Analyzing Seismicity of the 2021 ML 4.9 Seogwipo Sea Earthquake in South Korea and Its Sequence by Using the Matched-Filter and the VEL/HYPOELLIPSE Methods

EasyChair Preprint 8085

Abstract

A moderate sized Seoqwipo earthquake (ML 4.9) occurred off-shore of southwest Jeju island, the largest volcanic island of the Republic of Korea, in December 2021 and it followed by several aftershocks. In the study area there were a few M3 events before the mainshock of ML 4.9 earthquake, and this was the first M4 class earthquake in the surrounding area since 1905. This event produced a maximum intensity V near Jeju island and III on the inland. To distinguish the seismicity and properties of the study area, we searched for more aftershocks within ten days after the mainshock with the Matched-Filter method. Then we detected about three times more events than the KMA (Korea Meteorological Administration) catalog. The 1-D velocity model has not been discovered yet for this area, so we used the VELELLIPSE location method for more accurate hypocentral parameters. This method is the combination of HYPOELLIPSE, one of the hypocentral inversion methods, and the velocity updating algorithm. After relocating the Seogwipo earthquake sequence, we found that the aftershocks distributed along the NE-SW direction which was corresponding to the strike of the mainshock according to the focal mechanism solution.

Keyphrases: Seismicity, aftershock detection, precise location, sea earthquake

@booklet{EasyChair:8085,
  author    = {Gyeongdon Chai and Jimin Lee and Hyewon Lee and Kyungmin Min and Mikyung Choi and Sun-Cheon Park},
  title     = {Analyzing Seismicity of the 2021 ML 4.9 Seogwipo Sea Earthquake in South Korea and Its Sequence by Using the Matched-Filter and the VEL/HYPOELLIPSE Methods},
  howpublished = {EasyChair Preprint 8085},
  year      = {EasyChair, 2022}}