中文摘要：

地表调查结果表明，发生在西藏中部的2004年懂错Ns5．6地震的极震区位于懂错东侧的贡巴淌一怕尔淌之间，最大烈度为Ⅶ度，宏观震中的地理坐标：31．70°N，91．26°E。此次地震是懂错盆地东缘边界断裂活动的结果。该断裂带是一条长40km左右、NNE走向的全新世活动正断层，在断裂带的北段发育可能形成于全新世晚期的古地震地表破裂带。地表的晚第四纪断裂活动和近期的地震活动特征显示，蓬错-懂错-错那-安多地堑系构成了西藏中部一个重要的长约120km的NE向地震活动带，其北段和中南段是其中应变积累时间更长的地段。

英文摘要：

The Ms 5.6 earthquake occurred in Amdo county of central Tibet on March 7, 2004. The epicenter is 31.68°N,91.31°E and 31.64°N,91.24°E from CENC （China Earthquake Networks Center） and NEIC （National Earthquake Information Center of America） respectively （Fig. 1 ）. It is the maximum magnitude earthquake near Golmud-Lhasa railway after the 2001 Ms 8.1 Kunlun earthlies between Gongbatang and Jianong at the east of Dung Co Lake （Photo 1,2）, so this earthquake is called the 2004 Ms 5.6 Dung Co earthquake. The intensity survey results suggest that the macroscopic epicenter is 31.70°N,91.26°E, which approximately coincides with the epicenter located based on instrument monitoring. The distribution of intensity indicates the earthquake probably results from faulting of NNE-trending fault zone along the eastern margin of the Dung Co basin. The results of active faults survey confirm that the fault zone controlling the earthquake is a main boundary normal fault zone of the Dung Co basin and called the eastern boundary fault zone of the NNE-trending Dung Co basin, which is a half graben about 10 ～ 15kin wide and 40kin long, connecting with the NNE-trending Peng Co basin to the south and adjacent to the NE-trending Tsona-Amdo graben to the north. The boundary fault zone of Dung Co graben is NNE-trending, about 40kin long and composed of three minor normal faults, all dipping to west and forming a right-stepped en echelon array indicating the left lateral strike-slip component of the fault zone （ Fig. 3 ）. Surface observation along the faults shows that the fault underwent prominent normal faulting during late Quaternary. The severe faulting is expressed by the prominent northwest facing triangular facets along mountain front and multiple generations of fault scarps in late Quaternary sediments （Photo 5 ～ 7）. The results of in-suit measurement with level instrument and tape show that there are three sets of fluvial terrace surfaces and a piedmont slope that were vertically offset by 1 - 1.2m