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[BEIJING] China will start building a test satellite later this month (April) to detect electromagnetic anomalies in the atmosphere, as part of the country's proposed earthquake monitoring network, and hopes to launch it in 2014.

The China Seismo-Electromagnetic Satellite (CSES) has been in development since 2003 and is the first spaced-based component of the network. Its data will be correlated with data from ground-based monitoring systems.

The network is eventually intended to provide advance warning of earthquakes, such as the one off the coast of Japan last month (11 March).

Strong seismic activity often causes electromagnetic anomalies in the Earth's atmosphere and magnetic field, aiding the monitoring and prediction of earthquakes, studies suggest.

Shen Xuhui, a senior researcher at the Institute of Earthquake Science, China Earthquake Administration (CEA), and leader of the CSES working group, said the satellite will eventually be connected to a larger observation system. China hopes to launch another two satellites by 2017 and begin predicting earthquakes from 2020.

Michel Parrot, principal investigator of the French DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) microsatellite that studies similar anomalies, told SciDev.Net: "The CSES will study [electromagnetic] disturbances during seismic events. DEMETER has very often observed similar disturbances."

Simple data are not enough, however. "When you record a disturbance, you need to ensure that it is not caused by another factor, by comparing it with data at other locations," he said.

China's network is more ambitious than existing systems because it will use several satellites. "With a single satellite you can survey a given area for only a few minutes a day. With several satellites you can monitor a given location more often — if a disturbance is continuously observed at the same place, it is more reliable," added Parrot.

Since the DEMETER mission began six years ago, CEA researchers have been helping to analyse the data. China has also been working with other countries, including Italy, Russia and the Ukraine, that have their own seismo-electromagnetic systems.

Sergey Pulinets of the Fiodorov Institute of Applied Geophysics in Russia said that China has a more complicated task because, whereas DEMETER shows that earthquake precursors can be monitored from space, CSES will attempt to predict earthquakes. He said it could "make an important contribution to mankind's safety and prosperity".

Two days before Japan's earthquake last month, Chinese researchers detected abnormal electromagnetic signals in the area using ground-based systems, Shen told SciDev.Net. Following the earthquake, they analysed the signals and are sure these "have a close relationship" with the earthquake.

But the technique is still experimental and poses a risk of false alarms. "We therefore didn't do prediction or make any announcements," Shen said.