【作者】 李文军；

【导师】 王培德；

【作者基本信息】 中国地震局地球物理研究所 ， 固体地球物理， 2005， 博士

【摘要】 本篇博士学位论文通过对河北卢龙1982年10月19日M_L6.2级地震的余震序列的重新定位和求解震源机制,解释了华北地区活动地块的边界卢龙盆地的活动构造的形态、运动特征和动力学特征。 第一章通过对卢龙1982年10月19日6.2级地震余震近场数字地震资料的再处理,从391条记录中挑选出可用于精确定位的一共171条地震事件记录,采用Hypoinverse定位方法对45个事件进行了重新定位。 定位结果显示出由5条断层组成的一卧倒的反“F”形地震构造的形态。具体分析为两条NNE向断裂被一条NWW向断裂所截断,两组断裂呈脆性断裂常见的共轭状态产出,NNE向的地震断层与南北的已知断层似要相互连接,另两条断裂显示—左旋错动1km作用的地震断层组合,卢龙附近的滦河河谷是一个四面断裂包围的断陷盆地,卢龙地震的发震构造是一个走滑兼张性的断裂组合。 第二章通过矩张量反演的方法求解事件的震源机制,我们发现处于卢龙盆地不同部位的震源机制是各不相同的,盆地中和盆地边界的主压应力轴有时相差近90°,说明不同的构造部位应力状况是不一致的。 T轴和P轴的倾角统计的平均值为20°左右,最大和最小应力主轴产状较缓,中间应力轴产状较陡,区域的构造活动的驱动力来自水平方向。 区域应力场的主压应力轴为74°NE,而盆地的北边转为43°NE,可能是由于区域小块体的存在使这里的应力场发生了旋转,卢龙块体受到了来自其北部的燕山块体的推挤和限制作用。 计算的所有余震的双力偶节面的平均滑动角为-12°非常缓,说明这些余震从总体上说是以走滑为主的断裂活动造成的,但是兼有少量的张性成分。余震的节面倾角一般很陡达到60°以上,因此同样可以推断主压应力应该大致为水平方向。 第三章阐述了对卢龙地区的区域地质的研究和地表断层的考察,地表考察结果与精确定位和机制解所确定的断裂一致。我们认识到卢龙断裂是唐山断裂往北延伸的一支,它同时又处于张家口——渤海断裂带的东北角,是一个两组断裂构造的交汇处,在交汇的部位往往能孕育强烈地震。唐山断裂又是一强烈地震多发的活动构造,1976年这里曾经发生了M_L7.8级强烈地震,因此唐山断裂的活动一定会对邻近的卢龙地区产生重要影响。 通过地质调查,在可见的两条断层中,F4主要表现为张性断层的特征,在地表呈“Z”字型,而F5在地表表现为走滑或者有逆断层的性质。这似乎说明北东向的构造活动剧烈,但是在北西向断裂的阻挡作用下不能完全施展。 在卢龙盆地的不同部位,变形也不尽相同,盆地北部表现为褶皱和地层倾斜,在盆地的东部和南部断裂构造发育,整个断裂系统为一个盆地南错的走滑兼有张性性质的断裂系。 而盆地的基底与北部燕山块体的基底一致同为太古界中深变质岩系说明了卢龙盆地可能由燕山地块脱离的一块演变而来。 侏罗系的火山岩说明在中生代这个地区发生了强烈的裂谷作用,在凝灰岩的形成过程中同样有构造应力的影响。 第四章综合分析我们定位和震源机制求解的结果、地表的观测以及前人的研究,进一步阐述卢龙盆地的起源和演化。 与第二章中的卢龙盆地外围的情况相似,可以说明卢龙活动块体似乎受到了来自北东方向的推挤,这可以归结为燕山地块对活动构造发育的影响。更多还原

【Abstract】 In this paper, we relocated the aftershocks of October ,1982, M_L6.2 , Lulong earthquake and computed the focal mechanism. By this way we reveal the active tectonics feature of morphologic, kinematics and dynamics of Lulong Basin which locates on the blocks border in North China.In chapter 1, we re-processed the digital seismic data of the October 1982, M_L6.2 , Lulong earthquake. In total 391 records, we select 171 event records which can be precisely located, and 45 events were relocated by Hypoinverse program.The result of the relocation shows 5 seismic active faults which consists a reversal "F"-shaped seismic tectonics.Two NNE striking faults are truncated by a NWW striking fault. Two sets of the faults shows the conjugating state where are common in fragility faults. The NNE striking faults are feedthrough. The other two faults show a counterclockwise rotation fault set and they depart each other by 1km. Luanhe valley is a downfaulted basin surrounded by a series of faults. The seismic tectonics of Lulong earthquake is a strike tending fault assemblage with tensional fracture feature.In chapter 2, we computed the focal mechanism of each event by moment tensor inverse method and found that the focal mechanisms in different part of the Basin are different. The pressure axis inside the basin and which around the basin sometimes have an angle about 90 degrees. This illustrates the stress condition is not the same in different tectonic position.The statistics average value of dipping angel of T-axis and P-axis are both at about 20° . The dip angle of the maximum and the minimum press axis are low, intermediate axis is steep, that shows the actuating force is from horizontal direction.The region pressure axis is 74° NE, about in E-W direction, but it changes to 43° in the north of the basin. It is obvious that the stress field has rotated somewhere, it was caused by the movement of the small blocks. Lulong block is pushed and restricted by the Yanshan active block from north.The computed slip angel of double couple nodal planes is very small,-12.1° in average, it shows the aftershocks is mainly caused by striking fault but with a little tensor component. The dipping angel near the value of 60° or even higher. So we can also surpose the pressure axis is near horizontal.In chapter 3, we show the result of field investigates to the region geology and surface faults trace. We found that the fault determined by location is consisted with that by field investigated. Lulong fault is a branch stretch from Tangshan fault and also located in the northeast corner of Zhangjiakou-Bohai fault belt. It is an interjection part of two faults where strong earthquakes could breed. Tangshan fault is a strong seismic active tectonics. We know that an earthquake with M_L 7.8 occurred at Tangshan in 1976. So the activity of Tangshan fault must have important effect on Lulong region.We notice that two faults could be found on the surface and the other three are buried active tectonics. The five faults compose the seismic tectonics of Lulong earthquake.According to the geological investigation, F4 behave mostly as tensor fault like a "Z" sharp on the surface but F5 behave as a striking fault or have thrust feature ef. The hint the movement of northeast tectonics could not stretch completely because of the interdiction of northwest striking更多还原