Geophysicist Talks Earthquakes and Volcanic Eruptions
Thursday, April 29 10:02 am
The 7.2-magnitude earthquake in Mexico, the devastating earthquake in Haiti, and the recent eruption of Iceland’s Eyjafjallajokull volcano all serve as reminders of the power of geological events. On May 6, Dr. Stephen Malone, who was the principal scientist responsible for the seismic monitoring of Mount St. Helens, will speak at the American Museum of Natural History about the science behind forecasting earthquakes and volcanic eruptions.
Dr. Malone recently shared some thoughts about the most important type of earthquake forecast, reducing earthquakes’ devastating effects, and the relationship between earthquakes and volcanic eruptions.
What are some of the latest advances in predicting earthquakes? How much progress has been made in the last decade?
No real progress has been made in the deterministic prediction of a specific earthquake. However, the long-term statistical forecasting of earthquakes is continually being refined. Since the primary hazard from earthquakes is the failure of our engineered structures—buildings, bridges, factories—the most important forecast is that which tells the engineer how strong a building should be built to withstand them.
Do you think there is any hope that in the future we will receive warning before a catastrophic earthquake such as the recent one in Haiti?
Earthquakes may be inherently unpredictable. However, there are two improvements I see on the horizon that may help significantly reduce the disastrous effects of future earthquakes. We may be able to indicate areas or regions where the probability of a large earthquake is higher than in the past, allowing for extra mitigation to take place. Second, the technology currently exists to provide warning seconds to a minute or so before strong shaking arrives at vulnerable locations distant from an earthquake that has already started.
What sorts of patterns do earthquakes and volcanic eruptions tend to follow?
It is currently not possible to say when a volcano will erupt in more distant future, but most do show signs of unrest at least days to weeks before they erupt. Earthquakes, on the other hand, occur suddenly. Typically a large earthquake will be followed by a decreasing number of smaller earthquakes, or aftershocks, and occasionally may be preceded by small earthquakes.
What can earthquake activity tell us about volcanic eruptions, and vice versa?
Unfortunately, it is a one-way street. What we call “seismicity patterns,” tracking the timing and location of small earthquakes at volcanoes, allow us to infer the forces being generated by molten rock as it rises toward the earth’s surface. Such seismicity is rarely large or hazardous in its own right. The dangerous earthquakes are those caused by the much larger plate tectonic forces that cause the failure of major weaknesses in the earth’s crust, such as the San Andreas fault.
You were the principal scientist responsible for the seismic monitoring of Mount St. Helens. What did that involve? What did you learn about eruptions during that time?
Monitoring Mount St. Helens, like other volcanoes, involves operating real-time seismic stations on and near the volcano, recording the resulting seismic data on computers and doing a combination of automatic, computer analysis and manual review on a routine basis. Since 1980, when Mount St. Helens first became active, I have been involved in developing ways to recognize signs of unrest and with automating that recognition process as much as possible to increase the sensitivity and reliability of detecting and interpreting precursors to eruptions. It is very rare for volcanoes to erupt dangerously without some warning.
