Oscillation of a mountain root structure due to a Rayleigh wave incidence
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2001
Received: 23 February 2001
Accepted: 6 September 2001
Published: 18 June 2014
Spectral amplitudes of Rayleigh waves across a mountain root in the continental crust were studied by the use of the finite difference technique. The crust has a mountain root structure like that of the Tien Shan in China, and a maximum thickness of about 50 km. The waves are numerically simulated by implementing a plane Rayleigh wave incidence on the front of the mountain root structure. The spectral amplitudes of the vertical (W) component are shown to be strongly amplified by the mountain for periods from 20 to 50 s, with a maximum of about 7%, whereas those of the radial (U) component show a slight increase with an increase in period. For the mountain structure with small-scale low velocity zones (LVZ) in the bottom of the root and in the upper mantle, amplitudes of the W-component are enriched at periods slightly longer than those for the structure without the LVZ. For the mountain structure with a double large-scale LVZ in the lower crust and the upper mantle, amplitudes of the W-component are extensively amplified over a wide range beyond 50 s. The period range from 20 to 50 s with high amplifications of the W-component for the mountain root structure with or without the LVZ is consistent with periods, in which the Rayleigh to Love wave conversion is dominant in observed surface waves across the Tien Shan mountains (Pedersen et al., 1998).