How does fault geometry control earthquake magnitude?

Quentin Bletery, Amanda Thomas, Leif Karlstrom, Alan W. Rempel, Anthony Sladen, & Louis De Barros

Submitted August 15, 2016, SCEC Contribution #6408, 2016 SCEC Annual Meeting Poster #070

Recent large megathrust earthquakes, such as the Mw9.3 Sumatra-Andaman earthquake in 2004 and the Mw9.0 Tohoku-Oki earthquake in 2011, astonished the scientific community. The first event occurred in a relatively low-convergence-rate subduction zone where events of its size were unexpected. The second event involved 60 m of shallow slip in a region thought to be aseismicaly creeping and hence incapable of hosting very large magnitude earthquakes. These earthquakes highlight gaps in our understanding of mega-earthquake rupture processes and the factors controlling their global distribution. Here we show that gradients in dip angle exert a primary control on mega-earthquake occurrence. We calculate the curvature along the major subduction zones of the world and show that past mega-earthquakes occurred on flat (low-curvature) interfaces. A simplified analytic model demonstrates that shear strength heterogeneity increases with curvature. Stress loading on flat megathrusts is more homogeneous and hence more likely to be released simultaneously over large areas than on highly-curved faults.

Key Words
curvature, mega-earthquakes, shear strength, subduction

Bletery, Q., Thomas, A., Karlstrom, L., Rempel, A. W., Sladen, A., & De Barros, L. (2016, 08). How does fault geometry control earthquake magnitude?. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)