(April 30, 2013) Nature magazine reports that, while scientists agree that China’s deadly tremor at Ya’an (Lushan county) may hint at where future quakes will strike, they disagree on which seismic fault the next rupture is likely to occur.
Liu Qiyuan, a geophysicist at the China Earthquake Administration’s Institute of Geology in Beijing, told Nature that researchers calculated the stress changes in adjacent faults after the magnitude-7.9 2008 Wenchuan quake and found that the biggest stress increase was in the southern Longmenshan fault, where last week’s earthquake occurred.
As the stress has been released by the Ya’an quake, the fault is now safe,” says Liu. He predicts that the Xianshuihe and Anninghe faults — which intersect with the southern end of the Longmenshan fault from the west and east, respectively — now pose the greatest seismic hazards.
Both of those faults are very active and have produced several large earthquakes over the past 200 years. Moreover, the Wenchuan quake and the magnitude-6.9 Yushu quake in 2010 have added considerable stress in faults, says Liu. With a network of about 300 broadband seismometers in the region, “we are monitoring the crust movement very closely,” he says.
Mian Liu, a geophysicist at the University of Missouri in Columbia, however, does not agree. He told Nature that, based on seismic measurements, last week’s quake in Ya’an [Lushan] did not rupture the entire southern segment of the Longmenshan fault, but instead released only one-third of its accumulated energy.
The 60-kilometre intact stretch between the Ya’an and Wenchuan quakes is likely to rupture in the next few decades,” he says. “It’s still able to cause earthquakes of magnitude 6 to 7.
By comparison, Mian Liu thinks that the Xianshuihe and Anninghe faults are less risky because, although the crust movement has generated a lot of strain energy, they have ‘spent’ a lot in the past.
Read the full Nature story by Jane Qiu here.