Identifying active volcanic, tectonic, and geothermal deformation at the Northern Costa Rican Volcanic Arc using InSAR.

Abstract

Identifying active deforming regions is necessary for developing an understanding of the processes occurring in the Solid Earth and steering resources to mitigate hazards.Central America is a region of active tectonics caused by the relative motions between the Caribbean, Cocos and the North American plates and the Panama Microplate.This region is occupied by developing countries that can benefit from satellite technology that can reduce the high costs of equipment and maintenance.Based on a review of the seismogenic zones, key scientific questions that can be solved using InSAR were recognised.These are related to the Central American Forearc Sliver inner boundary and geothermal fields activity.Combining seismic information from the Costa Rican Seismic Network and satellite data from ALOS-2 and Sentinel 1, I used satellite radar interferometry (InSAR) to analyse deformation on the inner boundary of the Guanacaste Volcanic Arc Sliver, subduction earthquakes and deformation linked to the extraction activity on the Dr Alfredo Mainieri Protti geothermal field. ALOS-2 data was key to characterising the spatial pattern of deformation, and Sentinel 1 data was used to analyse the time series of deformation.I conducted a systematic study of all shallow (<20 km) earthquakes greater than Mw 5.0 that occurred in Costa Rica from 2016 to 2019. Co-seismic interferograms using ALOS-2 were used to analyse the slip distribution of a Mw 5.4 earthquake that occurred in Bijagua in July 2016. This earthquake was caused by ∼33 cm of right lateral slip on the Caño Negro fault, and triggered aseismic slip of ∼35cm on the nearby Upala fault. Sentinel 1 interferograms show that two subduction interface earthquakes generated surface deformation on the coast lines of ∼2 cm atJacó in November 2017 and of∼3 cm at Golfito in August 2018.Analysis of the surface deformation at the Dr Alfredo Mainieri Protti geothermal field showed alternating periods of subsidence and uplift of ∼3 cm each, over intervals of approximately 120 days. There is a strong relation between the extraction rates of the geothermal power plant andthe magnitude and direction of the deformation over the geothermal field. There is also a spatial relation between the recorded seismicity and the location of the border of the deformation pattern and with the injection wells.Throughout this research, it is clear that the geodetic results are complementary to the more commonly obtained seismic data.Satellite based analysis of the deformation patterns has improved our understanding of the seismogenic processes occurring in Costa Rica.

Date of Award	24 Mar 2020
Original language	English
Awarding Institution	University of Bristol
Sponsors	Universidad de Costa Rica
Supervisor	Juliet J Biggs (Supervisor) & John Michael Kendall (Supervisor)