Seismicity of west Texas
A four year seismic study has found the Basin and Range province of west Texas and the adjacent area of Mexico to be more seismically active then than heretofore known. A University of Texas five station seismic array around the Marfa Basin has located or detected approximately 800 local and regional earthquakes with S-P times of less than 30 sec. A crustal model for the Basin and Range is derived from natural and artificial sources and contains four layers having velocities of 3.60, 4.93, 6.11, and 6.60 km/sec, respectively, overlying a mantle of 8.37 km/sec. A moderate level of seismic activity has been detected near Van Horn, in the Marfa Basin, and along the Texas-Mexico border between latitudes 30 and 31/sup 0/N. Five earthquake sequences were recorded, two near the Texas-Mexico border and three in the Marfa Basin. Four of these sequences showed quiescent periods in foreshock activity preceding the main shock. On the eastern side of the Marfa Basin a diffuse linear seismic zone may represent an unmapped fault, striking N 50/sup 0/W that coincides with Muehlberger's proposed eastern boundary of Basin and Range faulting. A new epicenter for the Valentine, Texas earthquake of August 16, 1931 has been relocated instrumentally at the northern end of this diffuse zone. Regional and local teleseismic P-wave arrival time anomalies observed for the nearby Gnome underground nuclear explosion of 1961 are used to determine station corrections and thus to locate the new 1931 epicenter at 3.69/sup 0/N, 104.57/sup 0/W. Several estimates of magnitude (m/sub b/) based on intensity data range from 5.6 to 6.4. Fault-plane and composite fault-plane solutions support Muehlberger's hypothesis that the Basin and Range is undergoing extension in a SW-NE direction.
- OSTI ID:
- 5070458
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
EARTHQUAKES
SEISMICITY
TEXAS
REGIONAL ANALYSIS
EARTHQUAKE MAGNITUDE
EPICENTERS
GEOLOGIC FAULTS
SEISMIC P WAVES
FEDERAL REGION VI
GEOLOGIC STRUCTURES
NORTH AMERICA
SEISMIC EVENTS
SEISMIC WAVES
USA
510100* - Environment
Terrestrial- Basic Studies- (-1989)
580201 - Geophysics- Seismology & Tectonics- (1980-1989)