Numerical Modeling of Three-Component Seismic Ambient Noise: Insights into the Generation of Secondary-Microseism Love Waves

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise
Type: Oral
Date: 4/29/2020
Time: 10:45 AM
Room: 230 + 235
Description: 

In this study, we employ the spectral-element method to model three-component secondary microseisms at several seismic stations worldwide. Sources are a distribution of frequency-dependent pressure sources in the ocean computed with a state-of-the-art ocean wave model. For the propagation of seismic waves, we use realistic 3D crust and mantle models, including topography and bathymetry and an analytical correction for the propagation of P waves in the ocean. The resulting model is a necessary step towards full-wavefield ambient-noise tomography that accounts for a realistic distribution of sources as well as 3D heterogeneities.

We apply our method to study the generation of Love waves in the secondary microseism frequency band (0.1-0.3 Hz). Observations of secondary microseism Love waves date back to the early (e.g., Zoeppritz, 1908) and mid (e.g., Darbyshire, 1954) 20th century. While the mechanism currently accepted for the generation of secondary microseisms (Longuet-Higgins, 1950; Hasselmann, 1963) explains well the Rayleigh-wave content on the vertical component of seismic records, it does not explain the presence of Love waves on the horizontal components. We estimate the Love-to-Rayleigh spectral amplitude ratio at each station of the Global Seismic Network and find that the presence of 3D heterogeneities in the Earth structure plays a major role on the generation of Love waves.

Presenting Author: Lucia Gualtieri

Authors