P WAVE PARAMETERS MEASURED AT THE MONTANA LASA
Abstract
The raypath parameter, P, and the azimuth deviation of the source from the raypath direction have been computed from the first arrival P waves of over 600 earthquake events recorded at the Montana LASA during its first two years of operation. The epicenters of 247 of these events are located along a profile extending northwest of the reference station, LASA - AO, within the range of azimuth 300-320 degrees. The epicenters of 162 events are located along a profile toward the southeast in the range of azimuth 140-160 degrees. The observed p and azimuth deviations of the northwest profile are compared to those from the southeast, showing: (1) large effects due to either crustal structure or regional velocity gradients in the upper mantle beneath LASA, and (2) variations suggesting a large difference in the velocity of P waves within the mantle between 700 and 2000 kilometers. Comparison of our observations with those of Chinnery and Toksoz confirm their suggestion of velocity discontinuities in the mantle; our data imply an additional velocity discontinuity at a depth of approximately 1500 km along the northwest profile.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 26, 1968
- Accession Number
- AD0834914
Entities
People
- E. A. Flinn
- E. F. Chiburis
- P. R. Farnham
- R. L. Sax
Organizations
- Teledyne Technologies