A new study has broken some important ground in the way we analyze the earth: how to spot high risk earthquake locations and what triggers them.
Scientists Shimon Wdowinski presented his findings at the 2011 AGU Fall Meeting in San Fransisco. As an associate research professor of Marine Geology and Geophysics at the University of Miami Rosenstiel School of Marine and Atmospheric Science, he has found this research information helpful and, perhaps, ground breaking.
The biggest trigger, they discovered, are events that end up producing large amounts of rain. The heavy type of rain can create thousands and thousands of landslides, which, in turn, creates severe erosion. This removes ground material from the Earth’s surface. When this occurs, there is not as much of a stress load, and all of a sudden, fault lines are encouraged to move.
Wdowinski, along with a colleague from Florida International University, took the time to analyze various data that stemmed from earthquakes topping a magnitude-6 and above. They specifically focused on earthquakes that hailed from Taiwan and Haiti. The duo found a strong temporal relationship between the earthquakes, typhoons, and hurricanes. Basically, large, impactful earthquakes were occurring within four years after a particularly wet tropical cyclone season.
In the last fifty years there were three tropical cyclone events that were very wet. They were Typhoon Morakot, Typhoon Herb, and Typhoon Flossie. All three were followed within four years by major earthquakes in Taiwan’s mountainous regions.
The Morakot typhoon, which was in 2009, was followed by a M-6.2 earthquake that same year, and an M-6.4 in 2010. Over a decade before, the 1996 Typhoon Herb was followed by an M-6.2 earthquake in 1998 and an M-7.6 in 1999. Years before, the 1969 Typhoon Flossie had an M-6.2 earthquake occur a few years later in 1972.
With these in mind, so does Haiti. In 2010, the M-7 earthquake occurred in the mountainous region just one and a half years following two hurricanes, as well as two tropical storms, that completely flooded the area over a matter of twenty-five days.
The researchers involved in the study suggest that these landslides and excess rain results in eroded material being carried downstream. The result is that the surface load that is generally above the fault is decreased. This frees up the faults, which, in turn, can promote the activity of an earthquake.
The faults, which are actually fractures in Earth’s bedrock, build up stress as they try to make their way to slide past each other, periodically releasing the stress. This release of stress comes to fruition as an earthquake. In this case, it only is viable on any faults that are inclined, because have an significant vertical movement that is triggered.
There is a trend in the tropical cyclone/hurrican and earthquake patterning that exists in any earthquakes that are above M-5. Because of this newly found information, researchers can further analyze the various patterns in other areas that are struck by both natural disasters.
For more information, visit the University of Miami Rosenstiel School of Marine & Atmospheric Science.