W76 on Los Angeles
100 kt thermonuclear weapon · USA · Population 3,898,747 · Density 3,200/km²
About this scenario
This page calculates what would happen if the W76 (USA, 1978) detonated over Los Angeles (USA). Common SLBM warhead.
The second-most populous US city, sprawling across Southern California with a metro area of nearly 13 million. With an urban-core density of about 3,200 people per km², even a relatively small detonation over the city center would affect a large population.
The W76 delivers 100 kt of explosive yield — 7× more powerful than the Hiroshima bomb. The tables below show calculated effect radii for an air burst (optimized for blast spread) and a surface burst (which produces massive fallout).
Air-burst effects (W76 over Los Angeles)
| Effect zone | Radius | Est. affected |
|---|---|---|
| Fireball (vaporization, 100% fatal) | 0.91 km | ~8,415 |
| Severe blast (20 PSI, ~98% fatal) | 2.20 km | ~39,406 |
| Moderate blast (5 PSI, ~50% fatal) | 4.71 km | ~87,016 |
| Light blast (1 PSI, glass injuries) | 13.39 km | ~79,016 |
| 3rd-degree thermal burns | 4.43 km | — |
| 2nd-degree thermal burns | 7.93 km | — |
Estimated total fatalities: ~134,837 · Estimated total affected (inside 1 PSI light-blast radius): ~1,803,163.
Surface-burst effects (with fallout)
A surface burst trades blast spread for radioactive fallout — much smaller blast radii but a large lethal fallout plume drifting downwind. This is what would happen if the W76 struck ground level rather than detonating optimally above Los Angeles.
| Effect zone | Radius (surface burst) |
|---|---|
| Fireball | 0.73 km |
| Severe blast (20 PSI) | 1.21 km |
| Moderate blast (5 PSI) | 2.59 km |
| Light blast (1 PSI) | 7.37 km |
| 3rd-degree thermal burns | 2.66 km |
| Lethal fallout zone | ~75.7 km |
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See the actual blast zones overlaid on a map of Los Angeles with population-density-based casualty estimates updated in real time as you move the detonation point.
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FAQ
What would happen if the W76 detonated over Los Angeles?
In an air burst over Los Angeles, the W76 (100 kt) would produce a fireball about 0.91 km in radius. The 5 PSI moderate-blast zone — where most residential buildings collapse — would extend to 4.71 km. Light blast damage and shattered windows would reach 13.39 km. Given Los Angeles's urban density (~3,200/km²), this scenario yields an estimated 134,837 immediate fatalities and about 79,016 additional injured.
How many people would die in Los Angeles from a W76 strike?
An air burst of the W76 over Los Angeles could cause an estimated 134,837 immediate fatalities and 79,016 additional injuries. The fireball alone (radius 0.91 km) would kill approximately 8,415 people; the severe-blast zone (20 PSI, radius 2.20 km) would add 39,406; the moderate-blast zone (5 PSI, radius 4.71 km) would add 87,016 more. Real numbers depend heavily on time of day, sheltering, weather, and altitude of detonation.
What is the blast radius of the W76 on Los Angeles?
For an air burst over Los Angeles: fireball 0.91 km, severe blast (20 PSI) 2.20 km, moderate blast (5 PSI) 4.71 km, light blast (1 PSI) 13.39 km. Thermal radiation causes 3rd-degree burns out to 4.43 km. A surface burst would shrink the blast radii by roughly 40 percent but generate massive radioactive fallout extending ~76 km from ground zero.
Is the W76 bigger than the bomb that hit Hiroshima?
The Hiroshima bomb (Little Boy) had a yield of about 15 kilotons. The W76 at 100 kt is 7× more powerful than the Hiroshima bomb.