Characteristics of Seismicity Distribution along the Sunda Arc: Some New Observations

Abstract

Spatio-temporal variations of earthquake activity along the Sunda arc were investigated. We prepared a strain release map for this century. Adjacent to the zones of high strain release, presence of seismically quiet zones was noted. A careful inspection of the depth distribution of the earthquakes revealed that in the eastern Sunda arc, possibly there exists a zone of scarce seismicity at an intermediate depth. We discussed the probable implications. We also analysed the patterns of temporal distributions of earthquakes at the three different seismotectonic provinces of the Sunda arc--Sumatra, Java, and the Lesser Sunda Islands. We could clearly see that, although the causative geodynamic situations for seismicity vary significantly in space along the length of the arc, the period of increase or decrease in seismicity is largely space invariant. The locally differing levels of seismicity are superposed on the common background of long period seismicity fluctuation. Finally, clustering of seismicity at some patches along the Sunda arc was studied with respect to the altimetric gravity anomaly data. We noted some apparent conformities. For some of our present observations, there exists much scope for detailed future investigations, which we discussed.