Abstract

Convergence of the Indo-Australian and Eurasian plates along the Sunda subduction zone generates large earthquakes and tsunamis, exemplified by the 2004 Mw9.2 event. The subduction zone is a classic example of slip partitioning, where oblique convergence is partitioned between the megathrust and upper plate strike-slip faults. Upper plate faults are highly active, but their location and slip rates offshore are not well known. Additionally, the distribution of locked and creeping areas along the fault systems is not well resolved.

In this talk, I’ll share initial results from two studies investigating this tectonic system. We first use earthquake and GPS data to resolve fault slip rates through block modelling. We find several new features of the tectonic system, including the separation of the forearc into two independent blocks and a rapid slip rate of the Andaman-Nicobar fault in the Andaman Sea. Second, to better understand the geometry and behaviour of the Great Sumatran Fault in Northern Sumatra, we deployed 130 seismic nodes primarily for microseismicity detection and subsurface imaging. Our ~18 months of data reveal pronounced differences in seismicity along the fault. One segment appears to be creeping, with abundant shallow microseismicity and repeating earthquakes, while the other appears to have a locked upper crust.