【摘要】 1668年郯城8 1/2级地震,发震断层南起郯城窑上北到莒县土岭,全长为130 km,由5条北北东走向的活断层段组成。郯城地震断层南段沿沂沭断裂带内的F₂断裂分布,倾向南东东,倾角为30°～60°。北段紧邻F₁断裂分布,倾向不稳定,倾角较陡（多为70°以上）。南段表现为右行逆冲或逆右行的运动性质,北段则以右行走滑为主。郯城地震断层南、北两段均发育断层泥带、断层角砾带和碎裂带,南段总宽度为几米到十几米,北段总宽度为几十米到近百米,局部发育多条断层泥带。郯城地震断层的排列方式及其几何学特征表明:为老断层复活,而非新生断层。通过断层擦痕的反演同震应力场显示:北段为北东东—南西西向挤压应力场,南段为北东—南西向的挤压应力场,该地震是发生在区域性挤压应力场状态下。这种应力场空间变化可能是地震断层几何学空间变化导致的。其同震应力场与该地区现代区域应力场是一致的,这说明郯城地震并未造成震后应力场调整或震后应力场调整时间较短,未影响到现今应力场。更多还原

【Abstract】 The faults causing 1668 M 8 1/2 Tancheng earthquake extends from Yaoshang,Tancheng in the south to Tuling,Juxian in the north,and is as long as 130 km.The earthquake faults consist of 5 NNE-striking active faults.The southern segment of the Tancheng earthquake faults goes along the F₂ fault and dips SEE with dip angles of 30°～60°.The northern segment of the faults is close to the F,fault,and shows varied dips steeply with dip angles mostly higher than 70°. The southern segment is dextral thrusting or dextral with thrusting components whereas the northern segment is dextral mostly.The both southern and northern segments are made up of gouge belt,breccia belt and cataclastic belt.Widths of the southern segment range from several meters to more than ten meters while those of the northern segment are from tens of meters to nearly one hundred meters.Arrangement and geometry of the Tancheng earthquake faults suggest that it originated from reactivity of pre-existing faults rather than newly formed faults. Stress inversion from measured fault-slip data shows co-seismic ENE-WSW compression for the northern segment and NE-SW compression for the southern segment,and regional compression stress field for the earthquake occurrence.The stress orientation variation may result from a geometry change of the earthquake faults.The co-seismic stress field is consistent with present regional stress field,indicating that there was no post-seismic stress adjustment after the Tancheng earthquake or post-seismic stress adjustment after the Tancheng earthquake did not affect the present stress field.更多还原