Skip Top Navigation
The Disaster Area Email Search Home

Intensity Scales

Hurricanes - The Saffir Simpson Scale

Category Category Description Level Of Damage
1 Wind Speed: 74 - 95 MPH
Storm Surge: 4 - 5 Feet Above Normal
Primary damaged to unanchored mobile homes, shrubbery, and trees. Some coastal road flooding and minor pier damage. Little damage to building structures.
2 Wind Speed: 96 - 110 MPH
Storm Surge: 6 - 8 Feet Above Normal
Considerable damage to mobile homes, piers, and vegetation. Coastal and low-lying escape routes flood 2 - 4 hours before arrival of hurricane center. Buildings sustain roofing material, door, and window damage. Small craft in unprotected moorings break moorings.
3 Wind Speed: 111 - 130 MPH
Storm Surge: 9 - 12 Feet Above Normal
Mobile homes destroyed. Some structural damage to small homes and utility buildings. Flooding near coast destroys smaller structures; larger structures damaged by floating debris. Terrain continuously lower than 5 feet. ASL may be flooded up to 6 miles inland.
4 Wind Speed: 131 - 155 MPH
Storm Surge: 13 - 18 Feet Above Normal
Extensive curtain wall failures with some complete roof structure faiture on small residences. Major erosion of beaches. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet. ASL may flood (and require mass evacuations) up to 6 miles inland.
5 Wind Speed: Over 155 MPH
Storm Surge: Over 18 Feet Above Normal
Complete road failure on many homes and industrial buildings. Some complete building failures. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of low ground residential areas may be required.

[Back to Top]

Tornadoes - The Fujita Scale

Category Category Description Level Of Damage
F-0 Gale Tornado
40 - 72 MPH
Chimneys damaged; branches broken off trees; shallow-rooted trees uprooted; sign boards damaged.
F-1 Moderate Tornado
73 - 112 MPH
Roof surfaces peeled off; mobile homes pushed off foundations or overturned; moving autos pushed off roads.
F-2 Significant Tornado
113 - 157 MPH
Roofs torn off frame houses; mobile homes demolished; box cars pushed over; large trees snapped or uprooted; light-object projectiles generated.
F-3 Severe Tornado
158 - 206 MPH
Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.
F-4 Devastating Tornado
207 - 260 MPH
Well-constructed houses leveled; structures with weak foundations relocated; cars thrown and large projectiles generated.
F-5 Incredible Tornado
261 - 318 MPH
Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized projectiles hurtle through the air in excess of 100 yards; trees debarked; other incredible phenomena expected.

[Back to Top]

Earthquakes - The Modified Mercalli Scale & The Richter Scale

The Modified Mercalli Scale Level Of Damage The Richter Scale
1-4 Instrumental to Moderate No damage. </= 4.3
5 Rather Strong Damage negligible. Small, unstable objects displaced or upset; some dishes and glassware broken. 4.4 - 4.8
6 Strong Damage slight. Windows, dishes, glassware broken. Furniture moved or overturned. Weak plaster and masonry cracked. 4.9 - 5.4
7 Very Strong Damage slight-moderate in well-built structures; considerable in poorly-built structures. Furniture and weak chimneys broken. Masonry damaged. Loose bricks, tiles, plaster, and stones will fall. 5.5 - 6.1
8 Destructive Structure damage considerable, particularly to poorly built structures. Chimneys, monuments, towers, elevated tanks may fail. Frame houses moved. Trees damaged. Cracks in wet ground and steep slopes. 6.2 - 6.5
9 Ruinous Structural damage severe; some will collapse. General damage to foundations. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground; liquefaction. 6.6 - 6.9
10 Disastrous Most masonry and frame structures/foundations destroyed. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Sand and mud shifting on beaches and flat land. 7.0 - 7.3
11 Very Disastrous Few or no masonry structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines completely out of service. Rails bent. Widespread earth slumps and landslides. 7.4 - 8.1
12 Catastrophic Damage nearly total. Large rock masses displaces. Lines of sight and level distorted. > 8.1

[Back to Top]

Volcanic Eruptions - The Volcanic Explosivity Index

Category Category Description
0 Non-Explosive (Hawaiian)
Plume: < 100 m/Volume: > 1000 m3
1 Gentle (Hawaiian - Strombolian)
Plume: 100 - 1000 m/Volume: >10,000 m3
2 Explosive (Strombolian - Vulcanian)
Plume: 1 - 5 km/Volume: > 1,000,000 m3
3 Severe (Vulcanian)
Plume: 3 - 15 km/Volume: > 10,000,000 m3
4 Cataclysmic (Vulcanian - Plinian)
Plume: 10 - 25 km/Volume: > 100,000,000 m3
5 Paroxysmal (Plinian)
Plume: >25 km/Volume: > 1 km3
6 Colossal (Plinian - Ultraplinian)
Plume: > 25 km/Volume: > 10 km3
7 No Adjectival Description
Plume: > 25 km/Volume: > 100 km3
8 No Adjectival Description
Plume: > 25 km/Volume: > 1,000 km3

[Back to Top]

FEMA for Kids footer graphic