Geophys. J. Int. (2020) 220, 461–489 doi: 10.1093/gji/ggz461 Advance Access publication 2019 October 14 GJI Geodynamics and tectonics Tectonic deformation in the Santorini volcanic complex (Greece) as inferred by joint analysis of gravity, magnetotelluric and DGPS observations A. Tzanis , S. Chailas, V.Sakkas and E. Lagios Section of Geophysics, Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 157 84, Greece. E-mail:
[email protected] Downloaded from https://academic.oup.com/gji/article-abstract/220/1/461/5586995 by guest on 13 November 2019 Accepted 2019 October 11. Received 2019 March 17; in original form 2019 September 23 SUMMARY Tectonic activity is very difficult to study in the Santorini volcanic complex (SVC) as it comprises a cluster of small/awkwardly shaped islands covered by pyroclastic deposits from which tell-tale markers are swiftly erased, while seismicity is generally absent. We address the problem by combining geophysical exploration methods to evaluate the long-term effects of tectonic deformation and time-lapse differential GPS to directly evaluate the magnitude and kinematics of present-day deformation. The former comprise 3-D gravity modelling to investigate the footprint of tectonics on the pre-volcanic Alpine basement and natural-field EM induction to map conductivity anomalies epiphenomenal to fluid circulation in faults. Our analysis identified the following principal tectonic elements: The Trans-Santorin Divide (TSD), a segmented NNW–SSE dextral strike-slip fault splitting the SVC sideways of the line joining Cape Exomytis, the Kammeni Islets and the Oia–Therassia Strait. It is collocated with a major vertical conductive zone and forms a series of dents and depressions in the basement.