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Shallow fault rupture of the Milun Fault in the 2018 Mw 6.4 Hualien earthquake; a high-resolution approach from optical correlation of Pleiades Satellite imagery

Yu-Ting Kuo, Yu Wang, James Hollingsworth, Shao-Yi Huang, Ray Y. Chuang, Chih-Heng Lu, Yi-Chun Hsu, Hsin Tung, Jiun-Yee Yen and Chung-Pai Chang
Shallow fault rupture of the Milun Fault in the 2018 Mw 6.4 Hualien earthquake; a high-resolution approach from optical correlation of Pleiades Satellite imagery
Seismological Research Letters (November 2018) 90 (1): 97-107

Abstract

We use high-resolution Pleiades optical satellite imagery to study the distribution and magnitude of fault slip along the Milun fault surface rupture, which broke during the 2018 Hualien earthquake (Mw 6.4) in eastern Taiwan. Correlation of pre- and postearthquake stereo Pleiades images reveals detailed 3D surface displacements along the 8-km-long Milun fault, with maximum approximately 1 m left-lateral offsets across the fault. Along the northern section of the Milun fault, our correlation results indicate a localized deformation zone, with offset values slightly larger than the maximum offsets reported in the field ( approximately 77 cm). To the south, the left-lateral offsets become increasingly distributed, producing arctangent shapes in displacement profiles crossing the fault. In places, the deformation zone reaches widths of 200+m and can be explained by a shallow east-dipping fault rupture extending from 2 to 3 km depth to 70-120 m below the surface. A very shallow coseismic rupture on the Milun fault is consistent with a shallow locking depth interpreted from previous geodetic analyses from the interseismic period. Despite a few highly discontinuous and irregular surface ruptures reported along the southern section of the fault, our results suggest the main fault slip (up to 1 m) stopped at very shallow depths below the surface, in which approximately 60% of the deformation may be accommodated as off-fault deformation (OFD). In this upper approximately 100 m of the crust, OFD may be promoted by a significant change in material strength, as the fault crosses from bedrock and/or consolidated sediments into weaker, water-rich, poorly consolidated alluvial sediments.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 90
Serial Issue: 1
Title: Shallow fault rupture of the Milun Fault in the 2018 Mw 6.4 Hualien earthquake; a high-resolution approach from optical correlation of Pleiades Satellite imagery
Affiliation: Academia Sinica, Institute of Earth Scieinces, Taipei, Taiwan
Pages: 97-107
Published: 20181107
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 48
Accession Number: 2019-002322
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N23°30'00" - N24°30'00", E121°15'00" - E121°40'00"
Secondary Affiliation: National Taiwan University, TWN, TaiwanUniversite Grenoble Alpes, FRA, FranceNational Dong Hwa University, TWN, TaiwanNational Central University, TWN, Taiwan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201903
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