Central Virginia Regional Seismic Network: crustal velocity structure in central and southwestern Virginia. [To compute epicentral distance, surface velocity as function of azimuth, in FORTRAN for IBM 370]

Technical Report · Tue Jan 01 04:00:00 EST 1980

OSTI ID:5499803

Bollinger, G A; Chapman, M C; Moore, T P

(I) A crustal velocity model was derived by analysis of P-wave travel times for seven earthquakes which occurred within or near the Piedmont province of Virginia. In addition, upper crustal P- and S-wave velocities were determined by use of an 80-km reversed refraction profile. The P-wave velocity of the deep crust was determined by use of a network of three stations in central Virginia. The preferred crustal velocity structure model consists of two layers. The upper layer is 15 km thick, with P- and S-wave velocities of 6.09 and 3.53 km/s. The intermediate layer has P- and S-wave velocities of 6.5 and 3.79 km/s. Upper-mantle velocities appropriate for the region are 8.18 and 4.73 km/s for P and S waves. Crustal thickness varies from 39 km beneath the Blue Ridge Mountains to a minimum value of 31 km beneath the central Piedmont. (II) Two crustal models are presented for southwestern Virginia as possible interpretations of unreversed refraction profiles and earthquake-phase arrival data. The preferred crustal model has a 49 km thickness. The layer velocities (km/s) and thicknesses (km) are as follows: Vpl = h1 = 10, h2 = 39, and upper mantle Pn and Sn velocities of 8.18 and 4.79 km/s. The alternate model is Vp1 = 5.63, Vs1 = 3.44, Vp2 - 6.05, Vs2 = 3.52, Vp3 = 5.63, Vs3 = 3.84, h1 = 5.7, h2 = 9, h3 = 36, and upper mantle Pn and Sn velocities of 8.18 and 4.79 km/s. A velocity anisotropy (10%) was measured in the Valley and Ridge province by use of quarry blast data. The P-wave velocity was6.03 km/s parallel to structural trend and 5.45 km/s prependicular to it. 37 figures, 10 tables.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg (USA). Dept. of Geological Sciences
• OSTI ID: 5499803
• Report Number(s): NUREG/CR-1217
• Country of Publication: United States
• Language: English

Related Subjects

510100 -- Environment
Terrestrial-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CENTRAL REGION
COMPUTER CODES
COMPUTERS
DATA
DATA FORMS
DIMENSIONS
EARTH CRUST
EXPERIMENTAL DATA
FORTRAN
GRAPHS
IBM COMPUTERS
INFORMATION
ISOLATED VALUES
NORTH AMERICA
NUMERICAL DATA
PROGRAMMING LANGUAGES
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC WAVES
STRUCTURAL MODELS
THICKNESS
USA
VELOCITY
VIRGINIA
WAVE PROPAGATION