- Email: [email protected]
Lateral variations in shear velocity and attenuation in the upper mantle
Tectonophysics, 56 (1979) 97 @ Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
97
LATERAL VARIATIONS IN SHEAR VELOCITY AND ATTENUATION IN THE UPPER MANTLE
STUART A. SIPKIN AND THOMAS H. JORDAN Scripps Institution 92093 (U.S.A.)
of Oceanography,
University
of California,
San Diego,
La Jolla,
CA
(Received July 10, 1978)
ABSTRACT
We have used digitally recorded long period seismic data from the HGLP and SRO networks to obtain estimates of multiple ScS travel times and spectra and have used these to place constraints on the lateral variations in uppermantle shear velocity and attenuation structure. The travel time results are consistent with our previous findings: to a first approximation, upper-mantle heterogeneity as expressed in vertical travel time differences can be correlated with surface tectonic features. A spectral stacking procedure for retrieving the attenuation operator for SH polarized multiple ScS waves has been applied to seismograms representing a variety of tectonic provinces. The spectral analysis has yielded stable estimates of the phase and amplitude response of the attenuation operator in the frequency interval 6-60 mHz. These estimates indicate that the apparent Q can also be correlated with surface tectonic regimes. REFERENCES Jordan, T.H. and Sipkin, S.A., 1977. Estimation of the attenuation operator for multiple ScS waves. Geophys. Res. Lett., 4: 167-170. Sipkin, S.A. and Jordan, T.H., 1976. Lateral heterogeneity of the upper mantle determined from the travel times of multiple ScS. J. Geophys. Res., 81: 6307-6320.
97
LATERAL VARIATIONS IN SHEAR VELOCITY AND ATTENUATION IN THE UPPER MANTLE
STUART A. SIPKIN AND THOMAS H. JORDAN Scripps Institution 92093 (U.S.A.)
of Oceanography,
University
of California,
San Diego,
La Jolla,
CA
(Received July 10, 1978)
ABSTRACT
We have used digitally recorded long period seismic data from the HGLP and SRO networks to obtain estimates of multiple ScS travel times and spectra and have used these to place constraints on the lateral variations in uppermantle shear velocity and attenuation structure. The travel time results are consistent with our previous findings: to a first approximation, upper-mantle heterogeneity as expressed in vertical travel time differences can be correlated with surface tectonic features. A spectral stacking procedure for retrieving the attenuation operator for SH polarized multiple ScS waves has been applied to seismograms representing a variety of tectonic provinces. The spectral analysis has yielded stable estimates of the phase and amplitude response of the attenuation operator in the frequency interval 6-60 mHz. These estimates indicate that the apparent Q can also be correlated with surface tectonic regimes. REFERENCES Jordan, T.H. and Sipkin, S.A., 1977. Estimation of the attenuation operator for multiple ScS waves. Geophys. Res. Lett., 4: 167-170. Sipkin, S.A. and Jordan, T.H., 1976. Lateral heterogeneity of the upper mantle determined from the travel times of multiple ScS. J. Geophys. Res., 81: 6307-6320.