Earthquake catalog and continuous waveforms from a two-week distributed acoustic sensing experiment on Kefalonia Island, Greece

In this work, we present a new, high-resolution earthquake catalog for the Kefalonia region, Greece, together with the distributed acoustic sensing (DAS) waveform dataset used for its construction (https://doi.org/10.60517/cv43p1601, Bocchini et al., 2025; https://doi.org/10.5281/zenodo.20558686, Bocchini, 2026). We build the catalog from DAS data recorded between 1 August 2024, 23:00 UTC and 15 August 2024, 23:00 UTC, combined with open-access seismic-station recordings from the Hellenic Unified Seismic Network (HUSN). The DAS dataset consists of continuous strain measurements acquired along a 15 km long telecommunications fiber-optic cable connecting northern Kefalonia and Ithaki. We use a semblance-based detector on the DAS waveforms to identify 5734 earthquakes within ∼50 km of the cable origin. We jointly locate 356 high-SNR (SNR > 12 dB) events with DAS and seismic stations and calculate their local magnitudes from seismic records. We then apply waveform cross-correlation to match unlocated detections with the most similar template events and estimate relative magnitudes from amplitude ratios to enhance the newly constructed catalog. Enhancement adds 2515 earthquakes, resulting in 2871 events with assigned locations and magnitudes and represents a ∼32-fold increase in the number of earthquakes with respect to the official National Observatory of Athens (NOA) catalog. Most events (2790) cluster within a ∼5 km radius offshore northwest of Kefalonia, where seismicity rates reach > 100 events per hour. We achieve a ∼38-fold increase in the number of earthquakes with respect to the official catalog from NOA in the region encompassing the earthquake cluster northwest of Kefalonia. Our dataset provides a detailed spatio-temporal view of seismicity in a region with limited station coverage and demonstrates the value of integrating DAS with conventional seismic networks to monitor intense earthquake sequences. The combination of high seismicity and open-access data from the HUSN makes this DAS dataset particularly valuable for the seismological community. We provide a 2-week-long catalog, the full detection list (local and distant events and false detections), and two weeks of continuous DAS recordings. Possible applications of the datasets include testing and benchmarking DAS processing algorithms for tectonic earthquakes, as well as studies of physical processes associated with complex seismic sequences.