Latitude: 35°42'41"
Longitude: 117°43'16"

Length: 1255.2m
Number of Bench marks: 37

Number of Surveys to 2000: 9
Date of Initial Survey: 10 July 1983
Date of Latest Survey: 15 Jan 1996

Permission to Trespass on the property bearing this array is required and must be obtained well in advance of anticipated work.

From Mojave, drive Hwy 395 north and northeast about 44 miles to Hwy 178. Proceed eastward 13 miles to Ridgecrest and to the entrance of the China Lake Naval Weapons Center. To reach the surveying site, proceed east on E. Inyokern Blvd. to Lauritsen Road. Turn left; proceed 0.6 mi to Lauritsen Gate - check in - proceed 0.1 mi on Lauritsen Road to raod intersection, proceed 0.1 mi and then veer left on to Pole Line Road, thence north northeast 1.8 mi, thence left on Water Road. Proceed 1.8 mi then veer right at the Range Control Center. Drive 2.6 miles from the Range Control Center. Fifty meters after a radar reflector consisting of a tetrahedron mounted on two poles, turn left on a paved road. Drive 1.3 miles and stop 50 m before another gate. Point AF21 is 15 m south of the paved road and is marked by an 8" x 8" fence post.

This is one of two L-shaped arrays across one of the N-S normal faults evincing surface rupture following an earthquake swarm in Indian Wells Valley in 1982 (Roquemore and Zellmer, 1983). It is located five and one-half miles NNW of the town of Ridgecrest .

Bench marks fluctuate +/- 1 mm nonsystema tically among seven levelings from July 1983 to July 1992. The fluctuations are nearly equal to the allowable closure error. The height differences change character from 1987 to 1992. They may be related to the swarm of M 4 earthquakes that occurred in the China Lake area a few days after the Landers earthquake sequence of 28 June 1992, but because the changes are so small, further speculation is idle. Height changes were not observed following the 1995 earthquake sequence on the east side of Indian Wells Valley.


Roquemore, G. R., and J. T. Zellmer, 1983. Ground cracking associated with the 1982 magnitude 5.2 Indian Wells Valley earthquake. California Geology 30 (9), 197-200.

Sylvester, A. G., J. Feltman, L. Hasbargen, T. Bruskotter, D. Korengold, S. Dougherty, G. Bawden, and L. Mitchell, 1992. Negligible afterslip with 28 June 1992 Landers earthquake and no nearfield triggered slip on southern San Andreas fault. EOS Transact ions, 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, 20, 1079-1082.

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