[S-SS07] Environmental Seismology: from deep earth to surface process

[SSS07-P04] Higher Mode Rayleigh Waves in Taiwan: Insights from Seismic Ambient Noise Cross-Correlation

*Chun-Fu Liao¹, Ying-Nien Chen², Yuancheng Gung¹ (1.Department of Geosciences, National Taiwan University, 2.Department of Earth and Environmental Sciences, National Chung Cheng University)

Keywords:higher mode, microseism, interferometry, excitation

This study focuses on a type of seismic noise known as microseism, which is continuous ground vibration primarily caused by the interaction between ocean waves and the Earth. While most research in this field has focused on the fundamental mode of Rayleigh waves within microseism, this study focuses on a higher mode, a less studied aspect. We specifically examined the behavior of this higher mode in Taiwan, employing spatiotemporal characterization that analyzes the correlation of these vibrations across various locations. Our findings indicate that both fundamental and higher mode vibrations are present in the frequency band associated with short period secondary microseism. We observed that the energy changes in these vibrations correlate with ocean wave height and the conditions in the shallow waters surrounding the island. Furthermore, the energy relationship between the fundamental and higher mode vibrations provides insights into underground structures in Taiwan. Understanding both modes of vibration can improve depth resolution of tomographic studies, which image the Earth’s interior.