Lake level observations to detect crustal tilt: San Andreas Lake, California, 1979-1989

Journal Article · Sat Jul 01 00:00:00 EDT 1989 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL016i007p00661· OSTI ID:5668004

Mueller, R J; Johnston, M J.S.; Myren, G D ^[1]; Murray, T ^[2]

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1. Geological Survey, Menlo Park, CA (USA)
2. Cascades Volcano Observatory, Vancouver, WA (USA)

A pair precision lake level gauging stations, installed in 1978, have been monitoring differential crustal uplift (crustal tilt) at San Andreas lake, California, near the suspected epicenter on the San Andreas fault of the M = 8.3, 1906 San Francisco earthquake. The stations are installed in the lake with a 4.2 km station separation parallel to the San Andreas fault. The gauging stations use quartz pressure transducers that are capable of detecting intermediate to long-term vertical displacements greater than 0.4 mm relative to a fluid surface. Differencing data from the two sites reduces the noise contributed by atmospheric pressure, temperature, and density changes, and isolates the relative elevation changes between the ends of the lake. At periods less than 20 minutes, the differenced data are dominated by lake seiches which have a fundamental mode at a period of 13 {plus minus} 0.3 minutes. These seiche harmonics can be filtered or predicted and removed from the data. Wind shear, typically lasting several days, can generate apparent short term tilt of the lake and large seiche amplitudes. The tilt noise power spectrum obtained from these data decreases by about 15 dB/decade of frequency. Monthly averages of the data between 1979-1989 indicate a tilt rate of 0.02 {plus minus} 0.08 microradians/yr (down S34{degree}E). No measurable horizontal tilt has apparently occurred in this region of the San Andreas fault during the last decade, however, measurements of trilateration networks show this region to be undergoing a horizontal strain of 0.6 {plus minus} 0.2 {mu}strain/yr.

• OSTI ID: 5668004
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Vol. 16:7; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
CONTINENTAL CRUST
GROUND UPLIFT
LAKES
MONITORING
EARTHQUAKES
EPICENTERS
GEOLOGIC FAULTS
INCLINED STRATA
LEVEL INDICATORS
LEVELS
OPERATION
DEVELOPED COUNTRIES
EARTH CRUST
FEDERAL REGION IX
GEOLOGIC FRACTURES
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
MEASURING INSTRUMENTS
NORTH AMERICA
SEISMIC EVENTS
SURFACE WATERS
USA
580000* - Geosciences