Stress, rigidity and sediment strength control megathrust earthquake and tsunami dynamics

Abstract

Megathrust faults host the largest earthquakes on Earth which can trigger cascading hazards such as devastating tsunamis. Determining characteristics that control subduction zone earthquake and tsunami dynamics is critical to mitigate megathrust hazards, but is impeded by structural complexity, large spatio-temporal scales, and scarce or asymmetric instrumental coverage. Here we show that tsunamigenesis and earthquake dynamics are controlled by along-arc variability in regional tectonic stresses together with depth-dependent variations in rigidity and yield strength of near-fault sediments. We aim to identify dominant regional factors controlling megathrust hazards. To this end, we demonstrate how to unify and verify the required initial conditions for geometrically complex, multi-physics earthquake-tsunami modeling from interdisciplinary geophysical observations. We present large-scale computational models of the 2004 Sumatra-Andaman earthquake and Indian Ocean tsunami that reconcile near- and far-field seismic, geodetic, geological, and tsunami observations and reveal tsunamigenic trade-offs between slip to the trench, splay faulting, and bulk yielding of the accretionary wedge. Our computational capabilities render possible the incorporation of present and emerging high-resolution observations into dynamic-rupture-tsunami models. Our findings highlight the importance of regional-scale structural heterogeneity to decipher megathrust hazards.

Assessing Margin‐Wide Rupture Behaviors Along the Cascadia Megathrust With 3‐D Dynamic Rupture Simulations

“…Velocity‐strengthening , or in our case, slip‐strengthening, friction is a common assumption in dynamic rupture simulations for subduction zones to represent the frictional behavior of sediments near the trench (Kozdon & Dunham, 2013). One may also explicitly incorporate a subducting sediment channel structure with depth‐varying rigidity using slip‐weakening friction (i.e., Ulrich et al., 2020). The presence of clays or fluids within the megathrust fault zone can complicate the frictional behavior, however (Saffer & Tobin, 2011).…”

Assessing Margin-Wide Rupture Behaviors along the Cascadia Megathrust with 3-D Dynamic Rupture Simulations

“…Velocity-weakening, or in our case, slip-strengthening, friction is a common assumption in dynamic rupture simulations of megathrust earthquakes to represent the frictional behavior of sediments near the trench (Kozdon and Dunham, 2013). One may also explicitly incorporate a subducting sediment channel structure with depth-varying rigidity using slip-weakening friction (i.e., Ulrich et al, 2020). The presence of clays or fluids within the megathrust fault zone can complicate the frictional behavior, however (Saffer and Tobin, 2011).…”