Earthquake in a Maze: Compressional Rupture Branching During the 2012 M _w 8.6 Sumatra Earthquake

Abstract

Earthquake in a Maze The 11 April 2012 magnitude 8.6 earthquake offshore of Sumatra was the largest measured earthquake along a strike-slip boundary that modern seismological instruments have ever recorded. Despite its size and proximity to a large population, there was no subsequent tsunami and there were no reported fatalities. Meng et al. (p. 724 , published online 19 July) used teleseismic data from seismological networks in Japan and Europe to image the source of high-frequency radiation generated by the earthquake to understand the mechanics of this unique event. The resultant back projections showed that the earthquake slowly ruptured along a complex series of faults. The deeper-than-usual rupture path and large stress drop are both features that may not be unique to this earthquake, suggesting that regions in a similar tectonic environment may have the potential for more complex—or larger—intraplate earthquakes than might have been expected.

Seismic evidence of a two-layer lithospheric deformation in the Indian Ocean

“…On the other hand, some studies found that the Mw ¼ 8.6 event also ruptured NWN-SES faults 12,18 , which are unrelated to the oceanic fabric. On the contrary, a recent bathymetric and seismic study indicates the absence of any such WNW-ESEtrending faults 44 .…”

“…The 10 January foreshock (Mw ¼ 7.2) and 11 April aftershock (Mw ¼ 8.2) seem to have ruptured the re-activated fracture F6 (Fig. 1), but the slip during the Mw ¼ 8.6 earthquake is more complex, involving several near-orthogonal fault segments 12,18,19 . While some authors argue that only the NNE-SSW fault plane along a fracture zone (F6) (Fig.…”

“…While some authors argue that only the NNE-SSW fault plane along a fracture zone (F6) (Fig. 1) was re-activated 20 , some others suggest that new lithospheric faults, not the existing fabric, were initiated 18 .…”

Detailed rupture imaging of the 25 April 2015 Nepal earthquake using teleseismic P waves

“…Since its introduction by Ishii et al [2005] for the 2004 Sumatra earthquake, the backprojection method has been widely applied to large earthquake imaging, most often using regional arrays such as Hi-net or USArray [e.g., Meng et al, 2011;Wang et al, 2012;Meng et al, 2012;Koper et al, 2011;Kiser and Ishii, 2012]. However, in principle, higher resolution can be obtained using globally distributed stations [e.g., Walker et al, 2005;Yagi et al, 2012;Okuwaki et al, 2014] and this is the approach we adopt here.…”

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

“…The 11 April 2012 M w 8.6 and 8.2 great strike-slip earthquakes ( Figure 1) ruptured a mix of north-south and east-west trending strike slip faults in the Cocos Basin (north Wharton Basin) [e.g., Duputel et al, 2012;Satriano et al, 2012;Meng et al, 2012;Yue et al, 2012;Ishii et al, 2013;Wei et al, 2013;Hill et al, 2015], and there are many other strike-slip events along the outer rise ( Figure S1). The M w 8.6 earthquake is the largest recorded intraplate event and also the largest recorded strike-slip event.…”