HR: 1340h
AN: S33B-0316    [Abstracts]
TI: The GEOsensor: A measurement device for earthquake-induced rotational ground motions
AU: * Schreiber, U
EM: schreiber@wettzell.ifag.de
AF: Forschungseinrichtung Satellitengeodaesie, Wettzell, Koetzting, 93444 Germany
AU: Igel, H
EM: heiner.igel@lmu.de
AF: Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AU: Vernon, F
EM: flvernon@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AU: Velikoseltsev, A
EM: alex@wetttzell.ifag.de
AF: Department of Earth and Environmental Sciences, Theresienstr. 41, Munich, 80333 Germany
AU: Sasagawa, G
EM: gsasagawa@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AU: Hansen, T
EM: tshansen@nlanr.net
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AB: Recent advances in ring laser technology have led to the successful construction of highly sensitive gyroscopes suitable for the study of seismic induced rotation. By vastly up-scaling the size of navigational ring lasers, one obtains improved instrument sensitivity several orders of magnitude above commercially available sensors. We measured rotations from teleseismic earthquakes, which are consistent in waveform and amplitude with collocated recordings of transverse accelerations of a standard seismometer. This achievement marks an important step towards a complete six degrees of freedom measurement of seismic events. The GEOsensor is a seismic measurement platform, comprising a large ring laser, a standard seismometer, and auxiliary devices like a GPS referenced time base, a temperature, and a pressure sensor, etc. Following completion of the system at the Geodetic Observatory Wettzell (Germany), we installed the GEOsensor at a UCSD seismic observatory located in Piñon Flats, CA (USA). The ring laser, installed in Winter 2005, measures the vertical component of the rotation vector (i.e. rotation, twist, or spin around a vertical axis). We will present technical details of the installation and instrument properties and show observations from the instrument before and after it was installed in California. The database up to now consists of a few dozen seismic events with epicentral distances ranging from a few hundred to a few thousand kilometers. Collocated observations of rotations, strain, and translations will allow for the theoretical estimation of horizontal phase velocities of transversely polarized waves as well as the direction of propagation. Additionally, we will compare the accuracy of these estimates with respect to those derived from standard seismic array measurements.
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005