Structure of the Earth's crust from spectral behavior of long-period body waves

Abstract

Long‐period P waves from distant earthquakes have been analyzed from seismograms recorded at Albuquerque and Bermuda in the light of Haskel's theory of the spectral response of a layered crust. By using the ratio of the vertical spectrum to the horizontal component spectrum, we obtain a function which depends on structure beneath the station. Because of the poorly understood nature of the signal which follows the first P wave motion, the methods of power spectrum analysis are applied and a lag window selected to discriminate against long time correlations within the signal. Corrections for the differing responses of the three components are made by using the power spectral matrix of calibration signals. A range of crustal models has been found which agrees with the data. We are restricted primarily in choosing models for the lower half of the crust; variations of structure in the upper half do not noticeably affect the theoretical curves in the period range considered (0.02 to 0.20 cps). At Albuquerque the crust is about 40 km thick and the lower crust has velocities in the range 6.6 to 7.0 km/sec. The Mohorovicic (M) discontinuity under Bermuda is 12 km below sea level, and the structure appears to be a normal oceanic crust depressed elastically by the weight of the volcanics which compose the island.

Anomalous seismic structure beneath the Klyuchevskoy Group, Kamchatka

“…[10] Teleseismic P-waves generate accompanying shear waves as a result of interaction between the primary wave and encountered material interfaces [Phinney, 1964;Vinnik, 1977]. Receiver functions (RFs) describe recorded sequences of P-to-S converted wave phases generated at each interface encountered by the primary wave.…”

Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions

“…[9] The teleseismic receiver function technique represents a straightforward method to extract information on the structure of the lithosphere in the vicinity of the recording station [e.g., Phinney, 1964;Helmberger and Wiggins, 1971;Langston, 1979]. Using deconvolution, the technique essentially strips off the P wave energy except for the direct arrival, and leaves enhanced P-to-S conversions and reverberations on the resulting waveform.…”

Inferences of a Layered Structure from S Wave Spectra Part 3. SH and SV Waves and Some Related Problems

“…computed for the six models numbered as 5, 9, 11, 14, 17 and 18 with an oceanic crust, which fit reasonably well the P wave spectrum (PHINNEY, 1964), but three of them are given in the above figure. Comparison in Fig. 7 shows that model 5 yields a satisfactory agreement with the observations in the positions of the first peak and the first trough both in the amplitude ratio and the phase difference curves.…”