Abstract: For regional seismicity the phenomenon of accelerating moment release (AMR) usually appears preceding strong earthquakes. In this paper, taking the 1976 M_S7. 8 Tangshan earthquake, the 1998 M_S6. 2 Zhangbei earthquake and the 2006 M_S5. 1 Wen' an earthquake in the northern North China as the target events, we study the AMR phenomena and their characteristics that appeared in circular areas with radii 40 to 120 km centered at the epicenters and within the periods of 4 to 8 years before the three mainshocks. Our result shows that AMR acceleration anormalies appeared in different degrees before both the M_S7. 8 Tangshan earthquake and the M_S6. 2 Zhangbei earthquake, but did not appear before the M_S5. 1 Wen' an earthquake. Moreover, we find that the radius of 80 km would be an efficient and reasonable spatial scale for scanning and searching AMR acceleration anomalies in the study region. Based on the understanding from the three case studies, we further calculate and analyze two regions, the border region among Shanxi, Hebei and Inner Mongolia, as well as the region of the Capital circle. As a result, areas with AMR acceleration anomalies have been identified, and the result may be as a reference in analyzing and determining the future seismic risk in the northern North China.

Key words: ccelerating moment release, Time-to-failure method, Seismicity of North China