Earthquakes may come from cyclones, says study

Earthquakes, including the recent 2010 earthquakes in Haiti and Taiwan, might occur as a result of tropical cyclones (hurricanes and typhoons) according to a new study.

Shimon Wdowinski, associate research professor of marine geology and geophysics at University of Miami’s Rosenstiel School of Marine and Atmospheric Science led the study. Wdowinski said:

Very wet rain events are the trigger. The heavy rain induces thousands of landslides and severe erosion, which removes ground material from the Earth’s surface, releasing the stress load and encouraging movement along faults.

Wdowinski and a colleague from Florida International University analyzed data from quakes magnitude-6 and above in Taiwan and Haiti. They found a strong temporal relationship between the two natural hazards. Large earthquakes occurred within four years after a very wet tropical cyclone season.

During the last 50 years three very wet tropical cyclone events – Typhoons Morakot, Herb and Flossie – preceded major earthquakes in Taiwan’s mountainous regions within four years. The 2009 Morakot typhoon preceded an M-6.2 in 2009 and M-6.4 in 2010. The 1996 Typhoon Herb preceded an M-6.2 in 1998 and M-7.6 in 1999 and the 1969 Typhoon Flossie was followed by a M-6.2 in 1972.

Typhoon Morokot. Image credit: NASA

The 2010 M-7 earthquake in Haiti occurred in the mountainous region one-and-a-half years after two hurricanes and two tropical storms drenched the island nation within 25 days.

Rainfall may cause earthquakes

The researchers suggest that rain-induced landslides and excess rain carries eroded material downstream. As a result the surface load above the fault is lessened. Wdowinski said:

The reduced load unclamp the faults, which can promote an earthquake.

Fractures in Earth’s bedrock from the movement of tectonic plates, known as faults, build up stress as they attempt to slide past each other, periodically releasing the stress in the form of an earthquake.

According to the scientists, this earthquake-triggering mechanism is only viable on inclined faults, where the rupture by these faults has a significant vertical movement.

Wdowinski also shows a trend in the tropical cyclone-earthquake pattern exists in M-5 and above earthquakes. The researchers plan to analyze patterns in other seismically active mountainous regions – such as the Philippines and Japan – that are subjected to tropical cyclones activity.

Wdowinski will discuss his findings during a presentation at the 2011 AGU Fall Meeting in San Francisco.

Bottom line: A new study by scientists at University of Miami suggests that earthquakes, including the recent 2010 temblors in Haiti and Taiwan, might be triggered by tropical cyclones (hurricanes and typhoons.)

December 9, 2011

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