Thumbnail
Access Restriction
Open

Author Langbein, J. O. ♦ Burford, R. O. ♦ Slater, L. E.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword GEOSCIENCES ♦ CALIFORNIA ♦ GEOLOGIC FAULTS ♦ GEODETIC SURVEYS ♦ STRESS ANALYSIS ♦ CORRELATIONS ♦ CREEP ♦ DATA ANALYSIS ♦ EARTHQUAKES ♦ FLUCTUATIONS ♦ RAIN ♦ SLIP ♦ SPACE DEPENDENCE ♦ STRAINS ♦ TIME DEPENDENCE ♦ ATMOSPHERIC PRECIPITATIONS ♦ DEVELOPED COUNTRIES ♦ FEDERAL REGION IX ♦ GEOLOGIC FRACTURES ♦ GEOLOGIC STRUCTURES ♦ GEOPHYSICAL SURVEYS ♦ MECHANICAL PROPERTIES ♦ NORTH AMERICA ♦ SEISMIC EVENTS ♦ SURVEYS ♦ USA ♦ VARIATIONS ♦ Geosciences
Abstract The length measurements, characterized by a precision approaching 0.1 ppm, reveal large fluctuations in the rates of baseline extension. Principal mode analysis of the length change data indicates that the two largest components of the signal are (1) secular extensions and contractions consistent with surface slip on the main strand of the San Andreas fault, and (2) a large seasonal oscillation with no obvious spatial coherence. The second component appears to be in phase with seasonal rainfall. When data of the seasonal signal are excluded, the remaining data can be modeled in terms of both spatial and temporal variations in surface slip, variations in the components of the changes in uniform strain, and the possible displacement of the central monument in this radial network. Comparison of the inferred values of surface slip from the model with the observed fault slip measured by very short baseline creep meters indicates close agreement in secular rates, but the short-term variations observed with the creep meters are either highly attenuated or nonexistent in the modeled slip since the modeled slip is a spatial average which smooths out possible short-wavelength variations in the surface slip for which the creep instruments are most sensitive. An interesting conclusion from the two-color data is that surface slip on the San Andreas fault appears to be spread over a 2-km-wide zone on the south flank of Middle Mountain but is confined to a very narrow zone to the south as the fault passes through the center of the network. The largest observed strain change is an extensional strain coincident with the Kettleman Hills earthquake M5.5 in August 1985.
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1990-03-10
Publisher Place United States
Journal Journal of Geophysical Research
Volume Number 95
Issue Number B3


Open content in new tab

   Open content in new tab