Abstract
We show that high-rate GPS can have a vital role to play in near real-time monitoring of potentially destructive earthquakes. We do this by investigating the potential of GPS in recording strong ground motions from earthquakes in Switzerland and Japan. The study uses finite-fault stochastic ground motion simulation based on Fourier amplitude spectra and duration models previously developed for both countries, allowing comparisons in terms of both Fourier and time domain characteristics (here the Peak Ground Velocity, PGV). We find that earthquakes of magnitude Mw>5.8 can be expected to be recorded by GPS in real-time at 10 km distance, i.e. their Fourier spectrum exceeds the noise of the instruments enough to be used in strong motion seismology. Post-processing of GPS time series lowers the noise and can improve the minimum observable magnitude by 0.1-0.2. As GPS receivers can record at higher rates (> 10 sps), we investigate which sampling rate is sufficient to optimally record earthquake signals and conclude that a minimum sampling rate of 5 sps is recommended. This is driven by recording events at short distances (below 10 km for magnitude 6 events and below 30 km for magnitude 7 events). Furthermore, the Maximum Ground Velocity derived from GPS is compared to the actual PGV for synthetic signals from the stochastic simulations and the 2008 Mw=6.9 Iwate earthquake. The proposed model, confirmed by synthetic and empirical data, shows that a reliable estimate of PGV for events of about magnitude 7 and greater can be basically retrieved by GPS in real-time and could be included for instance in ShakeMaps for aiding post-event disaster management.
Highlights
In earthquake engineering, understanding the seismic ground motion at intermediate and long periods (T > 0:5 s) is useful to estimate the nonlinear response of large structures, such as long bridges or tall buildings, to earthquakes (Cauzzi and Faccioli, 2008)
For the case of seismic time histories, where we focus on the high-frequency component of the Global Positioning System (GPS) data, the troposphere and orbits are evolving much slower than the ground motion (Houlié et al, 2016) and they are expected to play a minor role in the precision of the retrieved GPS time series
We compare the Fourier spectra of the GPS noise recordings with the Fourier amplitude spectrum (FAS) models for Switzerland (Fig. 1) and Japan (Fig. 2) for typical magnitudes and distances (Switzerland: magnitude 5–6.5, 20 km distance; Japan: magnitude 5.5–7, 100 km distance)
Summary
In earthquake engineering, understanding the seismic ground motion at intermediate and long periods (T > 0:5 s) is useful to estimate the nonlinear response of large structures, such as long bridges or tall buildings, to earthquakes (Cauzzi and Faccioli, 2008). 3 s or more showed large amplifications of the long-period Rietbrock et al, 2013; Cauzzi et al, 2015) They are based ground motion during the Tohoku-Oki event, which are not on combining earthquake Fourier amplitude spectrum (FAS). FAS model are stress parameter (Atkinson and Beresnev, In this article, we first quantified the capabilities of GPS 1997), anelastic attenuation κ (Anderson and Hough, 1984), to record ground motion in terms of event size and distance and geometrical decay. Positioning System (GPS) noise series and magnitude 5–6.5 earthquakes at 20 km distance using the Swiss stochastic model (Edwards and Fäh, 2013) for the (a) horizontal and (b) vertical component. The PSD values are represented in decibels (dB) as PSDdB 10 log PSD 10 log (2FAS2=d) with d denoting duration, as obtained from the duration model
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