Journal ArticleDOI
Investigations of tilt measurements using shallow borehole tiltmeters
Frank K. Wyatt,Jon Berger +1 more
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In this paper, the authors examined the coherence of the data from an array of shallow borehole tiltmeters at Pinon Flat Observatory and compared with the corresponding data from three 732-m laser strainmeters.Abstract:
An array of shallow borehole tiltmeters has been operated at Pinon Flat Observatory since early in 1977. The data from this array are examined for coherence between the individual instruments and compared with the corresponding data from three 732-m laser strainmeters. In general, there is no significant coherence between the signals from the tiltmeters outside the microseismic and tidal bands even though they are spaced as closely as 10 m apart. Comparisons with the strain records show that the observed tilt noise power exceeds the strain noise power by 25-40 dB over the band from 0.000001 to 1 Hz. Analysis of the coherence estimates establishes the necessity for an unacceptably large (approximately 1000) array of instruments in order to determine the common tectonic signals. The observed secular tilt rates are from 40 to 450 times the observed secular strain rates for the same period. The theoretical noise power limit of the tilt transducer renders the instrument incapable of recording background noise at a quiet site over the band from 0.0001 to 0.1 Hz.read more
Citations
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Journal ArticleDOI
Strainmeters and tiltmeters
TL;DR: In this article, the techniques and instrument designs developed for continuously recording tiltmeters and strainmeters are reviewed, and the importance of comparison tests is demonstrated, and it is concluded that good results cannot be obtained at low cost or without careful attention to details.
Journal ArticleDOI
Displacement of surface monuments: Horizontal motion
TL;DR: In this article, the authors show that the actual horizontal displacements for massive near surface monuments, eraplaced in competent, weathered granite, are of the order of 50 tzm/yr.
Journal ArticleDOI
Thermoelastic strain in a half-space covered by unconsolidated material
Yehuda Ben-Zion,Peter Leary +1 more
TL;DR: In this article, an algorithm to predict crustal thermoelastic strain from observed local atmospheric temperature is given and applied to a 24-month crustal strain record of one test strainmeter site located near Bouquet Reservoir in southern California.
Journal ArticleDOI
Coherence of seismic body waves from local events as measured by a small‐aperture array
TL;DR: In this paper, a small-aperture seismic array at Pinyon Flat, California, was used to record eight local earthquakes during the operation of a seismic array, and the amplitude spectral ratios for the same signal measured at different stations had average values of less than 2 and maximum values of 7.
Journal ArticleDOI
The effects of seismic rotations on inertial sensors
Robert Pillet,Jean Virieux +1 more
TL;DR: In this paper, a review of previous studies related to the effects of rotations on both horizontal and vertical components of various sensors is presented, which suggests that sensor installation should follow a protocol that will better guarantee the verticality of the sensors.
References
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Journal ArticleDOI
Displacements, strains, and tilts at teleseismic distances
TL;DR: In this paper, the dislocation theory representation of faulting is used to compute the residual displacement, strain, and tilt fields at intermediate and large distances from major earthquakes, and it is shown that the distant fields are large enough to be detected by modern instruments.
Journal ArticleDOI
Earth noise, 5 to 500 millicycles per second: 1. Spectral stationarity, normality, and nonlinearity
TL;DR: In this paper, the cross-frequency coherence is used for nonstationary effects such as earthquakes, and the more generalized two-dimensional spectrum appears to be the appropriate one for looking at transient events.
Journal ArticleDOI
Biotite-induced grussification of the Boulder Creek Granodiorite, Boulder County, Colorado
Dana Isherwood,Alayne Street +1 more
TL;DR: A petrographic study of the grus, impregnated in plastic resin to retain its original fabric, reveals expanded biotite fragments separated by void space with numerous microfractures through quartz and feldspar grains.
ReportDOI
Tables of the distribution of the coefficient of coherence for stationary bivariate gaussian processes
D E Amos,L H Koopmans +1 more
Journal ArticleDOI
Vertical seismic noise at very low frequencies
Duncan Carr Agnew,Jon Berger +1 more
TL;DR: In this paper, the Project IDA modified LaCoste gravimeters were used to investigate ground noise at frequencies from 1 to 10 mHz at Pinon Flat Geophysical Observatory, showing that the noise power increases as ƒ−2.7 for frequencies between 1 and 0.001 mHz.