GPS Seismometers: the Implementing Issues

Linlin Ge, Liwen Dai, Shaowei Han, Chris Rizos, Yuzo Ishikawa and Yasuhiro Yoshida

Abstract:	Using a GPS receiver as a seismometer was first proposed in 1994. Recent GPS seismometer experiments, with GPS Real-Time Kinematic (RTK) systems, have demonstrated very encouraging results. However, several implementing issues have to be investigated before the concept of a GPS seismometer is feasible. In order to design the layout of reference and rover stations for distant seismic events, a configuration consisting of a reference station in the center of a ring formed by a few rover stations is proposed. For seismic events local to the ring (within the "rover ring"), combined processing of moving baseline RTK and DGPS positioning can be a so- lution. To test the possibility of noise reduction using measure- ments from adjacent days, two Trimble MS750 GPS re- ceivers were connected with a null modem to collect data at 20Hz rate at UNSW for about 3 hours, everyday on 5 successive days. By using an adaptive filter in processing the various combinations of the RTK time series, it has been shown that the noise can be reduced significantly. A zero-baseline test at 10Hz sampling rate with two Leica CRS1000 GPS receivers indicates that the L1 phase measurements are truly independent, L2 phase measure- ments are partially independent, and pseudo-range meas- urements of P1 and P2 are highly correlated. Since Frame Relay circuits have already been used in some broadband seismic networks, data communication is not such a big problem if using high data rate GPS as seismometer. Discussions on the pros and cons of using GPS as seismometer are presented. In conclusion, it would appear that a GPS RTK system can be used as a strong motion amplitude seismometer, and would therefore complement current seismometers.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	75 - 83
Cite this article:	Ge, Linlin, Dai, Liwen, Han, Shaowei, Rizos, Chris, Ishikawa, Yuzo, Yoshida, Yasuhiro, "GPS Seismometers: the Implementing Issues," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 75-83.
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