Global Navigation Satellite Systems Seismology for the 2012 Mw 6.1 Emilia Earthquake: Exploiting the VADASE Algorithm

Abstract

The Global Positioning System (GPS) has been repeatedly proven to be a powerful tool to estimate coseismic displacements and waveforms, with accuracies ranging from few millimeters to few centimeters. These promising results were achieved following two main strategies: differential positioning (DP) and precise point positioning (PPP;Bock et al. [1993], Kouba [2003], Larson et al. [2007], Larson [2009], Ohta et al. [2012], Xu et al.[2012], and Hung and Rau [2013]). In particular, both the modeling of fault rupture and the seismic moment estimation could benefit from GPS-derived displacements, because GPS is not affected by the saturation problems experienced by seismometers located near the epicenters of strong earthquakes. Thanks to the robustness of the GPS-derived displacement waveforms, in the last years some authors (Bock et al., 2000;Langbein and Bock, 2004;Blewitt et al., 2006;Bock and Genrich, 2006) addressed the problem to retrieve them in real time, with accuracies of a few centimeters, from GPS high-rate observations (1 Hz or more). In this context, the Variometric Approach for Displacements Analysis Standalone Engine (VADASE) has been proposed (Colosimo et al. [2011a], Colosimo [2013]). The approach is based on time single differences of carrier phase observations continuously collected using a standalone GPS receiver and on standard GPS broadcast products (orbits and clocks) that are available in real time. Therefore, one receiver works in standalone mode and the epoch-by-epoch displacements (equivalent to velocities) are estimated. Then, they are summed over the time interval when the earthquake occurred to retrieve displacements. Because VADASE does not require either additional technological complexity or a centralized data analysis, in principle, it can be embedded into the GPS receiver firmware and therefore can work in real time. Moreover, differently from DP and PPP, VADASE does not re-MO05 station (1 Hz observations over 120 s interval

Real-Time Geophysical Applications with Android GNSS Raw Measurements

“…In fact, using these approaches, displacements with centimeter accuracy can be obtained only with an external infrastructure able to provide differential correction from a base station or precise products-orbits, clock, and earth orientation parameter (EOP)-in real-time. Contrariwise, VADASE needs only broadcast parameters and, not requiring any ambiguity resolution algorithm, is able to estimate real-time velocity and displacements with accuracy comparable to traditional techniques on geodetic class receivers without the need for convergence time [14,15].…”

Real‐Time Magnitude Characterization of Large Earthquakes Using the Predominant Period Derived From 1 Hz GPS Data

“…The τ g time series analyses would be routinely conducted estimating the values for the short‐ and long‐period smoothing factors and by calculating the corresponding statistical characteristics (e.g., mean and spread) that could provide the existing seismic warning systems with additional information to constrain the size of an earthquake of magnitude M W > 7. The potential collocation of GPS and strong‐motion sensors would lead potentially to even more accurate computation of the velocity through Kalman filtering (Bock et al, 2011) or other existing EEW algorithms (Benedetti et al, ) and enhance the performance of τ g .…”

A Review of Global Navigation Satellite System (GNSS)-Based Dynamic Monitoring Technologies for Structural Health Monitoring

“…This method can be implemented by carrier phase observation and broadcast ephemeris. Compared to traditional methods, reference station and precise ephemeris are not required in this method for monitoring real-time relative changes [67][68][69][70][71][72][73]. The core formula is as follows:…”