Seismicity Controlled by a Frictional Afterslip During a Small‐Magnitude Seismic Sequence (ML < 5) on the Chihshang Fault, Taiwan. Issue 2 (28th February 2018)

• Record Type: Journal Article
• Authors: Canitano, Alexandre; Godano, Maxime; Hsu, Ya‐Ju; Lee, Hsin‐Ming; Linde, Alan T.; Sacks, Selwyn
• Is Part Of: Journal of geophysical research. Volume 123:Issue 2(2018)
• Page Start: 2003
• Page End: 2018
• Publication Date: 2018-02-28
• Subjects: afterslip -- Taiwan -- dilatometer -- Chihshang Fault -- seismic‐aseismic coupling; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2017JB015128
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: 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. Key Points: We present a rare observation of seismic‐aseismic fault coupling during a small‐magnitude seismic sequence ( M < 5) We show that the cumulative aseismic moment of the postseismic phase is at least equivalent to the coseismic moment of the sequence We estimate the frictional properties of the Chihshang Fault using the volumetric strain signal recorded during a shallow afterslip