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Seismological Investigations of Induced Earthquakes Near the Hutubi Underground Gas Storage Facility
Author(s) -
Zhou Pengcheng,
Yang Hongfeng,
Wang Baoshan,
Zhuang Jiancang
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb017360
Subject(s) - induced seismicity , seismology , geology , poromechanics , tectonics , aftershock , fault (geology) , pore water pressure , geotechnical engineering , porous medium , porosity
The Hutubi underground gas storage facility in Xinjiang, China, with a maximum gas storage capacity of 10.7 billion m 3 , provides a good opportunity to study seismicity potentially induced by the annually cyclic injection and extraction of natural gas. To statistically distinguish induced seismicity from the tectonic background, we investigate the background seismicity probability of each event using the space‐time epidemic‐type aftershock sequence model and a stochastic declustering method. Our statistical results suggest a potential link between gas injection and two groups of seismicity, with very low background seismicity probabilities during the first and second injection periods in August 2013 and May 2014, respectively. To better understand the earthquake physics, we relocate earthquakes by incorporating a dedicated mobile seismic network after refining the regional 1D velocity model by utilizing an artificial source. After double‐difference relocations, those two groups of earthquakes move much closer to the faults bounding the rock storage units and are situated at a depth around 4 km, slightly deeper than the reservoir formation. Focal mechanism solutions of the two largest earthquakes ( M w 2.8 and 3.0) in August 2013 show a possibly unmapped reverse fault gently dipping to the south. Based on our high‐resolution earthquake locations, we propose that these on‐fault earthquakes are not hydrologically connected with the reservoir formation but are likely induced by poroelastic stress perturbations due to gas injection. Poroelastic stressing can have a larger impact on seismicity rate than pore pressure diffusion at large distances; hence, the distributions and sizes of preexisting faults might play a key role in seismic hazard assessments in our study region.