Tremendous Shift of Tectonic Plate Border Boundary after Great East Japan Earthquake
In 2011, shortly after the Great East Japan Earthquake, which induced a destructive tsunami, a research collaboration of Japanese, Swiss and German geoscientist worked out expedition plans to investigate the consequences of the earthquake. Many earthquakes are cause by the overlay movement of two tectonic plates. In the case of Japan the Pacific Plates is sliding underneath the Okhotsk Plate. The magnitude 9 earthquake, in March 2011, was cause by a sudden tension release at the seized border of those two plates.
The international research team mapped along the Japan Trench using echo sounders and compared their results with data collected in 1999 and 2004. In addition sediment cores were extracted and carefully analyzed. “Based on these studies, we concluded that the earthquake caused a 50-meter displacement of the earth’s crust, which triggered large slumps along the edge of the Japan Trench,” states Michael Strasser, Professor of Sediment Dynamics at ETH Zürich, in a press release, “In some places these slumps compressed the seabed sediments, forming troughs and ridges at the base of the Japan Trench.
The results from these expeditions present that a large part of the seafloor (~28 km2) slid down in to the Japan Trench. In addition, they could show that the near-surface boundary of the Pacific and the Okhotsk plate shifted two to three kilometers towards the east, a process which usually takes hundreds to millions of years.
The reference paper „A slump in the trench: Tracking the impact of the 2011 Tohoku-Oki earthquake” was published in journal Geology.