Tracking the rupture of the Mw = 9.3 Sumatra earthquake over 1,150 km at teleseismic distance

Abstract

On 26 December 2004, a moment magnitude Mw = 9.3 earthquake occurred along Northern Sumatra, the Nicobar and Andaman islands, resulting in a devastating tsunami in the Indian Ocean region. The rapid and accurate estimation of the rupture length and direction of such tsunami-generating earthquakes is crucial for constraining both tsunami wave-height models as well as the seismic moment of the events. Compressional seismic waves generated at the hypocentre of the Sumatra earthquake arrived after about 12 min at the broadband seismic stations of the German Regional Seismic Network (GRSN), located approximately 9,000 km from the event. Here we present a modification of a standard array-seismological approach and show that it is possible to track the propagating rupture front of the Sumatra earthquake over a total rupture length of 1,150 km. We estimate the average rupture speed to be 2.3-2.7 km s(-1) and the total duration of rupture to be at least 430 s, and probably between 480 and 500 s.

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake

“…In the backprojection analysis, the source position of the seismic radiation is inferred by projecting the seismic wavefront of ground velocity recorded by an array of stations at teleseismic distances onto the source region 9,34 . The source location is chosen as the area in the source region leading to the best overlap between the traces.…”

“…1, 2a). Second, we use the backprojection technique applied to stations in North America to map the radiation of high frequency seismic waves (HFSR; 1-4 Hz) 9,10 . The latter technique is not sensitive to absolute slip amplitudes, but rather to changes in slip and rupture velocity.…”

The 2 March 2016 Wharton Basin Mw 7.8 earthquake: High stress drop north‐south strike‐slip rupture in the diffuse oceanic deformation zone between the Indian and Australian Plates

“…Backprojection of short-period P waves from regional and global networks has proved valuable for identifying fault planes, rupture extent, and rupture speed for many events since the initial application to the 2004 Sumatra earthquake [Ishii et al, 2005;Krüger and Ohrnberger, 2005]. We use the method described by Xu et al [2009] to backproject teleseismic P wave recordings in the period range 0.5-2.0 s from large aperture networks of 53 stations in Australia and 127 stations in Europe to a horizontal subevent grid centered on the source region.…”

Landslide tsunami hazard in the Indonesian Sunda Arc

“…According to the Harvard Centroid-Moment-Tensor Catalog, more than 30 earthquakes with magnitude 7 or greater took place during the last 30 years in the Sunda subduction zone (www.globalcmt.org). The largest event with M w =9.3 was the Sumatra-Andaman earthquake of 2004 that ruptured over 1000 km (Krüger and Ohrnberger, 2005;Lay et al, 2005;Ishii et al, 2005) generating a catastrophic ocean-wide tsunami. Maximum runup in Aceh reached more than 30 m (Borrero et al, 2006) and nearly 20 m in Thailand (Tsuji et al, 2006).…”