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

• Published in: Nature geoscience 2022-01, Vol.15 (1), p.67-73
• Main Authors: Ulrich, Thomas, Gabriel, Alice-Agnes, Madden, Elizabeth H.
• Format: Article
• Language: English
• Subjects: 704/2151/508; 704/4111; 704/829/2737; Accretion; Cascading; Complexity; Computer applications; Dynamics; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Earthquakes; Geochemistry; Geological faults; Geology; Geophysics/Geodesy; Hazard identification; Hazard mitigation; Heterogeneity; Initial conditions; Mathematical analysis; Mathematical models; Modelling; Ocean models; Oceanic trenches; Oceans; Physics; Rigidity; Sediments; Seismic activity; Subduction; Subduction (geology); Tectonics; Tsunami models; Tsunamis
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/s41561-021-00863-5

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 use high-performance computing multi-physics simulations to show that tsunami genesis 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 modelling 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 and will be applicable to other large megathrust earthquakes. Our findings highlight the importance of regional-scale structural heterogeneity to decipher megathrust hazards. Tsunamis generated by megathrust earthquakes are controlled by regional-scale structural heterogeneity, according to numerical modelling based on the 2004 Indian Ocean earthquake and tsunami.