Source Contributions at Far-Regional Distances
Scientific Technical rept., No. 1
SOUTHERN METHODIST UNIV DALLAS TX DEPT OF GEOLOGICAL SCIENCES
Pagination or Media Count:
In order to investigate source contributions at far-regional distances as far as 2,000 km, a reliable model of the upper mantle structure is necessary. In many cases successful discriminants are based on the S wave part of far-regional seismograms including Sn, Sg, Lg and surfaces waves. Therefore it is mandatory to place corresponding weight on constraining the upper mantle S wave structure for the region under consideration. This current report hence provides an investigation of the mantle shear structure for the Western U.S. from body and surface wave inversion. Earthquakes on the coast of northern California and off the coast of southern Oregon 5.5 Ms 7.1 have provided a set of data at LTX showing clear mantle S arrivals that become very impulsive at distances near 2,400 km. The great circle paths for these events to LTX coincide with the LTX-NTS path. These data allow the interpretation of the S velocity structure for the Western U.S. to depths of the upper mantle transition zone from the body waves and give constraints for the shallower structure from surface waves from inversion of Rayleigh and Love waves, summarized in the two papers contained in this report.