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Published February 2018 | Supplemental Material
Journal Article Open

Source Characteristics of the 2016 Meinong (M_L 6.6), Taiwan, Earthquake, Revealed from Dense Seismic Arrays: Double Sources and Pulse‐like Velocity Ground Motion

Abstract

The 5 February 2016, Meinong, Taiwan, earthquake brought extensive damage to nearby cities with significant pulse‐like velocity ground motions. In addition to the spatial slip distribution determination using filtered strong‐motion data, we show that, with the advantage of the densely distributed seismic network as a seismic array, we can project the earthquake sources (asperities) directly using nearly unfiltered data, which is crucial to the understanding of the generation of the pulse‐like velocity ground motions. We recognize that the moderate but damaging M_L 6.6 Meinong earthquake was a composite of an M_w 5.5 foreshock and an M_w 6.18 mainshock with a 1.8–5.0 s time delay. The foreshock occurred at the hypocenter reported by the official agency, followed by the mainshock with a centroid located at 12.3 km to the north‐northwest of the hypocenter and at a depth of 15 km. This foreshock–mainshock composition is not distinguishable in the finite‐fault inversion because it filtered the seismic data to low frequencies. Our results show that the pulse‐like velocity ground motions are mainly attributed to the source of mainshock with its directivity and site effects, resulting in the disastrous damages in the city of Tainan. Although finite‐fault inversion using filtered seismic data for spatial slip distribution on the fault has been a classic procedure in understanding earthquake rupture processes, using a dense seismic network as a seismic array for unfiltered records helps us delineate the earthquake sources directly and provide more delicate information for future understanding of earthquake source complexity.

Additional Information

© 2018 Seismological Society of America. Manuscript received 4 June 2017; Published Online 2 January 2018. The authors appreciate the helpful comments from Associate Editor Michel Bouchon, three reviewers, Hiroo Kanamori, Victor C. Tsai, and Zachary E. Ross, who helped us improve this article. The authors thank Hsin‐Hua Huang at the Institute of Earth Sciences (IES), Academia Sinica, Taiwan, for providing Taiwan 3D velocity structure. Thanks to the Central Weather Bureau (CWB) for providing the Real‐Time Data (RTD) records and source parameters, including earthquake location and focal mechanism, of the Meinong earthquake. This research was supported by the Taiwan Earthquake Research Center (TEC), funded through the Ministry of Science and Technology (MoST) with Grant Numbers MOST 103‐2628‐M‐001‐004‐MY3 and MOST 106‐2119‐M‐008‐006. T.‐R. A. Song is supported by Natural Environment Research Council (NERC) Grant Number NE/P001378/1. The TEC Contribution Number for this article is 00140.

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Created:
August 19, 2023
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October 18, 2023