Aftershock decay analysis of the 5th August 2020 Sumba earthquake

Abstract

On 5^th August 2020, an earthquake occurred at Sumba and was felt by people who lived in Tambolaka, Waingapu, Waitabula, Bima with III MMI. Based on BMKG (Indonesian Agency for Meteorology, Climatology and Geophysics) analysis, the earthquake occurred at 15.27.12 WIB with magnitude (M) 5.2, depth 11km, epicenter at 9.82° S and 119.11°E. This earthquake was preceded by several foreshocks and produced hundreds of aftershocks. In this study, we estimated the earthquake decay using early aftershock data with 4 empirical scaling relations: 1) Omori’s law; 2) Mogi 1’s law; 3) Mogi 2’s law, and 4) Utsu’s law. The data were obtained from BMKG data repository. The results of this study are aftershocks estimated to end: on day 72 by the Omori’s law (r = 0.29), on day 522 by the Mogi I (r = 0.29), on day 29 by the Mogi 2 (r = 0.29) and on day 516 by the Utsu law (r = 0.29). The appropriate method for determining earthquake decay in the Sumba region is the Mogi 2 method with r = -0.63, i.e. the aftershocks will end on September 3^th, 2020. This was in good agreement with the data from BMKG, where the aftershock ended on September 2^nd, 2020.