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Seismicity Controlled by a Frictional Afterslip During a Small‐Magnitude Seismic Sequence ( M L < 5) on the Chihshang Fault, Taiwan
Author(s) -
Canitano Alexandre,
Godano Maxime,
Hsu YaJu,
Lee HsinMing,
Linde Alan T.,
Sacks Selwyn
Publication year - 2018
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 - 10.1002/2017jb015128
Subject(s) - aftershock , seismology , geology , hypocenter , magnitude (astronomy) , geodetic datum , moment magnitude scale , seismic moment , fault (geology) , induced seismicity , sequence (biology) , borehole , geodesy , foreshock , geometry , geotechnical engineering , physics , mathematics , astronomy , scaling , biology , genetics
We report evidence for frictional afterslip at shallow depths (about 5 to 7 km) during a small‐magnitude seismic sequence (with M L <5) along the Chihshang Fault, a main active structure of the Longitudinal Valley, in southeast Taiwan. The afterslip, which was recorded by a nearby borehole dilatometer, lasted about a month with a cumulative geodetic moment magnitude of 4.8 ± 0.2. The afterslip comprised two stages and controlled the aftershock sequence. The first postseismic stage, which followed a M L 4.6 earthquake, lasted about 6 h and mostly controlled the ruptures of neighboring asperities (e.g., multiplets) near the hypocenter. Then, a 4 week duration large afterslip event following a M L 4.9 earthquake controlled the rate of aftershocks during its first 2 days through brittle creep. The study presents a rare case of simultaneous seismological and geodetic observations for afterslip following earthquakes with magnitude lower than 5. Furthermore, the geodetic moment of the postseismic phase is at least equivalent to the coseismic moment of the sequence.