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| Titel |
Continuous Observation of Crustal Deformation with a New Borehole Multi-component Instrument |
| VerfasserIn |
Zuxi Ouyang, Jun Zhang, Tao Li, Zheng Chen, Liheng Wu, Jieshan Shi, Zhongrun Zhang, Guosheng Fan |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047122
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| Zusammenfassung |
| The significance of in situ long-term observations of the Crustal deformation in the areas of
major tectonic activity, which usually cover earthquake-prone regions, in order to study
strain build up before earthquakes and its development becomes more and more
important.
Deep borehole observation can eliminate effectively various earth’s surface interferences,
providing considerable advantage over other geophysical measurements made at the
ground, and improve greatly our capability to detect very small deformations and
vibrations in the surrounding strata. This new technology will promote consequently our
understanding of presently active geological processes and its relation to earthquakes
and tectonic activities. Based on experiences of developing RZB type borehole
strainmeter a new multi-component borehole instrument for deep boreholes has been
developed. The new system, namely RZB-3 multi-component borehole observation
system consists of down-hole probe, ground instruments including data logger,
communication equipment and power supply. The down-hole probe is a complete
package comprising of horizontal strain, vertical strain, tilt, strain seismic waves
and ground temperature measurement units in a stainless-steel pressure cylinder
with 102mm outside diameter and about 5m in length, which can be installed in
150m~400m deep boreholes with an expansive grout. Arbitrary combination and addition
of more sensors are possible. Furthermore, another three subsystems provide the
assistant measurements including well temperature, well water level and atmospheric
pressure.
Owing to adopting of digital capacitance displacement transducers, which are
characterized of low noise, high sensitivity and large dynamic range, the new system can run
at maximum sensitivity to provide strain resolution of 0.1nanostrain with the basic
dynamic range of ±500microstrain and tilt resolution of 1nanorad with the basic
dynamic range of ±500microrad. The total dynamic range can be extended to 4 times
larger to satisfy the needs of long-term observations. Up to now the new instruments
have been installed at a few sites in Beijing area, Fujian province, Sichuan and
Yunnan provinces, and observed clear tidal signals, strain-steps associated with large
earthquakes, and other strain changes of geophysical interests. Especially, because of
the superiority of the 4-component borehole strain observation, the 4 capacitance
displacement transducers mounted on the steel cylinder with 45Ë apart, the obtained data
show that RZB borehole strainmeter has high measurement accuracy of area strain
in Crustal horizontal strain field. The borehole strain meters are calibrated firstly
by the manufacturer in a laboratory. They are also calibrated in-situ using tidal
analysis. The in-situ calibration involves comparing the strain changes induced
by the earth tides as measured by the instrument with those predicted by theory.
Some details related to correction for the observed earth tides and calculation of the
area and shear strain were presented, and primary analyses were discussed as well. |
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