GNSS Seismology and Seismogeodesy

Product

List of Earthquakes

This product consists of an archive of 1-5 Hz GNSS displacements ("GNSS seismology") and 100 Hz seismogeodetic displacement and velocity waveforms ("Seismogeodesy") for a catalog of historical earthquakes. High-rate data are useful for a range of applications such as modeling coseismic & postseismic slip to understand their underlying processes, determining the transition from coseismic to early postseismic deformation (Zhang et al., 2020; Golriz et al., 2021), and earthquake and tsunami early warning systems.

Background

Continuous GPS networks have been developed since the early 1990's to observe crustal deformation at plate boundaries with higher temporal resolution compared to GPS surveys (campaigns). Other applications became apparent, for example, GNSS meteorology. Initially, cGNSS networks operated at a 15-30s sampling rate and data were downloaded once per day.  These data were used to create daily GNSS displacement time series some of which now extend nearly 30 years. High-rate data, ≥ 1 sample per second (1 sps – also expressed as “1 Hz”, 10 sps = 10 Hz), were first applied to study crustal deformation, specifically deploying small-aperture kinematic surveys of locked or freely slipping (creeping) geological faults (Genrich and Bock 1992), and subsequently for dynamic applications such as movement of ice sheets for climate studies, georeferencing of airborne lidar surveys (Zwally et al. 2002), GPS-Acoustics (GPS-A) for seafloor positioning (Yokota et al. 2016) and engineering seismology (Saunders et al. 2016). In the early 2000's, cGNSS networks began to be upgraded to high-rate observations and streamed and processed in real-time. "GNSS seismology" provides coseismic displacements, both static (permanent) and dynamic, during earthquake shaking (Bock et al. 2000; Nikolaidis et al. 2001; Larson 2009; Genrich and Bock 2006; Langbein and Bock 2004). A comprehensive archive of  high-rate GNSS displacements, in seismic format, of 29 earthquakes from 2003-2018 with moment magnitudes of Mw 6.0-9.0 is described by (Ruhl et al. 2018). We also maintain an archive of these seismic displacement and add new significant earthquakes to this historical record, as they occur.

                                                             Seismogeodetic method

 

Furthermore, we also archive seismogeodetic displacement and velocity waveforms, a product of an optimal combination of high-rate GNSS and seismic data (Bock et al. 2011;Saunders et al., 2016). Seismogeodesy provides a broadband seismometer that does not clip in the near field of significant earthquakes, a measure of permanent displacement for rapid magnitude estimation, and an instrument that does not experience magnitude saturation for large earthquakes (Goldberg and Bock, 2018).

 

 

Advantages of seismogeodesy compared to GNSS-only and seismic-only methods.

 

Seimogeodetic waveforms for the July 6, 2019 Mw7.1 Ridgecrest earthquake