Effects of Megasplay Fault Activity on Earthquake Hazards: Insights from
Discrete Element Simulations
Abstract
Deep-water megasplay faults may promote or limit earthquake rupture and
tsunami genesis. To better understand how megasplay faults affect
earthquake rupture and associated tsunami potential, we build on recent
modeling efforts based on observations of coseismic ruptures in the
Japan Trench forearc and Chile Margin. We model the upper plate as a
wedge that is partitioned into a seismic (velocity-weakening) inner
wedge and an outer aseismic (velocity-strengthening) wedge, combined
with a splay fault rooting from the decollement. We examine the effects
of dip and friction along the splay fault and the width of the outer
(velocity-strengthening) wedge during earthquake rupture. Our results
suggest that along-strike variations in width of the
velocity-strengthening outer wedge along the Chile Margin may play a key
role in splay fault activity in the rupture segment of the 2010 Maule
earthquake. However, our model fit to the published slip distribution
for the 2010 Maule earthquake, suggests that megasplay fault activation
did not significantly impact earthquake size along the SC Chile Margin.
In contrast, our model fit to the slip distribution for the 2011 Tohoku
earthquake shows that megasplay fault reactivation may have moderately
affected earthquake coseismic rupture. Splay faults can slip
coseismically thus contributing to associated tsunamis. However, the
presence of a velocity-strengthening outer wedge is the predominant
constraint on rupture size and tsunami generation.