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

Sydenham, Peter H.

doi:10.1111/j.1365-246x.1974.tb04129.x

Cited by 9 publications

(2 citation statements)

References 4 publications

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“…It has a temperature coefficient similar to that of Invar (Table 2) and may not be as stable, though this depends on the type used [Hauksson et al, 1979]. Fused quartz (in the form of 2-m rods hooked together) was used by Sydenham [1974b]; it has a slightly larger Lw than Invar (6.8x 106 m) but is much more fragile and introduces many more contact surfaces.…”

Section: Significant Changes In Both Were Made Bymentioning

confidence: 99%

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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Section: Significant Changes In Both Were Made Bymentioning

confidence: 99%

Strainmeters and tiltmeters

Agnew¹

1986

Reviews of Geophysics

230

125

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“…1 shows a plan view of the installation. A detailed comparison of the design and results of the tube and catenary strain meters is given by Sydenham (1974). The vertical strainmeter is a simple modification of the horizontal tube design (Blair 1975).…”

Section: The Strain Metersmentioning

confidence: 99%

A Tidal Strain Model for Hillgrove Gorge, Eastern Australia

Blair

Sydenham

1976

Geophysical Journal International

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Experimental tidal strain results obtained at the Cooney Observatory are presented for a period of nine days. Data are given for six mechanical strain meters, three of which are positioned in different horizontal directions, and one in the vertical. The experimental results for horizontal strain are compared with the theory developed for the particular topographic and ocean load models and quite a reasonable agreement is found. The significant spectral difference between the theoretical and observed vertical strains is attributed to the cavity effect on the vertical strain meter. 141

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Kinematical Regime—Members and Linkages

Sydenham¹

2005

Handbook of Measuring System Design

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

Cited by 9 publications

References 4 publications

Strainmeters and tiltmeters

Strainmeters and tiltmeters

A Tidal Strain Model for Hillgrove Gorge, Eastern Australia

Kinematical Regime—Members and Linkages

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