Investigating the volcano-tectonic interactions in the East African Rift System

The East African Rift System (EARS) is an active tectonic region associated with seismicity and magmatism with around 80 volcanoes considered active during the Holocene. In past decades, remote sensing and especially Radar Interferometry (InSAR) became a relevant technique to study volcanic ground deformation at the scale of plate boundaries. Previous InSAR surveys carried out along the EARS during the period of 1993-2010 and 2015-2020 have detected ground deformation signals for more than ten volcanic centers (Biggs et al., 2009, 2011 ; Albino et al., 2021). For most of them (e.g., Haledebi, Tullu Moje and Olkaria), patterns of deformation could be controlled by pre-existing tectonic structures. However, geodetic signals are often modelled by analytic/numerical solutions assuming an isotropic and homogeneous medium. In the rift setting, this assumption is not valid anymore as large networks of fractures and faults will induce crustal heterogeneities. The aim of the project is to better understand the nature of the interactions between the tectonic structures and the magmatic systems. First, the student will process Sentinel-1 SAR data using NSBAS processing chain developed at ISTerre (Doin et al., 2011) to extend InSAR time series for the year 2021. Then, the student will perform geodetic modelling of the InSAR time series and compare results associated with two approaches : i) analytical models in homogeneous medium (using the Matlab toolbox GBIS : Bagnardi et al., 2018, https://comet.nerc.ac.uk/gbis/) and numerical models in heterogeneous medium (using the Multiphysics software COMSOL, Hickey et al., 2014).

Albino, F., & Biggs, J. (2021). Magmatic Processes in the East African Rift System : Insights From a 2015–2020 Sentinel‐1 InSAR Survey. Geochemistry, Geophysics, Geosystems, 22(3), e2020GC009488.

Bagnardi, M., & Hooper, A. (2018). Inversion of surface deformation data for rapid estimates of source parameters and uncertainties : A Bayesian approach. Geochemistry, Geophysics, Geosystems, 19(7), 2194-2211.

Biggs, J., Bastow, I. D., Keir, D., & Lewi, E. (2011). Pulses of deformation reveal frequently recurring shallow magmatic activity beneath the Main Ethiopian Rift. Geochemistry, Geophysics, Geosystems, 12(9).

Biggs, J., Anthony, E. Y., & Ebinger, C. J. (2009). Multiple inflation and deflation events at Kenyan volcanoes, East African Rift. Geology, 37(11), 979-982.

Doin, M. P., Guillaso, S., Jolivet, R., Lasserre, C., Lodge, F., Ducret, G., & Grandin, R. (2011, September). Presentation of the small baseline NSBAS processing chain on a case example : the Etna deformation monitoring from 2003 to 2010 using Envisat data. In Proceedings of the Fringe symposium (pp. 3434-3437). Frascati, Italy : ESA SP‐697.

Hickey, J., & Gottsmann, J. (2014). Benchmarking and developing numerical Finite Element models of volcanic deformation. Journal of Volcanology and Geothermal Research, 280, 126-130.