“Are the number of earthquakes increasing?” and other common earthquake questions

Viewers often depend on their local meteorologist for information and explanations about earthquakes. The answers to many of their questions are on the Web, but the information isn't always easy to find and sort through for the clearest explanation. To help reduce this obstacle, a set of short mini-lessons will be presented, accompanied where possible by simple animations and visualizations to illustrate the concepts. Questions to be addressed include:

1. Earthquakes seem to be in the news much more often now. Are the number and/or size of earthquakes increasing? Is hydraulic fracturing, as used by energy companies, causing earthquakes?

2. From what I learned in school, earthquakes happen along major fault zones at plate boundaries like in California. Why do we hear about earthquakes occurring outside of typical fault zones?

3. There seems to be a tsunami watch for any major offshore or coastal earthquake, but there isn't always a tsunami. Why do only some undersea earthquakes cause tsunamis?

4. The USGS says a recent earthquake was due to thrusting on a plate boundary, but the earthquake was 20 miles deep. How do seismologists figure out the type of faulting when the fault doesn't reach the surface?

5. There have been recent claims of successful earthquake predictions, but the USGS says that earthquakes can't be predicted. Are earthquakes predictable or can they be forecast the way you forecast the weather?

For answers to additional questions, the Incorporated Research Institutions for Seismology (IRIS, www.iris.edu) is a consortium of over 115 universities who engage in seismology research and education, and many of the seismologists at member universities are available after major earthquakes to answer questions from a local perspective. The IRIS Education and Public Outreach program, which has a range of earthquake-related materials designed for the general public, also seeks to learn what other questions are asked of broadcast meteorologists and the sorts of materials that would be helpful in answering them.