Earthquake Catalog and Continuous Waveforms from a Two-Week Distributed Acoustic Sensing experiment on Kefalonia Island, Greece

Abstract. This work presents a high-resolution earthquake catalog for the Kefalonia region, Greece, built from the analysis of Distributed Acoustic Sensing (DAS) data recorded on a telecommunications cable between 1 August 2024, 23:00 and 15 August 2024, 23:00, together with open-access seismic station recordings. The DAS data consist of continuous strain recordings on a 15 km-long telecommunication optical fiber connecting northern Kefalonia and Ithaki. We use a semblance-based detector on the DAS waveforms to identify 5,734 earthquakes within ~ 50 km of the fiber origin. We jointly locate 284 high-SNR 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 constructed catalog. Enhancement adds 2,496 earthquakes, resulting in 2,780 events with assigned locations and magnitudes. Most events (2,718) cluster within a ~ 5 km radius offshore northwest of Kefalonia, where seismicity rates reach >100 events per hour. 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 Hellenic Unified Seismic Network 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. The aim is to provide a resource for researchers to test, develop, and benchmark DAS processing algorithms on tectonic earthquakes and to investigate the physical processes that drive complex seismic sequences.