We describe the setup of testing regions for the China Earthquake Forecast Testing Center and provide preliminary forecast results in the scope of the Collaboratory for the Study of Earthquake Predictability (CSEP) project.We investigate the spatiotemporal variations of the completeness magnitude Mc by using the frequency-magnitude distribution of the China Earthquake Networks Center (CENC) catalog. We find three periods of significantly different Mc histories: (I) 1 January 1970-30 September 2001, (II) 1 October 2001-30 September 2008, and (III) 1 October 2008-31 August 2011. Mc mapping provides median values M c = 2:6, 2.2, and 1.6 for the three periods of time, respectively, showing the improvement in catalog completeness over time. We recommend using data from periods II and III to define a baseline long enough for retrospective forecast testing. Small magnitude events from period I should be used with caution due to important fluctuations in completeness. For period III, coordinates of all national and regional seismic stations are available, and we therefore apply the Bayesian magnitude of completeness (BMC) technique, mapping Mc continuously by using prior information on the relationship between Mc and the density of seismic stations. We define four potential testing/collection areas for CSEP-China: (A) All China, (B) North-South Seismic Belt (NSSB), (C) North and West Xinjiang Seismic Region, and (D) North China Seismic Region. In the current phase of CSEP-China, only the NSSB (region B) is considered. To demonstrate the type of earthquake predictability experiment that will be performed in the Chinese Testing Center, we present a series of retrospective forecast experiments with TripleS, a smoothed seismicity model.
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