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Abstract The North China area is divided into 11 sub-districts. Based on the recent 1 111 focal mechanism solutions of moderate and small earthquakes in North China，distribution features of the principal stress direction are analyzed employing grid test method. The result shows that the horizontal action plays a main role in the present tectonic stress filed in North China and the predominant directions of the maximam principlal compressive stress are NEE and EW. The directions of the maximam principlal compressive stress are EW in Tangshan sub-district and Southern Shanxi sub-district. The directions of the maximam principal compressive stress in other sub-districts of North China are NEE with values between 60° and 80°. The in-situ stress measurement by hydraulic fracturing in deep rock in Wanfu coal mine shows that the direction of the maximum horizontal compression stress is between 40° and 80°，which is well consistent with the analysis result of focal mechanism solutions of moderate and small earthquakes in the southwest of Shandong Province. Based on a tectonic comparison，the deep stress state in Wanfu coal mine is closely related to the tectonic stress filed in the southwest of Shandong Province.
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Received: 14 January 2009
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