The 2011 off the Pacific Coast of Tohoku Earthquake Tsunami Observed by GPS Buoys

Abstract

The 2011 off the Pacific coast of Tohoku Earthquake Tsunami has been observed by the ten GPS buoys of NOWPHAS, drifting on the sea surface at the location of 100-400 meters in depth, on the Pacific coast of Tohoku to Shikoku Districts, Japan. The first tsunami crest of higher than 6 m reached the GPS buoys off the Tohoku Coast approximately 30 minutes after the earthquake. The water level rose relatively slowly in the first part of the first crest and then rose quickly in the latter part. In some locations, the GPS buoy caught the tsunami crest earlier than the nearby coastal wave gauge and tide gauge by several minutes to dozens of minutes. The tsunami was recorded at almost all the tide gauges of NOWPHAS over Japan, including ones on Kanmon Channel and Ariake Bay apart from the Pacific Ocean.