How much does geometry of seismic sources matter in tsunami modeling? A sensitivity analysis for the Calabrian subduction interface

New Orleans

The geometry of seismogenic sources could be one of the most important factors concurring to control the
generation and the propagation of earthquake-generated tsunamis and their effects on the coasts. Since the
majority of potentially tsunamigenic earthquakes occur offshore, the corresponding faults are generally poorly
constrained and, consequently, their geometry is often oversimplified as a planar fault. The rupture area of
mega-thrust earthquakes in subduction zones, where most of the greatest tsunamis have occurred, extends
for tens to hundreds of kilometers both down dip and along strike, and generally deviates from the planar
geometry. Therefore, the larger the earthquake size is, the weaker the planar fault assumption become.
In this work, we present a sensitivity analysis aimed to explore the effects on modeled tsunamis generated by
seismic sources with different degrees of geometric complexities. We focused on the Calabrian subduction
zone, located in the Mediterranean Sea, which is characterized by the convergence between the African and
European plates, with rates of up to 5 mm/yr. This subduction zone has been considered to have generated
some past large earthquakes and tsunamis, despite it shows only in-slab significant seismic activity below 40
km depth and no relevant seismicity in the shallower portion of the interface. Our analysis is performed by
defining and modeling an exhaustive set of tsunami scenarios located in the Calabrian subduction and using
different models of the subduction interface with increasing geometrical complexity, from a planar surface to a
highly detailed 3D surface. The latter was obtained from the interpretation of a dense network of seismic
reflection profiles coupled with the analysis of the seismicity distribution. The more relevant effects due to the
inclusion of 3D complexities in the seismic source geometry are finally highlighted in terms of the resulting
tsunami impact.

De la Asunciòn et al., Comput Fluids, 2013
Maesano, Tiberti, Basili (2017) The Calabrian Arc: three-dimensional modelling of the subduction interface, Scientific Reports 7, Article number: 8887, doi:10.1038/s41598-017-09074-8