Latitude: N 34°10'12"
Longitude: W 117°31'42"
Number of Bench marks: 14
Number of Surveys to 2000: 2
Date of Initial Survey: 1977 (CDMG)
Date of Latest Survey: 19 August 1994 (UCSB)
Trespass Permission: Cucumonga County Water Department
Directions: From Claremont proceed eastward on I-10 13 miles to Etiwanda Avenue, exit and proceed northward 7.9 miles to its termination at a powerline road. Locked gates preclude access farther up the canyon and into the array.
Comments: This array was established across the Cucumonga fault at the mouth of Day Canyon in 1977 by the California Division of Mines and Geology (Bennett, 1984).
Results: One bench mark, located on a power stanchion, had a height change of 10 mm in 19 years; the heights of all others had not changed more than 2 mm in the same time. A permissive case may be made that the height difference increased 4 mm across one of the main and youthful fault traces, but it is hazardous to assert that the height change is tectonic, let alone to postulate its cause. Judging solely from the leveling results, one may conclude that displacement has not occurred across faults in the Day Canyon seg ment of the Sierra Madre frontal fault zone since 1977.
Bennett, J. H., 1984. Geodetic measurements across the Cucumonga fault at
Day Canyon, San Bernardino County, California, in Cramer, C. H., J. M.
Harrington, G. W. Chase, and J. H. Bennett, 1984. Microearthquake, Geophysical
and Geodetic Surveys for Earthquake Hazards Evaluation, eastern San Gabriel
Mountains and upper Pomona Valley areas, San Bernardino County, California.
Open-File Report 84-23SAC, California Division of Mines & Geology,
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