Spatiotemporal Evolution of Stormquake Energy along the East Coast of North America and Implications for Excitation Mechanisms

Summary

Stormquakes are generated by ocean storms, radiating clear coherent surface waves. Understanding the excitation mechanism of stormquakes is important for probing dynamic coupling among the atmosphere, ocean, and solid Earth. However, the underlying source mechanism of these signals is poorly understood and several key aspects have not been studied, including the spatiotemporal evolution of energy release and the dominant energy band. In this study, we developed a new multi-array back-projection approach that combines arrays with complementary azimuthal coverage to locate stormquakes, improving location accuracy while simultaneously estimating their relative coherent energy using normalized beam power. Specifically, we analyzed five storms along the east coast of North America and used arrays from North America and Europe to locate stormquakes and track their energy spatiotemporally. Source locations cluster in two segments of the east North American margin that coincide with abundant ocean banks. Stormquakes off New England (Region 1) are systematically more energetic than those off the Florida margin (Region 2). After single-frequency frequency-wavenumber analysis, we found their dominant frequency bands also differ, with Region 1 (0.04–0.17 Hz) and Region 2 (0.04–0.07 Hz), indicating that stormquake frequencies can be broader than previously reported (0.02–0.05 Hz). Improved location accuracy also reveals a ring-like spatial pattern in Region 1 that was not recognized in previous localization results. By combining these observations with bathymetry, sediment thickness, and ocean wave fields, we infer that the ring-like stormquake pattern is compatible with local site effects within Region 1, and that temporal variations in stormquake energy are associated with changes in local significant wave height, both consistent with microseism theory. Our results show more precise stormquake locations and indicate that their excitation mechanisms share similarities with those of microseisms, highlighting the potential of stormquakes for studying multi-sphere coupling and Earth’s interior structure.