dt/d delta Measurement of Short Period P Waves in the Upper Mantle for the Western North America using LASA
Abstract
Seismic ray parameter (dt/d delta) has been measured in the distance range delta = 8-344 utilizing LASA. An upper mantle velocity structure for P waves applicable to the Western Part of North America has been derived from these data. Measurement of dt/d delta was accomplished by calculating with a least squares procedure the dt/d delta from the measured arrival time at each sub-array or by forming beams with LASA from which dt/d delta was picked from the beams that gave the maximum amplitude. The velocity models were calculated by a Monte Carlo technique and show a low velocity region centered at a depth of 120 km and two zones of rapid velocity increase at 350 km and 650 km where the velocity changes from 8.7 to 9.6 km/sec and 10.2 to 10.9 km/sec, respectively. Our dt/d delta data supports the accumulating evidence that dt/dA is azimuthally dependent at LASA. Also, the data suggests that this azimuthal dependence is a result of structural anisotropy under LASA.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1969
- Accession Number
- ADA574029
Entities
People
- Jack C. Wolfe
Organizations
- Massachusetts Institute of Technology