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SALT LAKE CITY -- It's bad enough to have a hurricane come roaring through your town and destroy everything its winds touch and drench the place in unimaginable amounts of rain. But precisely these effects are likely to lead to another horrifying natural disaster - earthquakes.
Nature apparently loves to add insult to injury. In a study of the last 50 years of earthquakes in Taiwan, researchers from the University of Miami - Rosenstiel found that there is a predictable relationship between large tropical cyclone events and earthquakes that occur years later.
"Very wet rain events are the trigger," said Dr. Shimon Wdowinski, lead author of the study.
But how does that work? It's actually fairly intuitive. In an extremely heavy rain event, the amount of rain that normally falls in a year - or even more - can fall on a fault line in just a couple days.
This leads to all sorts of effects, like massive erosion and mudslides. Essentially, the earth is picked up and hauled off by the rain, relieving a tremendous amount of pressure on the fault. After a few years of this, the fault will spring up like toast from a toaster, causing a massive earthquake.
There are certain caveats, of course. This finding only affects areas where there are two key elements - hurricanes or typhoons and mountainous, vertical faults. A lateral fault, like the San Andreas in California, moves sideways, and so relieving downward pressure may not cause a change in the situation at the fault. But with vertical faults in mountainous regions, moving all that earth can make all the difference.
The space between the rain and the earthquake is generally less than four years. In Taiwan, a typhoon in 2009 led to two earthquakes in 2010. A 1996 typhoon was followed by an earthquake in 1998, and the same thing happened with a typhoon in 1969 and an earthquake in 1972.
Utahns need not worry any time soon, since we don't ever see nearly the kind of rain it would take to produce such an effect on faults in the state. But for countries like Haiti, being able to prepare ahead of time after a particularly bad hurricane season could make all the difference in preventing another tragedy like the one that occurred when a massive earthquake leveled much of the island in Jan. 2010. Reliable predictions of earthquakes are nearly impossible, and this study is a huge step forward.
Email: dnewlin@ksl.com
