures is a progressive and cumulative failure process. Obtaining a better understanding of the SCFEs of slopes can provide a scientific basis for the identification of the seismic damage status and appropriate seismic reinforcement. • The seismic cumulative failure effect (SCFE) of a rock slope was investigated. • The applicability of the dynamic displacement parameters for analysing the SCFE of the slope was discussed. • The effects of the frequency components of waves on the landslide SCFE were discussed.

Seismic study and spatial observations of a & b – values for the different earthquake hazard zones of India

This paper study the recent seismicity in Earthquake hazard zones in India. A large historical earthquake event catalog to cover the period of 1900-2018, the parameters date, time, latitude, longitude, depth and magnitude has been used to calculating frequency-magnitude distribution (b-value) of seismic hazard zones in India. To convert different magnitude scales into a single moment magnitude scale, the general orthogonal regression relation is used. Gamma distribution used for variable corrections also de-clustering method has used for removal of any non-Poisson distribution. The Indian seismic hazard zones are divided into five major seismic sources zones. The seismicity is characterized by Gutenberg-Richter relation. The parameter ‘b’ of FMD and relationship have been determined for these five seismic zones having different vulnerability environment. The ‘b’ values ranges between 0.43 to 1.16. The difference between the b parameters and seismic hazard level from seismic zones II to V considered for the study of high seismo-tectonic complexity and crustal heterogeneity, the parameter ‘a’ value changes accordingly the seismicity of the regions. The lowest b-values found in seismic zone II. The highest FMD b-value has been found in the seismic zone IV. Such high seismicity b-values may be associated with high heterogeneity. In this high b-value predict the low strength in the crust as well as seismic instabilities of that zone. These observations recommend not suggesting the location of important projects like atomic power stations, hydroelectric power stations, neutrino observatory projects, satellite town projects.

GIS-based approach for the measurement of variability in tectonomorphic signatures using DEM's data: a case study from the Habo Dome in the Kachchh area, India

The Kachchh region of western India is located in a plate interior region, but falls under one of the highest seismic zones of India, having very active crustal deformation and erosion. The drainage system, as well as the geomorphic evolution of the region under a semi-arid climate zone with high to very high strength of rocks in areas with high relief, is dominantly controlled by the seismic instability associated with continual tectonics. In the present paper, we have analysed a block close to the epicentre of the 2001 Bhuj earthquake to understand the role of relative active tectonics in the evolution of domal landscape morphology. Shuttle Radar Topographic Mission Digital Elevation Model data were used to extract drainage network in the GIS platform and evaluate active tectonics using different geomorphic indices of the Habo Hill, the second largest domal structure situated in Northern Hill Range of the Kachchh region. The average cumulative weightage of different geomorphic indices provides a quantitative tool, Index of Relative Active Tectonics (IRAT), which shows significant variations in and around the Habo Dome. Activation of earlier lineaments and generation of new lineaments controlled the morphometric evolution of the fault bound block of the region to form the Habo Dome. The undulating topography in addition to the domal shape of the study area resulted from the differential movements along several active transverse faults striking NE–SW, N–S, and NW–SE, and the regional faults striking E–W (the Kachchh Mainland Fault, the Kas Fault, and the Jikadi Fault). Stress propagations from the Himalayan range in the northeast and Suleiman range in the northwest are identified to be the causative factors for active tectonics and drainage anomalies in the area.

Nucleation of Stick-Slip Instability Within a Large-Scale Experimental Fault: Effects of Stress Heterogeneities Due to Loading and Gouge Layer Compaction.

Geodetic observations and large‐scale laboratory experiments show that seismic instability is preceded by slow slip within a finite nucleation zone. In laboratory experiments rupture nucleation is studied mostly using bare (rock) interfaces, whereas upper crustal faults are typically filled with gouge. To investigate effects of gouge on rupture nucleation, we performed a biaxial shearing experiment on a 350 mm long saw‐cut fault filled with gypsum gouge, at room temperature and a minimum horizontal stress σ 2 = 0.3–5 MPa. The gouge layer was sandwiched between polymethylmethacrylate (PMMA) plates For reference also a fault without gouge was deformed. Strain gauges and Digital Image Correlation were used to monitor the deformation field along the fault zone margins. Stick‐slip behavior occurred on both the gouge‐filled fault and the PMMA fault. Nucleation of instability on the PMMA fault persistently occurred from one location 2/3 to 3/4 along the fault adjacent to a slow slip zone at the fault end, but nucleation on the gouge‐filled fault was more variable, nucleating at the ends and/or at approximately 2/3 along the fault, with precursory slip occurring over a large fraction of the fault. Nucleation correlated to regions of high average fault stress ratio τ/σ n, which was more variable for the gouge‐filled fault due to small length scale variations in normal stress caused by heterogeneous gouge compaction. Rupture velocities and slip rates were lower for the gouge‐filled fault than for the bare PMMA fault. Stick‐slip persisted when σ 2 was lowered and the nucleation zone length increased, expanding from the center to the sample ends before transitioning into instability.

Seismic Performance Evaluation of Steel Moment-Resisting Frames Designed According to 3rd and 4th Editions of 2800 Seismic Code

Current design codes have prepared linear analysis methods instead of nonlinear ones in order to reduce time, cost and other factors such as less need of these methods for expert knowledge. In linear analysis method, elastic strength demand of structure is decreased by applying a response modification factor called behavior factor (R) and by considering the design code regulations, structure members will be permitted to experience nonlinear response (in the time of middle-to-severe earthquakes). Because of different assumptions for linear (force-based method that has deficiencies) and nonlinear methods and whereas seismic stability or instability is not merely related to the strength of structure, rather it depends largely on the capability of structure to resist drifts, seismic performance evaluation of structures designed by linear procedure appears to be necessary using standards for evaluation. In this research, seismic performance of steel moment frames once designed based on 3rd edition of 2800-Iranian seismic code and allowable stress design (ASD) method and another time based on new ones, the 4th edition of 2800 seismic code and load and resistance factor design (LRFD) method, are compared with each other through nonlinear pushover and time-history analyses according to ASCE/SEI 41–13. Results showed positive change of design codes procedure with respect to alteration of design method in both types of ductile design, intermediate and special. Since mean of overstrength values and mean of ductility values have increased a little, mean of behavior factor values has become closer to the recommended values of the new seismic code. Also, a small number of structures met total collapse during nonlinear time-history analyses.

Energy-based seismic stability analysis of single-layer reticulated dome structures

Seismic stability of single-layer dome structures is closely related to both the external seismic ground motions and structural properties. The physical mechanism of seismic instability of single-layer reticulated dome structures is investigated from the perspective of energy, which can take into account both the external excitations and structural properties. First, the energy balance equation is established and the accuracy for calculating each energy component of structures is verified. Then, the energy-based criterion is introduced as a quantitative index for the identification of seismic stability/instability, where the first-passage of the intrinsic energy over the input energy demonstrates the seismic instability of single-layer reticulated dome structures. Besides, some qualitative indices are also employed to further confirm the judgement by the energy-based criterion. By using the proposed criterion, the critical peak ground acceleration for seismic stability of single-layer reticulated dome structures can be identified by using the incremental dynamic analysis. The energy-based criterion is also validated by comparisons with the B-R criterion. Parametric analyses are implemented to investigate the impacts of different structural parameters on seismic stability and characteristic responses of single-layer dome structures. • Seismic stability of single-layer reticulated dome structures relates to both structural parameters and external excitation. • An energy based criterion is introduced to identify the seismic instability. • The proposed criterion is validated by the comparison with the B-R criterion. • Parametric analyses are conducted to investigate the impacts of different parameters.

UNDRAINED CYCLIC SHEAR BEHAVIOR OF CLAY UNDER DRASTICALLY CHANGED LOADING RATE

The earthquake damage prediction is mainly focused on the seismic instability of sandy foundations although the clayey foundation could also be vulnerable to earthquake damage. Moreover, it is known that clayey soil shows a marked loading rate dependency in monotonic shear behavior due to its low permeability. Therefore, this paper aims to determine the undrained cyclic shear behavior of clayey soilunder a drastically changed loading rate. Reconstituted clayey samples were subjected to undrained cyclic triaxial compression/extension tests with loading rate from 1.0Hz to 0.0042Hz by stress control, and 0.01%/min by strain control. The cyclic loading was stopped when the double amplitude exceeded 5%. Then, the specimen was left for a while in an undrained condition, until the value of pore water pressure converged.Results revealed that as the loading rate decreases, the number of cycles that corresponds to DA=2% and 5% also decreased. Therefore, the degree of strain evolution varies depending on the loading rate and the undrained shear strength also varies depending on the cyclic loading rate. This is because when the cyclic loading rate was high; the pore water did not migrate sufficiently, leading to the non-uniform distribution of the excess pore water pressure inside the specimen. However, the final values of excess pore water pressure after the homogenization process was the same regardless of the loading rate. This means that if sufficient time is left after cyclic loading, the final mean effective stress value becomes equal regardless of the loading rate

Seismic fragility analysis of a High Arch Dam-Foundation System based on seismic instability failure mode

Seismic stability of concrete arch dams has always been a critical issue in seismic safety evaluation. In this paper, a high concrete arch dam is selected as a case study for the seismic fragility analysis based on instability failure mode. A comprehensive approach considering the opening and closing of contraction joint, probable sliding rock mass of dam abutments, the interface between the dam and foundation as well as the effect of foundation radiation damping is presented. The random and uncertain parameters containing the friction coefficients and cohesions are generated with Latin hypercube sampling method (LHS). The approximate IDA is performed, and the slippage and sliding area ratio are chosen as the engineer demand parameters (EDP). Different damage levels are identified by the slippage-based rule and sliding area ratio-based rule respectively according to their corresponding overall mean IDA curves. In addition, seismic fragility curves are developed for the defined damage levels. The results reveal that the damage levels defined based on different EDP-based rules could be different, while the ultimate capacity of the concrete arch dam reflected by selected EDPs are basically the same. Sliding area ratio-based rule can better reveal the whole process of sliding development of the arch dam abutment and the influence of residual cohesions. The existence of residual cohesion delays the sliding development and enhances the seismic stability of arch dam-foundation systems. Furthermore, a comparative analysis is performed based on the extended limit states. Seismic fragility analysis is of great significance for quantitatively evaluating the seismic performance of concrete dams from the probability point of view.

Susceptibility assessment of regional submarine landslides triggered by seismic actions

Submarine landslide and even its evolution to high-speed sliding masses can seriously threaten the safety of ocean engineering. Earthquakes are the most frequent trigger factors for landslides, and thus, seismic instability evaluation of submarine slopes has become a hot topic. However, the mechanism of submarine slope failures triggered by earthquakes is enormously complex. Although certain satisfactory results have been achieved in specific slopes, submarine landslides are still difficult to monitor and control, meaning that prevention-oriented research remains the mainstream. Regional slide predictive analyses of vast submarine slopes should be emphasized, but relevant research is notably rare. In this paper, a regional assessment methodology for submarine slope instabilities under seismic loads is proposed, and susceptibility mapping of landslides is established. First, considering the quasi-static bidirectional seismic action and the marine soil strength-weakening effect, an infinite slope sliding mode is used to establish the stability evaluation formula for a multiple soil-layer slope. Second, according to water depth data and GIS techniques, slope gradients are investigated, and the safety factors of submarine slopes located at specific stations are acquired. Furthermore, discrete stations are taken as sample points, and susceptibility mapping of submarine landslides is achieved using the inverse distance weighted and GIS techniques. Finally, regional seismic instability assessments of submarine slopes are conducted in the northeastern South China Sea, and various factors that influence submarine landslides are briefly discussed. This study offers an important basis for the development of marine resources and the risk assessments in ocean engineering.

Characteristics and Mechanism of Loess Landslides Induced by Strong Earthquake in The Loess Plateau of China

The Loess Plateau is the main loess distribution area in China with strong tectonic activity and frequent earthquakes. This paper systematically summarizes the characteristics and mechanism of loess landslides induced by strong earthquakes. The geometric characteristics of loess seismic landslide are gentle slope with 10°∼25°. The motion characteristics of earthquake-induced loess landslides are high-speed and long-distance. The distribution characteristics of loess seismic landslides are also basically consistent with the distribution of earthquake active region, and mainly distribute in loess hilly and gully area or the edges of the loess tableland. Based on the mechanism of seismic instability of loess slope, we consider that there are three types of loess landslides: seismic subsidence type, liquefaction type and tension-shear coupling type.

Seismic Stability Sensitivity and Uncertainty Analysis of a High Arch Dam-Foundation System

Parameter uncertainty associated with concrete arch dams always arises from modeling assumptions and the lack of knowledge or information of the engineering geological situations, especially in the seismic stability analysis of arch dams. In this research, a high arch dam is selected as a case study for probabilistic analysis of the seismic stability performance. The arch dam abutment and the dam are coupled as a system. A comprehensive approach considering contraction joints, boundaries of the probable sliding rock mass and the dam-foundation interface is presented. The contact nonlinearity is solved by using the dynamic contact model with Lagrange multiplier method. The main parameters of the probable sliding block are considered as random variables containing the friction coefficients and cohesions. Both the slippage and sliding area ratio are chosen as the engineering demand parameters (EDP). The sensitivity analysis is performed to reveal the relative influence of each parameter separately by the approximate incremental dynamic analysis (IDA) method. The friction coefficients are shown to be more crucial than the cohesions on the dam’s resistance to seismic instability. The sliding area ratio can be better used for unveiling the sliding process of the arch dam of concern, while the slippage is useful for one to judging the stability of the arch dam under seismic hazards. The Latin hypercube sampling (LHS) with approximate moment estimation is used to investigate the parameter uncertainty to the seismic stability performance of the high arch dam. The results provide a useful reference for using the median/mean-parameter model to accurately estimate the median/mean response of the dam.

Nucleation and Arrest of Dynamic Rupture Induced by Reservoir Depletion

AbstractSeismic events induced by the depletion of hydrocarbon reservoirs can cause damage to housing and cause societal and economic unrest. However, the factors controlling the nucleation and size of production‐induced seismic events are not well understood. Here we used geomechanical modeling of production‐induced stresses and dynamic rupture modeling to assess the conditions controlling down‐dip rupture size. A generic model of (offset) depleting reservoir compartments separated by a fault was modeled in 2‐D using the Finite Element package DIANA FEA. Linear slip‐weakening was used to control fault friction behavior. Fault reactivation was computed in a quasi‐static analysis simulating stresses during reservoir depletion, followed by a fully dynamic analysis simulating seismic rupture. The sensitivity of reactivation and rupture size to in situ stress, dynamic friction, critical slip distance, and reservoir offset was evaluated. After reactivation, a critical fault length was required to slip before seismic instability could occur. In a subsequent fully dynamic analysis the propagation and arrest of dynamic rupture was simulated. Rupture remained mostly confined to the reservoir interval but could also propagate into the overburden and underburden or sometimes transition into a run‐away rupture. Propagation outside the reservoir interval was promoted by a critical in situ stress, a large stress drop, a small fracture energy, and no or little reservoir offset. With increasing offset (up to the reservoir thickness), reactivation was promoted but dynamic rupture size decreased.