Upper mantle anelasticity and tectonic evolution of the western United States from surface wave attenuation

摘要: Rayleigh wave phase and group velocities attenuation coefficients in the period range 18 to 120 s have been determined for three regions along nine paths across western United States using a two-station technique. The were found increase from east west between Rocky Mountains Pacific coast. inverted, differential procedure, obtain shear velocity models regions. These then used an inversion process where Qβ−1 as function of depth was obtained observations attenuation. results show that Qβ values upper mantle are lowest coastal westernmost Basin Range highest Great Plains. Intermediate appear occur beneath province Columbia Colorado plateaus, although uncertainties data prevent clear separation region Low crust, higher lower uppermost 20 km all these overlie low-Q zone which decrease west, (15–20) being similar those observed above descending slabs Pacific. regional pattern Q is crustal inferred surface studies Lg coda values. patterns variations correlate with temporal sequence tectonic magmatic activity States, both ranges occurring has most recent. Partial melting and/or enhanced dislocation motion volume interstitial hydrothermal fluids cracks crust may be ultimately due processes occurred during plate consumption interaction near margin States.