GPS工程测量(变形监测).docVIP

★ 1 Detection of arbitrarily large dynamic ground motions with a dense high‐rate GPS network We describe the detection of teleseismic surface waves from the 3 November 2002 Mw 7.9 Denali fault earthquake in Alaska with a dense network of 1 Hz GPS stations in southern California, about 3900 km from the event. Relative horizontal displacements with amplitudes in excess of 15 mm and duration of 700 seconds agree with integrated velocities recorded by nearby broadband seismometers with an rms difference of 2–3 mm. The displacements are derived from independent 1 Hz instantaneous positions demonstrating that a GPS network can provide direct measurements of arbitrarily large dynamic and static ground horizontal displacements at periods longer than 1 s and amplitudes above 2 mm, with an inherent precision (signal to noise) that improves indefinitely with amplitude without clipping and in real time. High‐rate, real‐time GPS networks can enhance earthquake detection and seismic risk mitigation and support other applications such as intelligent transportation and civil infrastructure monitoring. Citation: Bock, Y., L. Prawirodirdjo, and T. I. Melbourne (2004), Detection of arbitrarily large dynamic ground motions with a dense high‐rate GPS network , Geophys. Res. Lett. , 31 , L06604, doi:10.1029/2003GL019150. 2 Modified sidereal filtering: Implications for high‐rate GPS positioning High‐rate (1‐Hz) Global Positioning System (GPS) data are beginning to be used for a variety of geophysical monitoring purposes, including seismology. Improving the precision of high‐rate GPS position estimates will increase the value of these 1‐Hz GPS monitoring systems. One technique that has been used to improve high‐rate GPS positioning takes advantage of the ground track repeat period of the satellites. This study investigates the GPS orbital repeat period and determines that it varies for each satellite and differs significantly from the generally assumed sidereal period. Orbit repeat period