We try to detect an unidentified signal from the surface motion at northeastern Japan immediately after the 2011 Tohoku earthquake. A focused frequency range is 10–100 mHz (10–100 s). We find a peaky signal with frequency of about 38 mHz (26 s) based on the horizontal-tovertical (H/V) spectral ratio using the high-rate GNSS data at 382 GEONET stations. We are not able to identify locality o…