Hurricanes might trigger big tropical earthquakes
Heavy rains cause landslides, and that may set off a shift in tectonic regions By Stephanie Pappas
SAN FRANCISCO — Typhoons and hurricanes can trigger large earthquakes in tropical regions, a new study suggests.
By dumping rain and causing landslides, these storms can change the weight of the Earth in tectonically-stressed regions, releasing loads that had been keeping the faults locked in tight. The result is that faults already under pressure seem more likely to break in the years after very wet tropical cyclones.
Earthquakes including Haiti's 2010 magnitude-7.0 temblor and a 6.4-magnitude quake that struck Kaohsiung, Taiwan, the same year, fit this pattern, according to study . . . .
Disaster chain reaction
Wdowinski and his colleague Igor Tsukanov of Florida International University became interested in whether tropical cyclones interact with earthquakes after noticing that both the 2010 Taiwan earthquake and the 2010 Haiti quake were preceded relatively closely by big storms. . . .
researchers found that 85 percent of magnitude-6-and-above quakes occurred within the first four years after a very wet storm. That was five times what would have been expected from background quake rates, Wdowinski said. . . . .
Timing is everything
Previous researchers have suggested that extremely low pressure from storms can trigger quakes in already-strained areas in the very short term, Wdowinski said, but these longer-term linkages are likely caused by a different mechanism. These areas are already tectonically active, with faults building up strain as landmasses creep against one another. These strained faults are destined to rupture and eventually cause quakes, Wdowinski said.
But when a very wet typhoon or hurricane dumps lots of rain, it often causes large landslides in mountainous areas. Extra rain over the following months further erodes mountains and hills scarred by these landslides. This shifting of sediment lifts the weight that keeps faults locked. The burden lifted, the fault suddenly slips, causing a quake. . . .
"The main engine that's actually responsible for the earthquake is not the wet typhoon," Wdowinski said. "The wet typhoon just determines the timing."
http://www.msnbc.msn.com/id/45605013/ns/technology_and_science-science/
