Orlando Alvarez Pontoriero
CONICET-IGSV
Argentina
Title: Satellite gravity measurements for great earthquake rupture zones forecasting and monitoring: insights from satellite GOCE mission
Biography
Biography: Orlando Alvarez Pontoriero
Abstract
Satellite gravimetry is a useful tool to identify mass anomalies along a subduction interface, interpreted as heterogeneities related to the rupture process during megathrust earthquakes. Different works with data derived from satellite gravity missions as GRACE and GOCE, have analyzed the static component of the Earth gravity field and its temporal variations. During the last decade the Chilean margin has been affected by three megathrust earthquakes with Mw>8. Then, the recently completed GOCE mission offered a unique opportunity to study this events by means of gravity gradients, which allowed mapping density heterogeneities with greater detail than the gravity anomaly which has been used in most studies up to now.
We derived the vertical gravity gradient from GOCE, corrected by the topographic effect and by the sediments on depocenters of the offshore region at the Peru-Chile margin, in order to study a spatial relationship between different lobes of the gravity derived signal and the seismic sources of large megathrust earthquakes. Then we find a good correlation between vertical gravity gradients and main rupture zones, correlation that becomes even stronger as the event magnitude increases. A gravity fall in the gravity gradient and in geoid heights was noticed over the area of the main slip patch at least for the two years before 2014 Mw=8.2 Pisagua earthquake. Additionally, we found temporal variations of the gravity field after 2010 Mw=8.8 Maule event, related to coseismic deformation. Therefore, we analyzed variations in the gravity field as an indirect measure of the variable seismic coupling. These relationships exemplify the strong potential of the satellite only derived models as a predictive tool to determine potential seismic energy released in a subduction segment, determining the potential size of a potential rupture zone, and in particular internal slip distribution that allows inferring coseismic displacement field at surface.