On simultaneous tilt and creep observations on the San Andreas Fault

Johnston, M. J. S.; McHugh, Stuart; Burford, R. O.

doi:10.1038/260691b0

Cited by 21 publications

(6 citation statements)

References 4 publications

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“…The short-period tilt data suggest that (1) a change in tilt amplitude of 10-8-10 -6 rad associated with creep events will be observed only if the tilt meter is less than 0.5-1.0 km from the fault trace, (2) the vertical extent of the slip zone associated with surface creep events may be less than a couple of kilometers but greater than about 0.5 km, (3) creep events on this part of the San Andreas fault do not appear to propagate uniformly over more than a couple of kilometers, and (4) the model presented in this paper suggests that about 0.5-1.0 mm of dipslip displacement is required to produce the residual deflection in the tilt wave forms observed at MEL during a creep event [Johnston et al, 1976].…”

Section: Discussionmentioning

confidence: 88%

Short-period nonseismic tilt perturbations and their relation to episodic slip on the San Andreas Fault in central California

McHugh¹,

Johnston²

1976

J. Geophys. Res.

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Data from four tilt meters and several creep meters along the San Andreas fault in central California 30 km south of Hollister were selected to investigate nonseismic short-period tilt perturbations of minutes to hours duration. The group of short-period tilt amplitude changes with residual deflections was chosen because many nonseismic creep events have similar durations. Although each of the four tilt meters recorded many short-period events, the distribution in space and time suggests that most of these events are due to causes other than slip on the San Andreas fault, such as local strain release. Only at one station used in this investigation (MEL) were creep-related tilt changes observed. A quasi-static dislocation model was constructed to predict the tilt changes associated with propagating slip. Comparing predicted to observed tilt wave forms and amplitudes and comparing the tilt event data to creep event data suggest that (I) a tilt amplitude change of 10 -8-10 -8 rad associated with nonseismic creep events will be observed only if the tilt meter is less than 0.5-1.0 km from the fault, (2) the vertical extent of the slip zone associated with these creep events is greater than about 0.5 km but perhaps not more than a couple of kilometers, (3) nonseismic episodic slip on this part of the San Andreas fault does not appear to propagate uniformly over more than a couple of kilometers, and (4) the model presented in this paper requires 0.5-1.0 mm of dip-slip displacement to reproduce the residual deflection in the creep-related tilt wave forms observed.

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Section: Discussionmentioning

confidence: 88%

Short-period nonseismic tilt perturbations and their relation to episodic slip on the San Andreas Fault in central California

McHugh¹,

Johnston²

1976

J. Geophys. Res.

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“…2000). Tectonically induced creep events in tilt data have repeatedly been observed near major faults in California (Johnston et al . 1976; McHugh & Johnston 1976; Mortensen et al .…”

Section: Various Types Of Tilt Signalsmentioning

confidence: 95%

Point stability at shallow depths: experience from tilt measurements in the Lower Rhine Embayment, Germany, and implications for high-resolution GPS and gravity recordings

Kümpel

Lehmann

Fabian

et al. 2001

Geophysical Journal International

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Summary From 1996 to 1999, we have studied ground tilts at depths of between 2 m and 5 m at three sites in the Lower Rhine Embayment (LRE), western Germany. The LRE is a tectonically active extensional sedimentary basin roughly 50 km × 100 km. The purpose of the tilt measurements was (a) to provide insight into the magnitude, nature and variability of background tilts and (b) to assess possible limitations of high‐resolution GPS campaigns and microgravity surveys due to natural ground deformation. The tilt readings, sensed by biaxial borehole tiltmeters of baselength 0.85 m, cover a frequency range from 10−8 Hz to 10−2 Hz (periods from minutes to years). Assuming that the tilt signals represent ground displacements on a scale typically not larger than several times the tiltmeters' baselength, and that tilt signals at shallow depth could in a simple geometric way be related to changes in surface elevation and gravity, we try to estimate the magnitude level of point movements and corresponding Bouguer gravity effects that is generally not surpassed. The largest tilt signals observed were some ± 50 µrad yr−1. If they were observable over a ground section of extension, e.g. 10 m, the converted rates may correspond to about ± 0.5 mm per 10 m yr−1 in vertical ground displacement, and ± 0.1 µgal yr−1 in Bouguer gravity effect, respectively. Large signals are mostly related to seasonal effects, probably linked to thermomechanical strain. Other causes of ground deformation identified include seepage effects after rainfalls (order of ± 10 µrad) and diurnal strains due to thermal heating and/or fluctuations in the water consumption of nearby trees (order of ± 1 µrad). Episodic step‐like tilt anomalies with amplitudes up to 22 µrad at one of the observation sites might reflect creep events associated to a nearby active fault. Except for short‐term ground deformation caused by the passage of seismic waves from distant earthquakes, amplitudes of non‐identified tilt signals in the studied frequency range seem not to exceed ± 2 µrad. As the larger tilt signals are close to the precision achieved with modern GPS systems and superconducting gravimeters when converted into height and gravity changes, further enhancement in resolution of these techniques may require simultaneous recording of local ground deformation at the observation sites.

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“…Near-field investigations of propagating fault creep have indicated that events of less than 3-ram amplitude are generally shallower than 2 km [Stewart et al, 1973;Johnston et al, 1976;McHugh and Johnston, 1978 Aside from its proximity to the permanent MWDM network [Slater and Huggett, 1976], the location provides the following advantages: (1) the near equivalence of the topography to half-space conditions for the comparatively localized and high spatial wavenumber strain fields associated with propagating creep, (2) the thick sedimentary infill within the propagating episodic fault creep activity, much of which occurs in large, regular events of about 5-mm amplitude.…”

Section: On a Larger Scale Periods Of Localized Activity Consisting mentioning

confidence: 99%

Propagating episodic creep and the aseismic slip behavior of the Calaveras Fault north of Hollister, California

Evans¹,

Burford²,

King³

1981

J. Geophys. Res.

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A detailed kinematic study of fault slip occurring from the surface to a depth of about 7 km on the Calaveras fault north of Hollister was conducted during the summer of 1977. The observations coincided with a period of propagating episodic fault creep activity sensed along the fault trace. Data used in the investigation consist of creepmeter records, near-field strainmeter observations, and high-resolution geodetic measurements, all collected contemporaneously over a period of 4 months. Detailed descriptions and analyses of the creepmeter and geodetic data have been presented elsewhere. The near-field strain measurements are here reported in detail, and their analysis draws upon the previous two data sets for support. The strainmeter observations are most sensitive to slip occurring in the upper 2 km; hence the emphasis of the paper is placed upon the role of propagating episodic creep in the broad-scale behavior of the fault. The results suggest that propagating episodic fault creep as sensed along the fault trace is confined to the upper kilometer or so of the crust and represents the response of the surface layers to a longer-term form of episodic aseismic slip occurring below. The mean form of the advancing rupture front within the upper kilometer is ostensibly the same as that indicated by records from the surface creepmeters. Evidence is presented, however, which suggests that propagating creep events may not always break the surface and may propagate at velocities much slower and at amplitudes significantly larger than those generally observed at the surface.Paper number 80B 1713. 0148-0227/81/080B-1713501.00 (over periods of weeks) fault displacement observed at the surface, and 'propagating episodic fault creep' (or 'episodic creep') will refer to the class of characteristically rapid-onset accelerated slip episodes (creep events) observed at the surface that are thought to result from expanding aseismic shear-failure ruptures along limited sections of the fault surfaces.From the viewpoint of fault mechanics, it is important to establish the physical mechanism that gives rise to propagating episodic fault creep. Several mechanisms have been proposed [Savage, 1971;Ida, 1974;Rice and Simons, 1976;Rutter and Mainprice, 1979]; however, it is difficult to evaluate their applicability without first establishing a thorough kinematic description of the failure process itself, against which the various model predictions may be tested. Clearly, this task demands that the slip behavior of the fault below the weathered free-surface layer be established. The elastic field to which propagating failure gives rise provides a window for viewing subsurface slip. However, as the elastic-field sample points are generafly restricted to the free surface, resolution will generafly deteriorate with increased depth, even for perfect data. This paper presents the results of a kinematic study of the behavior of the Calaveras fault down to depths of •7 km during periods of propagating episodic fault creep monitored during the summ...

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On simultaneous tilt and creep observations on the San Andreas Fault

Cited by 21 publications

References 4 publications

Short-period nonseismic tilt perturbations and their relation to episodic slip on the San Andreas Fault in central California

Short-period nonseismic tilt perturbations and their relation to episodic slip on the San Andreas Fault in central California

Point stability at shallow depths: experience from tilt measurements in the Lower Rhine Embayment, Germany, and implications for high-resolution GPS and gravity recordings

Propagating episodic creep and the aseismic slip behavior of the Calaveras Fault north of Hollister, California

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