Characterization of interseismic strain rate and hydrological interannual signals in Southern Apennines (Italy) from a combined analysis of GNSS and InSAR time series

Advisors : Erwan Pathier, Anne Socquet, Nicola d’Agostino (INGV)

In Southern Italy, ∼3 mm/yr of extensional strain is accommodated tectonically across the Apennines (e.g. d’Agostino et al. 2008, d’Agostino 2014), leading to an important seismic hazard, as it was sadly illustrated by the Irpinia earthquake in 1980 (Mw=6.8) that is the strongest instrumentally recorded earthquake in Italy. Recently, the analysis of GPS time series near to large karst aquifers in this area showed that the extensional strain is superimposed by seasonal and interannual horizontal movements linked to groundwater recharge/discharge of karst aquifers (Silverii et al. 2016).
The objective of this master internship is to refine the spatial variability of the deformation in the area, and to deconvoluate the interseismic loading from the hydrological signal. This will ultimately allow to better target potentially loaded faults in the area, and to better characterize spatial extent of the karstic area affected by hydrological charge /discharge and to better understand its behavior.

To do this, we plan to perform InSAR time series using Sentinel-1 data. In the target area, 170 images on the descending track (relative orbit 124) should be available from 2014-12-01 to Feb. 2018. These data will be processed with the NSBAS chain developed in ISTerre laboratory (Doin et al. 2011). The InSAR time series will then be analyzed jointly with GNSS times series available in the frame of EPOS project (Plate Observing Plate System, https://www.epos-ip.org/), that are generated in INGV and UGA (https://isterre.fr/recherche/projets-de-recherche/projets-en-cours/projets-europeens/article/epos-ip-gnss-products), in order to separate hydrology from tectonics. Eventually these signals will be modeled following a simple elastic approach.

A solid background in Mathematics, Physics and Computation is required for this master project. The student will work within the “Seismic cycle and transient deformation” team in ISTerre laboratory, and in collaboration with N. d’Agostino in INGV, Rome.

References
D’Agostino, N., A. Avallone, D. Cheloni, E. D’Anastasio, S. Mantenuto, and G. Selvaggi (2008), Active tectonics of the Adriatic region from GPS and earthquake slip vectors, J. Geophys. Res., 113, B12413, doi:10.1029/2008JB005860.
D’Agostino, N. (2014), Complete seismic release of tectonic strain and earthquake recurrence in the Apennines (Italy), Geophys. Res. Lett., 41, 1155–1162, doi:10.1002/2014GL059230.
Silverii, F., N. D’Agostino, M. Métois, F. Fiorillo, and G. Ventafridda (2016), Transient deformation of karst aquifers due to seasonal and multiyear groundwater variations observed by GPS in southern Apennines (Italy), J. Geophys. Res. Solid Earth, 121, 8315–8337 doi:10.1002/2016JB013361.

MP Doin, S Guillaso, R Jolivet, C Lasserre, F Lodge, G Ducret, R Grandin, Presentation of the small baseline NSBAS processing chain on a case example : the Etna deformation monitoring from 2003 to 2010 using Envisat data, Proceedings of the Fringe Symposium, 3434-3437, 54, 2011.