Cyclone-Induced Microseismic Signals Recorded in Sumatra During Tropical Cyclone Senyar

On 27 November 2025, Tropical Cyclone (TC) Senyar impacted northeastern Sumatra, providing the first opportunity to study cyclone-induced microseismic signals in Indonesia. The characteristics of the cyclone were analyzed using continuous seismic data recorded between 24 and 30 November 2025 from the seismic network across Sumatra. Recent advances in noise interferometry allow the estimation of empirical Green’s functions through the calculation of cross-correlation tensors. These functions are dominated by surface waves, enabling the monitoring of seismic velocity and anisotropy through Horizontal Polarization Anomaly (HPA). In this study, we evaluate the seismic effects of TC Senyar on ambient seismic noise. The results show an amplification of ambient seismic noise dominated by microseismic activity in the frequency range of 0.10 to 0.25 Hz, characterized by an enveloped waveform associated with TC Senyar. Seismic displacement and energy were detected several hours after the cyclone passed near the observation area, at distances of approximately 20 to 30 km from the cyclone location. The cyclone reorganized the ocean wave field, and ocean wave–wave interactions likely generated multiple second order microseism sources. The observed HPA pulse reflects a temporary change in the ambient noise source, demonstrating the strong coupling between tropical cyclone dynamics and near-surface seismic observations in the Indonesian region.