固体地球物理学术报告通知-Prof. Xiaowei Chen
The earthquake rate in Oklahoma has been dramatically increasing since 2009. Recent management efforts in disposal volume reduction led to reduction in seismicity rate since late 2015. Yet, three M5 earthquakes occurred in 2016 in Oklahoma, including the M5.0 Fairview earthquake in February, the M5.8 Pawnee earthquake in September, and the M5.1 Cushing earthquake in November. Are these earthquakes expected? What we know and we don’t know about induced earthquakes in Oklahoma? What other processes lead to induced seismicity besides fluid diffusion? In this study, we focus on the occurrence patterns of larger events, and demonstrates that full spectrum of earthquake triggering processes need to be considered in understanding the spatial-temporal evolutions of induced seismicity. I begin by an overview of occurrence patterns of earthquakes in Oklahoma, and their relationship with injection zones. Then, I focus on several individual sequences, including the Pawnee earthquake to demonstrate the complexity in triggering mechanism. Finally, I present results from coupled elastic stress modeling to show the effect of additional processes beyond fluid diffusion. These observations lead to the proposal that full spectrum of triggering processes needs to be considered for induced seismicity, and to unravel the occurrence of large earthquakes, detailed analysis of proceeding microearthquakes is of great importance.