Integrating Dense DAS Arrays and Conventional Networks for Earthquake Monitoring in the Southeastern Adriatic Sea region

The Dubrovnik region of southern Croatia is characterized by complex tectonic interactions along the convergent boundary of the Adriatic microplate and the Dinaric fold-and-thrust belt. To improve seismic monitoring in this high-risk area, we utilize two Distributed Acoustic Sensing (DAS) arrays: a 17 km terrestrial dark-fiber cable and a 40 km hybrid onshore–offshore cable traversing the Adriatic seafloor and nearby islands. While these arrays provide unprecedented spatial sampling, their integration into standard seismological routines requires new automated approaches.
In this work, we present a comparative analysis between a baseline automated workflow using conventional regional seismometers and an augmented framework that incorporates DAS data. We investigate how incorporating dense DAS picks improves earthquake location accuracy and helps detect small events missed by the regional network. By integrating automated phase picks from the DAS arrays with arrival times from the permanent regional network, we demonstrate that combined earthquake locations yield lower spatial uncertainties compared to those derived from the sparse regional network alone. Furthermore, the DAS arrays successfully capture low-magnitude local events that remain below the detection threshold of the standard seismometer stations, thereby lowering the local magnitude of completeness.
A significant observation in our DAS records is the presence of distinct phase conversions (P-to-S) originating from offshore earthquake sources. These converted phases are prominently captured by the dense fiber geometry but pose a challenge for standard automatic picking frameworks. We are currently testing specialized algorithmic solutions within our processing pipeline to accurately identify and utilize these conversions. Successfully characterizing these phases will provide critical constraints on the velocity structure and sediment thickness of the Adriatic shelf.
This poster discusses the technical challenges of multi-instrument integration, the reduction of hypocentral errors through hybrid monitoring, and the ongoing development of picking strategies to handle complex phase arrivals in fiber-optic data. Our results highlight the transformative potential of DAS in complementing traditional networks for high-precision seismic monitoring in complex tectonic settings.