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中国地震局地球物理勘探中心芦山MS7.0地震现场工作队在地震应急考察期间发现了WNW向的箭杆林地表破裂带,并详细考察了该地表破裂带的产状、破裂面上的擦痕及断错特征,讨论了对该地表破裂带的不同认识以及对发震构造研究的意义.箭杆林地表破裂带位于雅安市上里镇箭杆林村二组西侧海拔1 529—1 578m、坡度30°—40°的山坡上.在长约80m的范围内,该地表破裂带分3段近直线展布,每段长6—10m,最宽约40cm.破裂带总体走向120°,破裂面平整,倾向SW,倾角62°—85°.破裂通过的岩性多为黏土,破裂面上有两组明显的新鲜擦痕,倾伏角较大的一组擦痕一般仅保留在距地面10—20cm以上的范围内,其下倾伏角较小的一组擦痕则覆盖倾伏角较大的一组擦痕.破裂经过处见一直径约4cm的树根被明显错断,上盘上升15cm,并向SE方向平移10cm;另见上盘地层发生翻转现象.经探槽揭示,破裂带上盘黑色腐植土层相对下盘上升约15cm.综合分析表明,箭杆林地表破裂带在芦山MS7.0地震期间经历了先逆冲、后左旋平移的运动过程.震源机制解表明,芦山MS7.0地震是错断面为NE走向的逆冲型地震.WNW向箭杆林地表破裂带可能是芦山地震产生的次级破裂带,是否存在NW--WNW向的发震构造值得研究.芦山MS7.0地震箭杆林地表破裂带的发现为发震构造和震害研究提供了重要的基础资料.
China Earthquake Administration of Geophysical Survey Center Lushan MS7.0 earthquake field team during the emergency investigation found WNW to the shaft forest surface rupture zone and a detailed examination of the surface rupture zone of the occurrence of scratches on the rupture surface And fault characteristics of the surface rupture zone, discussed the different understanding of the surface rupture zone and the significance of research on the seismogenic structure.The surface rupture zone of the shaft forest was located at the elevation of 1 529-1 578m on the west side of the second group of Xinglin Lincun in Shangli Town, Ya’an City, Slope of 30 ° -40 ° in the range of about 80m, the surface rupture zone is divided into three sections near the straight line, each section length 6-10m, the maximum width of 40cm. The rupture zone to the overall direction of 120 °, rupture Surface smooth, inclined to SW, dip angle 62 ° -85 °. Most of the lithology through the rupture of the clay, the rupture surface has two distinct groups of fresh scratches, a larger pitch of a set of scratches generally only remain in the ground 10 -20cm above the range, the lower the pessimistic angle of a set of scratches covered a larger pitch group of scratches .Breaking through the Department to see a diameter of about 4cm of the root is obviously wrong, the plate up 15cm , And to the SE direction of translation 10cm; see also found on the floor turn over phenomenon revealed by the trenches, rupture zone The black humus soil of the upper plate rose about 15cm relative to the lower plate, and the comprehensive analysis showed that the surface rupture zone of the arrowhead forest underwent the first thrusting and left-lateral translation during MS7.0 Lushan earthquake.The focal mechanism solutions suggested that the Lushan MS7 .0 earthquakes are thrust earthquakes whose fault surface is NE trending. The surface rupture zone of the NWW forest may be a secondary rupture zone produced by the Lushan earthquake and whether the NW-WNW seismogenic structure is worth studying. .0 The discovery of the rupture zone of the arrow shaft forest in earthquake has provided important basic data for the study of seismogenic structures and earthquake damage.