Polarization anomaly of Love waves caused by lateral heterogeneity |
| |
Authors: | Reiji Kobayashi |
| |
Institution: | Department of Geophysics, Kyoto University, Kyoto 606-8502, Japan |
| |
Abstract: | We calculate surface waves propagating in a laterally heterogeneous structure beneath the Kuril trench, where significant Love-wave polarization anomalies, called quasi-Love waves, are generated. Since 3-D wave propagation in the two-dimensionally heterogeneous structure can be assumed, we apply the 2.5-D finite difference method to the surface-wave calculations. The calculations show that a velocity contrast of 7 per cent at depths of less than 210 km beneath the Kuril trench cannot generate quasi-Love waves, and that an unlikely contrast of 20 per cent is required to generate clear quasi-Love waves. The possible cause of the quasi-Love waves inferred from previous studies on coupled free oscillations is a lateral variation in azimuthal anisotropy. The lateral variation in azimuthal anisotropy beneath the Kuril trench suggests a change in the mantle flow induced by the subducting slab. |
| |
Keywords: | finite difference method lateral heterogeneity Love waves subduction synthetic seismograms upper mantle |
|
|