东昆仑山断裂带及昆仑山口西8.1级地震垂直形变研究

VERTICAL DEFORMATIONS OF THE EASTERN KUNLUN FAULT ZONE AND WEST OF KUNLUN MOUNTAIN PASS M_S 8.1 EARTHQUAKE

沿格尔木—五道梁公路测线 1979,2 0 0 1年的 2期水准观测资料表明 :1)东昆仑山及可可西里地区现今相对于柴达木盆地仍在发生继承性的隆升运动。 1979— 2 0 0 1年期间 ,昆仑山口主峰一带相对于格尔木约上升了 2 80mm ,上升速率高达 15mm/a ;五道梁相对于格尔木上升了约 2 10mm ,上升速率约 10mm/a。 2 )昆仑山口至五道梁之间的可可西里地区 ,在相对于柴达木盆地以 7mm/a的速度整体抬升的同时 ,还相对于南、北两侧的五道梁和昆仑山隆起区以 3～ 7mm/a的速度下沉。 3)格尔木—五道梁剖面垂直形变整体符合俯冲 -逆掩地壳增厚模式 ,其中 ,沿西大滩断裂、中昆仑山断裂和昆仑山北缘断裂带的逆冲推覆运动 ,占了整个东昆仑山现今构造隆起的大部分 ,其逆冲推覆运动有自南向北衰减的特点。 4 )地质调查结果表明 ,沿 2 0 0 1年 11月 14日昆仑山口西MS8.1地震 35 0km的左旋破裂带 ,可以划分出若干个不均匀错动段 ,错动量最大可达 6m ,最小只有 2m。基于Okada (1985 )位错模型的理论计算结果表明 ,地震断层不均匀左旋错动可以在昆仑山口破裂带南北两侧产生 10 0多毫米的差异性垂直位移。 1979— 2 0 0 2年实测垂直位移中 ,西大滩断裂谷地水准点的异常上升、昆仑山口测点的异常下降等都与发震断层的不均匀错动密切相?

Leveling measurements in1979and2002along Golmud-Wudaoliang level line reveal that:(1)The Eastern Kunlun Fault zone and Hoh Xil block are continuing their inherited upwarping process relative to Qaidam basin.During the period of1979to2001,the peak of Eastern Kunlun Mountains at the Kunlun Mountains Pass was uplifted about280mm in maximum at a rate of15mm/yr with respect to Golmud,and Wudaoliang was uplifted about210mm at a rate of10mm/yr with respect to Golmud during the same peri-od.(2)The Hoh Xil block between the Kunlun Mountains and Wudaoliang upwarped zone,was uplifted at a rate of7mm/yr relative to Golmud,and subsided at a rate of3～7mm/yr relative to the Kunlun Moun-tains and Wudaoliang upwarped zone.(3)The vertical deformation of Golmud-Wudaoliang profile conforms on the whole to the subduction-overthrust crustal thickening model for the Tibetan Plateau,while the over-thrust movements along Xidatan-dongdatan,mid-Kunlun and north-Kunlun Faults constitute the most part of the recent uplift of the Eastern Kunlun Fault zone.The weakening of overthrust movement from southern Kunlun region to northern Kunlun margin can also be clearly recognized.(4)Geological investigations show that along the350km-long left-lateral rupture zone of the Kunlun M S 8.1earthquake of November14,2001,there exist several slip segments with different left-lateral displacements,among which the max-imum may reach6m,and the minimum is only2m.Theoretical calculation based on Okada(1985)dislo-cation model demonstrates that uneven left-lateral displacements of the Kunlun earthquake fault might cause differential vertical deformation up to100mm or more across the rupture zone near the Kunlun Mountain Pass.Abnormal uplift of the Xidatan fault valley and abnormal subsidence of the Kunlun summit near the Kunlun Mountain Pass are both closely related to the uneven left-lateral slip of the Kunlun seismic fault zone.