Animals' abnormal activities might not be reliable evidence for a coming earthquake, a Chinese seismologist told a Xinhua reporter in an exclusive interview on Thursday.

Chinese netizens posted on blogs and bulletin boards, citing the abnormal migration of tens of thousands of toads before May 12 in Mianyang, a city close to Wenchuan, the epicenter of the 7.8-magnitude earthquake in southwest China's Sichuan Province, as a sign of a coming quake.

"There are complicated reasons for the anomaly of animals and underground water. An earthquake is only one of them along with climate change and weather conditions," said Zhang Guomin, a research fellow with the Research Institute of Seismology under China Seismological Bureau.

Earthquake forecasts was always based on scientific analysis, and not tailored to political requirements, said Zhang.

He said no seismological authorities in any country could accurately predict earthquakes.

Deputy director of China Earthquake Networks Center Zhang Xiaodong said:"To find out about the relationship between the abnormal natural phenomenon and earthquakes is actually one of the most important and difficult topics for studies in earthquake forecasting."

He said it would be a big breakthrough for earthquake research if there was any clear index of natural phenomenon before earthquakes happen. "The problem is that phenomenon which features the prelude of one earthquake might not happen before another earthquake in another place."

He added that it also increased the difficulty of data collection for earthquake forecasting because of the small probability of strong earthquakes repeatedly hitting the same area in a short period of time. So the sampling of similar abnormal phenomenon before earthquakes in one area could take dozens, hundreds or even thousands of years.

"Earthquake forecasting remains a puzzle for the world," said Zhang Xiaodong.

He explained that it is difficult to resolve this problem because it is almost impossible to access the inside of the earth, with still limited drilling capacity. The reason and development of earthquake is a very complicated process, and it varies in different geological structures at different times.

(Xinhua News Agency May 15, 2008)