Evidence of Forearc Uplift, Earthquake Segmentation, and Great Earthquakes Associated with Large Subducting Features

American Geophysical Union, Fall Meeting 2019, abstract #T31G-0353

Singh, S. C. (IPG Paris, Paris Cedex 05, France); Mukti, M. M. (Institut de Physique du Globe de Paris, Paris, FranceAF: Indonesian Institute of Sciences, Bandung, Indonesia); Deighton, I. (TGS, Surbiton, United Kingdom)

It is now well accepted that subducting topographic features influence earthquake process, but how these features control the size of great earthquakes and upper plate morphology remain unknown. Using high-resolution seismic reflection data, here we report the presence of large vertical uplift in the Mentawai fore arc basin, which coincides with the 2007 Mw 8.4 earthquake rupture area. The high-resolution seismic reflection image shows the existence of thick (6 km) sediments that have been uplifted by 750 m in the 2007 earthquake rupture area, whereas deep seismic reflection image indicates a sub-horizontal reflection at ~20 km depth that coincides with arc parallel aftershocks, defining the up-dip limit of the great earthquake. The lower limit of the 2007 earthquake is marked by the Mw 7.9 earthquake and deeper arc parallel aftershocks at ~40 km depth, and boundary of the seafloor uplift. Taken together, these results indicate the presence of a 240 km and 80 km topographic feature on the down-going plate, suggesting that the 2007 great earthquake ruptured this patch of the high topographic feature. Using seafloor bathymetry and seismic reflection data from other part of the Sumatra-Java subduction system, we show that there is a generic link between high topography on the down-going plate, uplift of upper plate, and rupture area of great earthquakes. These results indicate that the seafloor uplift could be used as a proxy to determine the nature of down going plate and estimate both the along strike and across dip limits of possible great earthquakes.

Publication: American Geophysical Union, Fall Meeting 2019, abstract #T31G-0353 Pub Date: December 2019 Bibcode: 2019AGUFM.T31G0353S  Keywords: 7221 Paleoseismology; SEISMOLOGY; 8107 Continental neotectonics; TECTONOPHYSICS; 8118 Dynamics and mechanics of faulting; TECTONOPHYSICS; 8170 Subduction zone processes; TECTONOPHYSICS