Open AccessSurface‐wave sensitivity to 3‐D anelasticity
Author(s) -
Zhou Ying
Publication year - 2009
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2009.04230.x
Subject(s) - amplitude , geophysics , geology , mantle (geology) , surface wave , phase velocity , earth structure , seismic wave , seismic tomography , love wave , wave propagation , inversion (geology) , physics , seismology , longitudinal wave , mechanical wave , tectonics , optics
SUMMARY Lateral variations in mantle anelasticity ( Q ) are important for understanding the Earth's thermal and chemical structure in the mantle. In the past decades, preliminary global 3‐D tomographic Q models have been developed based upon the assumption that traveltime (phase delay) anomalies are due to the Earth's elastic (velocity) structure whereas amplitude anomalies are dominated by 3‐D anelastic ( Q ) structure. In this paper, we calculate the 3‐D finite‐frequency sensitivity of fundamental‐mode surface‐wave phase delays and amplitudes to perturbations in anelasticity ( Q ). Calculations of Q and velocity sensitivity kernels show that (1) roughly 15–20 per cent of observed phase delays in long‐period surface waves can be explained by lateral variations in Q in the upper mantle; and (2) focusing and defocusing effects due to 3‐D velocity structure account for a major portion of observed amplitude perturbations in long‐period surface waves. The coupling between elastic and anelastic effects in both seismic traveltimes and amplitudes indicates that a joint inversion of 3‐D velocity and 3‐D Q structure accounting for both anelastic dispersion and associated focusing and defocusing effects is necessary in mapping lateral heterogeneities in the upper mantle.