Receiver functions from multiple-taper spectral correlation estimates

Teleseismic P waves are followed by a series of scattered waves, particular ly P-to-S converted phases, that form a coda. The sequence of scattered wav es on the horizontal components can be represented by the receiver function (RF) for the station and may vary with the approach angle and azimuth of t he incoming P wave. We have developed a frequency-domain RF inversion algor ithm using multiple-taper correlation (MTC) estimates, instead of spectral division, using the pre-event noise spectrum for frequency-dependent dampin g. The multitaper spectrum estimates are leakage resistant, so low-amplitud e portions of the P-wave spectrum can contribute usefully to the RF estimat e. The coherence between vertical and horizontal components can be used to obtain a frequency-dependent uncertainty for the RF. We compare the MTC met hod with two popular methods for RF estimation, time-domain deconvolution ( TDD), and spectral division (SPD), both with damping to avoid numerical ins tabilities. Deconvolution operators are often biased toward the Frequencies where signal is strongest. Spectral-division schemes with constant water-l evel damping can suffer from the same problem in the presence of strong sig nal-generated noise. Estimates of uncertainty are scarce for TDD and SPD, w hich impedes developing a weighted average of RF estimates from multiple ev ents. Multiple-taper correlation RFs are more resistant to signal-generated noise in test cases, though a "coherent" scattering effect, like a strong near-surface organ-pipe resonance in soft sediments, will overprint the Ps conversions from deeper interfaces. The MTC RF analysis confirms the broad features of an earlier RF study for the Urals foredeep by Levin and Park (1 997a) using station ARU of the Global Seismographic Network (GSN), but adds considerable detail, resolving P-to-S converted energy up to f = 4.0 Hz.