scholarly journals Surface Displacement and Ground Motion from Dynamic Rupture Models of Thrust Faults with Variable Dip Angles and Burial Depths

2020 ◽  
Vol 110 (6) ◽  
pp. 2599-2618
Author(s):  
Sirena Ulloa ◽  
Julian C. Lozos
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Ground Motions ◽  
Ground Surface ◽  
Surface Displacement ◽  
Initial Stresses ◽  
Thrust Faults ◽  
Dynamic Rupture ◽  
Blind Thrust ◽  
Dip Angle

ABSTRACT Thrust-fault earthquakes are particularly hazardous in that they produce stronger ground motion than normal or strike-slip events of the same magnitude due to a combination of hanging-wall effects, vertical asymmetry, and higher stress drop due to compression. In addition, vertical surface displacement occurs in both blind-thrust and emergent thrust ruptures, and can potentially damage lifelines and infrastructure. Our 3D dynamic rupture modeling parameter study focuses on planar thrust faults of varying dip angles, and burial depth establishes a physics-based understanding of how ground motion and permanent ground surface displacement depend on these geometrical parameters. We vary dip angles from 20° to 70° and burial depths from 0 to 5 km. We conduct rupture models on these geometries embedded in a homogeneous half-space, using different stress drops but fixed frictional parameters, and with homogeneous initial stresses versus stresses tapered toward the ground surface. Ground motions decrease as we bury the fault under homogeneous initial stresses. In contrast, under tapered initial stresses, ground motions increase in blind-thrust faults as we bury the fault, but are still the highest in emergent faults. As we steepen dip angle, peak particle velocities in the homogeneous stress case generally increase in emergent faults but decrease in blind-thrust faults. Meanwhile, ground motion consistently increases with steepening dip angle under the stress gradient. We find that varying stress drop has a considerable scalar effect on both ground motion and permanent surface displacement, whereas changing fault strength has a negligible effect. Because of the simple geometry of a planar fault, our results can be applied to understanding basic behavior of specific real-world thrust faults.

Multicycle Simulation of Strike-Slip Earthquake Rupture for Use in Near-Source Ground-Motion Simulations

2021 ◽  
Author(s):  
Percy Galvez ◽  
Anatoly Petukhin ◽  
Paul Somerville ◽  
Jean-Paul Ampuero ◽  
Ken Miyakoshi ◽  
...  
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Slip Rate ◽  
Rupture Process ◽  
Earthquake Rupture ◽  
Rupture Velocity ◽  
Source Inversion ◽  
Dynamic Rupture ◽  
Wide Range ◽  
Source Scaling

ABSTRACT Realistic dynamic rupture modeling validated by observed earthquakes is necessary for estimating parameters that are poorly resolved by seismic source inversion, such as stress drop, rupture velocity, and slip rate function. Source inversions using forward dynamic modeling are increasingly used to obtain earthquake rupture models. In this study, to generate a large number of physically self-consistent rupture models, rupture process of which is consistent with the spatiotemporal heterogeneity of stress produced by previous earthquakes on the same fault, we use multicycle simulations under the rate and state (RS) friction law. We adopt a one-way coupling from multicycle simulations to dynamic rupture simulations; the quasidynamic solver QDYN is used to nucleate the seismic events and the spectral element dynamic solver SPECFEM3D to resolve their rupture process. To simulate realistic seismicity, with a wide range of magnitudes and irregular recurrence, several realizations of 2D-correlated heterogeneous random distributions of characteristic weakening distance (Dc) in RS friction are tested. Other important parameters are the normal stress, which controls the stress drop and rupture velocity during an earthquake, and the maximum value of Dc, which controls rupture velocity but not stress drop. We perform a parametric study on a vertical planar fault and generate a set of a hundred spontaneous rupture models in a wide magnitude range (Mw 5.5–7.4). We validate the rupture models by comparison of source scaling, ground motion (GM), and surface slip properties to observations. We compare the source-scaling relations between rupture area, average slip, and seismic moment of the modeled events with empirical ones derived from source inversions. Near-fault GMs are computed from the source models. Their peak ground velocities and peak ground accelerations agree well with the ground-motion prediction equation values. We also obtain good agreement of the surface fault displacements with observed values.

Dynamic Rupture Simulations of the 1920 Ms 8.5 Haiyuan Earthquake in China

2019 ◽  
Vol 109 (5) ◽  
pp. 2009-2020 ◽  
Author(s):  
Xiurong Xu ◽  
Zhenguo Zhang ◽  
Feng Hu ◽  
Xiaofei Chen
Keyword(s):  
Ground Motion ◽  
Intensity Distribution ◽  
Strong Ground Motion ◽  
Ground Surface ◽  
Peak Ground Velocity ◽  
The Tibetan Plateau ◽  
Dynamic Rupture ◽  
Seismogenic Fault ◽  
Maximum Displacement ◽  
Strong Ground

Abstract The Haiyuan fault is a major seismogenic fault on the northeastern edge of the Tibetan–Qinghai plateau. The 16 December 1920 Ms 8.5 Haiyuan, China, earthquake is the largest and most recent event along the eastern Haiyuan fault (the Haiyuan fault in the article). Because only a few near‐field seismic recordings are available, the rupture process remains unclear. To understand the source process and intensity distribution of the 1920 Haiyuan earthquake, we simulated the dynamic rupture and strong ground motion of said earthquake using the 3D curved‐grid finite‐difference method. Considering the differences in epicenter locations among various catalogs, we constructed two models with different source points. For each model, three versions with different fault geometries were investigated: one continuous fault model and two discontinuous fault models with different stepover widths (1.8 and 2.5 km, respectively). A dynamic rupture source model with a final slip distribution similar to that observed on the ground surface was found. The maximum displacement on the ground surface was ∼6.5  m. Based on the dynamic rupture model, we also simulated the strong ground motion and estimated the theoretical intensity distribution. The maximum value of the horizontal peak ground velocity occurs near Haiyuan County, where the intensity reaches XI. Without considering the site conditions, the intensity values in most regions, based on the dynamic scenarios, are smaller than the values from field investigation. In this work, we present physically based insights into the 1920 Haiyuan earthquake, which is important for understanding rupture processes and preventing seismic hazards on the northeastern boundary of the Tibetan plateau.

Source Modeling for Predicting Ground Motions and Permanent Displacements Very Close to the Fault Trace

2018 ◽  
Vol 12 (04) ◽  
pp. 1841005 ◽  
Author(s):  
Shinya Ikutama ◽  
Takeshi Kawasato ◽  
Yosuke Kawakami ◽  
Masahiro Nosho ◽  
Atsuko Oana ◽  
...  
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Ground Surface ◽  
Time History ◽  
Source Modeling ◽  
Seismogenic Layer ◽  
Seismic Fault ◽  
Strong Ground Motion Prediction ◽  
Fault Trace ◽  
Strong Ground

A conventional “recipe” for strong ground motion prediction has been applied to the seismic fault (deep fault; located within seismogenic layer). In order to perform assessments of strong ground motions and permanent displacements at sites very close to the fault trace, we proposed the method of modeling that takes the entire ruptured fault from the ground surface to the seismic fault into account. Our approach was validated by the simulation of observed records obtained at stations very close to the fault trace of the mainshock of the 2016 Kumamoto Japan, earthquake (Mw7.1). Also, through the ground motion assessment performed for a hypothetical strike-slip fault with a 90[Formula: see text] dip angle, we found that adding the shallow fault had virtually no effect on acceleration time history, but it had a clear effect on the fault-parallel component of velocity and displacement time histories in the area close to the fault trace.

scholarly journals Dynamic Rupture Modeling to Investigate the Role of Fault Geometry in Jumping Rupture Between Parallel‐Trace Thrust Faults

2019 ◽  
Vol 109 (6) ◽  
pp. 2168-2186 ◽  
Author(s):  
Paul Peshette ◽  
Julian Lozos ◽  
Doug Yule ◽  
Eileen Evans
Keyword(s):  
Near Field ◽  
Stress Conditions ◽  
Parameter Study ◽  
Thrust Faults ◽  
Dynamic Rupture ◽  
Long Distance ◽  
Fault Strength ◽  
Stress Changes ◽  
Dip Angle ◽  
3D Finite Element Method

Abstract Investigations of historic surface‐rupturing thrust earthquakes suggest that rupture can jump from one fault to another up to 8 km away. Additionally, there are observations of jumping rupture between thrust faults ∼50  km apart. In contrast, previous modeling studies of thrust faults find a maximum jumping rupture distance of merely 0.2 km. Here, we present a dynamic rupture modeling parameter study that attempts to reconcile these differences and determines geometric and stress conditions that promote jumping rupture. We use the 3D finite‐element method to model rupture on pairs of thrust faults with parallel surface traces and opposite dip orientations. We vary stress drop and fault strength ratio to determine conditions that produce jumping rupture at different dip angles and different minimum distance between faults. We find that geometry plays an essential role in determining whether or not rupture will jump to a neighboring thrust fault. Rupture is more likely to jump between faults dipping toward one another at steeper angles, and the behavior tapers down to no rupture jump in shallow dip cases. Our variations of stress parameters emphasize these toward‐orientation results. Rupture jump in faults dipping away from one another is complicated by variations of stress conditions, but the most prominent consistency is that for mid‐dip angle faults rupture rarely jumps. If initial stress conditions are such that they are already close to failure, the possibility of a long‐distance jump increases. Our models call attention to specific geometric and stress conditions where the dynamic rupture front is the most important to potential for jumping rupture. However, our models also highlight the importance of near‐field stress changes due to slip. According to our modeling, the potential for rupture to jump is strongly dependent on both dip angle and orientation of faults.

Near-Source Ground Motions and Their Variability Derived from Dynamic Rupture Simulations Constrained by NGA-West2 GMPEs

2021 ◽  
Author(s):  
Ľubica Valentová ◽  
František Gallovič ◽  
Sébastien Hok
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Synthetic Data ◽  
Ground Motion Prediction Equations ◽  
Dynamic Rupture ◽  
Motion Modeling ◽  
Mixed Effect ◽  
Effect Model ◽  
Stress Drops ◽  
Strong Ground

ABSTRACT Empirical ground-motion prediction equations (GMPEs) lack a sufficient number of measurements at near-source distances. Seismologists strive to supplement the missing data by physics-based strong ground-motion modeling. Here, we build a database of ∼3000 dynamic rupture scenarios, assuming a vertical strike-slip fault of 36×20  km embedded in a 1D layered elastic medium and linear slip-weakening friction with heterogeneous parameters along the fault. The database is built by a Monte Carlo procedure to follow median and variability of Next Generation Attenuation-West2 Project GMPEs by Boore et al. (2014) at Joyner–Boore distances 10–80 km. The synthetic events span a magnitude range of 5.8–6.8 and have static stress drops between 5 and 40 MPa. These events are used to simulate ground motions at near-source stations within 5 km from the fault. The synthetic ground motions saturate at the near-source distances, and their variability increases at the near stations compared to the distant ones. In the synthetic database, the within-event and between-event variability are extracted for the near and distant stations employing a mixed-effect model. The within-event variability is lower than its empirical value, only weakly dependent on period, and generally larger for the near stations than for the distant ones. The between-event variability is by 1/4 lower than its empirical value at periods >1  s. We show that this can be reconciled by considering epistemic error in Mw when determining GMPEs, which is not present in the synthetic data.

A Study of the Vibration Impact of Underground Circular Structure on the Surrounding Buildings

2011 ◽  
Vol 243-249 ◽  
pp. 2245-2249
Author(s):  
Qing Ren ◽  
Xue Liu
Keyword(s):  
Finite Element ◽  
Ground Motion ◽  
Ground Surface ◽  
Surface Displacement ◽  
Element Model ◽  
Artificial Boundary ◽  
Incident Wavelength ◽  
Circular Structure ◽  
Vibration Impact ◽  
The Finite Element Model

The finite element model with artificial boundary was used to simulate dynamic response of an underground circular structure (tunnel, cavern) and displacement of the ground surface under incidence of Rayleigh wave, and to quantitatively analyze the effects of incident wavelength, diameter of structure, and liner stiffness on ground surface displacement amplification. The numerical results show that, the surface displacement amplitude with a tunnel can be 1.3 times of that for the case of without the tunnel. It is suggested that the effects of a tunnel on ground motion should be considered when the tunnel is planned and designed.

scholarly journals Influence of the Site-Specific Component of Kappa on the Magnitude-Dependency of Within-Event Aleatory Variabilities in Ground-Motion Models

2020 ◽  
Vol 92 (1) ◽  
pp. 238-245
Author(s):  
Christopher Brooks ◽  
John Douglas
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Ground Motions ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Specific Component ◽  
Site Specific ◽  
Motion Models ◽  
Earthquake Ground Motions ◽  
Aleatory Variability

Abstract The aleatory-variability component (standard deviation) of a ground motion has a large influence on results of a probabilistic seismic hazard assessment. kappa, a measure of high-frequency attenuation, has site- and record-specific effects that have been suggested as reasons for observing heteroscedastic aleatory variability within earthquake ground motions. Specifically, kappa has been proposed as a reason why ground motions from small earthquakes are more variable than those from large earthquakes, which is modeled by magnitude-dependent within-event standard deviations in ground-motion prediction equations (GMPEs). In this study, we use ground motions simulated using the stochastic method to examine the influence of the site-specific component of kappa on aleatory variability of earthquake ground motions and examine the hypothesis that this could be a cause of the observed heteroscedasticity in this variability. We consider simulations with both fixed and continuous stress drop distributions and the site-specific component of kappa to demonstrate that variation in the stress drop parameter contributes minimally to magnitude-dependency, unlike the site-specific component of kappa, which causes significant magnitude-dependency. Variation in the site-specific component of kappa is, therefore, proposed to be at least partially responsible for the magnitude-dependency captured in the aleatory-variability components of some recent GMPEs. It is found, however, that the expected impact of the site-specific component of kappa on aleatory variability is much greater than modeled in these GMPEs, which suggests that there could be a mitigating effect that is not captured within the simulations (e.g., correlated inputs to the simulations).

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