Comparison of Coseismic Displacement Obtained from GEONET and Seismic Networks

It is generally recognized that permanent displacements estimated by the double integration of acceleration records need a suitable baseline correction. Current baseline correction methods have been validated by comparing the displacements with those from the Global Positioning System (GPS) records nearby, but GPS stations that are sufficiently close to a strong-motion station are scarce. Because the M(w)9.0 Tohoku-Oki earthquake produced geodetic displacements in a wide area and because dense strong-motion and GPS networks are available in Japan, we interpolated the displacements calculated from GPS records to estimate the permanent displacements at 508 strong-motion stations. The estimated results were used to evaluate uncertainties in permanent displacements obtained using two baseline correction methods, and results were found to be reliable only for KiK-net's borehole acceleration records. A new joint parameter search method for the surface and borehole records was further proposed, and reliable results were obtained for KiK-net's surface records.