Large-aperture time difference of arrival localization of submarine volcanic T-phase sources

Introduction: Monitoring submarine volcanic eruptions is essential for mitigating coastal and maritime hazards, but direct observations remain limited. Conventional hydroacoustic monitoring using closely spaced hydrophone triplets can suffer from biases caused by horizontal refraction. This study investigates a large-aperture time difference of arrival (TDOA) approach for improving source localization of submarine volcanic T-phases. Materials and methods: T-phase arrivals were detected using short-term average/long-term average and kurtosis-based methods. TDOAs were measured by cross-correlation analysis, and source directions were estimated using a proposed large-aperture (more than 100 km) TDOA framework based on equations describing spherical hyperbola-like curves. Results: Thirteen hydroacoustic events associated with the October 2023 Sofu Seamount event were identified using hydroacoustic observations from the Wake Island International Monitoring System (IMS) station and seafloor seismic observations from the Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET). Consistent backazimuth estimates were obtained by combining multiple large-aperture sensor pairs, reducing directional ambiguity. Independent estimates from the two networks intersected near Sofu Seamount, consistent with tsunami and morphological observations indicating an explosive submarine eruption. Conclusions: Large-aperture TDOA analysis provides a valuable complement to conventional triplet-based hydroacoustic methods. Integrating independent hydroacoustic and seafloor seismic networks improves source localization and enhances monitoring capabilities for submarine volcanic activity and associated maritime hazards.