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https://doi.org/10.5194/egusphere-2024-1696
https://doi.org/10.5194/egusphere-2024-1696
08 Aug 2024
 | 08 Aug 2024

Quaternary surface ruptures of the inherited mature Yangsan fault: implications for intraplate earthquakes in Southeastern Korea

Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, and Moon Son

Abstract. Earthquake prediction in intraplate regions, such as South Korea, is challenging due to the complexity of fault zones. This study employed diverse methods and data sources to detect Quaternary surface rupturing along the Yangsan Fault to improve seismic hazard assessment. Paleoseismic data were analyzed to reveal insights into seismic activity, displacement, and structural patterns. Observations from five trench sites indicate at least three faulting events during the Quaternary, with the most recent surface rupturing occurring approximately 3,000 years ago. These events resulted in a cumulative displacement of 3.1–94.0 m and maximum estimated magnitude of 6.7–7.2. The average slip rate of 0.14 mm/yr suggests a quasi-periodic model with possible recurrence intervals exceeding 10,000 years. The structural patterns imply the reactivation of a pre-existing fault core with top-to-the west geometry, causing a dextral strike-slip with a minor reverse component. This study underscores the continuous faulting along the inherited mature fault, the Yangsan Fault, since at least the Early Pleistocene, contributing valuable insights for seismic hazard assessment in the region and offering a broader understanding of intraplate earthquake dynamics for earthquake prediction.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, and Moon Son

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1696', Anonymous Referee #1, 11 Aug 2024
    • AC2: 'Reply on RC1', Moon Son, 02 Nov 2024
  • RC2: 'Comment on egusphere-2024-1696', Anonymous Referee #2, 18 Sep 2024
    • AC1: 'Reply on RC2', Moon Son, 01 Nov 2024
Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, and Moon Son
Sangmin Ha, Hee-Cheol Kang, Seongjun Lee, Yeong Bae Seong, Jeong-Heon Choi, Seok-Jin Kim, and Moon Son

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Short summary
Unlike episodic plate boundary earthquakes, their randomness makes predicting intraplate earthquakes challenging. This study aids seismic hazard assessment by analyzing paleoearthquake records of the Yangsan Fault in Korea. Five trench sites revealed three Quaternary surface-rupturing earthquakes, the latest 3,000 years ago, with Mw 6.7–7.2. The right lateral fault has a 0.14 mm/yr slip rate, and a recurrence interval over 10,000 years, continuously active since the Quaternary.