An Experiment for GPS Strain Seismometer

Abstract

An experiment for OPS strain seismometer, which possibly records largeamplitude near-field seismic motions with flat frequency responses from zero to several 0.1 Hz, has been conducted. Assigning displacement motions with the double amplitude of 15 cm and with periods of 25-300 seconds to a GPS rover antenna, we have made 3-hour GPS observations also at 2 other base sites 160 m and 160 km apart from the rover site, with a sampling interval of 1 second. Post-processing kinematic analyses determine the rover site motion every second from two base sites. Comparison of post-processing results determined from two base sites 60 m and 160 km apart from the rover site show that kinematic GPS can resolve horizontal displacement motions with an accuracy of 1-2 cm every second even from a site 160 km apart, though there exist drift components up to 10 cm during a period of 3 hours. These drift components are, however, mainly due to the use of broadcast ephemerides, and these components will be removed if using precise ephemerides. Thus, our experiment shows a possibility of GPS strain seismometer, which records large-amplitude nearfield ground displacement motion with flat frequency responses from zero to several 0.1 Hz.