Pilot Investigation of the Effects of Subducted Seamount on Megathrust Earthquakes


DOEI Funded Research: 2011


The largest and most devastating earthquakes on Earth occur in shallow subduction zones, capable of generating strong shaking and tsunami and causing major fatalities and property losses, as vividly illustrated by the March 11 Japan M=9.0 mega-earthquake.  It has been proposed that large seamounts riding on a subducting plate may play a critical role in controlling the characteristics of earthquakes of a subduction zone, including the maximum sizes of the potential mega-earthquakes.  However, the specific relationships between subducted seamounts and megathrust earthquakes are still poorly understood, partly owing to our limited knowledge of the physics of seamount interaction within a subduction system.  Here we propose to conduct a pilot investigation of the physical interaction of subducted seamounts with a subduction zone by considering (1) the rate and state friction properties of the subducting interface; (2) complete stressing cycles of earthquake faults; and (3) idealized and realistic fault geometry.  Through conducting a series of numerical modeling experiments and analysis, we seek to advance our understanding of the seamount-subduction interaction, including (1) under what conditions would subducted seamounts increase or decrease the seismic coupling between the overriding and subducting plates; and (2) what are the key parameters that control a subducted seamount to act as a “barrier” to stop or slow down a propagating coseismic rupture front or to act as an “asperity” that could initiate megathrust earthquakes.  This project will contribute directly to the basic theme of the WHOI Deep Ocean Exploration Institute (DOEI) on “Dynamic processes at the seafloor”.  The preliminary results from this pilot investigation will significantly enhance our chance of success for future proposals to external funding agencies, including the U.S.  Geological Survey, NSF-Marine Geosciences Program, and NSF-Geophysics Program.