Relationship between seismicity and crustal structure in the western Great Basin

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1979

OSTI ID:5267570

Cogbill, Jr, A H

This study searches for possible relationships between the Nevada Seismic Zone and the anomalous seismicity and the crustal and upper mantle structure of the western Great Basin. The data used are 16,629 gravity observations in the western Great Basin and relative teleseismic P-wave delays measured by a local network near Mina, Nevada. The velocities inferred from the seismic refraction studies are converted to densities using newly-derived density-velocity relations for crustal rocks. The instrumentally recorded seismicity of the western Great Basin is analyzed for time trends in the mean locations of earthquakes of magnitudes greater than 4.0. Using crustal thicknesses and velocities inferred from refraction profiles as constraints, P-wave delays and gravity anomalies in the Excelsior Mountains Region are used to infer that a zone of partially melted crustal or upper mantle material underlies the southwestern part of the region. The gravity anomalies are consistent with the variation in crustal thickness inferred from refraction studies, but the P-wave delays are not completely accounted for by this parameter. Low-wavenumber free-air and Bouguer anomalies are compared to the corresponding low-wavenumber topography to infer fields and topography are interpretable by changes in the depth to the crust-mantle interface. Although a degree of spatial correlation between the Nevada Seismic Zone and the larger gradients in the depth to the crust-mantle interface exists, no causal relation between the seismic zone and the changing crustal thickness is evident.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• OSTI ID: 5267570
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
DENSITY
EARTH CRUST
EARTH MANTLE
EARTHQUAKE FOCI
EARTHQUAKE MAGNITUDE
EARTHQUAKES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GRAVITY SURVEYS
GREAT BASIN
LITHOLOGY
NORTH AMERICA
PHYSICAL PROPERTIES
REFRACTION
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC WAVES
SEISMICITY
SURVEYS
USA
VELOCITY