Performance of High‐Rate GPS Waveforms at Long Periods: Moment Tensor Inversion of the 2003 M w 8.3 Tokachi‐Oki Earthquake

Abstract

Abstract We present a comparison of long‐period (30 T M w 8.3) with both very broadband seismograms and synthetic waveforms. We show that GPS provides valuable waveform data between 40 and 160 s periods, especially in the near field of the earthquake where seismograms are saturated. There are no long‐period broadband seismic data available in the near field of large earthquakes (∼100 km for earthquakes M w >7 and ∼500 km for earthquakes M w >8). The comparison with synthetic seismic displacement waveforms shows that the GPS waveforms are performing well at periods of 40–80 s at epicentral distances between 150 and 600 km and at periods of 80–160 s at epicentral distances between 150 and 400 km. At longer periods and larger epicentral distances, the amplitudes do not always exceed the noise level (∼2–3 mm), but we still observe at selected GPS sites that the phase and the amplitude of the surface waves are of good quality, up to ∼1200 km. We conclude that GPS waveforms in the near field of a large event can be used for seismological applications. In this article, we recover the focal mechanism of the Tokachi‐Oki event by inverting the GPS data recorded within 300 km of the epicenter.