Precursory seismicity changes prior to major earthquakes along the Sumatra-Andaman subduction zone: A region-time-length algorithm approach

Abstract

In this study, we investigated the precursory seismicity changes related to the major earthquakes posed along the Sumatra-Andaman subduction zone (SASZ) using the region-time-length (RTL) algorithm. Based on the suitable RTL characteristics of r 0 = 100 km and t 0 = 2 years, the anomalous RTL score representing the quiescence stage mostly started 0.1-5.2 years before the subsequent major earthquake, while no activation stage was illustrated. For the spatial investigation, the RTL anomalies also clearly illustrated the location of the subsequent major earthquakes. Thus, in order to determine the prospective areas of upcoming earthquakes, the series of RTL maps calculated during the recent 5-year (2010-2014) time span was used. The obtained results reveal four risk areas along the SASZ that might pose a major earthquake in the future, namely (i) Sittwe city, western Myanmar; (ii) offshore northern Nicobar Islands; (iii) Aceh city, northernmost of Sumatra Island; and (iv) offshore western Sumatra Island. Therefore, both a tsunami hazard in the Indian Ocean and a seismic hazard in the far-field cities should be recognized urgently.