The Seismotectonic Movements in the Period Range of a Few Minutes before the Catastrophic Earthquake of March 11, 2011 in Japan

We studied records of vertical ground velocity near broadband seismic stations installed around the epicenter of the magnitude 9, March 11, 2011 Tohoku earthquake. The MAJO station had been recording a stable daily behavior of seismic noise during 15 years before the earthquake. The station is the nearest to the epicenter, and is at a distance of 386 km from it. In 2009 pulses were identified exceeding 10% of the daily behavior. The pulses were gradually increasing and decreasing in amplitude, and lasted a few minutes. They occurred under quiet meteorological conditions and geomagnetic activity. No pulses of this kind were recorded at stations farther than 700 km from the epicenter. It is supposed that the earthquake was preceded by movements in the lithosphere beneath Japan and in the adjacent part of the Pacific Ocean.