EXTRA Level Line

Latitude: N 33°07'33"
Longitude: W 115°54'10"

Length: 280.0m
Number of Bench marks: 8

Number of Surveys to 2000: 6
Date of Initial Survey: 29 March 1989
Date of Latest Survey: 12 November 1994

Trespass Permission: None needed, although the Bureau of Land Management believes it should be notified of our activities.

From Indio, take Hwy 86 about 45 miles south to Hwy 78. Turn right, proceed 2.6 miles, and park. Part of the array crosses the road at that point.

This short line is part of a quadrilateral that was established to monitor future activity on a northeast-striking fault thought to be connected seismotectonically to the Superstition Hills fault and to the seismo-mechanics of the Salton basin (Hudnut et a l., 1989).

The two levelings are compared in an accompanying diagram. The height changes of the bench marks vary insignficantly among three levelings in three years.

Hudnut, K. W., L. Seeber, and J. Pacheco, 1989. Cross-fault triggering in the November 1987 Superstition Hills earthquake sequence, southern California. Geophysical Research Letters 16 (2),

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