Observation of earthquake co- and post-seismic signals with the Next Generation Gravity Mission (NGGM)
Karim Douch (2), Clara Bützler (2), Gabriele Cambiotti (1), Stefano Cesare (3), Nico Sneeuw (2), Alberto Anselmi (3), Anna- Maria Marotta (1) and Roberto Sabadini (1)
1) Department of Earth’s Sciences, Università degli Studi di Milano, Milan, Italy
2) Geodetic Institute of Stuttgart, University of Stuttgart, Stuttgart, Germany
3) Domain Exploration & Science Italy, Thales Alenia Space Italia S.p.A, Torino, Italy
The possibility to detect in GRACE data the signature of magnitude MW 9 earthquakes has raised the interest of geophysicists for gravitational seismology. As more performant gravity missions are foreseen, the question of whether NGGM can extend to lower magnitudes the range of observable earthquakes has arisen. To addressed this question, we have undertaken a closed-loop numerical simulation of a 12-year long NGGM to output realistically degraded monthly solutions of a known gravitational field. Then, these solutions have been inverted to assess statistically how well the earthquake signals could be recovered. More specifically, our simulation background gravitational field consists of a static part, the ESA updated ESM for the time-variable part and the gravitational signal associated with the co- and post-seismic phase of a number of different earthquakes. In particular, we have tested the detection of earthquakes with normal, inverse and strike-slip focal mechanisms striking with different azimuth, at the earth surface or in depth, occurring inland, off-shore or close to the coastlines, at the beginning (2-4 years), the middle (5-7 years) or the end (8-10 years) of the 12-year period. The results of the inversion will be discussed with respect to the aforementioned parameters, the earthquake magnitude and the ability to correctly and jointly estimate the background time-variable gravity field, which proved to be a challenging task.
2019-11-21 05:30 +0530