Latitude: N 33°56°'03"
Longitude: W 116°28'00"
Number of Bench marks: 22
Number of Surveys to 2000: 11
Date of Initial Survey: 7 September 1985
Date of Latest Survey: 5 September 1996
Trespass Permission: None needed.
From I-10 take Palm Drive north 3.1 miles toward Desert Hot Springs to Dillon Road. Turn right onto Dillon Road, drive east 1.5 miles to Mountain View Road. Turn left onto Mountain View road, drive 0.5 mile to a paved road on the right that is about 100 m before a power line. Drive east on the paved road for 200 m until it turns sharply left. Do not turn left but go straight on a dirt road. The dirt road will curve to the left and follow a wash into the hills. The center of the level line is located where a power line crosses the dirt road.
This line was established across the Mission Creek strand of the San Andreas fault two miles southeast of Desert Hot Springs.
The line was surveyed 10 days after the 28 June 1992 Landers earthquake sequence (M 7.3) to determine if that earthquake or the 22 April 1992 Joshua Tree earthquake (M 6.1) had perturbed the San Andreas fault.
Six levelings covering the period September 1985 to July 1992 are compared in an accompanying figure. A southwestward tilt of about 2 microradian in 7 years may be inferred from the graph, but there is no step at the fault. Bench mark MH07 see ms to be unstable relative to the others. Judging by the accompanying figure, the 1992 earthquakes had no surficial effect on the fault.
Clark, M. M., 1984. Map showing recently active breaks along the San Andreas fault and associated faults between Salton Sea and Whitewater River - Mission Creek, California. U.S. Geological Survey Map I-1483, 1:24,000.
Sylvester, A. G., J. Feltman, L. Hasbargen, T. Bruskotter, D. Korengold, S. Dougherty, G. Bawden, and L. Mitchell, 1992. Negligible aftersl ip with 28 June 1992 Landers earthquake and no nearfield triggered slip on southern San Andreas fault. EOS Transactions, American Geophysical Union, v. 73, 380.
Sylvester, A. G., 1993. Investigation of nearfield postseismic slip following the M W 7.3 Landers earthquake sequence of 28 June 1992, California. Geophysical Research Letters, in press.
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