October 25, 2012
Strange Bedfellows: Earthquakes And Rain Storms
Brett Smith for redOrbit.com — Your Universe Online
The idea of “earthquake weather” can be traced back to the ancient Greeks, when Aristotle is said to have determined that winds trapped underground cause earthquakes by moving about or escaping through cracks in the surface.However, the scientific community has largely dismissed weather-driven earthquakes as myths or relics of an earlier, more mystical society. In fact, the state government of California has listed “earthquake weather” as a myth on its official website.
“The common misconception that earthquakes occur during hot and dry weather dates to the ancient Greeks. Earthquakes take place miles underground, and can happen at any time in any weather,” a statement on the website reads.
Despite these dismissive attitudes, several recent studies have pursued the idea that weather, more specifically severe storms, can cause earthquakes–albeit months after the storms hit.
Researchers at the California Institute of Technology´s Seismological Laboratory have been investigating a correlation between South Asian monsoons and seismic activity along the Main Himalayan Thrust (MHT) Fault.
“When you look at the seismicity (along the MHT), you see that you have more seismicity in the winter than you do in the summer “¦ you see that there seems to be a response to the load due to the monsoon,” Thomas Ader, a graduate student at the university recently told EarthMagazine.org.
According to the researchers, the monsoons and earthquakes have an indirect relationship, with the seismic activity peaking six months after, but in relation to, the severe storms. They theorize that the weight of the massive rains relieves building stress on the MHT by weighing down the Indian Plate, on one side of the fault, enough to slightly pull it away from the Eurasian Plate, on the other side.
Ader conceded that the changes of stress on the fault due to the weight of the water are “extremely small,” however he noted “we see changes in the seismicity rate on the order of about 10 to 20 percent.”
Another group of researchers, based in Florida, is studying the correlation between tropical storms and seismic activity. In their studies, they examined how the 2008 tropical storm season that resulted in four major storms passing over Haiti could have contributed to the 2010 earthquake that decimated the island nation.
According to their theory, the heavy rains in 2008 caused a myriad of landslides and rapid erosion – between 20 and 25 millimeters of debris per year that was washed out to sea. This removal of mass released some of the pressure on the underlying fault, enabling the plates along the fault to move more readily.
“By unloading the system, it makes it easier for the forces applied by tectonic plates to actually rupture the fault and cause an earthquake,” said Shimon Wdowinski, a geophysicist at the University of Miami, who is researching the connection.
The two research teams are undoubtedly aware that they are conducting their studies under a heavy cloud of skepticism, but the advent of new seismographs and satellite imaging technology has allowed for this potential correlation to be explored in greater detail.