Three-dimensional curved grid finite-difference modelling for non-planar rupture dynamics

The 2015 Mw 7.8 Gorkha earthquake has drawn interest due to its complex fault geometry. Both geodetic and geologic studies have focused on the dip variations. In this study we invert the coseismic geodetic data for the 2‐D dip variations of the earthquake. The best fit model confirms that the dip varies with depth, and suggests that there is a significant lateral dip anomaly along strike. The depth‐dependent dip variation suggests that the earthquake ruptured a ramp‐flat fault. The shallow ramp may have prevented the rupture breaking through the surface. In addition, a lateral large‐dip anomaly is found in the northeastern corner of the slip area, which supports the previous findings of inferred interseismic fault coupling, coseismic high‐frequency radiations, and the aftershock mechanisms. This lateral dip anomaly is likely associated with local tearing within the Indian slab. It may have blocked the east‐southeastward rupture propagations of the Gorkha earthquake, implying important controls on the earthquake scale and the spatial limits of ruptures.

Section: Discussionmentioning

confidence: 94%

Significant lateral dip changes may have limited the scale of the 2015 M_w 7.8 Gorkha earthquake

Yong

Wang

Walter

et al. 2017

“…The fault is governed by a simple slip‐weakening friction law [ Ida , ], for which the shear strength is given by

τ (δ) = ({, \begin{matrix} (μ_{s} - (μ_{s} - μ_{d}) δ / d_{0}) σ_{n}, & δ \leq d_{0}, \\ μ_{d} σ_{n}, & δ > d_{0}, \end{matrix})

where σ n is the normal stress, μ s is the static friction coefficient, μ d is the dynamic friction coefficient, δ is slip distance, and d 0 is the critical slip distance. We solve the elastodynamic equations coupled with the friction law (equation ) by using a finite‐difference method that was introduced and validated by Zhang et al [, ].…”

Section: Methods and Modelsmentioning

confidence: 69%

The effects of barriers on supershear rupture

Zhang

Chen

2016

Self Cite

A barrier may induce a supershear rupture transition in some cases, whereas it may prevent the further propagation of a supershear rupture in other cases. We investigate the effects of a barrier on the supershear rupture propagation on a planar fault in a 3‐D half‐space. Our results show that the effect of a barrier on supershear is strongly dependent on its size, strength, and location. For larger sizes, shallower buried depths, and relatively higher strengths, the barrier tends to prevent supershear propagation more strongly. When the barrier is located on the free surface and near the critical distance, it prevents the further propagation of supershear rupture. If a barrier is located far from the critical distance, the first supershear daughter crack is slowed down and a new supershear daughter crack is generated after the rupture front passes through the barrier. This mechanism greatly lengthens the supershear transition distance.

“…The final slip at the peak of a hill is larger than that at the bottom of a canyon. This effect of topography on the distribution of the final slip has been discussed by Zhang et al []. The amplified and reduced slip caused by hill‐ and canyon‐shaped topographies, respectively, can influence the subshear‐to‐supershear transition, as discussed in the next section.…”

Section: Resultsmentioning

confidence: 99%

“…The effect of surface topography on a rupture is significant, as demonstrated by Ely et al [] in their modeling of the rupture of the southern San Andreas Fault. Our preliminary results [ Zhang et al , ] indicate that an irregular free surface can change the rupture style and that both the hill‐ and canyon‐shaped topographies can delay or prevent the subshear‐to‐supershear transition. To obtain detailed conclusions about this effect, we perform additional simulations with a larger number of example cases in this study.…”

Section: Introductionmentioning

confidence: 99%

The supershear effect of topography on rupture dynamics

Zhang

Chen

2016

Self Cite

The Earth's free surface is a critical boundary for dynamic rupture propagation that plays an important role in influencing rupture patterns, especially the subshear‐to‐supershear transition. Surfaces with irregular topographies, which are prevalent in nature, may change this supershear transition mechanism. Using the curved grid finite‐difference method, which can be employed to solve elastodynamic equations in curvilinear coordinates, we model spontaneous dynamic rupture on faults with irregular free surfaces. We investigate its effect on the dynamic rupture process with extensive numerical simulations. The simulated results show that the effect of topography on a rupture is dependent on the shape and epicentral distance of the topography.