M9.1 Earthquake – 2011 Great Tohoku Earthquake, Japan
A great magnitude 9.1 earthquake struck near 2011 Great Tohoku Earthquake, Japan at a shallow crustal depth of 29.0 km, releasing seismic energy equivalent to approximately 674 Mt of TNT. Tracked live on Earthquake Today, here is the verified OFFICIAL telemetry, interactive epicenter map, and ground shaking assessment.
Seismic Telemetry Specifications
9.1MWW
Great Seismic Class
29.0km
Crustal Layer
38.297° N, 142.373° E
GPS Coordinates
674 Mt
TNT Equivalent Power
OFFICIAL
USGS Real-time Feed
Epicenter Location & Tectonic Fault Map
Is This Earthquake Dangerous?
A magnitude 9.1 event is classified as a great earthquake. Devastating seismic event capable of near-total destruction across regional epicenters. Can generate destructive trans-oceanic tsunamis and aftershock sequences.
Estimated Shaking Across Nearby Communities
Considerable damage in ordinary buildings with partial collapse; heavy furniture overturned.
Considerable damage in ordinary buildings with partial collapse; heavy furniture overturned.
Considerable damage in ordinary buildings with partial collapse; heavy furniture overturned.
Did You Feel This Earthquake?
Help seismologists and community members map real-world ground shaking near Japan.
Your immediate response verifies shaking boundaries and helps ground-truth instrumental models.
What Does Magnitude 9.1 Mean?
Earthquake strength is measured on a logarithmic scale. Compare this event with the full seismic scale:
Logarithmic Energy Multiplier
Because seismic scales are logarithmic, each whole integer increase represents:
Why Did This Earthquake Happen?
Japan sits at the complex collision intersection of four major tectonic plates: the Pacific, Philippine Sea, Eurasian, and North American plates. Subduction of the Pacific Plate beneath the Japanese archipelago creates intense strain that releases as high-frequency megathrust earthquakes and volcanic activity along the Pacific Ring of Fire.
Originating at a depth of 29.0 km (Earth's Crust (0–70 km)), this rupture occurred occurred within the brittle upper crust. shallow earthquakes produce the highest peak ground acceleration and the sharpest surface shaking.
Aftershock Outlook & Secondary Tremors
Following an earthquake of magnitude 9.1, an active aftershock sequence is expected over the coming days and weeks. In accordance with Omori's Law and Båth's Law of seismology, secondary tremors decrease in frequency over time, with the largest expected aftershock historically averaging approximately 1.0 to 1.2 magnitude units below the mainshock. Local residents should remain vigilant for secondary shaking, particularly when inspecting older structures or unreinforced masonry.
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Earthquake Safety Action Plan
Complete Safety Guide →- •Drop, Cover, and Hold On: Take cover beneath a sturdy table or desk.
- •Stay indoors away from exterior glass windows and heavy unanchored fixtures.
- •If outdoors, move into an open area away from power lines and building facades.
- •Inspect utilities for damaged gas lines, water leaks, or electrical hazards.
- •Expect Aftershocks: Secondary tremors frequently strike after significant events.
- •Avoid damaged structures and listen to official emergency broadcasts.
- •Maintain a 72-hour emergency go-bag with water, food, and first aid.
- •Anchor heavy furniture, water heaters, and appliances to structural studs.
- •Establish a family emergency communication protocol and meeting point.
Frequently Asked Questions
Common questions and answers about this earthquake.
No. No tsunami warning, watch, or advisory was issued by the Pacific Tsunami Warning Center (PTWC) or the USGS for this M9.1 event. The focal depth (29.0 km) and magnitude did not generate sufficient vertical seafloor displacement to trigger a hazardous tsunami wave.
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