One-off deep crustal earthquake swarm in a stable intracontinental region of the southwestern Korean Peninsula

Tae Kyung Hong, Seongjun Park, Junhyung Lee, Dongchan Chung, Woohan Kim

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Abstract

A deep crustal strike-slip earthquake swarm that occurred in the intracontinental region of the southwestern Korean Peninsula is investigated. The earthquakes are detected using matched filter analysis. The hypocenters are then refined, showing more than 500 micro to small strike-slip earthquakes concentrated on a fault plane with dimensions of 500 m by 300 m at a depth of ~21 km. The low temperature in the source depth facilitates the seismicity. The earthquake swarm was transiently active for 15 days from 25 April 2020 to 12 May 2020, presenting a high seismicity rate with a Gutenberg-Richter b value of 2.01 (±0.05). The earthquake swarm began in the central area and expanded outward with time. The spatiotemporal seismicity distribution reflects bilateral rupture. The focal mechanism solutions suggest a left-lateral strike-slip fault with a strike of 103.6 ± 3.2 and a dip of 73.3 ± 11.7. The spatial distribution of seismicity generally agrees with the focal mechanism solutions. The orientation of the inverted stress field agrees with the ambient stress field, suggesting that the earthquake swarm occurred as a consequence of ambient lithostatic stress loading. Coulomb stress changes suggest that the stress increased in the directions of WNW-ESE and NNE-SSW from the fault. The transiently active earthquake swarm began to occur after the 2011 MW9.0 Tohoku-Oki megathrust earthquake, suggesting a rapid release of accumulated stress in response to changes in the properties of the medium caused by the megathrust earthquake.

Original languageEnglish
Article number106582
JournalPhysics of the Earth and Planetary Interiors
Volume308
DOIs
Publication statusPublished - 2020 Nov

Bibliographical note

Funding Information:
We thank Professor Vernon Cormier (editor) and two anonymous reviewers for constructive review comments. The seismic records were collected from Korean Meteorological Administration (KMA) and Korea Institute of Geoscience and Mineral Resources (KIGAM). This work was supported by the Korea Meteorological Administration Research and Development Program under grant KMI2018-02910. Additionally, this research was partly supported by the Basic Science Research Program of National Research Foundation of Korea (NRF-2017R1A6A1A07015374, NRF-2018R1D1A1A09083446).

Funding Information:
We thank Professor Vernon Cormier (editor) and two anonymous reviewers for constructive review comments. The seismic records were collected from Korean Meteorological Administration (KMA) and Korea Institute of Geoscience and Mineral Resources (KIGAM). This work was supported by the Korea Meteorological Administration Research and Development Program under grant KMI2018-02910 . Additionally, this research was partly supported by the Basic Science Research Program of National Research Foundation of Korea ( NRF-2017R1A6A1A07015374 , NRF-2018R1D1A1A09083446 ).

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

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