University of Miami Study: Hurricanes Can Trigger Earthquakes

The following article was published in the South Florida Sun Sentinel on January 2, 2012:

UM Study:  Tropical systems can trigger earthquakes

By Ken Kaye

Florida is used to dealing with most of the effects of powerful hurricanes — blasting winds, storm surge, twister-like vortexes.

But hurricanes have another impact — they can help trigger earthquakes, according to a new University of Miami study. Although Florida is far less vulnerable because its land is stable and flat, wet tropical storms are a danger to Haiti and other regions with rugged terrain.

The study found that tropical rains can produce landslides and severe erosion in mountainous areas, moving thousands of tons of mud. That shift in weight can unclamp tectonic plates below the surface, commencing the earthquake process.

“Very wet rain events are the trigger,” said Shimon Wdowinski, the study’s lead author and an associate research professor of marine geology at UM’s Rosenstiel School of Marine and Atmospheric Science.

The 2008 storms killed more than 700 people, destroyed 22,702 homes, wiped out about 70 percent of Haiti’s crops and caused a total of more than $1 billion in damage.

The earthquake, centered about 15 miles west of the capital of Port-au-Prince, killed more than 200,000, left about 1 million people homeless and caused between $8 billion and $14 billion in damage.

Wdowinski found that in the past 50 years, three typhoons inundated Taiwan’s mountainous region. In each case, earthquakes occurred within four years and all were magnitude 5 or stronger.

Earthquakes occur when tectonic plates below the Earth’s surface move and slide past each other, building up underground stress and creating faults. Scientists estimate 14,000 earthquakes occur each year, or about 40 a day, of various magnitudes.

Typically, 17 or 18 major earthquakes, magnitude 7 to 7.9, occur each year. And about one magnitude 8 or higher earthquake hits once per year with the same energy as 790 nuclear bombs. Most quakes are followed by a number of aftershocks and occasionally tsunamis.

“An earthquake can occur anywhere in the world, but the chances of large earthquake are much greater where tectonic plates meet,” said Greg Durocher, of the U.S. Geological Survey Earthquake Hazards Program, in Anchorage, Alaska.

Because Florida is on the middle of a plate, the earth below is relatively stable, Wdowinski said.

Although it likely was not triggered by tropical systems, Florida did experience a minor earthquake in 1879, when plaster was knocked off the walls of homes in St. Augustine. In January 1880, Key West felt severe shock waves after two strong earthquakes were recorded in Cuba.

More commonly, the state feels minor shocks from quakes hundreds of miles away. Such was the case in September 2006, when a magnitude 6 earthquake took place in the Gulf of Mexico about 260 miles southwest of Tampa.

Find this article here:  http://www.sun-sentinel.com/news/broward/fl-hurricane-earthquake-pattern-20111229,0,2868728.story