| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
DEPARTMENT OF OCEANOGRAPHY OREGON STATE UNIVERSITY, CORVALLIS, OREGON
Abstract
Travel-time curves were constructed for the Pacific Northwest states based on recordings of recent local earthquakes. Average velocities of Pn and S waves were found to be 4 per cent lower in the region west of the Cascade Mountains than they are to the east of the Cascades, while velocities of P* and 
waves are essentially the same in the two provinces. West of the Cascades the velocities obtained are 7.67 km/sec for Pn, 4.37 for Sn, 6.61 for P*, and 5.48 for . East of the Cascades they are 7.96 km/sec for Pn, 4.56 for Sn, 6.60 for P*, and 5.53 for . Intercept times indicate that the crust (above the Mohorovicic discontinuity) is 5 to 10 km thinner to the west than east of the Cascades. Pn velocities are found to be independent of epicentral distance to distances of 1000 km, implying that the corresponding mantle materials and densities are uniform down to the low-velocity layer in each province. In both provinces Poisson's ratio in the mantle is 0.26. From the travel-time curves and gravity data, it appears that the section above the low-velocity layer east of the Cascades is approximately typical or "normal," while the corresponding mantle west of the Cascades consists of a different or anomalous material. The likelihood of crystal alignment, temperature anomalies, and normal velocity-density relations in the upper mantle sections are discussed.
This article has been cited by other articles:
|
|
 |
|
  Seismic evidence for widespread serpentinized forearc upper mantle along the Cascadia margin Geology, March 1, 2003; 31(3): 267 - 270.
|
|
|
|
 |
|
 C. E. ZERVAS and R. S. CROSSON Pn observation and interpretation in Washington Bulletin of the Seismological Society of America, April 1, 1986; 76(2): 521 - 546. [Abstract] [PDF]
|
|
|
|
|
|
C. A. LANGSTON and D. E. BLUM The April 29, 1965, Puget Sound earthquake and the crustal and upper mantle structure of western Washington Bulletin of the Seismological Society of America, June 1, 1977; 67(3): 693 - 711. [Abstract] [PDF]
|
|
|
|
|
|
R. L. MCCOLLOM and R. S. CROSSON An array study of upper mantle velocity in Washington State Bulletin of the Seismological Society of America, April 1, 1975; 65(2): 467 - 482. [Abstract] [PDF]
|
|
|
|
|
|
R. J. WETMILLER An earthquake swarm on the Queen Charlotte Islands Fracture Zone Bulletin of the Seismological Society of America, December 1, 1971; 61(6): 1489 - 1505. [Abstract] [PDF]
|
|
|
|
|
|
J. D. UNGER and R. W. DECKER The microearthquake activity of Mt. Rainier, Washington Bulletin of the Seismological Society of America, December 1, 1970; 60(6): 2023 - 2035. [Abstract] [PDF]
|
|
|
|
|
|
S. H. JOHNSON and R. W. COUCH Crustal structure in the North Cascade Mountains of Washington and British Columbia from seismic refraction measurements Bulletin of the Seismological Society of America, August 1, 1970; 60(4): 1259 - 1269. [Abstract] [PDF]
|
|
|
|
|
|
K. L. KAILA, P. R. REDDY, and H. NARAIN Crustal structure in the Himalayan foothills area of north India, from 'P' wave data of shallow earthquakes Bulletin of the Seismological Society of America, April 1, 1968; 58(2): 597 - 612. [Abstract] [PDF]
|
|
|
|
|
|
C. LOMNITZ and B. A. BOLT Evidence on crustal structure in California from the CHASE V explosion and the Chico earthquake of May 24, 1966 Bulletin of the Seismological Society of America, October 1, 1967; 57(5): 1093 - 1114. [Abstract] [PDF]
|
|
|
|
|
|
J. W. BERG Jr., L. TREMBLY, D. A. EMILIA, J. R. HUTT, J. M. KING, L. T. LONG, W. R. MCKNIGHT, S. K. SARMAH, R. SOUDERS, J. V. THIRUVATHUKAL, et al. Crustal refraction profile, Oregon coast range Bulletin of the Seismological Society of America, December 1, 1966; 56(6): 1357 - 1362. [Abstract] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
