Magnitude-Rupture Area Scaling Derived From Global Earthquakes Of Moderate To Large Sizes: Implications For Seismic Hazards In Indonesia

Abstract

Earthquake size can be estimated using magnitude-rupture area scaling developed from modelled fault dimensions and measured moment magnitudes. In this study, a measure of a fault plane geometry was provided by rupture area A and the size scaled with moment magnitude Mw. Using global earthquakes datasets containing 90 events with varying magnitudes 4.45 ≤ Mw ≤ 9.20 during years of 1960-2015, we classified the data into separate strike-slip, dip-slip (normal and reverse) and subduction-zone earthquakes. The study aims to search for reliable scaling used for magnitude prediction of earthquakes around the globe for each type of source mechanism. We found from the Mw−A scaling proposed in this study that the magnitude for subduction events was likely to saturate to a maximum value possible Mw ≈ 9.3 at rupture areas much larger than those for strike-slips and dip-slips. This suggests that rocks in the subduction-zone are able to accumulate high stress, implying large seismic energy release via strong ground motion when an earthquake occurs at the plate boundary. Taking into account cases under consideration that included intraplate-fault and subduction processes covering a wide range of magnitudes from moderate to large sizes, the results are relevant to Indonesian tectonic settings, where active crustal faults have been recently found throughout the country and in particular a future megathrust subduction-zone earthquake of Mw ~ 9.0 is possible to occur off the south coasts of Java Island, the most densely populated island in Indonesia. These potential seismic threats call for increasing awareness of disaster preparedness, particularly for local community in regions with a high level of vulnerability to tsunami and earthquake disasters. Therefore, a reliable earthquake early warning is of primary importance, which is best integrated into an existing tsunami early warning for maximum security from future seismic hazards.