Complex multifault geometry of the 2018 Mw 6.4 Hualien, Taiwan, offshore earthquake and its implications for seismic hazard and subduction boundary
Abstract
The 2018 Mw 6.4 Hualien offshore earthquake struck the Hualien city in eastern Taiwan along the surface rupture zones of the Milun fault (MLNF) and Lingding fault (LNDF), which have been proposed as the plate boundary of Eurasian plate and Philippine Sea plate. We collected the geodetic data from 24 continuous GNSS stations, 16 campaign-mode GNSS stations, a precise leveling route, and SAR images from Sentinel-1A & 1B satellites to estimate the coseismic surface displacement fields. The horizontal coseismic displacements are approximately 6.6-519.8 mm, indicating that the MLNF and LNDF are both left-lateral strike-slip faults. The vertical displacement pattern from leveling measurements indicate the major fault dipping to the west. The optimized modeling result shows two major fault planes, a deep west-dipping fault and a shallow east-dipping fault. These fault geometries are also comparable to the main shock and aftershock distribution of this event. Coseismic slip is concentrated at the depth of about 10 km with maximum slip of about 650 mm. The geodetic moment of the deep west-dipping fault is 7.35 x 1025 dyne-cm, corresponding to a moment magnitude of Mw 6.54 while the geodetic moment along the MLNF and LNDF is 9.41 x 1024 dyne-cm and Mw 5.95. Coulomb stress change caused by the coseismic source model indicates that the shallow east-dipping fault could be triggered by the deep major west-dipping fault. Comparing with the uplift of coastal line detected by the tide gauge during the 1951 M7 Hualien-Taitung earthquake sequence, we first proposed that the northern end of source faults of the 1951 event are same as this earthquake. Comparing with the source fault of the 2013 Rueisuei earthquake about 20-km south of this event, we proposed that the deep west-dipping seismogenic fault is the interface of the plate boundary, identifying the west boundary of the Philippine Sea plate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T32A..02C
- Keywords:
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- 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8107 Continental neotectonics;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS