Spatio-temporal evolution of the 2020 Haenam, Korea, earthquake sequence

Abstract:

From 26 April to 23 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. After two weeks of a quiescence period, a M_W 1.5 earthquake occurred on 23 May. 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 km ± 0.05 km, which indicates that the earthquakes in the sequence occurred within a rupture radius of the mainshock. Furthermore, the cross-section shows that the distribution of the events is bent at a depth of the mainshock and decreases in dip by up to about 15%, indicating that the mainshock had a complex fault geometry. With regard to spatiotemporal evolution, the sequence started from the middle of the west part of the mainshock. The foreshocks propagated east-southeastward and scattered on a horizontally elongated plane along a line striking 100°. Following the mainshock on 3 May, aftershocks spread downward and throughout the rupture area over two days. From May 5, they moved back to the western tip of the rupture area.