Real-Time Coseismic Slip Estimation via the GNSS Carrier Phase to Fault Slip Approach: A Case Study of the 2016 Kumamoto Earthquake

We investigate the feasibility of Global Navigation Satellite System (GNSS)-based deformation monitoring that detects coseismic fault slip directly from GNSS carrier phases without conventional positioning analysis. This method, which we call the phase-to-slip (PTS) method, does not require high-quality orbital information because it relies only on changes in azimuthal site-to-satellite ranges. With this method, computational costs for real-time seismic monitoring can be reduced. Here we applied the PTS method to the mainshock of the 2016 Kumamoto earthquake by modifying the original algorithm and using both precise orbits by International GNSS Service (IGS) and broadcast orbits. In both cases, obtained coseismic slip distributions agree well with previous studies. Calculated surface displacements from inferred slip distributions also agree with traditional positioning analysis. These results suggests that the PTS method may be useful as a supplement to currently operated deformation monitoring system, especially when external orbit and clock information are not accessible.