Analytical Approach for the Precise GNSS-A Seafloor Geodetic Observation: Extraction of Ocean Disturbance Effect

The Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) has achieved many historical geoscientific observations-a coseismic huge deformation following the 2011 Tohoku-oki earthquake, an interseismic coupling condition along the Nankai Trough megathrust zone, and so on. However, even with the latest observation technology, it takes about 3 years to detect an interseismic small deformation. We then cannot detect a small coseismic event or a slow slip event. In order to exceed such detection limit, elimination of errors--especially errors from marine fields-by analytical approaches is required. In the current analysis strategy, only an analyzing of the shallowest ocean structure with the most disturbances has been conducted. Here, we developed a new analytical strategy that can extract a gradient field of a deeper structure and applied it to actual data. Resultant extracted ocean fields were consistent with the JCOPE-2 ocean model and real ocean fields. Resultant time series of the seafloor crustal deformations were also refined by this new strategy. These total results show the validity of the new analysis technique and the extracted natural phenomenon.