Earthquake-cycle deformation along the Kunlun fault constrained by GPS observations
Abstract
The Kunlun fault (KLF) is a major strike-slip fault that accommodates part of extrusion of the Tibetan plateau eastward. Several M>7 earthquakes in the past 100 years, including the most recent Mw7.8 2001 Kokoxili earthquake, ruptured most segments of the KLF except for the Xidatan-Dongdatan segment next to the 2001 rupture. Here we use continuous GPS data recorded across the Xidatan (XDT) segment since 2007, to re-revisit the earthquake-cycle deformation models constrained by both pre- and post-Kokoxili GPS data. We show that the XDT GPS "interseismic" velocities contain sharp asymmetric post-seismic transients of the 2001 event and have a potential to highlight the heterogeneity of mechanical properties across the KLF. We first consider elastic/viscoelastic block models without any lateral heterogeneity. Elastic models, with block rotation, back-slip, and afterslip on deep continuation of the fault segments that ruptured during past earthquakes explain both pre- and post-Kokoxili GPS velocities well. We next use viscoelastic block modeling approach in which steady block motion is punctuated by the instantaneous co-seismic deformation and the follow-up time-decaying deformation due to viscoelastic relaxation of the earthquake-induced stress. The times of the last earthquakes along the regional active faults are set according to the paleoseismological results. We systematically explore series of earthquake-recurrence intervals and viscosities. The preferred models fit the GPS data well, but long-term slip rates of some active faults are not well constrained due to trade-offs between parameters such as recurrence interval and slip rate for the KLF, and between block rotation and viscoelastic-correction term for the Altyn Tagh fault. In both models, if the contribution from afterslip in the elastic block models and viscoelastic relaxation effects in the viscoelastic block models are removed from the model predictions, the residuals at the XDT sites clearly show gentle asymmetric post-seismic transients due to left-lateral faulting.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.T43C0701L
- Keywords:
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- 9320 Asia;
- GEOGRAPHIC LOCATION;
- 7221 Paleoseismology;
- SEISMOLOGY;
- 8107 Continental neotectonics;
- TECTONOPHYSICS;
- 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS