Modified Mercalli Intensity X MMI X: Extreme shaking
MMI X is extreme shaking. Most masonry and frame structures destroyed with foundations. Wooden structures and bridges destroyed. Large landslides. Rails bent greatly. Typical peak ground acceleration is over 124% of gravity, and the damage potential is very heavy.
What MMI X does
- Perceived shaking
- Extreme
- Damage potential
- Very heavy
- Peak acceleration
- over 124% g
- Peak velocity
- over 219 cm/s
What people feel
- Few or no masonry structures remain standing
- Bridges destroyed; roads impassable
What objects do
- Railroad rails bent greatly
- Pipelines put completely out of service
- Dams, dikes, and embankments seriously damaged
What happens to buildings
- Most masonry and frame structures destroyed with foundations
- Wooden structures and bridges destroyed
- Large landslides; broad fissures in ground
- Fault slipping visible at surface
Also at this level, in other versions of the scale
- Water thrown on banks of canals, lakes, rivers Wood & Neumann (1931), Bulletin of the Seismological Society of America 21, 277-283
Sources: the USGS Modified Mercalli Intensity scale (Wood and Neumann, 1931; Richter, 1958); ground-motion ranges from the USGS ShakeMap documentation (Worden et al., 2012), approximate and overlapping between neighbouring levels. See instrumental intensity. An older example: MMI X on YouTube.
Seen on camera: 2 clips rated MMI X
Each clip is rated from the effects it shows. A rating describes one camera at one place, not a whole town.
Showing all 2 clips rated MMI X. Wanted at this level: Long period, Pools, Trees, Homes, Stores, Public spaces, Warehouse, Skyscraper.
Recently at MMI X in our region
Earthquakes in the western United States and northern Mexico whose strongest shaking at a named place reached this level.
No earthquake in our records reached MMI X at a named place.
How MMI X is estimated
From instruments
USGS ShakeMap converts peak ground acceleration and velocity recorded at seismic stations into intensity. About over 124% g of acceleration corresponds to MMI X.
From people's reports
USGS Did You Feel It? turns answers from thousands of people into a community intensity for each place. If you felt an earthquake, report it there.
From footage
We rate each clip with questions built from the scale's own statements: what people, objects and buildings do on camera. A rating describes one camera at one place.
Common questions
What magnitude causes MMI X?
It depends on distance and ground conditions, not magnitude alone. A small earthquake can produce MMI X close by, and a large one can produce it far away.
What does MMI X feel like?
Few or no masonry structures remain standing. Bridges destroyed; roads impassable.
How strong is the ground motion at MMI X?
Peak ground acceleration is typically over 124% g and peak velocity over 219 cm/s.
How is intensity different from magnitude?
Magnitude measures the energy an earthquake releases and is one number per earthquake. Intensity describes the shaking at one place, so a single earthquake produces many intensities, strongest near the fault and weaker with distance.