An integrated geophysical study of the Knight Peak graben
Keith Davis, Steven Harder, Roger W. Greensfelder, and James Ni
An integrated geophysical study using seismic refraction and gravity data was performed in the Knight Peak graben area in southwestern New Mexico. The objective of the study was to model the graben structure, with special attention to the location of the unexposed northeastern bounding fault, the extent of the buried Tertiary tuffs and the maximum depth to the Precambrian basement.
Seismic refraction data were taken along a 12 km long and two shorter profiles, all of which spanned the graben perpendicular to its strike. Delay times for distant quarry blasts were observed at 26 stations distributed along the entire length of the profile. The two shorter refraction lines were sited near the center of the long profile: one, 2.2 km in length, was a reversed explosion line; the other, 100 m in length, was an unreversed hammer line. Gravity data were also obtained at 68 stations along the 12 km profile.
Joint modeling of the seismic and gravity data indicates a half graben, formed by a block of granite and volcanic tuff which has rotated downward to the northeast against a subsurface fault. The graben has a width of about 2 km, and structural relief of about 400 m, making it smaller than has been indicated in the literature.
- Davis, Keith; Harder, Steven; Greensfelder, Roger W.; Ni, James, 1988, An integrated geophysical study of the Knight Peak graben, in: Cretaceous and Laramide tectonic evolution of southwestern New Mexico, Mack, G. H.; Lawton, T. F.; Lucas, S. G., New Mexico Geological Society, Guidebook, 39th Field Conference, pp. 77-81.