On May 12 this year, the 7.9 magnitude Wenchuan earthquake devastated the region along the Longmenshan area close to Chengdu, a city with 11 million inhabitants in the southern center of China. Based on their research, experts in the field claim that it is pretty likely that another major replica is bound to strike again soon.

 

An earthquake is defined as a rapid, sudden shaking of the Earth's surface, caused by the breaking and shifting of the rock beneath it. Although such events are fairly common in Asia, this one was unusual in that it happened within the continent, along a fault which had been dormant for thousands of years, close to two other much more seismically active regions. Seventy thousand of the victims of the earthquake were instantly killed, while eighteen thousand more have gone missing or are presumed to be dead.

 

The research group was led by Shinji Toda from the Geological Survey of Japan, together with Jian Lin from the Woods Hole Oceanographic Institution (WHOI), Mustapha Meghraoui from the Institute of Geophysics in Strasbourg (France), and Ross Stein of the U.S. Geological Survey (USGS). The geophysicist team analyzed the region's seismic activity in the past 10 years, and also used computer models in order to estimate the stress changes along the strip-like faults of Xianshuihe, Kunlun, and Min Jiang. These faults are located 150 to 450 km (90 to 280 miles) from the Longmen Shan rupture that caused the recent catastrophic quake.

 

Their study concluded that the respective event doubled the occurrence chances of similar quakes on the two fault lines. More precisely, the probability of another earthquake of a 6 or higher magnitude occurring in the area was estimated at 57 to 71% for the next 10 years, dropping to only 8 to 12% for the case of a magnitude 7 one in the same period of time. This rises again, though, to about 21-31% for the next 3 decades.

 

As Stein says, “One great earthquake seems to make the next one more likely, not less. We tend to think of earthquakes as relieving stress on a fault. That may be true for the one that ruptured, but not for the adjacent faults.” There have been many cases of high-scaled quakes that were soon followed by major similar events. Researchers attribute this to the domino effect, as the movement of one part of the planet's crusts affects the others nearby. Although some crust stress is released from certain regions, it is transferred to the nearby faults.

 

Toda also detailed the biggest problem for geophysicists trying to predict earthquakes, “Earthquake prediction is a bit like the thundercloud and lightning. We can forecast that lightning will come from a thundercloud, but we cannot predict the exact time and place where the lightning will hit. With earthquakes, we can roughly forecast the probability of activity over broad ranges of time, magnitude, and location, but we cannot determine the exact value for any of these.”