Geology And Geophysics
Flood in Old Mandeville, Louisiana from Hurricane Ike

Torrential Rains Trigger Earthquakes



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Flood in Old Mandeville, Louisiana from Hurricane Ike
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"Torrential Rains Trigger Earthquakes"
Caption: Flood in Old Mandeville, Louisiana from Hurricane Ike
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In a report on scientific findings to fellow scientists attending the annual meeting of American Geophysical Society held this year in San Francisco, Shimon Wdowinski and his colleague Igor Tsukanov presented a stunning new theory linking torrential rains to earthquakes.

They believe evidence shows that the torrential rains brought by cyclones and hurricanes not only can create landslides, but also trigger quakes. The link, they say, is the change of weight bearing down on existing faults in certain regions that are already tectonically stressed. The data they accumulated suggests the likelihood that faults already subjected to incredible pressure can break after heavy, unrelenting rains.

The rains, in essence, are the straw that breaks the camel's back—or in this case precipitates moderate to strong temblors.

Heavy rains the trigger

Wdowinski, an associate research professor of marine geology and geophysics at the University of Miami told the group that "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."

The two scientists—Wdowinski and colleague Tsukanov of the Florida International University—grew interested in the anecdotal evidence that seemed to support a link between heavy rainfall and subsequent earthquakes in the same general areas. The two poured over reams of data collected on major quakes rating a magnitude six and higher.

Going back in time half a century, the researchers focused on two tectonically active regions: Taiwan and Haiti. The data indicated that in many cases significantly large earthquakes followed within 48 months of a hurricane or cyclone seasons that dropped abnormally large quantities of rain. Surprisingly, the pattern suggested a rate of cyclone/hurricane destruction followed by 6.0 or greater magnitude quakes 85 percent of the time.

Deadly one-two punch

Some of the most spectacular examples that support their theory were also the most deadly.

The 2009 storm Typhoon Morakot slammed into Taiwan causing massive flooding. Just months later, the island nation was rocked by a quake registering 6.2 and then another in 2010 that seismographs recorded as 6.4 on the scale.

Whole villages were swept away or collapsed leaving a swath of misery and destruction behind including 614 people officially declared dead and 75 others unaccounted for to this day.

In 1996 Typhoon Herb caused massive destruction and caused the death of many hundreds Taiwan and the Chinese mainland. Several years after the typhoon two earthquakes struck: a 6.2 in 1998 followed by a 7.6 during 1999.

Other typhoons dumping record amounts of rain on Taiwan were also followed by major earthquakes.

The same pattern was evident in the Haitian data. "The cyclone itself is a disaster, there is a lot of flooding, then there are landslides and then the earthquakes come," Wdowinski told the scientists at the meeting.

Insights into quake causes making progress

The link between heavy rainfall and earthquakes is just the latest insight that scientists have made concerning geophysical catastrophes. During the past several years other researchers have found evidence that large deposits of subterranean quartz crystals may facilitate fault line slippage and ruptures, while the all-encompassing theory of global rupture and cascading earthquakes has found new followers.

Sources

Study links tropical cyclones to earthquakes


Hurricanes might trigger big tropical earthquakes

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