Title: Fault-valve behaviour and episodic gas flow in overpressured aquifers - evidence from the 2010 Ms5.1 isolated shallow earthquake in Sichuan Basin, China
Authors: Xinglin Lei; Shengli Ma; Xiaolong Wang; Jinrong Su
Addresses: Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, AIST Central #7, Higashi 1-1-1, Tsukuba, Ibaraki, 305-8567, Japan; State Key Laboratory of Earthquake Dynamics, China Earthquake Administration, Institute of Geology, Beijing 100029, China ' State Key Laboratory of Earthquake Dynamics, China Earthquake Administration, Institute of Geology, Beijing 100029, China ' Chonqing Earthquake Administration, Chongqing 401147, China ' Sichuan Earthquake Administration, Chengdu 610041, Sichuan-Province, China
Abstract: We investigated the 2010 Ms5.1 Suining earthquake (a temporally and spatially isolated event) centred in Moxi gas field in the tectonically stable central region of Sichuan Basin, China. The focal depth is estimated to be approximately 2.8 km and thus the earthquake is nucleated in Triassic marine sediment, coincident with the depths of the top boundary of an overpressured gas reservoir. The strike/dip/rake of the estimated source fault is 223/48/122, showing a rupture area of a dimension of ∼2.4 km along a blind reverse fault in agree with the geological structures and regional stress regime of this area. Through an integrated analysis, we propose that the associated fault slip of this earthquake was most probably initiated and driven by gas injection from the underlying overpressured reservoir into the shallower gas reservoirs. No aftershocks following the Suining earthquake indicates that the gas injection from the deeper reservoir is somewhat episodic and a fault-valve behaviour.
Keywords: overpressured reservoirs; fault valve behaviour; episodic fluid flow; numerical simulation; overpressured aquifers; shallow earthquakes; China; gas fields; tectonically stable regions; gas reservoirs; fault slip; gas injection.
Progress in Computational Fluid Dynamics, An International Journal, 2017 Vol.17 No.1, pp.2 - 12
Published online: 23 Jan 2017 *