Based upon examination of patterns of smaller earthquakes in the same region in recent years, Keilis-Borok and his colleagues predict that a quake of Richter magnitude 6.4 or larger will strike the area before 5 September this year. The team point to what they claim to be a successful prediction of the magnitude 6.5 San Simeon earthquake that struck central California last December to support their latest call.
The prediction has been endorsed by the California Earthquake Prediction Evaluation Council, even though they have not been able to validate the physical basis for the prediction. In fact the so-called 'prediction' is actually a forecast - a broader estimate of the timing and area of occurrence of a future event. The Keilis-Borok team can only say that the quake might occur somewhere in an area of 31,000 square kilometres, sometime in the next few months. Furthermore, this is an area that is so seismically active that it has experienced two earthquakes in excess of Richter magnitude 7 in the last 12 years, and has a 10 % chance of a magnitude 6.4 earthquake occurring randomly before the 5 September deadline.