Hazard and Disaster Magnitude Units
Additional Information About the Hazard Extent
Some disaster types may have a reported magnitude in the Magnitude and Magnitude Scale columns of the EM-DAT Public Table. EM-DAT disaster magnitude scales vary depending on the disaster type. The table below specifies magnitude property and units for related disaster types.
Warning
The EM-DAT team has been notified that earthquakes contain magnitudes sometimes expressed on the Richter scale, and sometimes with the moment of magnitude (Mw) scale. The earthquake entries are under review to correct that issue. In a future release, the Richter scale will be replaced by the moment of magnitude. In the meantime, users can carefully check the magnitude values reported by the USGS earthquake catalog.| Disaster Type | Magnitude property | Magnitude Unit or Scale |
|---|---|---|
| Earthquake | Amplitude of seismic waves | |
| Flood | Flood extent (area) | km² (square kilometers) |
| Drought | Drought extent (area) | km² (square kilometers) |
| Extreme temperature | The recorded extreme temperature (maximum or minimum depending on whether it is a heat or a cold wave) | °C |
| Epidemic | Number of vaccinated people | Vaccinated people2 |
| Wildfire | Wildfire extent (area) | km² (square kilometers) |
| Storm | Recorded wind speed | kph (kilometer per hour) |
| Industrial accident (Chemical spills) | Chemical discharged volume | m³ (cubic meter) |