3D Finite-Element Modeling of Dynamic Rupture and Aseismic Slip over Earthquake Cycles on Geometrically Complex Faults

2020 ◽  
Vol 110 (6) ◽  
pp. 2619-2637
Author(s):  
Bin Luo ◽  
Benchun Duan ◽  
Dunyu Liu
Keyword(s):  
Finite Element ◽  
Spontaneous Rupture ◽  
Recurrence Time ◽  
Thrust Faults ◽  
Earthquake Cycle ◽  
Fault Geometry ◽  
Aseismic Slip ◽  
Geometrically Complex ◽  
Dip Angle ◽  
Earthquake Cycles

ABSTRACT We develop a new dynamic earthquake simulator to numerically simulate both spontaneous rupture and aseismic slip over earthquake cycles on geometrically complex fault systems governed by rate- and state-dependent friction. The method is based on the dynamic finite-element method (FEM) EQdyna, which is directly used in the simulator for modeling 3D spontaneous rupture. We apply an adaptive dynamic relaxation technique and a variable time stepping scheme to EQdyna to model the quasi-static processes of an earthquake cycle, including the postseismic, interseismic, and nucleation processes. Therefore, the dynamic and quasi-static processes of an earthquake cycle are modeled in one FEM framework. Tests on a vertical strike-slip fault verify the correctness of the dynamic simulator. We apply the simulator to thrust faults with various dipping angles, which can be considered as the simplest case of geometrically complex faults by breaking symmetry, compared with vertical faults, to examine effects of dipping fault geometry on earthquake cycle behaviors. We find that shallower dipping thrust faults produce larger seismic slip and longer recurrence time over earthquake cycles with the same rupture area. In addition, we find an empirically linear scaling relation between the recurrence interval (and the seismic moment) and the sinusoidal function of the dip angle. The dip-angle dependence is likely due to the free-surface effect, because of broken symmetry. These results suggest dynamic earthquake simulators that can handle nonvertical dipping fault geometry are needed for subduction-zone earthquake studies.

scholarly journals Dynamic models of earthquake rupture along branch faults of the eastern San Gorgonio Pass region in California using complex fault structure

Geosphere ◽  
2020 ◽  
Vol 16 (2) ◽  
pp. 474-489 ◽  
Author(s):  
Roby Douilly ◽  
David D. Oglesby ◽  
Michele L. Cooke ◽  
Jennifer L. Hatch
Keyword(s):  
Finite Element ◽  
Los Angeles ◽  
Southern California ◽  
San Andreas Fault ◽  
Recurrence Time ◽  
Fault Geometry ◽  
Regional Stress ◽  
Coachella Valley ◽  
San Andreas ◽  
Valley Segment

Abstract Geologic data suggest that the Coachella Valley segment of the southern San Andreas fault (southern California, USA) is past its average recurrence time period. At its northern edge, this right-lateral fault segment branches into the Mission Creek and Banning strands of the San Andreas fault. Depending on how rupture propagates through this region, there is the possibility of a throughgoing rupture that could lead to the channeling of damaging seismic energy into the Los Angeles Basin. The fault structures and potential rupture scenarios on these two strands differ significantly, which highlights the need to determine which strand provides a more likely rupture path and the circumstances that control this rupture path. In this study, we examine the effect of different assumptions about fault geometry and initial stress pattern on the dynamic rupture process to test multiple rupture scenarios and thus investigate the most likely path(s) of a rupture that starts on the Coachella Valley segment. We consider three types of fault geometry based on the Southern California Earthquake Center Community Fault Model, and we create a three-dimensional finite-element mesh for each of them. These three meshes are then incorporated into the finite-element method code FaultMod to compute a physical model for the rupture dynamics. We use a slip-weakening friction law, and consider different assumptions of background stress, such as constant tractions and regional stress regimes with different orientations. Both the constant and regional stress distributions show that rupture from the Coachella Valley segment is more likely to branch to the Mission Creek than to the Banning fault strand. The fault connectivity at this branch system seems to have a significant impact on the likelihood of a throughgoing rupture, with potentially significant impacts for ground motion and seismic hazard both locally and in the greater Los Angeles metropolitan area.

scholarly journals EQsimu: a 3-D finite element dynamic earthquake simulator for multicycle dynamics of geometrically complex faults governed by rate- and state-dependent friction

2019 ◽  
Vol 220 (1) ◽  
pp. 598-609 ◽  
Author(s):  
Dunyu Liu ◽  
Benchun Duan ◽  
Bin Luo
Keyword(s):  
Finite Element ◽  
Message Passing Interface ◽  
Fault System ◽  
Second Phase ◽  
Finite Element Code ◽  
Earthquake Cycle ◽  
Hexahedral Elements ◽  
Earthquake Simulator ◽  
State Dependent ◽  
Geometrically Complex

SUMMARY We develop a finite element dynamic earthquake simulator, EQsimu, to model multicycle dynamics of 3-D geometrically complex faults. The fault is governed by rate- and state-dependent friction (RSF). EQsimu integrates an existing finite element code EQdyna for the coseismic dynamic rupture phase and a newly developed finite element code EQquasi for the quasi-static phases of an earthquake cycle, including nucleation, post-seismic and interseismic processes. Both finite element codes are parallelized through Message Passing Interface to improve computational efficiency and capability. EQdyna and EQquasi are coupled through on-fault physical quantities of shear and normal stresses, slip-rates and state variables in RSF. The two-code scheme shows advantages in reconciling the computational challenges from different phases of an earthquake cycle, which include (1) handling time-steps ranging from hundredths of a second to a fraction of a year based on a variable time-stepping scheme, (2) using element size small enough to resolve the cohesive zone at rupture fronts of dynamic ruptures and (3) solving the system of equations built up by millions of hexahedral elements. EQsimu is used to model multicycle dynamics of a 3-D strike-slip fault with a bend. Complex earthquake event patterns spontaneously emerge in the simulation, and the fault demonstrates two phases in its evolution. In the first phase, there are three types of dynamic ruptures: ruptures breaking the whole fault from left to right, ruptures being halted by the bend, and ruptures breaking the whole fault from right to left. As the fault bend experiences more ruptures, the zone of stress heterogeneity near the bend widens and the earthquake sequence enters the second phase showing only repeated ruptures that break the whole fault from left to right. The two-phase behaviours of this bent fault system suggest that a 10° bend may conditionally stop dynamic ruptures at the early stage of a fault system evolution and will eventually not be able to stop ruptures as the fault system evolves. The nucleation patches are close to the velocity strengthening region. Their sizes on the two fault segments are different due to different levels of the normal stress.

Repeating earthquakes follow afterslip gradient in the aftermath of the 16th April 2016 M7.8 Pedernales earthquake in Ecuador

2021 ◽  
Author(s):  
Caroline Chalumeau ◽  
Keyword(s):  
Template Matching ◽  
Earthquake Forecasting ◽  
Double Difference ◽  
Recurrence Time ◽  
Fault Mechanics ◽  
Aseismic Slip ◽  
Earthquake Triggering ◽  
Repeating Earthquakes ◽  
Waveform Cross Correlation ◽  
One Year

<p>Repeating earthquakes are earthquakes that repeatedly break a single, time-invariant fault patch. They are generally associated with aseismic slip, which is thought to load asperities, leading to repeated rupture. Repeating earthquakes are therefore useful tools to study aseismic slip and fault mechanics, with possible applications to earthquake triggering, loading rates and earthquake forecasting.</p><p>In this study, we analyze one year of aftershocks following the 16<sup>th</sup> April 2016 Mw 7.8 Pedernales earthquake in Ecuador to find repeating families, using data recorded by permanent and temporary seismological stations. In our area, seismicity during both the inter-seismic and post-seismic periods has been previously linked to aseismic slip. We calculate waveform cross-correlation coefficients (CC) on all available catalogue events, which we use to sort events into preliminary families, using a minimum CC of 0.95. These events were then stacked and used to perform template-matching on the continuous data. In total, 376 earthquakes were classified into 62 families of 4 to 15 earthquakes, including 8 from the one-year period before the mainshock. We later relocated these earthquakes using a double-difference method, which confirmed that most of them did have overlapping sources.</p><p>Repeating earthquakes seem to concentrate largely around the areas of largest afterslip release, where afterslip gradient is the highest. We also find an increase in the recurrence time of repeating events with time after the mainshock, over the first year of the postseismic period, which highlights a possible timeframe for the afterslip’s deceleration. Our results suggest that while most repeating aftershocks are linked to afterslip release, the afterslip gradient may play a bigger role in determining their location than previously thought.</p>

Toward Advanced Earthquake Cycle Simulation

2009 ◽  
Vol 4 (2) ◽  
pp. 99-105
Author(s):  
Kazuro Hirahara ◽  
Keyword(s):  
Earthquake Cycle ◽  
Activity Data ◽  
Megathrust Earthquake ◽  
Friction Laws ◽  
Megathrust Earthquakes ◽  
Cycle Simulation ◽  
Simulation Based ◽  
Rate And State Friction ◽  
Earthquake Cycle Simulation ◽  
Earthquake Cycles

Recent earthquake cycle simulation based on laboratory derived rate and state friction laws with super-parallel computers have successfully reproduced historical earthquake cycles. Earthquake cycle simulation is thus a powerful tool for providing information on the occurrence of the next Nankai megathrust earthquake, if simulation is combined with data assimilation for historical data and recently ongoing crustal activity data observed by networks extending from the land to the ocean floor. Present earthquake cycle simulation assumes simplifications in calculation, however, that differ from actual complex situations. Executing simulation relaxing these simplifications requires huge computational demands, and is difficult with present supercomputers. Looking toward advanced simulation of Nankai megathrust earthquake cycles with next-generation petaflop supercomputers, we present 1) an evaluation of effects of the actual medium in earthquake cycle simulation, 2) improved deformation data with GPS and InSAR and of inversion for estimating frictional parameters, and 3) the estimation of the occurrence of large inland earthquakes in southwest Japan and of Nankai megathrust earthquakes.

scholarly journals Finite Element Analysis for Whole Machine of Link-Type Ladle Turret

2011 ◽  
Vol 2-3 ◽  
pp. 861-864
Author(s):  
Ling Ling Li ◽  
Guang Pu Xu ◽  
Bing Bing Cui
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bearing Capacity ◽  
Molten Steel ◽  
Mechanical Analysis ◽  
Maximum Displacement ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Capacity Calculation ◽  
Dip Angle

The mechanism withstands 220t high temperature molten steel. In case of damage, molten steel pours. There will be major security incidents. Therefore, it is necessary to calculate carrying capacity of the mechanism. However, the part of components of the mechanism is made up of a crisscross of steel plate. This is used to withstand the bending and stretching. If we rely on traditional mechanical analysis, a large number of simplifying must be adopted, and accuracy of the calculation can be reduced. Therefore, this paper uses the COSMOSWorks Plug-in of SolidWorks software to carry out finite element calculation of whole machine for the mechanism. It avoids these shortcomings mentioned above. And this makes bearing capacity calculation to be more close to the actual circumstances. And the results show that: (1) the maximum stress of parts in the mechanism is only 52.8Mpa and much less than permissible stresses of its materials. As a result, the mechanism has sufficient bearing capacity. (2) The maximum displacement of whole machine is 2.637 mm. And the displacement will cause dip angle when lifting molten steel and it is less than its allowable stiffness. Therefore, the deformation is to meet requirements for the mechanism. In conclusion, the finite element analysis of the whole machine avoids complex force analysis and simplification of structure. The calculation has high accuracy. It is one of effective methods in the design of intensity and stiffness of complex structures.

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