JAPAN EARTHQUAKE
Tōhoku Megathrust Earthquake & Tsunami (2011)
BACKGROUND & CAUSES
The Event: On March 11, 2011, at 2:46 PM local time, a massive 9.0 magnitude earthquake
struck 250 miles off the northeast coast of Japan's main island, Honshu. It occurred at a
relatively shallow depth of 20 miles.
Tectonic Setting: Japan lies on a destructive plate margin where the oceanic Pacific Plate is
subducting beneath the continental Eurasian Plate. Friction caused the plates to lock and build
immense pressure. When the pressure was finally released, it triggered a 'megathrust'
earthquake.
Geological Force: The energy released was equivalent to 600 million times that of the
Hiroshima nuclear bomb. The seabed near the epicentre shifted by 24 metres, and the sheer
force of the quake shifted the Earth's axis by 10 to 25 cm, shortening the length of a day by 1.8
microseconds.
PRIMARY IMPACTS
• Casualties: Tragically, 15,894 people lost their lives, with over 26,000 injured and thousands
more reported missing.
• Widespread Destruction: Over 332,000 buildings, 2,126 roads, 56 bridges, and 300
hospitals were severely damaged or destroyed.
• Infrastructure Failure: More than 4.4 million households in North-East Japan were left
completely without electricity.
• Liquefaction: This occurred heavily in parts of Tokyo built on reclaimed land, damaging over
1,000 buildings.
SECONDARY IMPACTS
• The Tsunami: The sudden seabed shift triggered devastating tsunami waves reaching up to
40 metres high, penetrating up to 6 miles inland and destroying entire coastal communities.
• Economic Disaster: It became the most expensive natural disaster in history, with an
estimated economic cost of US$235 billion.
Tōhoku Megathrust Earthquake & Tsunami (2011)
BACKGROUND & CAUSES
The Event: On March 11, 2011, at 2:46 PM local time, a massive 9.0 magnitude earthquake
struck 250 miles off the northeast coast of Japan's main island, Honshu. It occurred at a
relatively shallow depth of 20 miles.
Tectonic Setting: Japan lies on a destructive plate margin where the oceanic Pacific Plate is
subducting beneath the continental Eurasian Plate. Friction caused the plates to lock and build
immense pressure. When the pressure was finally released, it triggered a 'megathrust'
earthquake.
Geological Force: The energy released was equivalent to 600 million times that of the
Hiroshima nuclear bomb. The seabed near the epicentre shifted by 24 metres, and the sheer
force of the quake shifted the Earth's axis by 10 to 25 cm, shortening the length of a day by 1.8
microseconds.
PRIMARY IMPACTS
• Casualties: Tragically, 15,894 people lost their lives, with over 26,000 injured and thousands
more reported missing.
• Widespread Destruction: Over 332,000 buildings, 2,126 roads, 56 bridges, and 300
hospitals were severely damaged or destroyed.
• Infrastructure Failure: More than 4.4 million households in North-East Japan were left
completely without electricity.
• Liquefaction: This occurred heavily in parts of Tokyo built on reclaimed land, damaging over
1,000 buildings.
SECONDARY IMPACTS
• The Tsunami: The sudden seabed shift triggered devastating tsunami waves reaching up to
40 metres high, penetrating up to 6 miles inland and destroying entire coastal communities.
• Economic Disaster: It became the most expensive natural disaster in history, with an
estimated economic cost of US$235 billion.
