map showing real and potential earthquakes
An earthquake forecast map.
This week's magnitude 5.4 earthquake in Southern California marks another demonstration of an ongoing experiment by a NASA/Department of Energy-funded research team to forecast the location of large earthquakes in California.

This forecast map was published in the journal Seismological Research Letters in January 2007. Red boxes mark the locations forecast to be the sites of future earthquakes having magnitudes greater than five. The red boxes were computed using only data through August 31, 2005. The blue circles are the earthquakes greater than magnitude five that have occurred since Sept 1, 2005, up to this week's magnitude 5.4 Chino Hills earthquake. It can be seen that the red boxes are accurately forecasting future large earthquakes. This is a true prospective test, since the answer (locations of future large earthquakes) was not known in advance. The forecast is based on a mathematical analysis of previous small earthquakes. The red boxes indicate not that large earthquakes will necessarily occur in these regions, but rather that the large earthquakes that do occur are likely to be located near those regions. These regions represent a small subset of the regions that government agencies such as the United States Geological Survey have already identified as being susceptible to large earthquakes.

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