Large-Scale FE Simulation of Fault Dynamic Rupture with Slip-Weakening Friction Law

Geological observations show variations in fault-surface topography not only at large scale (segmentation) but also at small scale (roughness). These geometrical complexities strongly affect the stress distribution and frictional strength of the fault, and therefore control the earthquake rupture process and resulting ground-shaking. Previous studies examined fault-segmentation effects on ground-shaking, but our understanding of fault-roughness effects on seismic wavefield radiation and earthquake ground-motion is still limited.&#160;&#160;In this study we examine the effects of fault roughness on ground-shaking variability as a function of distance based on 3D dynamic rupture simulations. We consider linear slip-weakening friction, variations of fault-roughness parametrizations, and alternative nucleation positions (unilateral and bilateral ruptures). We use generalized finite difference method to compute synthetic waveforms (max. resolved frequency 5.75 Hz) at numerous surface sites&#160; to carry out statistical analysis.&#160;&#160;Our simulations reveal that ground-motion variability from unilateral ruptures is almost independent of&#160; distance from the fault, with comparable or higher values than estimates from ground-motion prediction equations (e.g., Boore and Atkinson, 2008; Campbell and Bozornia, 2008). However, ground-motion variability from bilateral ruptures decreases with increasing distance, in contrast to previous studies (e.g., Imtiaz et. al., 2015) who observe an increasing trend with distance. Ground-shaking variability from unilateral ruptures is higher than for bilateral ruptures, a feature due to intricate seismic radiation patterns related to fault roughness and hypocenter location. Moreover, ground-shaking variability for rougher faults is lower than for smoother faults. As fault roughness increases the difference in ground-shaking variabilities between unilateral and bilateral ruptures increases. In summary, our simulations help develop a fundamental understanding of ground-motion variability at high frequencies (~ 6 Hz) due small-scale geometrical fault-surface variations.

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3D linked megathrust, dynamic rupture and tsunami propagation and inundation modeling: Dynamic effects of supershear and tsunami earthquakes

10.5194/egusphere-egu21-15257 ◽

2021 ◽

Author(s):

Sara Aniko Wirp ◽

Alice-Agnes Gabriel ◽

Elizabeth H. Madden ◽

Maximilian Schmeller ◽

Iris van Zelst ◽

...

Keyword(s):

Subduction Zones ◽

Large Scale ◽

Dynamic Models ◽

Initial Conditions ◽

Poisson Ratio ◽

Fault Slip ◽

Moment Magnitude ◽

Dynamic Rupture ◽

S Wave ◽

Tsunami Propagation

Earthquake rupture dynamic models capture the variability of slip in space and time while accounting for the structural complexity which is characteristic for subduction zones. The use of a geodynamic subduction and seismic cycling (SC) model to initialize dynamic rupture (DR) ensures that initial conditions are self-consistent and reflect long-term behavior. We extend the 2D geodynamical subduction and SC model of van Zelst et al. (2019) and use it as input for realistic 3-dimensional DR megathrust earthquake models. We follow the subduction to tsunami run-up linking approach described in Madden et al. (2020), including a complex subduction setup along with their resulting tsunamis. The distinct variation of shear traction and friction coefficients with depth lead to realistic average rupture speeds and dynamic stress drop as well as efficient tsunami generation.&#160;We here analyze a total of 14 subduction-initialized 3D dynamic rupture-tsunami scenarios. By varying the hypocentral location along arc and depth, we generate 12 distinct unilateral and bilateral earthquakes with depth-variable slip distribution and directivity, bimaterial, and geometrical effects in the dynamic slip evolutions. While depth variations of the hypocenters barely influence the tsunami behavior, lateral varying nucleation locations lead to a shift in the on-fault slip which causes time delays of the wave arrival at the coast. The fault geometry of our DR model that arises during the SC model is non-planar and includes large-scale roughness. These features (topographic highs) trigger supershear rupture propagation in up-dip or down-dip direction, depending on the hypocentral depth.In two additional scenarios, we analyze variations in the energy budget of the DR scenarios. In the SC model, an incompressible medium is assumed (&#957;=0.5) which is valid only for small changes in pressure and temperature. Unlike in the DR model where the material is compressible and a different Poisson&#8217;s ratio (&#957;=0.25) has to be assigned. Poisson&#8217;s ratios between 0.1 and 0.4 stand for various compressible materials. To achieve a lower shear strength of all material on and off the megathrust fault and to facilitate slip, we increase the Poisson ratio in the DR model to &#957;=0.3 which is consistent with basaltic rocks. As a result, larger fault slip is concentrated at shallower depths and generates higher vertical seafloor displacement and earthquake moment magnitude respectively. Even though the tsunami amplitudes are much higher, the same dynamic behavior as in the twelve hypocenter-variable models can be observed. Lastly, we increase fracture energy by changing the critical slip distance in the linear slip-weakening frictional parameterization. This generates a tsunami earthquake (Kanamori, 1972) characterized by low rupture velocity (on average half the amount of s-wave speed) and low peak slip rate, but at the same time large shallow fault slip and moment magnitude. The shallow fault slip of this event causes the highest vertical seafloor uplift compared to all other simulations. This leads to the highest tsunami amplitude and inundation area while the wavefront hits the coast delayed compared to the other scenarios.

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FE simulation of ceiling deployment of a large-scale inflatable structure for tunnel sealing

Thin-Walled Structures ◽

10.1016/j.tws.2019.03.043 ◽

2019 ◽

Vol 140 ◽

pp. 272-293 ◽

Cited By ~ 1

Author(s):

Iole Pecora ◽

Eduardo M. Sosa ◽

Gregory J. Thompson ◽

Ever J. Barbero

Keyword(s):

Large Scale ◽

Fe Simulation ◽

Inflatable Structure

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A Linearized Bottom Friction Law for Large-Scale Oceanic Motions

Journal of Physical Oceanography ◽

10.1175/1520-0485(1972)002<0509:albflf>2.0.co;2 ◽

1972 ◽

Vol 2 (4) ◽

pp. 509-510 ◽

Cited By ~ 9

Author(s):

Claes Rooth

Keyword(s):

Large Scale ◽

Bottom Friction ◽

Friction Law

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Study on exit temperature evolution during extrusion for large-scale thick-walled Inconel 625 pipe by FE simulation

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-014-6354-x ◽

2014 ◽

Vol 76 (5-8) ◽

pp. 1421-1435 ◽

Cited By ~ 6

Author(s):

Li Dang ◽

He Yang ◽

Liang Gang Guo ◽

Wen da Zeng ◽

Jun Zhang

Keyword(s):

Large Scale ◽

Fe Simulation ◽

Temperature Evolution ◽

Inconel 625 ◽

Exit Temperature

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Stress, rigidity and sediment strength control megathrust earthquake and tsunami dynamics

10.31219/osf.io/9kdhb ◽

2020 ◽

Author(s):

Thomas Ulrich ◽

Alice-Agnes Gabriel ◽

Elizabeth Madden

Keyword(s):

Large Scale ◽

Computational Models ◽

Initial Conditions ◽

Regional Scale ◽

Structural Complexity ◽

Structural Heterogeneity ◽

Indian Ocean Tsunami ◽

Dynamic Rupture ◽

Earthquake Dynamics ◽

Trade Offs

Megathrust faults host the largest earthquakes on Earth which can trigger cascading hazards such as devastating tsunamis.Determining characteristics that control subduction zone earthquake and tsunami dynamics is critical to mitigate megathrust hazards, but is impeded by structural complexity, large spatio-temporal scales, and scarce or asymmetric instrumental coverage.Here we show that tsunamigenesis and earthquake dynamics are controlled by along-arc variability in regional tectonic stresses together with depth-dependent variations in rigidity and yield strength of near-fault sediments. We aim to identify dominant regional factors controlling megathrust hazards. To this end, we demonstrate how to unify and verify the required initial conditions for geometrically complex, multi-physics earthquake-tsunami modeling from interdisciplinary geophysical observations. We present large-scale computational models of the 2004 Sumatra-Andaman earthquake and Indian Ocean tsunami that reconcile near- and far-field seismic, geodetic, geological, and tsunami observations and reveal tsunamigenic trade-offs between slip to the trench, splay faulting, and bulk yielding of the accretionary wedge.Our computational capabilities render possible the incorporation of present and emerging high-resolution observations into dynamic-rupture-tsunami models. Our findings highlight the importance of regional-scale structural heterogeneity to decipher megathrust hazards.

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3D Linked Subduction, Dynamic Rupture, Tsunami, and Inundation Modeling: Dynamic Effects of Supershear and Tsunami Earthquakes, Hypocenter Location, and Shallow Fault Slip

Frontiers in Earth Science ◽

10.3389/feart.2021.626844 ◽

2021 ◽

Vol 9 ◽

Author(s):

Sara Aniko Wirp ◽

Alice-Agnes Gabriel ◽

Maximilian Schmeller ◽

Elizabeth H. Madden ◽

Iris van Zelst ◽

...

Keyword(s):

Subduction Zones ◽

Large Scale ◽

Slip Rate ◽

Building Blocks ◽

Fault Slip ◽

Tsunami Source ◽

Dynamic Rupture ◽

Earthquake Scenarios ◽

Sloping Beach ◽

Tsunami Amplitude

Physics-based dynamic rupture models capture the variability of earthquake slip in space and time and can account for the structural complexity inherent to subduction zones. Here we link tsunami generation, propagation, and coastal inundation with 3D earthquake dynamic rupture (DR) models initialized using a 2D seismo-thermo-mechanical geodynamic (SC) model simulating both subduction dynamics and seismic cycles. We analyze a total of 15 subduction-initialized 3D dynamic rupture-tsunami scenarios in which the tsunami source arises from the time-dependent co-seismic seafloor displacements with flat bathymetry and inundation on a linearly sloping beach. We first vary the location of the hypocenter to generate 12 distinct unilateral and bilateral propagating earthquake scenarios. Large-scale fault topography leads to localized up- or downdip propagating supershear rupture depending on hypocentral depth. Albeit dynamic earthquakes differ (rupture speed, peak slip-rate, fault slip, bimaterial effects), the effects of hypocentral depth (25–40 km) on tsunami dynamics are negligible. Lateral hypocenter variations lead to small effects such as delayed wave arrival of up to 100 s and differences in tsunami amplitude of up to 0.4 m at the coast. We next analyse inundation on a coastline with complex topo-bathymetry which increases tsunami wave amplitudes up to ≈1.5 m compared to a linearly sloping beach. Motivated by structural heterogeneity in subduction zones, we analyse a scenario with increased Poisson's ratio of ν = 0.3 which results in close to double the amount of shallow fault slip, ≈1.5 m higher vertical seafloor displacement, and a difference of up to ≈1.5 m in coastal tsunami amplitudes. Lastly, we model a dynamic rupture “tsunami earthquake” with low rupture velocity and low peak slip rates but twice as high tsunami potential energy. We triple fracture energy which again doubles the amount of shallow fault slip, but also causes a 2 m higher vertical seafloor uplift and the highest coastal tsunami amplitude (≈7.5 m) and inundation area compared to all other scenarios. Our mechanically consistent analysis for a generic megathrust setting can provide building blocks toward using physics-based dynamic rupture modeling in Probabilistic Tsunami Hazard Analysis.

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Stochastic Analysis of the Kamishiro Earthquake Considering a Dynamic Fault Rupture

Journal of Earthquake and Tsunami ◽

10.1142/s1793431118410099 ◽

2018 ◽

Vol 12 (04) ◽

pp. 1841009

Author(s):

Yuta Mitsuhashi ◽

Gaku Hashimoto ◽

Hiroshi Okuda ◽

Fujio Uchiyama

Keyword(s):

Large Scale ◽

Time History ◽

Strong Motion ◽

Bayesian Optimization ◽

Underground Structures ◽

Dynamic Rupture ◽

Motion Generation ◽

Nonlinear Fem ◽

Need To Evaluate ◽

Time Histories

In recent years, a new demand has appeared for evaluations of earthquake fault displacements, to address the need to evaluate the soundness of underground structures. Fault displacements are caused by the rupturing of earthquake source faults, and are investigated through the use of methods such as the finite difference method and the finite element method (FEM). We conducted dynamic rupture simulations on the Kamishiro Fault Earthquake using a nonlinear FEM, focused on time history of fault displacement and response displacement, and demonstrated an ability to simulate observed values to a certain extent. During these simulations, we created models of homogeneous faults using the ground as the solid element and fault planes as joint elements. Although we were able to roughly simulate displacement time histories, obstacles to achieving more precise simulations still exist. In this research, we conducted investigations to model strong motion generation areas (SMGA). We conducted a searching analysis using Bayesian optimization with SMGA distribution within faults as parameters, and estimated the optimal parameters for simulating time histories of displacement. In addition, we compared our results with estimations of SMGA derived from different methods, and demonstrated that our distributions qualitatively matched. In addition, we evaluated the stochasticity of response displacement considering the randomness of the parameter of the fault. To conduct the simulation, we introduced joint elements from Goodman et al. that had been expanded to the FEM code FrontISTR, which makes it possible to analyze large-scale models.

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The influence of heterogeneity on the strength and stability of faults

10.5194/egusphere-egu21-8058 ◽

2021 ◽

Author(s):

Daniel Faulkner ◽

John Bedford ◽

Nadia Lapusta ◽

Valère Lambert

Keyword(s):

Shear Stress ◽

Large Scale ◽

Small Scale ◽

Dynamic Rupture ◽

Slip Rates ◽

Average Shear Stress ◽

Lower Shear ◽

Scale Heterogeneity ◽

Fault Strength ◽

Average Shear

<div>Heterogeneity of fault zones is seen at all scales in nature. It may manifest itself in terms of the variability of material property distribution over the fault, of stress heterogeneity brought about by the history of previous earthquake ruptures, and of fault geometry. In this contribution, we consider the effect on fault strength and stability of small-scale heterogeneity in laboratory experiments and large-scale heterogeneity from numerical dynamic rupture modeling. In model laboratory faults at slow slip rates (0.3 and 3 microns/s), the area occupied by rate-weakening gouge (quartz) versus rate-strengthening gouge (clay) was systematically varied and the results compared with homogenized mixtures of the two gouges. We found that the heterogeneous experimental faults were weaker and less stable than their homogenized counterparts, implying that earthquake nucleation might be promoted by fault zone heterogeneity. In elasto-dynamic numerical simulations of sequences of earthquakes and aseismic slip based on rate and state friction but with enhanced dynamic weakening (EDW) through pore fluid pressurization, uniform material properties on the fault plane are assumed, and heterogeneity spontaneously develops by stress variations along the fault arising from differing histories of motion at points along the fault. In these models, ruptures spontaneously nucleate in favorably prestressed regions. Larger ruptures - that result in greater degrees of EDW - are capable of propagating through areas of lower shear stress that would arrest smaller events. This behavior leads to a relationship between rupture size and the average shear stress over the rupture plane before the earthquake occurs. Faults that host larger events may overall appear to be driven by lower average shear stress and hence appear &#8216;weaker&#8217;. It is clear that the apparent fault strength and stability is difficult to predict from either simple homogeneous gouge experiments, or from scaling up of these results. Heterogeneity at all scales will affect the slip behaviour of faults.</div>

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