Historical context

It is well know that Japan sits precariously at the meeting of several tectonic plates and hence that it is prone to seismic activity. The horrible events that started off the Oshika Peninsula on 11/3/11 have a shocking lineage in Japanese history. The Sendai earthquake of 2011, which had its hypocentre at a depth of 24.4km just off the coast of Oshika, has been of such severity that it is termed a megathrust earthquake (magnitude 8.9 or 9.0) and it generated tsunami of 10m in height. This is the most powerful earthquake to have hit Japan since records began, and amongst the 5 most severe earthquakes in the world
(the more severe being: Validivia, Chile, 1960 (9.5); Alaska, USA, 1964 (9.2); Indian Ocean, Indonesia, 2004 (9.1); Kamchatka, Russia, 1952 (9.0)). The Sendai quake was so powerful that many of its hundreds of aftershocks also rate as amongst the most serious earthquakes of modern times in their own right. The associated tsunami struck Kamaishi, Miyako and Yamadamachi and generated tsunami warnings in 19 other countries.

Kamaishi in March 2011

Texas Tech have produced a real-time viewer that maps the aftershocks:

In the twentieth century alone, Japan has survived a host of terrible quakes, only the most famous of which are:

September 1923
Perhaps the most iconic and devasting quake of modern times in Japan, the Great Kanto earthquake was of magnitude 8.3. Its epicentre was near the twin cities of Tokyo and Yokohama, and it is estimated that approx142,800 people lost their lives, largely as a result of the firestorms that devastated the area after the quake, reducing approx. 50% of residences to ruins. The quake was accompanied by 12m tsunami in the Sagami Bay.

March 1933Taking place in an area rather close to the 2011 quake (almost exactly 78 years later), the so-called Sanriku earthquake hit with a magnitude of 8.4. It is estimated that 3,000 lives were lost. As in 2011, most of the casualties appear to have been caused by a large tsunami that devastated the area, especially around Kamaishi Bay, Iwate.

Kamaishi in March 1933

Kamaishi in March 2011

June 1948
The Fukui earthquake (of magnitude 7.3) caused massive structural damage to approx.. 70,000 homes and claimed 3,769 lives.

June 1978
Also in the Sendai area, the so-called Miyagi earthquake was of magnitude 7.7.

January 1995
Most people today will remember the devastation of the Hyogo earthquake (of magnitude 6.9), which struck the Kobe area and claimed 5,500 lives. The earthquake, whose hypocentre was 16 km beneath its epicentre on Awaji Island (20km from the city of Kobe) destroyed approx. 200,000 buildings with 90% of the casualties being reported on the southern coast of Honshu between Kobe and Nishinomiya.