abstract
Borehole strain gauge can be used for observation and research of strain solid tide, strain seismic wave, slow earthquake and earthquake strain precursor detection. Its excellent long-period performance can simultaneously record the spherical and annular components of the earth's free oscillation. YRY-4 pressure-volume borehole strain gauge developed by Professor Chi Shunliang, member of Seismological Society of China Seismological Observation Technology Committee and Hebi Institute of Earthquake Prevention Technology, is an excellent downhole tensor instrument, which can measure both volume strain and shape strain (four-component instrument). The instrument has the characteristics of high sensitivity, ultra-wide band, strong anti-interference ability and low power consumption. In addition, YRY borehole strain gauge has been ahead of the international multi-component instrument of the same type, realizing the exclusive four-component in-plane configuration. A complete three-component plane strain (volume strain, shear strain and principal stress direction) can be obtained from the output signals of four radial micrometer sensors arranged in the same plane, and the reliability of the measured data can be verified by a redundant component. When used in earthquake strain precursor observation, it plays an important role in judging abnormal events and preventing misjudgment and omission. This is of great significance to earthquake analysis and prediction. This technology has obtained the national patent. The instrument has made a breakthrough in self-checking. The correlation coefficient between S 1 +S3 and S2 +S4 is above 0.99, which basically meets the ideal requirements and is the world's leading level.
The instrument adopts non-expansive cement coupling mode, which solves the key problem of seamless coupling between probe and borehole. After several days of installation, the instrument can meet the requirements of stable observation. Dr. agnew, an American geophysicist, praised Chi Shunliang in his letter: "Your instrument is much better than any instrument working at high frequency on our PFO platform." YRY-4 component borehole strain gauge has good high frequency performance, and a data collector with appropriate sampling rate can record clear strain seismic waves.
The tidal factors in any direction on the ground can be calculated from the four-component data, and then the position of the reflector can be obtained.
Compilation and monograph of geophysical instruments
The rose diagram of tidal response of fault structure and geological characteristics has been verified many times, and the strain azimuth response of finite element fault block model is consistent with the azimuth response measured by the station. The instrument is expected to play a role in the research fields of geological structure research, urban fault detection, micro-dynamics of block activity and seismic intensity zoning. It can also provide reference for improving tidal displacement correction of space geodetic observation data such as GPS.
Compilation and monograph of geophysical instruments
After years of practical operation and continuous improvement, the measuring range of YRY borehole strain gauge has been greatly expanded once. In most cases, the instrument does not need to be zeroed for several years, and the functions of remote automatic calibration, remote automatic zeroing, digital output and network communication have been realized, which is convenient for the operation and management of the instrument.
Key technical indicators
1. Resolution: better than 5×10–11.
2. Drift: less than10–9/day
3. passband: 0 ~ 20h (z note: the ultra-wideband of the new model is 0 ~ 5000 Hz, which can record the ground sound, that is, the high-frequency microseisms caused by the micro-fracture of the formation).
4. Sensitivity: better than 5×10–11strain.
5. Main range: the strain is greater than 2×10–4.
6. Overall range: the strain is greater than/kloc-0 /×10–3.
7. Calibration method of calibrator: voltage calibration (automatic) with calibration repeatability ≤0.5%.
8. Output: digital output (five and a half bits)
9. Power supply: AC 220v 20% or 12V DC.
Application fields and examples
YRY borehole strain gauge was established in the State Science and Technology Commission on 1978, 1984 passed the national appraisal, and 1996 won the second prize of scientific and technological progress of China Academy of Sciences. YRY-4 borehole strain gauge probe, combined with ground data acquisition equipment and telemetry equipment, can be used for unattended or unattended stations to obtain digital ground strain data of a single or regional, and is an important observation means for earth science research and earthquake monitoring and prediction research. 1984 passed the appraisal, and it was gradually improved in the observation test of 18, and more than ten instruments were installed in Beijing, Shanghai, Hangzhou, Hebi and other places. YRY-2 borehole strain gauge installed at Tai 'an Reference Seismic Station has been ranked first in the country for many years after 199 1 year. YRY-4 strain gauge at Sheshan Station won the first place in China in the evaluation of observation data of borehole strain gauge in 2009. At stations with good site conditions, the relative observation accuracy of YRY borehole strain gauge can reach the highest international level of 0.00 1.
In 2004, 40 YRY-4 borehole strain gauges entered the Tenth Five-Year Plan of China Digital Seismic Observation Network. YRY-4 four-component borehole strain gauge is used as observation equipment in this project. The equipment includes four-component strain probe, water level and air pressure auxiliary observation probe, EP-ⅲ IP data acquisition control cabinet, fully isolated power supply, signal output isolation optical fiber and other parts. The strain resolution of the instrument system is 5×10–11,the frequency response of the strain probe is DC-20 Hz, and the sampling rate is once per minute.
YRY-4 four-component borehole strain gauge was used as observation equipment in the National Digital Seismic Network Project. Before 2005 10, the sensitivity, resolution, linearity, passband, range, calibration repeatability and power consumption of the instrument were tested in China Seismological Bureau, and the production license was obtained.
Because the ability of transmitting shear strain in weak stratum is much higher than that of bulk strain, YRY-4 borehole strain gauge can be installed in both rock holes and weak stratum. YRY-4 instrument is also used in the soil stress experiment conducted by Wen 'an Platform Stress Research Institute in Hebei Province. Since the work began in September 2008, good observation results have been achieved.
During the Tenth Five-Year Plan period, during the increasingly active earthquake activity, 40 strain gauges were tested quickly, and a large number of valuable real scientific data were obtained. Reliable precursory anomaly data were obtained at Guzan Station, which is 150km away from Wenchuan epicenter. Strong earthquakes are ultimately the result of formation strain accumulation. According to the observation data accumulated in the past, laying a borehole strain dense observation network can provide important observation data support for the scientific prediction of strong earthquakes.
Stability and reliability
YRY borehole strain gauge works stably and reliably. It has been the first in China to obtain observation data for many years in Taian Station, and has worked for more than ten years. In thunderstorm season, precursor instruments are always seriously damaged by lightning, which greatly affects the quality of precursor data. In the tenth five-year plan strain network project, YRY strain gauge has been tested for several years in thunderstorm season, and none of the stations installed according to the instrument specification are affected by lightning strike and run well.
YRY borehole strain gauge has unique and scientific design, small volume and light weight, which is convenient for industrial production. The delivery time is six months to one year, and the production and installation capacity is 200 units per year.
Production and Supply Unit
YRY borehole strain gauge is produced by Hebi Institute of Earthquake Prevention Technology in Henan Province and Shanghai Jinkun Seismic Instrument Co., Ltd. All products provide after-sales service and quality assurance according to national standards.