Hundreds of aftershocks, dozens of magnitude 6.0 or greater and two of magnitude 7.0 or greater, followed in the days and weeks after the main quake.
(Nearly two years later, on December 7, 2012, a magnitude-7.3 tremor originated from the same plate boundary region.
Japan earthquake and tsunami of 2011, also called Great Sendai Earthquake or Great Tōhoku Earthquake, severe natural disaster that occurred in northeastern Japan on March 11, 2011. (The early estimate of magnitude 8.9 was later revised upward.) The epicentre was located some 80 miles (130 km) east of the city of Sendai, Miyagi prefecture, and the focus occurred at a depth of 18.6 miles (about 30 km) below the floor of the western Pacific Ocean.
The earthquake was caused by the rupture of a stretch of the subduction zone associated with the Japan Trench, which separates the Okhotsk microplate.) A part of the subduction zone measuring approximately 190 miles (300 km) long by 95 miles (150 km) wide lurched as much as 164 feet (50 metres) to the east-southeast and thrust upward about 33 feet (10 metres).
The thrusting moved Honshu about 2.4 meters eastward, and the seismic waves on the Pacific Ocean floor set off tsunami waves traveling at the speed of a jet plane (about 700 kilometers per hour).
Waves 3 to 38 meters tall pounded Honshu’s coastline, destroying towns and villages and flooding areas up to 10 kilometers inland.
The March 11 temblor was felt as far away as Petropavlovsk-Kamchatsky, Russia; Kao-hsiung, Taiwan; and Beijing, China.
It was preceded by several foreshocks, including a magnitude-7.2 event centred approximately 25 miles (40 km) away from the epicentre of the main quake.
As we have seen, it is indeed difficult to define any earth tremor as the main quake until after the whole sequence of earth shocks has occurred.
Furthermore, despite advances in our knowledge of how and where earthquakes happen, our capability to predict exactly where and when the next earthquake will hit is in its infancy.