Mechanism for normal faulting in the subducting plate at the Mariana Trench

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 42 (2015): 4309–4317, doi:10.1002/2015GL063917.We investigate the mechanisms of normal fault initiation and evolution in the subducting Pacific Plate near the Mariana Trench, through bathymetry analysis and geodynamic modeling. We model the subducting plate as an elastoplastic slab subjected to tectonic forcing at the trench, including vertical load, bending moment, and horizontal tensional force. In our simulations, normal faults initiate within the outer rise region and reach maximum throw toward the trench. This result holds over a wide range of tectonic forcing and is consistent with observations of the Challenger Deep region, where multibeam bathymetry data indicate faults initiate near the outer rise at 70–110 km from the trench and reach maximum throw at 10–35 km from the trench. However, models require a horizontal tensional force with magnitude comparable to axial vertical load to jointly explain the observed seafloor bathymetry, location of maximum normal fault throw, and prevalence of normal faults dipping toward the trench.This work was supported by the Mariana Trench Project of the South China Sea Institute of Oceanology of Chinese Academy of Sciences, Chinese National 985 project 1350141509, Ministry of Science and Technology 973 project award 2012CB417303, and Chinese Scholarship Council 201406260134.2015-12-0