Near-vertical and intermediate offset seismic reflection data from west of the Whipple Mountains, SE California
During a seismic reflection survey conducted by the California Consortium for Crustal Studies in the Basin and Range Province west of the Whipple Mountains, SE California, a piggyback experiment was carried out to collect intermediate offset data (12--31 km). These data were obtained by recording the Vibroseis energy with a second, passive recording array, deployed twice at fixed positions at opposite ends of the reflected lines. The reflection midpoints fall into a 3-km-wide and 15-km-long region in Vidal Valley, roughly parallel to a segment of one of the near-vertical reflection profiles. This data set makes three unique contributions to the geophysical study of this region. (1) From forward modeling of the observed travel times using ray-tracing techniques, a shallow layer with velocities ranging from 6.0 to 6.5 km/s was found. This layer dips to the south from 2-km depth near the Whipple Mountains to a depth of 5-km in Rice Valley. These depths correspond closely to the westward projection of the Whipple detachment fault, which is exposed 1 km east of the near-vertical profiles in the Whipple Mountains. (2) On the near-vertical profile, the reflections from the mylonitically deformed lower plate at upper crustal and mid crustal depths are seen to cease underneath a sedimentary basin in Vidal Valley. However, the piggyback data, which undershoot this basin, show that these reflections are continuous beneath the basin. Thus near-surface energy transmission problems were responsible for the apparent lateral termination of the reflections on the near-vertical reflection profile.
- Research Organization:
- Center for Computational Seismology, Lawrence Berkeley Laboratory, Berkeley, California
- OSTI ID:
- 6273853
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 94:B1
- Country of Publication:
- United States
- Language:
- English
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