HR: 1340h
AN: S33B-1097    [Abstracts]
TI: Rotary Transmitter For Active Monitoring By Seismic ACROSS (Accurately Controlled Routinely Operated Signal System)
AU: * Kunitomo, T
EM: kunitomo@tono.jnc.go.jp
AF: Tono Geoscience Center, 1-63 Yamanouchi Akeyocho , Mizunami Gifu, 509-6132 Japan
AU: Kumazawa, M
EM: mkz@tono.jnc.go.jp
AF: Tono Geoscience Center, 1-63 Yamanouchi Akeyocho , Mizunami Gifu, 509-6132 Japan
AB: The optimum designing is discussed on the seismic rotary transmitter, and several different operational modes and signal types are extensively tested to acquire the larger amount of new information through the tensor transfer function between the signal source and receiver for the structure exploration and monitoring of the deeper horizon of the Earth's crust. The shear wave transmission by controlled source has scarcely been made so far, whereas it is supposed to carry invaluable information on dispersion and polarization anisotropy that are more sensitive to the small temporal variation in the physical states of the polycrystalline rocks under stress. One of the successful systems is a single rotary type with a vertical rotation axis (generated force: 2x10$^{6}$ N at 25 Hz), which is installed within a large 'ground coupler' (steel reinforced concrete block (3.5x6m$^{2}$ and 2.3 m in thickness) embedded into the tertiary formation at Tono test site, in Japan. The large contact area of the coupler with ground guarantees the stability of transmitting characteristics by reducing the fatigue and non-linear effect at the contact zone even for the transmission of SH wave with large amplitude. Successive alternation of clockwise and anticlockwise rotations at every hour enables us to obtain a set of 6 components of transfer functions : H$_{ba}$ (b = radial, transverse or vertical, in received wave polarization referred to signal source, a = radial or transverse excitations from the source to any receiver station located at any azimuth), continuously over years. An optimization method of FM signal design is worked to obtain a set of spectral lines with almost uniform level of force amplitude in a prescribed frequency band. Several results of observed transfer functions and its time domain representation are demonstrated.
DE: 7294 Instruments and techniques
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2004 AGU Fall Meeting