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Surface Deformations and Rupture Processes Associated with the 2017 Mw 5.4 Pohang, Korea, Earthquake.

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Title: Surface Deformations and Rupture Processes Associated with the 2017 Mw 5.4 Pohang, Korea, Earthquake.
Authors: Jin-Hyuck Choi1 cjh9521@kigam.re.kr, Kyoungtae Ko1 kkt@kigam.re.kr, Yong Sik Gihm1 naress@kigam.re.kr, Chang Soo Cho1 nemex@kigam.re.kr, Hoonyol Lee2 hoonyol@kangwon.ac.kr, Seok Goo Song1 sgsong@kigam.re.kr, Eun-Seok Bang3 esbang@kigam.re.kr, Hong-Jin Lee4 leehj@kigam.re.kr, Han-Kyung Bae1 bhk1990@kigam.re.kr, Sung Won Kim1 sungwon@kigam.re.kr, Sung-Ja Choi1 sjchoi@kigam.re.kr, Sung Soon Lee4 gisyi@kigam.re.kr, Seung Ryeol Lee1 leesr@kigam.re.kr
Source: Bulletin of the Seismological Society of America. Apr2019, Vol. 109 Issue 2, p756-769. 14p.
Abstract: In November 2017, an Mw 5.4 earthquake with a shallow (~4 km) hypocenter occurred in the Pohang area, one of the most developing industrial cities in South Korea. This shock resulted in the costliest earthquake damages in modern Korean history. Immediately after the event, it was not easy to recognize the source fault due to the lack of clear coseismic surface ruptures but also the absence of previously mapped active faults around the epicenter. Based on satellite- and unmanned aerial vehicle (UAV)-derived images, with ground resolution higher than 0.5 m, and field observations, we investigate surface deformation such as sand blows and ground failures associated with the Pohang earthquake as well as bedrock fault exposures in the epicentral area. To better constrain the source fault and deformation mechanism, we combine both moment tensors with aftershock relocations and surface displacements estimated by Interferometric Synthetic Aperture Radar (InSAR). Our results indicate that (1) various types and distributions of secondary ground deformation were controlled by blind oblique-slip rupture; characterized by right-lateral and reverse-slip components, on a reactivated pre-existing segmented normal-fault system, and (2) local ground conditions could trigger or amplify ground deformations and their related earthquake damage. Our study highlights the importance of mapping the extent of coseismic deformation as well as the trace of active faults on improving seismic hazard assessments in the Korean Peninsula. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:In November 2017, an Mw 5.4 earthquake with a shallow (~4 km) hypocenter occurred in the Pohang area, one of the most developing industrial cities in South Korea. This shock resulted in the costliest earthquake damages in modern Korean history. Immediately after the event, it was not easy to recognize the source fault due to the lack of clear coseismic surface ruptures but also the absence of previously mapped active faults around the epicenter. Based on satellite- and unmanned aerial vehicle (UAV)-derived images, with ground resolution higher than 0.5 m, and field observations, we investigate surface deformation such as sand blows and ground failures associated with the Pohang earthquake as well as bedrock fault exposures in the epicentral area. To better constrain the source fault and deformation mechanism, we combine both moment tensors with aftershock relocations and surface displacements estimated by Interferometric Synthetic Aperture Radar (InSAR). Our results indicate that (1) various types and distributions of secondary ground deformation were controlled by blind oblique-slip rupture; characterized by right-lateral and reverse-slip components, on a reactivated pre-existing segmented normal-fault system, and (2) local ground conditions could trigger or amplify ground deformations and their related earthquake damage. Our study highlights the importance of mapping the extent of coseismic deformation as well as the trace of active faults on improving seismic hazard assessments in the Korean Peninsula. [ABSTRACT FROM AUTHOR]
ISSN:00371106
DOI:10.1785/0120180167