Abstract
From 26 April to 8 May 2020, an earthquake sequence occurred in the Haenam region in southwestern Korea. The main shock with a moment magnitude of 3.2 occurred on 3 May. It was preceded by 38 foreshocks that occurred over a week, with magnitudes ranging from 0.8 to 2.7, and was followed for another week by 35 aftershocks with magnitudes ranging from 0.5 to 2.4. The P-wave first-motion indicates that the focal mechanism of the mainshock was a strike of 193° or 102°, a dip of 83° or 78°, and a rake of –168° or –7°. The stress orientation of the focal mechanism is consistent with the regional tectonic stress field. Spectral analysis of the mainshock indicates that it occurred on a fault with a radius of 216 ± 4.58 m and a stress drop of 31.4 ± 2.35 bar. The hypocenters of the sequence, determined using the double-difference method, were shown to cluster along a trend striking 100° and dipping 65° to the south at a depth of 20.1 ± 0.05 km, which indicates that the earthquakes in the sequence occurred within a rupture radius of the mainshock. Detailed seismic analysis of the sequence indicates that closely located subfaults or small weak zones were related to the mainshock.
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Acknowledgments
The author would like to thank Dahyun Kwak, Hyeji Lee, and SeongJin Kim for helping with the acquisition of waveform data, and the Korea Meteorological Administration for providing the microearthquake catalog and making seismograms available. The author is also grateful to Min Huh and Jongyun Jung, who provided information about the geological background for the epicentral region. This work was funded by the Korea Meteorological Administration under Grant KMI2018-00911.
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Sheen, DH. Analysis of the 2020 Haenam, Korea, earthquake sequence. Geosci J 25, 33–42 (2021). https://doi.org/10.1007/s12303-020-0038-3
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DOI: https://doi.org/10.1007/s12303-020-0038-3