Accession Number : ADA262536


Title :   Modern Seismic Travel Time Tables and Station Corrections for P and S waves


Descriptive Note : Final rept. 13 Sep 90-13 Dec 92


Corporate Author : SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA


Personal Author(s) : Orcutt, John A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a262536.pdf


Report Date : 13 Dec 1992


Pagination or Media Count : 37


Abstract : (1) We refine estimates of inner core structure by examining PKP travel times and find that anisotropy is a simpler explanation than heterogeneity for the observed residual patterns. Our preferred model of inner core anisotropy contains velocities that are 0.5% faster in a N-S direction than an E-W direction. (2) We study various mantle differential travel times including SS-S, ScS-S, PP-P, and PcP-P and compare these results to those obtained from handpicked waveform data. Large-scale coherent patterns of residuals are seen which indicate,mantle heterogeneity. (3) We examine PKP travel times to study the possibility of outer core heterogeneity models which are suggested by observations of anomalous splitting in normal modes. We find that the travel times limit the scale of possible outer core heterogeneity to models much smaller than those required to explain the mode splitting data. (4) We develop computer codes which return travel time and ray geometries for a given seismic phase, source-receiver pair, and arbitrary 3-d earth models specified by their spherical harmonic expansions. Seismic travel times, Earth models, Core structure.


Descriptors :   *SEISMIC WAVES , *EARTH MODELS , *SEISMIC VELOCITY , *TRAVEL TIME , COMPUTER PROGRAMS , OBSERVATION , WAVEFORMS , HARMONICS , SPHERICAL HARMONICS , ESTIMATES , ANISOTROPY , RECEIVERS , PATTERNS , HETEROGENEITY , PRIMARY WAVES(SEISMIC WAVES) , EARTH MANTLE , SEISMOLOGICAL STATIONS , SECONDARY WAVES


Subject Categories : Geology, Geochemistry and Mineralogy
      Seismology


Distribution Statement : APPROVED FOR PUBLIC RELEASE