Global variation of body-wave attenuation in the upper mantle from teleseismic P wave and S wave spectra

摘要

We constrain the spatial variation of P-wave (t_P*) and S-wave (t_S*) attenuation by inverting 190,000 teleseismic P- and S-wave spectra up to 0.8 Hz. These spectra are derived from 250 deep earthquakes recorded at 880 broadband global and regional network stations. The variance and ratios of t_P* and t_S* values are consistent with PREM's upper mantle velocity and Q structures and conventional t_P* and t_S* values. High attenuation is resolved beneath stations in tectonically active regions characterized by high heat flow. Low attenuation marks stable continental regions. The maps of t _P* and t_S* correlate well with the variations of t_S* computed and inferred from (1) the most recent surface-wave Q model and (2) a thermal interpretation of shear-wave velocity tomography. This indicates that maps of body- and surface-wave attenuation reflect intrinsic attenuation and variable temperature in the mantle.