Seismicity of the Sanriku coast

Seismicity refers to the frequency, type and size of earthquakes experienced over a period of time.

[7] Major seismic activity on the Sanriku coast during the 20th century includes: Significant seismic events which devastated Sanriku coastal communities in the 21st century include: In the list of 45 most powerful earthquakes recorded worldwide since 1500, there are five that appear to be clustered in a 8-year span (in 2004, 2005, 2010, 2011, 2012) with the largest being the 2004 Indian Ocean earthquake of magnitude 9.1.

This does not fully demonstrate a relationship between events separated by longer periods and greater distances.

This motion pulls the upper plate down until the stress builds up enough to cause a seismic event.

Quakes of large magnitudes in the Sanriku region can have a rupture length of hundreds of kilometers; and this generally requires a long, relatively straight fault surface.