Mantle Q structure from S‐P differential attenuation measurements

Abstract

We describe a new one‐dimensional Q model for short‐period body waves derived from a data set of 15,000 differential t* measurements of teleseismic P and S waves recorded in broadband seismograms. Measured t* values are little affected by the source time function or instrument response since the P and S waves are recorded at the same station from the same event. We process the data using a waveform cross‐correlation method applied to the first half cycle of the waveforms to avoid reflection and conversion effects. We invert our t* measurements for a two‐layer QS model. Our new Q model has about the same attenuation in the upper mantle and less attenuation in the lower mantle than models derived from longer period data sets. This implies that the frequency dependence of Q is more apparent in the lower mantle and that the effects of attenuation in the upper mantle are approximately constant at frequencies below about 1 Hz. We also observe lateral variations of attenuation in the uppermost mantle by solving for station and event terms, which exhibit correlations with regional tectonics.