Niko Kareinen
Type of contribution: oral
Session: 5

Determination of Tsukuba VLBI station post-Tohoku earthquake coordinates using VieVS

Niko Kareinen, Aalto University Mets\"ahovi Radio Observatory Minttu Uunila, Aalto University Mets\"ahovi Radio Observatory

We determine the new coordinates for Tsukuba VLBI station, which was affected by the Tohoku earthquake on March 11, 2011. A total of 38 VLBI XA/XE sessions dating from 2011-01-03 to 2011-09-15 were pre-processed with Vienna VLBI Software (VieVS v. 1d), removing low quality data (e.g. TIGO station), clock breaks and outliers. A priori coordinates from NGS file headers were used for TSUKUB32 in order to exclude the station from NNT/NNR conditions. After the initial VieVS analysis, a visualization tool was written in Matlab to analyze the possible change in the coordinates and to detect possible low quality measurements missed by initial processing. The visualization tool has a functionality to transform the ECEF coordinates and errors acquired with VieVS to the local tangent plane of Tsukuba for better comparison possibilities. The visualization tool was written in a way that it could be added in the next version of VieVS as a general time series tool. The time series demonstrated a clear shift in the coordinates before and after the quake. A mean shift of (X,Y,Z) = (-38.4, -57.0, -4.3) cm $pm$ (0.4, 0.3, 0.6) cm was detected in ECEF and (E, N, U) = (68.3, 0.7, -8.3) cm $pm$ (0.5, 0.5, 0.3) cm in ENU. Also post-seismic movement was clearly seen in the time series.