Ray path of head waves with irregular interfaces |
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| Authors: | Hong Zhou Xiao-fei Chen |
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| Institution: | (1) Department of Earth Science, University of Bergen, Allegaten 41A, 5007 Bergen, Norway;(2) Ocean Research Institute, University of Tokyo, Tokyo, Japan;(3) Institute of Seismology and Volcanology, Hokkaido University, Sapporo, Japan |
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| Abstract: | Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.
However, the path that the rays travel along in media with irregular interfaces is not clear. Here we study the problem by
simulation using a new approach of the spectral-element method with some overlapped elements (SEMO) that can accurately evaluate
waves traveling along an irregular interface. Consequently, the head waves are separated from interface waves by a time window.
Thus, their energy and arrival time changes can be analyzed independently. These analyses demonstrate that, contrary to the
case for head waves propagating along a flat interface, there are two mechanisms for head waves traveling along an irregular
interface: a refraction mechanism and transmission mechanism. That is, the head waves may be refracted waves propagating along
the interface or transmitted waves induced by the waves propagating in the higher-velocity media. Such knowledge will be helpful
in constructing a more accurate inversion method, such as head wave travel-time tomography, and in obtaining a more accurate
model of subsurface structure which is very important for understanding the formation mechanism of some special areas, such
as the Tibetan Plateau. |
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| Keywords: | head waves irregular interface refracted waves transmitted waves ray path |
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