Dept. of Geosciences Colloquium: Static Green’s functions for subduction zone settings in the era of seafloor geodesy

Zoom: https://tau-ac-il.zoom.us/j/87073901428?pwd=Zay3aB8aBEigEH9SC4iEU9pByK9FCN.1

Abstract:

After an earthquake occurs, slip models of the event may be produced by inverting geodetic data for slip on a finite fault. This process generally requires static coseismic Green's functions, which must be calculated in advance. Until recently, the lack of seafloor geodetic instrumentation and the use of unrealistically simple, half-space based forward models have resulted in poor resolution of near-trench slip in subduction zone settings. Here, we investigate the effects of 3D structure, particularly topography, on forward models of coseismic deformation and on earthquake static slip inversions. Using the SPECFEM-X software package, we show that the presence of topography alters the shape of predicted coseismic surface deformation patterns for the 2010 Maule and 2015 Gorkha earthquakes. We then compute static Green's functions for these earthquakes in domains with and without topography, and perform Bayesian inversions using geodetic data. In both cases, we find that the use of Green's functions with topography yields a different distribution of slip. We then seek to generalize these findings through the use of a synthetic framework to investigate the impact of topography and geodetic data distribution on coseismic slip estimates in various subduction zone settings. We find that failure to account for topography in Green’s functions results in ensembles of recovered slip distributions that often do not include the target model, while the use of both topographic Green's functions and seafloor geodetic data enables an almost perfect recovery of a target slip model, even in the near-trench region.

Event Organizer: Dr. Ariel Lellouch