Tsunami earthquake

These slow rupture speeds lead to greater directivity, with the potential to cause higher run-ups on short coastal sections.

[1] Slow rupture velocities are linked to propagation through relatively weak material, such as poorly consolidated sedimentary rocks.

Most tsunami earthquakes have been linked to rupture within the uppermost part of a subduction zone, where an accretionary wedge is developed in the hanging wall of the megathrust.

Tsunami earthquakes have also been linked to the presence of a thin layer of subducted sedimentary rock along the uppermost part of the plate interface, as is thought to be present in areas of significant topography at the top of the oceanic crust, and where propagation was in an up-dip direction, possibly reaching the seafloor.

Modelling of tsunami generation that takes into account additional uplift associated with deformation of the softer sediments of the accretionary wedge caused by horizontal movement of the 'backstop' in the overriding plate has successfully explained the discrepancy, estimating a magnitude of Mw=8.0–8.1.