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The 2013 and 2017 M s 5 Seismic Swarms in Jilin, NEChina: Fluid‐Triggered Earthquakes?
Author(s) -
Zhang Guangwei,
Lei Jianshe,
Sun Daoyuan
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 - 10.1029/2019jb018649
Subject(s) - swarm behaviour , geology , seismology , induced seismicity , earthquake swarm , hypocenter , focal mechanism , thrust fault , fault (geology) , seismic hazard , mathematical optimization , mathematics
Understanding the mechanism of moderate earthquake swarm is important for the time‐dependent hazard assessment. Five M s ≥ 5.0 earthquakes occurred between October and November 2013 in Qianguo, Jilin, a region with low seismicity in northeast China. After 4 years, two more M s > 5.0 earthquakes struck Ningjiang, Jilin. To investigate the swarm mechanism and the relationship between these two swarm activities, we determine the full moment tensor solutions for 12 M s > 3.5 earthquakes, including the seven M s ≥ 5.0 events. The focal mechanisms show that the 2013 M s ≥ 5.0 events mostly exhibit thrust compression with significant volume closure components, whereas the 2017 M s ≥ 5.0 earthquakes illustrate a dominated strike‐slip type. In order to explain such differences, we conduct double‐difference tomography in the study region. Our tomographic results reveal that both swarms are located in the low‐velocity zones and the fault materials exhibit structural variations along the strike, possibly indicating that the structural contrast could be critical for the variations in the focal mechanism and hypocenter migration. The faults provide pathways for the upward intrusion of fluids that control the distribution and migration of the swarm sequences. A long‐term fluid‐rock interaction could lead to the fault materials intensely fractured in the 2013 swarm area but relatively less damaged in the 2017 swarm area. We can conclude that fluids play an important role in triggering the two seismic swarms.