北京大学地球物理星期五报告会

Exploring frictional property of San Andreas Fault and the implication for seismic hazard

圣安德烈斯断层摩擦属性、行为研究

及其在地震危险评估中的意义

王 丽 凤 博士

中国地震局地质研究所

时间：2020年10月9日（星期五）15:00

地点：北京大学理科2号楼2821W    

欢迎各位老师同学参加

内容简介： Understanding the physical control along the fault is important from the perspective of both seismic hazard evaluation and fault zone rheology. Parkfield segment as a transition from creeping to locking along the San Andreas Fault is marked by, besides the periodic M6 earthquakes, abundant deep low frequency earthquakes and deep slow slip event. In the framework of rate-and-state friction law, we use the long-term GPS data measured before, during and after the 2004 M6 earthquake to determine the frictional parameter. The data resolve apparent along-strike variation of friction parameter in the brittle upper crust ^[1]. On the other hand, the concurrent deep low frequency earthquake and slow slip event in Parkfield challenge our classical understanding of fault zone rheology, in which the middle crust is associated with stable creep that preventing stress accumulation. However, taking shear heating during fault sliding into account, temperature-weakening effect in friction strength may lead to fault instability. Therefore, we consider rate-state-temperature dependent friction to model the deep fault behaviors in Parkfield. The results well explain the behavior of deep fault instabilities. The simulated deep faulting could locally rise the temperature by hundreds of degree, reaching the condition for partial melting of wet granite, which provides an alternative physical understanding for pseudotachylite observed below the seismogenic zone ^[2].

[1] L. Wang, The Next M~6 Event in Parkfield Implied by a Physical Model Linking Interseismic, Coseismic, and Postseismic Phase. J. Geophys. Res. Solid Earth. 123, 8858–8873 (2018).

[2] L. Wang, S. Barbot, Excitation of San Andreas tremors by thermal instabilities below the seismogenic zone, Science Advances (2020).

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