Implications for megathrust earthquakes and tsunamis from seismic gaps south of Java Indonesia

S Widiyantoro,J Mori,A Muhari,N R Hanifa,N Rawlinson,H E Putra,A D Nugraha,P Supendi,H A Shiddiqi,E Gunawan,S Susilo

doi:10.1038/s41598-020-72142-z

Abstract

Relocation of earthquakes recorded by the agency for meteorology, climatology and geophysics (BMKG) in Indonesia and inversions of global positioning system (GPS) data reveal clear seismic gaps to the south of the island of Java. These gaps may be related to potential sources of future megathrust earthquakes in the region. To assess the expected inundation hazard, tsunami modeling was conducted based on several scenarios involving large tsunamigenic earthquakes generated by ruptures along segments of the megathrust south of Java. The worst-case scenario, in which the two megathrust segments spanning Java rupture simultaneously, shows that tsunami heights can reach ~ 20 m and ~ 12 m on the south coast of West and East Java, respectively, with an average maximum height of 4.5 m along the entire south coast of Java. These results support recent calls for a strengthening of the existing Indonesian Tsunami Early Warning System (InaTEWS), especially in Java, the most densely populated island in Indonesia.

Highlights

Seismic gaps off the southwest coast of Sumatra, which pose a risk for generating future megathrust events, have been studied in detail (e.g., Refs.[1,2,3,4])
We use new data taken from the Indonesian Tsunami Early Warning System (InaTEWS) catalog reported by BMKG, together with data from the International Seismological Centre (ISC) catalog, to investigate the potential for megathrust earthquakes and consequent tsunamis south of Java
Okal[23] presented a detailed study of the 1921, 1937 and 1943 intraplate earthquakes south of Java, and found that the Java subduction zone lacks large interplate thrust events for the entire era of instrumental seismicity. He remarked that this does not exclude the possibility that larger earthquakes occur over recurrence periods longer than the instrumental history, thereby leaving open the possibility that megathrust events will occur along the Java Trench

Summary

Introduction

Seismic gaps off the southwest coast of Sumatra, which pose a risk for generating future megathrust events, have been studied in detail (e.g., Refs.[1,2,3,4]). The absence of recent great earthquakes may indicate that even more powerful tsunamigenic events along the south coast of Java are a potential threat If this is true, the release of effective early warnings needs to be a high priority, since most people living in high tsunami risk areas will have little time to evacuate. We use new data taken from the Indonesian Tsunami Early Warning System (InaTEWS) catalog reported by BMKG, together with data from the International Seismological Centre (ISC) catalog, to investigate the potential for megathrust earthquakes and consequent tsunamis south of Java From this combined dataset, we extract P- and S-wave arrival-times from 436 seismic stations at local, regional, and teleseismic distances in the period from April 2009 to November 2018 (Supplementary Fig. 1a). Three different rupture scenarios are tested, with a focus on maximum wave height along the south coast of Java

Methods

Results

Conclusion