Influence of tropical cyclone activity on seismicity along the Pacific–Philippine plate boundary in the West North Pacific

Abstract

Abstract Introduction The West North Pacific (WNP) exhibits the highest tropical cyclone activity globally, averaging 24 storms annually; a significant portion of these develop during the boreal summer and traverse the Pacific–Philippine Plate boundary. This work examines the possible relationships between the variation in TC activity (1977–2021) and the earthquake occurrence over the Pacific–Philippine Plate Boundary. TCs were analyzed in terms of their activity (accumulated cyclone energy) and frequency. The earthquakes were analyzed at several earthquake depth levels. Results A clear relationship between tropical cyclone (TC) activity and earthquake occurrence was observed along the Pacific–Philippine plate boundary, particularly during years of high TC activity. The frequency of all TCs over the western North Pacific showed a strong positive correlation with earthquake occurrence, reaching 0.73 overall and becoming stronger for shallower earthquakes, increasing from 0.75 for depths below 120 km to 0.79 for depths below 30 km. A similar depth-dependent pattern was found for TCs crossing the plate boundary, where the correlation increased from 0.35 for all earthquakes to 0.66 for earthquakes shallower than 30 km. Interestingly, even TCs that did not cross the plate boundary exhibited correlations exceeding 0.70, indicating a potential remote influence of tropical cyclones on regional seismic activity. Accumulated cyclone energy (ACE) provides an even stronger correlation with the occurrence of earthquakes, which is 37% higher at 30 km compared to TC frequency. Fisher’s exact and Chi-square tests confirmed that ACE and TC-frequency-based classification are highly comparable; however, ACE is more representative of TC intensity. Conclusion This research demonstrates the existence of a relationship between tropical cyclone activity and earthquake occurrences over the WNP. More precisely, there is evidence that tropical cyclones’ activity, especially its intensity estimated through accumulated cyclone energy, might affect the shallow seismicity over the Pacific–Philippine plate boundary. Moreover, even without crossing to plate boundary, TCs formed in the WNP can potentially influence seismicity.