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  • Results from simulations of earthquake rupture in fault zones with along-strike heterogeneity

    work
    Creator:
    Huang, Yihe
    Description:
    Geological and geophysical observations reveal along-strike fault zone heterogeneity on major strike-slip faults, which can play a significant role in earthquake rupture propagation and termination. I present 2D dynamic rupture simulations to demonstrate rupture characteristics in such heterogeneous fault zone structure. The modeled rupture is nucleated in a damaged fault zone and propagates on a preexisting fault towards the zone of intact rocks. There is an intermediate range of nucleation lengths that only allow rupture to spontaneously propagate in the damaged fault zone but not in a homogeneous medium. I find that rupture with an intermediate nucleation length tends to stop when it reaches the zone of intact rocks, especially when the rupture propagation distance in the damaged fault zone is relatively short and when the damaged fault zone is relatively narrow or smooth in the fault-normal direction. Pronounced small-scale heterogeneity within the damaged fault zone also contributes to such early rupture termination. In asymmetric fault zones bisected by a bimaterial fault, rupture moving in the direction of slip of faster rocks tends to terminate under the same conditions as in symmetric fault zones, whereas rupture moving in the direction of slip of slower rocks can penetrate into the zone of intact rocks. Break-through rupture is allowed when a sufficiently-large asperity is located at the edge of the zone of intact rocks. The results suggest the along-strike fault zone heterogeneity can play a critical role in seismicity distribution. The data set contains multiple folders of simulation results from the SEM2DPACK that demonstrate the above findings. The folder name includes the model parameters in each simulation as explained in the README file. The Flt01_sem2d.data file in the folder documents the slip, slip rate and stresses from each simulation. The files are also explained in the manual of SEM2DPACK ( http://web.gps.caltech.edu/~ampuero/soft/users_guide_sem2dpack.pdf). Please refer to section 4.6 in the manual and use “sem2d_read_fault.m” in the POST folder of SEM2DPACK to plot the results.
    Keyword:
    Damaged fault zone, fault zone heterogeneity, earthquake rupture termination, and seismicity distribution
    Discipline:
    Science