Bulletin of the Seismological Society of America
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Bulletin of the Seismological Society of America; April 1988; v. 78; no. 2; p. 816-837
© 1988 Seismological Society of America
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by KRISHNA, V. G.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Crustal velocity models in the Western United States from travel times and amplitudes of seismic refraction data

V. G. KRISHNA

NATIONAL GEOPHYSICAL RESEARCH INSTITUTE, UPPAL ROAD, HYDERABAD 500 007, India

Abstract

Travel times and amplitude interpretation of crustal phases on the seismic refraction profiles Delta-west, Utah, in the northern Basin and Range and Lamar-west, Colorado, in the Southern Rocky Mountains-Great Plains provinces yielded new crustal P velocity-depth functions in the Western United States. The new velocity-depth functions not only confirm the broad features of the crustal structure inferred from earlier studies, but they also resolve more details of the crustal velocity variations in the region. The Basin and Range province is characterized by a thin crust (crustal thickness: 22 to 26 km), low-average crustal P velocity (~5.8 km/sec), and a low Pn velocity (~7.6 km/sec), with the presence of a very prominent upper crustal low-velocity layer (LVL) between 6 to 13 km depth with a minimum velocity of 5.30 km/sec. The top and bottom of this upper crustal LVL are transitional boundaries of 6.0 to 6.9 km and 9.4 to 12.9 km, respectively. There is also another LVL in the lower crust, between 20 km depth to the Moho discontinuity, with a minimum velocity of 6.05 km/sec in this region. The bottom of this lower crustal LVL is the Moho discontinuity, which is a sharp boundary in this region. There is also an indication for the presence of a discontinuity with a rather small velocity jump (7.60 to 7.65 km/sec) at a depth of 47 km in the upper mantle in the Basin and Range province. The Southern Rocky Mountains and the Great Plains provinces, on the other hand, are characterized by a much thicker crust (crustal thickness: 40 to 50 km), higher average crustal P velocity (~6.1 km/sec), and a higher Pn velocity (8.2 to 8.4 km/sec), with the absence of an upper crustal LVL. Instead, there are prominent velocity discontinuities at depths of 10 km (6.0 to 6.2 km/sec) and 21 to 23 km (6.2 to 6.6 km/sec). A lower crustal LVL, not well-constrained by the available data, is inferred in these regions also from about 30 km depth to the Moho discontinuity, with a minimum velocity of 6.15 to 6.20 km/sec. The bottom of this lower crustal LVL is the Moho discontinuity, which may be a 1-km-thick transitional boundary. The prominent features of the crustal P velocity-depth functions derived in the present study are qualitatively consistent with those of the new model of the continental crust proposed by Mueller (1977).




This article has been cited by other articles:


Home page
 Rocky Mountain GeologyHome page
G. R. Keller, C. M. Snelson, A. F. Sheehan, and K. G. Dueker
Geophysical studies of crustal structure in the Rocky Mountain region: A review
Rocky Mountain Geology, October 1, 1998; 33(2): 217 - 228.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1988 by the Seismological Society of America.