- 1Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, Paris, France (jpm@ipgp.fr)
- 2Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, Paris, France (riahi@ipgp.fr)
- 3Department of Earth Sciences, University of Geneva, Geneva, Switzerland (ali.riahi@unige.ch)
- 4Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, Paris, France (saade@ipgp.fr)
- 5Sixense Geophysics, Vinci Construction, Nanterre, France (saade@ipgp.fr)
- 6Storengy SAS - DIREX/DGSM, Engie Group, Bois-Colombes, Frances (alexandre.kazantsev@storengy.com)
- 7Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, Paris, France (stutz@ipgp.fr)
- 8Institut de Physique du Globe de Paris (IPGP), Université Paris Cité, Paris, France (metaxian@ipgp.fr)
Cyclones, typhoons or hurricanes over the ocean generate oceanic waves. The interactions between these waves produce pressure fluctuations close to the ocean surface, which are the source of secondary microseisms in the frequency range 0.1–1 Hz. This study investigates secondary microseisms generated by the cyclone Gillian, with a specific focus on the impact of Horizontal Polarization Anomaly (HPA) of surface waves.
Cyclone Gillian developed in March 2014 over the Indian Ocean near southern Indonesia. Initially, it moved westward across the Indonesian Islands, then it reached a minimum distance of ~200 km from the Indonesian shoreline on 21 March. The cyclone then shifted in a west-southwest direction, intensifying as it moved southward. By 23 March, Gillian reached its peak wind speed, with gusts of ~315 km/h, when it was located over 1000 km from Indonesia.
During Gillian's activity, a temporary seismic array consisting of 46 three-component seismometers, with interstation distances of ~2 km, was deployed around the Merapi volcano and its surrounding region in Indonesia. Analysis of this seismic dataset reveals that secondary microseism extended to higher frequencies (up to ~1 Hz) at most stations, coinciding with the cyclone’s closest approach to the array on 20–22 March. In addition, beamforming analysis shows that during periods of strong wind speeds (22–24 March), seismic waves at 0.11 Hz arrived at the network from multiple directions and with various slowness values.
To quantify the effect of the cyclone on secondary microseisms, the full seismic cross-correlation tensor was computed for the cyclone activity period and the subsequent seven months. The Optimal Rotation Algorithm (ORA) (Roux et al. 2009) was applied to estimate the horizontal polarization anomaly of surface waves (Saade et al. 2017). Results demonstrate a significant increase in HPA on 23 March, corresponding to the cyclone’s peak wind speed. The rapid release of the polarization anomaly following the end of the cyclone suggests that this pulse can be attributed to the effects of the cyclone, acting as a moving noise source.
References:
Roux, P. (2009). Passive seismic imaging with directive ambient noise: application to surface waves and the San Andreas Fault in Parkfield, CA. Geophysical Journal International, 179(1), 367-373.
Saade, M., Montagner, J. P., Roux, P., Shiomi, K., Enescu, B., Brenguier, F. (2017). Monitoring of seismic anisotropy at the time of the 2008 Iwate-Miyagi (Japan) earthquake. Geophysical Journal International, 211(1), 483-497.
How to cite: Montagner, J.-P., Riahi, A., Saade, M., Kazantsev, A., Stutzmann, É., and Métaxian, J.-P.: Seismic Ambient Noise and Horizontal Polarization Anomaly During Cyclone Gillian at the Merapi Volcanic Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16353, https://doi.org/10.5194/egusphere-egu25-16353, 2025.
