22 Earthquake Early Warning with GPS Data

The combined use of seismic and geodetic observations is now a common practice for finite-fault modeling and seismic source parametrization. With the advent of highrate 1Hz GPS stations the seismological community has recently begun looking at GPS data as a valid complement to the seismic-based methodologies for Earthquake Early Warning (EEW). In the standard approaches to early warning, the initial portion of the P-wave signal is used to rapidly characterize the earthquake magnitude and to predict the expected ground shaking at a target site, before the arrival of the most damaging waves. Whether the final magnitude of an earthquake can be predicted while the rupture process is underway, still represents a controversial issue; the point is that the limitations of the standard approaches when applied to giant earthquakes have become evident after the experience of the Mw 9.0, 2011 Tohoku-Oki earthquake. Here we explore the application of GPS data to EEW and investigate whether they can be used to provide reliable and independent magnitude estimations. The large size and the complex rupture process, together with the huge number of high-quality GPS records available, make the 2011 Tohoku-Oki earthquake a unique and ideal casestudy for our purposes.