Observations of creep-related tilt, strain, and water-level changes on the central San Andreas fault

abstract Several simultaneous observations of surface fault creep, tilt, strain, and water-level fluctuations have been recorded along the San Andreas fault in the vicinity of the Almaden-Cienega Winery south of Hollister, California. Creep events recorded on the winery creepmeters on February 16, 1975, and by the winery and Harris Ranch creepmeters on September 17, 1975, were modeled as migrating dislocations with geometries chosen to give results that match the observed tilt and strain data. Source depths for the February 16th and September 17th creep events were found to be relatively shallow, the depth to the lower boundary of the slip surface being 0.4 and 2.0 km, respectively. In both cases slip was found to propagate from the northwest toward the southeast, which is consistent with changes in water level observed in a well near the winery. Since the installation of the tiltmeter and strainmeter 0.8 km northwest of the Cienega Winery, six tilt and strain signals with durations typical of creep events have been related to observed surface creep, while 11 such signals appear unrelated to recorded surface creep. The latter may result from surface creep of limited extent or creep at depth.

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Water-level fluctuations and earthquakes on the San Andreas fault zone

Geology ◽

10.1130/0091-7613(1975)3<437:wfaeot>2.0.co;2 ◽

1975 ◽

Vol 3 (8) ◽

pp. 437 ◽

Cited By ~ 25

Author(s):

Robert L. Kovach ◽

Amos Nur ◽

Robert L. Wesson ◽

Russell Robinson

Keyword(s):

Water Level ◽

Fault Zone ◽

San Andreas Fault ◽

Water Level Fluctuations ◽

San Andreas

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Deformation near the junction of the creeping and locked segments of the San Andreas fault, Cholame Valley, California (1970-1980)

Bulletin of the Seismological Society of America ◽

10.1785/bssa0730051407 ◽

1983 ◽

Vol 73 (5) ◽

pp. 1407-1414

Author(s):

W. F. Slawson ◽

J. C. Savage

Keyword(s):

San Andreas Fault ◽

Level Line ◽

Dislocation Model ◽

Fault Creep ◽

Slip Rates ◽

Fault Surface ◽

Geodetic Networks ◽

San Andreas ◽

Elevation Changes ◽

Surface Creep

Abstract We have constructed a simple dislocation model of the San Andreas fault near Cholame, California, that reproduces the observed deformation of nearby geodetic networks as well as the transition from quasi-continuous slip (fault creep) to a no-slip (locked) condition on the surface trace. The model is specified by the slip rates imposed on the fault surface. Slip on the surface trace is given by the observed fault creep rates, and slip at depths greater than 12.6 km is taken to 30 mm/yr along the entire length of the fault (i.e., beneath creeping and locked sections alike). Slip at intermediate depths is assigned by a rather arbitrary extrapolation of the surface creep values. This postulated distribution of slip on the fault is tested by using it in a dislocation model to predict the deformation in two geodetic networks, a trilateration network (20-km aperture), and a 20-km-long level line. The calculated deformation of the trilateration network agrees with the observed deformation within the observational error. Agreement between the predicted and observed elevation changes along the level line was satisfactory in the sense that the predicted values were below the level of detection, and the observed changes were not significant.

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Local magnetic field measurements, fault creep observations and local earthquakes on the San Andreas fault

Open-File Report ◽

10.3133/ofr78809 ◽

1978 ◽

Cited By ~ 2

Author(s):

M.J.S. Johnston ◽

B.E. Smith ◽

Robert Martin Mueller

Keyword(s):

Magnetic Field ◽

San Andreas Fault ◽

Field Measurements ◽

Local Magnetic Field ◽

Fault Creep ◽

Local Earthquakes ◽

San Andreas ◽

Magnetic Field Measurements

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Spatiotemporal evolution of surface creep in the Parkfield region of the San Andreas Fault (1993–2004) from synthetic aperture radar

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2011.05.049 ◽

2011 ◽

Vol 308 (1-2) ◽

pp. 141-150 ◽

Cited By ~ 15

Author(s):

M. de Michele ◽

D. Raucoules ◽

F. Rolandone ◽

P. Briole ◽

J. Salichon ◽

...

Keyword(s):

Synthetic Aperture Radar ◽

San Andreas Fault ◽

Synthetic Aperture ◽

Spatiotemporal Evolution ◽

San Andreas ◽

Surface Creep ◽

Aperture Radar

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A Discussion on the measurement and interpretation of changes of strain in the Earth - Role of pore fluids in faulting

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1973.0056 ◽

1973 ◽

Vol 274 (1239) ◽

pp. 297-304 ◽

Cited By ~ 7

Keyword(s):

Pore Pressure ◽

San Andreas Fault ◽

Fault Creep ◽

Time Constants ◽

San Andreas ◽

The Earth ◽

Shallow Earthquakes ◽

Pressure Changes

We consider three in situ processes which involve fluid flow in the crust: fault creep, aftershocks and dilatancy. Measurements of water level in wells suggest that creep events on the San Andreas fault are coupled with pore pressure changes. Readjustment of transient pore pressure, induced by large shallow earthquakes, possess the correct time constants and magnitudes to explain the occurrence of aftershocks. And finally, temporal changes of travel times in the Gram district (U.S.S.R.) imply that dilatancy may occur in situ.

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Implication of seismicity for failure of a section of the San Andreas Fault

Bulletin of the Seismological Society of America ◽

10.1785/bssa0700010185 ◽

1980 ◽

Vol 70 (1) ◽

pp. 185-201

Author(s):

W. H. Bakun ◽

R. M. Stewart ◽

C. G. Bufe ◽

S. M. Marks

Keyword(s):

San Andreas Fault ◽

P Wave ◽

Seismogenic Zone ◽

Wave Radiation ◽

Focal Region ◽

Fault Creep ◽

Aftershock Activity ◽

Discontinuous Surface ◽

San Andreas ◽

Fault Trace

abstract On January 15, 1973, a magnitude ML 4.1 earthquake occurred near Cienega Road on the San Andreas Fault about 20 km south of Hollister, California. A 3-km-long segment of the fault southeast of the earthquake was aseismic for the 7 weeks preceding the event, although microearthquakes occurred at both its ends. The first day's aftershocks occurred at the northwest end of the aseismic segment; later aftershock activity migrated to the southeast, filling the remainder of the segment. If the discontinuous surface trace of the fault can be extrapolated to the focal region of the earthquakes to define fault geometry at depth, then aftershocks occurred primarily on one continuous segment of the fault and epicenter locations and direction of rupture propagation (inferred from the azimuthal pattern of P-wave radiation) of the precursory shocks correlate with the discontinuities in the trace that terminate the segment. The 1970 to 1976 deficit in seismic slip within the segment suggests that fault creep accounts for a significant part of cumulative slip within the segment. The pattern of seismicity is consistent with the hypothesis that creep on the segment before the main shock caused a buildup of stress at the ends of the segment or at the ends of adjacent offset segments. Correlation of seismicity and discontinuities or bends in the mapped fault trace are the basis for an extension and refinement of the “stuck” and “creeping” patch model of the San Andreas Fault in central California. Patch boundaries extend from the free surface down through the seismogenic zone. Creeping patches lie beneath smooth continuous segments of the fault trace. Stuck patches lie beneath discontinuities or bends in the fault trace.

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