Extensional Faulting Around Kolumbo Volcano, Aegean Sea—Relationships Between Local Stress Fields, Fault Relay Ramps, and Volcanism

Abstract

The Christiana-Santorini-Kolumbo (CSK) volcanic field has hosted more than 100 explosive eruptions in the past 250,000 years, including the 1650 CE eruption of Kolumbo Volcano. Previous studies have established a link between regional tectonics and volcanism in the CSK volcanic field. While 2D seismic reflection data have given valuable insight into regional faulting, detailed fault zone characterization has been precluded by the sparsely spaced profiles. Using 3D seismic reflection data around Kolumbo Volcano, we provide the first 3D characterization of fault zones in the CSK volcanic field. Beneath the volcano's northwestern flank, and farther to the northwest, normal faults are predominantly NE-SW trending, with mean fault trends between 044° and 049°. Normal faults beneath the southeastern flank are slightly more north-oriented, with mean fault trends between 028° and 038°. Our detailed fault zone analysis reveals clear NW-SE directed extension around the volcano, consistent with published focal mechanisms from microseismicity. The Kolumbo Fault Zone, ∼6 km northwest of Kolumbo Volcano, is characterized by distinct relay ramps between major overstepping normal faults. Regional 2D seismic profiles reveal a previously undocumented volcanic cone directly above the fault zone. Magma ascent to this cone has likely exploited enhanced vertical permeability associated with distributed deformation within a relay ramp. We suggest that fault relay structures may play an important role, over a range of spatial scales, in focusing magma ascent within the CSK volcanic field.