Co-seismic deformation of the 2017 Mw 6.6 Bodrum–Kos earthquake in speleothems of Korakia Cave (Pserimos, Dodecanese, Greece)

Abstract

Structural mapping and dating of damaged speleothems have been used to investigate earthquake records in caves, especially of large infrequent events. However, there are few reports of damages in caves visited before and after a particular earthquake, where the damage can be directly related to a recorded event. We mapped the previously unexplored Korakia Cave on Pserimos island in the Dodecanese (Greece) prior to the 2017 Mw 6.6 Bodrum–Kos earthquake. The Dodecanese is at the transition between the Aegean and Anatolian region and is known for its strong seismicity. Although several hundred stalactites with large height-to-width ratios are preserved on the roof of Korakia Cave, the cave has an extensive record of damaged speleothems, which have been caused by movements along normal faults. Here we present new data and 230Th/U-ages of paleoseismic events that are partly older than the limit of the dating method. A cave visit after the 2017 Mw 6.6 Bodrum–Kos earthquake revealed that c. 10 cm small stalactites, which were actively growing along fractures in the cave ceiling, had been chipped off by movements along the fractures during that earthquake. We conclude that movements along fractures or faults during seismic events can easily damage stalagmites and stalactites. However, damage related to the resonance frequency of the dripstones matching with the seismic wave frequency, which has been suggested to break dripstones with large height-to-width ratios, was not observed in Korakia Cave.