Earthquake Fatalities & Magnitude

Earthquake size has been measured a number of different ways. The earliest measures were estimates of the number of casualties and the economic costs of events. Later metrics were based on the intensity of shaking measured by the amount of damage done human-made structures and the landscape. Of course these quantities remain important today. The magnitude is an instrumental estimate of an earthquake's size, and quantifying the earthquake process with number is challenging. Above a certain threshold to produce serious damage in an earthquake, the magnitude does not correlate well with the number of fatalities. Other factors such as the depth of the rupture, its proximity to a substantial population, and the near-surface geology and the building practices of the people nearby play a strong role in the number of fatalities in a particular earthquake.

The National Earthquake Information Center of the U.S. Geological Survey has a project (PAGER - Prompt Assessment of Global Earthquakes for Response) to integrate information on all these issues and to forecast the number of fatalities and the economic consequences of larger earthquakes quickly after large earthquakes. 

For more information, please see the list of Seismology Texts or the list of popular-science books on earthquake science.

Above a certain threshold, earthquake magnitude is not the most important parameter related to the number of people killed in an earthquake. The correlation between magnitude and the number killed is poor. Data Source: USGS PAGER-CAT.