1312 N Scottsdale Rd
Scottsdale, AZ 85257
Speaker: Mostafa Khoshmanesh, ASU SESE PhD Student
Topic: Insights into fault behavior and underlying processes from geodesy, seismology, and geology
Geodetic techniques, measuring the ground surface movements at sub-millimeter precision, provide the seismotectonics community with an imperative opportunity to study faulting behavior at unprecedented details. Provided by these observations, we are now aware that part of the tectonic stress is released through aseismic slip or creep. The spatial extent and rate of creep determines the fault earthquake potential. Also, the temporal variation of creep rate, so-called Slow Slip Events (SSE) are capable of triggering major earthquakes. Kinematic models developed to integrate seismic and geodetic observations, allow resolving the spatiotemporal distribution of creep on the fault surface, disregarding the underlying mechanism. Focusing on the Central San Andreas Fault (CSAF) as my primary study area, in this presentation I will explain the methods that I developed to study spatial and temporal evolution of fault creep. My results show that creep rate on CSAF is not steady and episodic SSEs are observed on the entire seismogenic depth in a semi-periodic manner. I will briefly discuss the possible underlying mechanisms to explain the observed SSEs. I conclude that transient elevation of water pressure trapped in intergranular pore spaces, due to compaction of material within the fault zone is a feasible mechanism for initiating SSEs on the CSAF. I will also provide evidence for the link between SSEs on the CSAF and earthquakes on neighboring locked zones, including the 2004 Mw6.0 Parkfield earthquake. Studies of this kind can greatly improve the probabilistic earthquake forecasts models by considering the periodicity of these SSEs over the conventional assumption of constant loading rate.
Mostafa Khoshmanesh is a PhD candidate in the School of Earth and Space Exploration at Arizona State University. He received his BA in surveying engineering in 2010 and MS in Geodesy in 2013, both from Iran. Since the beginning of his PhD in geological science in 2014, he has been a research assistant in Remote Sensing and Tectonic Geodesy Laboratory at ASU. His main area of interest is tectonic geodesy, with concentration on studying seismic and aseismic faulting processes. For this purpose he uses advanced Interferometric Synthetic Aperture Radar (InSAR) methods, combined with other geodetic, seismic, and geologic data set. His recent research on the time-dependent model of creep along the Central San Andreas Fault in California, has been published in high ranked Journal of Geophysical Research and is one of the most accessed articles in 2015.