Real-time GPS seismology with a stand-alone receiver: A preliminary feasibility demonstration

Abstract

[1] We show the feasibility of a real-time estimation of waveforms and coseismic displacements, within a few centimeters in accuracy, with a stand-alone dual-frequency Global Positioning System (GPS) receiver using a so-called "variometric" approach. The approach is based on time single-differences of carrier phase observations collected at a high-rate (1 Hz or more) using a stand-alone receiver, and on standard GPS broadcast products (orbits and clocks), which are ancillary information routinely available in real time. In the approach, first, the time series of epoch-by-epoch displacements are estimated. Then, provided that the collected observations are continuous, they can be summed over the interval (limited to a few minutes) over which an earthquake occurs. Since epoch-by-epoch displacements divided by the interval between consecutive epochs are essentially equal to the epoch-by-epoch velocities, this is equivalent to saying that we are using the GPS receiver as a velocimeter. Estimation biases, due to the possible mismodeling of various intervening effects (such as multipath, residual clock errors, orbit errors, and atmospheric errors), accumulate over time and display their signature as a trend in coseismic displacements. The trend can be considered linear and easily removed, at least for short intervals. Since the proposed approach (named VADASE (Variometric Approach for Displacements Analysis Stand-alone Engine)) does not require either additional technological complexity or a centralized data analysis, in principle it can be embedded into GPS receiver firmware, thereby providing a significant contribution to tsunami warning and other hazard assessment systems. After a preliminary test using a simulated example, the effectiveness of this approach was proven using real data.

Integration of Single-Frequency GNSS and Strong-Motion Observations for Real-Time Earthquake Monitoring

“…Colosimo et al and Tu et al reported a linear shift in the estimated velocity in epoch difference calculations due to uncorrected atmosphere errors; this shift is stable over a period of around 10 min [1,16]. One to two minutes of velocity data prior to the earthquakes was selected to determine the initial shift by assuming that the time series of the GNSS velocity v(t) can be expressed as:…”

“…Epoch-differenced velocity estimation technology, which is based on single-frequency global navigation satellite system (GNSS) observations and satellite broadcast ephemeris, has the advantages of no ambiguity parameters, rapid initialization, high precision, low cost, and rapid turnaround; therefore, it is widely used in earthquake engineering applications, such as real-time earthquake monitoring, early warning, and rapid response [1]. In addition, other studies have focused on GNSS positioning from mass-market receivers for monitoring purposes and real-time earthquake monitoring activities [2][3][4][5].…”

Stochastic Models of Very High-Rate (50 Hz) GPS/BeiDou Code and Phase Observations

“…Note that ρ T i T j is assumed to be time-invariant and therefore not tagged with the epoch. Note that Q v|c y k is a symmetric matrix and only the upper-triangle elements are listed in Equation (18), similarly for the following (co)variance and cofactor matrices. Assuming totally nt observation types are considered, the number of cross correlation coefficients to be estimated is nt(nt − 1)/2, which can be listed as…”

“…where Q T i1 (k)T i2 (k) is described in Equation (18) and occupies the ((i1 − 1) · ns + 1)th to (i1 · ns)th rows and the ((i2 − 1) · ns + 1)th to (i2 · ns)th columns.…”

Precise Positioning of BDS, BDS/GPS: Implications for Tsunami Early Warning in South China Sea

“…Nonetheless, it should be pointed out that for Precise Point Positioning (PPP), ambiguity resolution needs a convergence phase that may be as long as 20 min. Fortunately, the Variometric Approach for Displacements Analysis Stand-alone Engine (VADASE) [39] and the Temporal Point Positioning (TPP) [40] are able to overcome this disadvantage. The TPP has been employed in this study.…”