PREDICTING EARTHQUAKES

August 18, 2004
		In recent years, scientists have been moving ever closer to one day being able to predict when and where a major earthquake could occur. A leading scientist in earthquake prediction answers your questions about the latest developments in the field.

Online NewsHour Special Report: Predicting Earthquakes Forum Introduction What is the difference between a "return interval" and a "recurrence interval"? Seismologists study earthquakes, but who studies how to mobilize society for disaster? Why is it that the New Madrid Fault is very rarely mentioned in quake discussions? If people could turn on their TVs to find out an earthquake was coming, wouldn't there be widespread panic? Are we going to have a 19-year quake cycle here in California? What are the chances of a major earthquake through the mid-U.S.A., where none has occurred since the early 1800s?	Chris Hartz of Cayucos, Calif., asks: What is the difference between a "return interval" and a "recurrence interval" with relation to ground motions on a specific fault (e.g., Hayward Fault, Hosgri Fault)? Dr. William Ellsworth responds: We commonly use "return interval" and "recurrence interval" in several different contexts, and one has to be careful as to which one is being used, as within context the terms are interchangeable. One type of recurrence interval that we consider is the average interval between the occurrence of an earthquake (of a given size) on a particular fault. Another type of recurrence interval is the average time between earthquake shaking of a given intensity.