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Computer algorithm for analyzing and processing borehole strainmeter data

Computers and Geosciences

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DOI: 10.1016/j.cageo.2009.08.011

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Abstract

The newly installed Plate Boundary Observatory (PBO) strainmeters record signals from tectonic activity, Earth tides, and atmospheric pressure. Important information about tectonic processes may occur at amplitudes at and below tidal strains and pressure loading. If incorrect assumptions are made regarding the background noise in the strain data, then the estimates of tectonic signal amplitudes may be incorrect. Furthermore, the use of simplifying assumptions that data are uncorrelated can lead to incorrect results and pressure loading and tides may not be completely removed from the raw data. Instead, any algorithm used to process strainmeter data must incorporate the strong temporal correlations that are inherent with these data. The technique described here uses least squares but employs data covariance that describes the temporal correlation of strainmeter data. There are several advantages to this method since many parameters are estimated simultaneously. These parameters include: (1) functional terms that describe the underlying error model, (2) the tidal terms, (3) the pressure loading term(s), (4) amplitudes of offsets, either those from earthquakes or from the instrument, (5) rate and changes in rate, and (6) the amplitudes and time constants of either logarithmic or exponential curves that can characterize postseismic deformation or diffusion of fluids near the strainmeter. With the proper error model, realistic estimates of the standard errors of the various parameters are obtained; this is especially critical in determining the statistical significance of a suspected, tectonic strain signal. The program also provides a method of tracking the various adjustments required to process strainmeter data. In addition, the program provides several plots to assist with identifying either tectonic signals or other signals that may need to be removed before any geophysical signal can be identified.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Computer algorithm for analyzing and processing borehole strainmeter data
Series title:
Computers and Geosciences
DOI:
10.1016/j.cageo.2009.08.011
Volume
36
Issue:
5
Year Published:
2010
Language:
English
Contributing office(s):
Earthquake Science Center
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Computers and Geosciences
First page:
611
Last page:
619
Number of Pages:
9