Progress in the Design of Tensioned-Wire Earth Strainmeters

Sydenham, Peter H.

doi:10.1111/j.1365-246x.1972.tb06162.x

Cited by 6 publications

(2 citation statements)

References 12 publications

(11 reference statements)

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“…This noise is sometimes correlated with the thermal record but not always. This bears out a conclusion that has previously been reported (Sydenham 1972)-single-point temperature measurements do not indicate the integrated thermal effect.…”

Section: Performancesupporting

confidence: 83%

“…The quartz-catenary instrument Tensioned Invar wire instruments have been shown to have many of the virtues required for en mane use of strainmeters. They do, however, usually suffer from excessive long-term drift (Gerard 1973;Sydenham 1972Sydenham , 1973. It was previously suggested that quartz would be superior to Invar (Sydenham 1972) on the grounds of probably providing better stability and because of its superior mechanical coefficients.…”

Section: The Quartz-tube Instrumentmentioning

confidence: 99%

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2000 hr Comparison of 10 m Quartz-tube and Quartz-catenary Tidal Strainmeters

Sydenham

1974

Geophysical Journal International

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Two quartz-standard tidal-sensitivity strainmeters have been installed together. One uses a tube in a somewhat conventional manner, the other a tensioned freely-hanging catenary of quartz-links. Constructional details and electronic circuits are presented. Records obtained from each, over a common 3-month period, enable their performances to be evaluated and positive conclusions about long-term strain changes to be stated. The instruments have stabilized to provide records that are identical (for periods ranging from 10 s to 500 hr) to within 5 parts in 1010 sd with a relative drift between them of 5 parts in 1012 per hour. Coupled with data regarding temperature effects, the results show that mechanical instruments are not necessarily inferior to laser interferometer alternatives and that using the data from a lone instrument of any kind could lead to incorrect conclusions. The close agreement of the two sets of data provides a basis for worthwhile discussion of long-term rock-strain secular variations. * Received in original form 1974 January 2. 3 77 378 P. H. Sydenharn Lr I t J The paper describes the design and installation features of each strainmeter including details of the auxiliary electronic units required with the marketed microdisplacement transducer used in each instrument.

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Section: Performancesupporting

confidence: 83%

Section: The Quartz-tube Instrumentmentioning

confidence: 99%

2000 hr Comparison of 10 m Quartz-tube and Quartz-catenary Tidal Strainmeters

Sydenham

1974

Geophysical Journal International

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Strainmeters and tiltmeters

Agnew¹

1986

Reviews of Geophysics

230

125

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Despite steady effort over the last century, continuously recording tiltmeters and strainmeters have not yet been successful except for earth tide measurements. This article reviews the techniques and instrument designs that have been developed in this field. The continuous measurement of true tectonic motions, which have rates of 10−14 s−1, requires extremely high instrument stability, but more rapid motions (tides and seismic waves apart) are even smaller and not much more easily detectable. Much past effort has been spent improving the transducers used in these instruments, which usually measure small displacements; the commonest choices are optical (the most accurate), capacitive (the most sensitive), and inductive (the most rugged). Nowadays building a transducer is the easiest part; a much harder task, equally important to a good design, is attaching the instrument to the ground so that it can detect the signal wanted. This part of the design includes choosing a location. A large underground opening is thermally stable but distorting; a surface installation is easy to build but noisy because of soil weathering; and a borehole is inaccessible to weather but also to the operator. All such installations (and indeed the whole field of strain and tilt measurement) of course rely on the assumption that the deformations of interest can be measured over baselengths of a few hundred meters or less; this is true for tides and seismic waves, but unproven for tectonic motions. Appropriate attachment techniques differ for each location, and many mundane details (such as cementing techniques for borehole instruments) remain to be worked out. The goal of measuring tectonic and tidal tilt has created many tiltmeter designs. Most are relatively small instruments that use some form of pendulum or bubble level; a few use a liquid surface to measure tilts over a long baseline. Repeated experience has shown the latter type, when well built, to be superior to the former, proving end‐monument motions to be a dominant source of noise. The same appears to hold true for strainmeters, the best results coming from long‐base laser instruments, though strainmeters using rigid or flexible material length standards are useful for special purposes, and borehole instruments show promise. Because achieving a good design has been so difficult, it is important to select the goals an instrument must meet and be prepared to compromise on others. The difficulty of validating results from this type of instrument makes comparison tests essential; such tests as have been made so far show that good results cannot be gotten at low cost or without careful attention to details.

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Solid tides recorded with 1 m interval mechanical strainmeter

Peters

Sydenham

1974

Nature

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Progress in the Design of Tensioned-Wire Earth Strainmeters

Cited by 6 publications

References 12 publications

2000 hr Comparison of 10 m Quartz-tube and Quartz-catenary Tidal Strainmeters

2000 hr Comparison of 10 m Quartz-tube and Quartz-catenary Tidal Strainmeters

Strainmeters and tiltmeters

Solid tides recorded with 1 m interval mechanical strainmeter

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