About HazardSim

HazardSim answers one question in six variations: if this happened here, how far would it reach, and who lives there?

Updated 18 September 2026

What it is

HazardSim is a free simulator that runs in the browser. Pick a place on a real map, choose a hazard and its size, and the site draws what it would reach: flooded streets for a tsunami or a rising sea, damage rings for a meteor, shaking intensity for an earthquake, pyroclastic flows and ash for a volcanic eruption, a storm surge and wind zones for a hurricane. It then estimates how many people live inside each zone.

There is nothing to install and no account to create. The interface is available in sixteen languages: English, Spanish, Chinese, Hindi, Arabic, Portuguese, Russian, Japanese, German, French, Indonesian, Turkish, Korean, Ukrainian, Italian and Polish.

Six hazards

• Tsunami — water of a chosen height comes ashore and runs inland over real elevation, losing height as it travels.
• Sea level rise — the ocean sits permanently at a chosen mark, from one metre to the melt of every glacier on Earth.
• Earthquake — shaking intensity around an epicentre, adjusted for how well the buildings are made.
• Volcanic eruption — pyroclastic flows and ash fall by eruption size on the Volcanic Explosivity Index, around real volcanoes from the Smithsonian catalogue.
• Meteor impact — crater, fireball, blast and broken-glass radii for stone, iron or ice bodies from a metre to three kilometres across.
• Hurricane — a storm surge pushed over real elevation by a hurricane of chosen wind speed, with wind zones by Saffir–Simpson category.

Real data underneath

The terrain is real: elevation comes from Mapbox Terrain-RGB tiles. City boundaries and population figures come from OpenStreetMap, volcano locations from the Smithsonian Institution's Global Volcanism Program. The physics on top is deliberately simple and is described in full, with every constant, on the How it works page.

What the numbers mean

Every result is an order of magnitude, not a forecast. A real disaster depends on things no browser tool can know: the shape of the seafloor, the fault that slipped, the wind on the day, the hour, whether people had warning and used it. HazardSim is built to make scale understandable — why a metre of sea matters more than it sounds, why a 50-metre iron rock is worse than a 50-metre stone one, why the same magnitude kills dozens in one country and tens of thousands in another. It is not a tool for emergency decisions; see the disclaimer.

Articles and the shared feed

The articles put the simulator's numbers next to what actually happened: the deadliest tsunamis, the strongest earthquakes, the largest eruptions, what each size of asteroid does, and which cities sea level rise reaches first. The Recent launches page shows, anonymously, what visitors around the world simulated in the last 30 days.

Contact

Found a bug, a wrong city boundary or a mistake in an article? Want to embed or cite the simulator? Write to [email protected] — more on the contact page.