HR: 0800h
AN: G51B-0077    [Abstracts]
TI: Four-Component Borehole Strain Meter: Observation and in-situ Calibration
AU: * QIU, Z
EM: qzhbh@163.com
AF: Institute of Crustal Dynamics of China Earthquake Administration, Box2855, Xisanqi, Haidian District, Beijing, 100085 China
AU: SHI, Y
EM: shiyl@gscas.ac.cn
AF: Graduate School of Chinese Academy of Science, 19, Yuquan Raod, Shijingshan District, Beijing, 100039 China
AU: Ouyang, Z
EM: zxo@ht.rol.cn.net
AF: Institute of Crustal Dynamics of China Earthquake Administration, Box2855, Xisanqi, Haidian District, Beijing, 100085 China
AB: Borehole strain meters are a key component of some important geo-scientific projects, such as PBO, to monitor seismic and aseismic tectonic strain phenomena. Observation using a four-component borehole strain meter, namely Ouyang borehole strain meter, has been kept continuous at Changping station, Beijing, for years. The plane strain changes are obtained at the depth of 120m and from 4 horizontal measurements, spaced 45 degrees apart, of the radial deformation of the borehole in which the instrument is installed. The challenge is that, according to the theory of elasticity, the sum of any two measurements perpendicular to each other should be the same as related to areal strain. The observation at Changping agrees pretty well with this rule and, with a relative in-situ calibration correction to the transducer factors based on the rule, the agreements can be yet much improved. Since the transducers were arranged well in the orientations of North, East, North West and North East, respectively, instrument shear strains can be simply given as the differences of the two correspondent perpendicular measurements. By applying theoretic Earth strain tide as a reference signal, in-situ absolute calibration can be carried out and the proportionality constants c and d, and the orientation error as well, can be calculated separately. Fore-component borehole strain meter has the advantages of giving more accurate and more reliable data for Earth strain and of easier processing as compared to three-component borehole strain meter.
DE: 1242 Seismic deformations (7205)
DE: 1249 Tides--Earth
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting