Submarine seismicity monitoring with distributed acoustic sensing near Santorini and Kolumbo Volcano

Sara Klaasen — 2026-01-16

Submarine volcanoes and faults pose hazards to nearby populated islands, yet their inaccessibility limits monitoring efforts. The Christiana-Santorini-Kolumbo volcanic field is capable of generating devastating eruptions, earthquakes and tsunamis. The 2025 earthquake swarm near Kolumbo, causing the evacuation of thousands from their homes, underlines the need for accurate and real-time monitoring. We interrogate a 45 km dark fibre that extended from Santorini past the submarine volcano Kolumbo for two months in 2021, comparing the performance of the fibre with the existing monitoring network for earthquake detection and location. The detected quakes originated all over Greece, coming from any azimuth. We can reliably identify events, doubling the number of detections in the vicinity of the fibre and Kolumbo. For event location, the azimuthal coverage of the existing seismometer network outperforms the fibre, emphasising the importance of a nonlinear fibre layout. Our findings suggest that while the higher detection sensitivity of DAS leads to an information gain, the data analysis remains challenging. The data quality may be insufficient for automated workflows. The need for human input limits the potential of DAS for real-time monitoring, although the enhanced detection sensitivity in remote areas justifies the continued research of DAS for submarine volcano monitoring.

Focal mechanisms in the southeastern South Island of Aotearoa New Zealand indicate scale-dependent partitioning of transpressional strain

Jack Williams — 2026-01-19

The classic Andersonian model of faulting is difficult to apply to plate boundaries with oblique motion, as displacement is accommodated across oblique-slip faults, or it is partitioned into distinct strike-slip and dip-slip faults. Here, we investigate how faults accommodate oblique plate motion by using the focal mechanism solutions of 126 M_LV 1.3-4.3 earthquakes in the transpressional southeastern South Island of Aotearoa New Zealand. Focal mechanisms were assigned an A-D quality, and of the 91 C or better quality solutions, 57 are strike-slip. In addition, when incorporated into a stress inversion, these focal mechanisms indicate a strike-slip stress state with an WNW-trending maximum principal compressive stress. By contrast, constraints on active crustal-scale faulting from the New Zealand Community Fault Model indicate reverse faulting in this region. A high stress shape ratio can partly account for the coexistence of reverse and strike-slip faults. However, we also propose that the focal mechanisms are typically sampling slip on optimally-oriented small-scale faults in intact crust, while the larger magnitude reverse faulting reflects local stress rotations within pre-existing faults and shear zones in the southeastern South Island. Our study therefore demonstrates how inherited structures influence the scale and orientation of faults onto which transpressional strain is partitioned.

Seismica

Submarine seismicity monitoring with distributed acoustic sensing near Santorini and Kolumbo Volcano

Focal mechanisms in the southeastern South Island of Aotearoa New Zealand indicate scale-dependent partitioning of transpressional strain