Wed, May 30, 2012
A number of seismologists are splitting with the Tangshan Seismological Bureau, which labeled two earthquakes that shocked northern China recently as aftershocks of the magnitude-7.8 Tangshan earthquake in 1976.
Two earthquakes, measuring a magnitude of 4.8 and 3.2 on the Richter scale, struck the area between Tangshan and Luanxian county in Hebei Province on Monday and Tuesday mornings, according to the China Earthquake Network Center (CENC).
Residents in downtown Tangshan and the neighboring megacities Beijing and Tianjin also felt the tremor, according to CENC.
"The two continuous shocks were both the aftershocks of the 1976 Tangshan earthquake, whose energy release is gradually decaying," according to the Tangshan Seismological Bureau Tuesday.
In 2010, the Xinhua News Agency also called two other temblors measuring 3.1 and 4.2 aftershocks, according to the Beijing News.
Yet experts and netizens are having a hard time understanding how 36 years after the devastating quake these small quakes can be classified as aftershocks.
"It makes sense if the expert can explain it from a professional perspective, but it's more important to convince the public and teach them to take precautions against the earthquake," an unverified Sina Weibo user said in his posting.
Sun Shihong, a researcher with CENC, told the Beijing Morning Post that it is inappropriate to call them aftershocks of the 1976 quake, 36 years after it occurred.
Chen Yongshun, director of the Institute of Theoretical and Applied Geophysics of Peking University, holds a different view.
"It's acceptable to say that they were aftershocks from the 1976 quake, based on the experience of experts," said Chen in an interview with the Global Times.
"It's such a controversial topic that divergent views among experts can be expected," Yin Baojun, director of the Earthquake Monitoring and Prediction Department from the Tangshan Seismological Bureau, told the Global Times Tuesday.
Yin said that there is no time limit that defines when an aftershock can occur but a rough conclusion can be drawn from statistics.
Yin Baojun said the two recent aftershocks are not a warning sign that a larger quake is imminent.
According to the Earthquake Prevention and Disaster Reduction Law, earthquake predictions should only be published by the relevant State agency.
Yin told the Global Times that earthquakes are somewhat predictable based on statistical probability.
