玛尼地震与玉树地震发震断层的破裂特征与复发模型

发布时间：2018-05-12 08:37

本文选题：地震复发模型 + 高分辨率遥感影像　；参考：《中国地震局地质研究所》2016年博士论文

【摘要】：55~60Ma以来,印度板块与欧亚板块发生碰撞形成了当今世界最年轻也是海拔最高的青藏高原,GPS数据表明现今这两大板块之间的相对汇聚速率依然达到35~42mm/a,受此影响,在高原内部及其周缘地震频发。前人研究表明,青藏高原周缘及其内部自南而北发育了一系列大型的活动断裂带:喜马拉雅断裂带、喀喇昆仑-嘉黎断裂带、甘孜玉树-鲜水河断裂带、东昆仑断裂带以及阿尔金断裂带等,这些断裂带将青藏高原划分为拉萨块体、羌塘块体、巴彦喀拉块体、柴达木块体等,能够产生地表破裂的高震级地震主要沿这些块体边界的断裂带发生,这些地震地表破裂的空间分布特征、破裂样式、位移量分布模式等特征是研究断层的同震活动性、沿断层的力学特征、地震复发模式的直接证据,这些自然形成的真实样本也为验证数值模拟结果的可靠性提供了对比的依据,最近取得长足进步的高分辨率遥感技术也为获得这些数据提供了可能,再结合活动构造定量研究的其他手段,如利用断错地貌获得断层长期滑动速率,利用古地震方法获得古地震复发序列等,根据这些信息就能对发震断层的长期活动性进行综合分析,进一步可以判定青藏高原上地壳变形行为、检验各种青藏高原运动学模型的可靠性。本博士学位论文通过分析地震复发模型和活动断层长期滑动习性定量研究相关的构造地貌、古地震、年代学和区域古气候变化对地貌面年代约束以及遥感技术等方法,系统研究了1997年玛尼地震和2010年玉树地震地表破裂特征、构造含义、长期滑动习性及复发模型,获得了如下主要结论:通过利用震后获取的最新的高分辨率卫星影像(0.5m)对1997年玛尼地震形成的地表破裂带进行详细填图,我们得到了全面精确的地表破裂信息,地表破裂西起(35°3'12.81"N,86°10'52.36"E),东到(35°24'7.62"N,88°0'1.81"E),全长170km,总体走向76°,同时也得到了更为精确的破裂位置和清晰的破裂样式,在此基础上主要根据破裂走向变化的几何特征将破裂分为7段,分别是玛尔盖茶卡湖西段、玛尔盖茶卡湖段、玛尔盖茶卡湖东段、朝阳湖段、朝阳湖东段、双端湖东段、东端点段。沿破裂也发育了丰富的地表破裂样式,指示了不同的构造含义:在玛尔盖茶卡湖段,由于断层走向发生明显偏转,结合断层两盘左旋走滑的运动特征,形成了局部的张性弯曲,玛尔盖茶卡湖即位于张性区域的下降盘,在另一盘则形成了相对上升的绥加山以及一系列的正断层陡坎1973年的mw6.9地震的震中也位于该区域附近,其具有的张性分量与局部构造环境相一致。在震中附近的朝阳湖段,受强地面振动和滑坡共同作用在山麓地带形成了垂直断层走向的逆冲变形,这些变形样式的形成主要受冻土控制。在朝阳湖东段北盘可以见到一系列的次级破裂,这些次级破裂和主破裂的夹角自西向东逐渐增大,这是由于破裂有在张性象限形成张性破裂的趋势造成的。在破裂的东端点段则形成了非常复杂的破裂样式,破裂走向在三联点附近发生近90°的大角度偏转,在沿弧形的先存断裂扩展后在尾端呈马尾状撒开,形成了玛尼地震的尾端构造,而没有沿原走向继续向东扩展,结合nubukik.的数值模拟结果可以发现之所以形成这样的破裂样式,是受先存断裂分布,区域主应力方向和破裂扩展速度等多种因素共同作用的。根据断层两侧地貌标志重建获得沿断层分布的210个位移数据,位移量从2m到249.8m不等,这其中既包含了1997年地震的同震位移,也包含了古地震的累积位移。通过对比根据高分辨率卫星影像进行位移重建获得的沿断层分布的最小位移量与前人利用insar得到的同震位移分布的结果,发现两种方法获得的位移分布具有一致性,以1997年地震的同震位移分布为标准,对比古地震的位移分布,可以发现断层活动存在最大为7米左右的特征位移的现象,根据河流阶地的断错量和气候变化的时间可以估算出玛尔盖茶卡断裂的长期滑动速率大约为8mm/a,这个速率略低于东昆仑断裂的其他部分,可能是由于有一部分形变分配给了其北侧的鲸鱼湖段;结合玛尼地震7米左右的最大位移,推测玛尼地震的复发周期为850~900a。根据高分辨率遥感影像结合实地调查,发现2010年玉树地震产生了总长度约65km的地表破裂,西起自隆宝镇南扎西才仁家附近(96.43863°e,33.22611°n),东至结古镇南巴曲东岸禅古寺附近(97.04354°e,3.94768°n),破裂总体走向约300°,是一个以左旋走滑为主,略有逆冲分量的地震事件,最大左旋位移为2.4米。沿断层形成了剪切破裂、张剪切破裂、挤压剪切破裂、张性破裂、地震鼓包和高原冻土区特有的冰裂缝等破裂样式,玉树地震地表破裂带整体上可划分为长约31km的结古次级地表破裂带和长约15km的结隆次级地表破裂带,两者呈左阶羽列展布,最大左旋走滑位移量分别为2.4m和0.66m,之间无地表破裂段长约17km,对应于Mw6.9和Mw6.4两个次级地震事件,这一同震位移分布样式与利用InSAR和地震破裂过程反演得出的结果相吻合。位于玉树县甘达村和石渠县满真村附近的三处河流阶地断错地貌研究表明:甘孜玉树断裂玉树段的长期滑动速率在9.7mm/a左右,这与川滇块体北边界其他段落的滑动速率协调一致,结合探槽中反应的古地震事件记录:记录到距今9.5~9.1ka、7.5~5.3ka、4.8~3.9ka、2.7ka四次古地震事件,且震级也有变化,推测甘孜-玉树断裂玉树段的复发行为更接近位移可变模型,即沿断层走向的滑动速率保持一致,但每次地震的位移并不一致,这可能是由于区域构造背景复杂,触发因素较多造成的,但鉴于得到的古地震位移分布数据还很有限,目前初步推测复发行为更接近位移可变模型。
[Abstract]:Since 55~60Ma, the collisions between the India and Eurasian plates have formed the youngest and highest Qinghai Tibet Plateau in the world today. The GPS data shows that the relative convergence rate between the two plates is still up to 35~42mm/a. A series of large active fault zones have been developed from south to North: the Himalaya fault zone, the Karakoram Jiali fault zone, the Yushu - fresh water river fault zone in Ganzi, the East Kunlun fault zone and the Altun fault zone, which divide the Qinghai Tibet Plateau into Lhasa block, Qiangtang block, Bayan Kara block and Qaidam block. The high magnitude earthquakes that produce the surface rupture mainly occur along the fracture zones of the boundary of these blocks. The characteristics of the spatial distribution characteristics of the surface rupture, the pattern of rupture and the pattern of displacement distribution are the study of the seismicity of the faults, the mechanical characteristics of the faults, the direct evidence of the mode of earthquake recurrence, and the real samples of these natural forms. It also provides the basis for the verification of the reliability of the numerical simulation results. The high resolution remote sensing technology which has recently made great progress has also provided the possibility for obtaining these data, and then combined with other means of quantitative study of active tectonics, such as using the fault geomorphology to obtain the long-term slip rate of the fault, and using the paleo seismic method to obtain the ancient earthquake complex. According to these information, the long-term activity of the seismogenic faults can be analyzed synthetically, and the deformation behavior of the upper crust in the Qinghai Tibet Plateau can be determined and the reliability of the kinematic models of the Qinghai Tibet Plateau can be tested. The characteristics of the surface rupture of the mani earthquake and the Yushu earthquake of 2010 in 1997, the tectonic implications, the tectonic implications, the long-term sliding habits and the recurrence models are systematically studied, and the following main conclusions are obtained: the latest conclusions obtained by using the earthquake after the earthquake. High resolution satellite image (0.5m) is a detailed mapping of the surface rupture zone formed by the mani earthquake in 1997. We have obtained full and accurate surface rupture information. The surface rupture (35 3'12.81 "N, 86 degree 10'52.36" E), east to (35 24'7.62 "N, 88 degree 0'1.81" E), a full length 170km, and the overall trend of 76 degrees, also got a more accurate rupture position. Based on the geometric features of the rupture trend, the rupture is divided into 7 segments, which are the western section of the Ma's Cha Hu Lake, the Mary cap tea Ka Lake section, the eastern segment of the Ma's tea card lake, the Chaoyang Lake section, the east section of the Chaoyang lake, the east end of the double end lake, and the rich pattern of surface rupture along the rupture. The different tectonic implications are shown: in the mamgea tea Ka Lake section, the local tensionic bending is formed due to the obvious deflection of the fault strike and the movement characteristics of the two disks in the fault, which is the drop plate in the tensionic area, and the relatively rising suijia mountain and a series of positive fault steepness in the other. The epicenter of the mw6.9 earthquake in 1973 is also located near the region, with its tensional component consistent with the local tectonic environment. In the Chaoyang Lake section near the epicenter, the thrust deformation of the vertical fault is formed by the joint action of strong ground vibration and landslides in the Piedmont. The formation of these deformation styles is mainly controlled by frozen soil. A series of secondary breakages can be seen on the North plate of the eastern Lake, which gradually increases from west to East, due to the tendencies of tensile rupture in the tensile quadrant, and a very complex fracture pattern formed at the eastern end of the rupture, which is nearly 90 degrees near the triplet. In the large angle deflection, the tail end of the arc is spread at the end of the arc. The tail end structure of the mani earthquake is formed, but it does not continue to spread eastward along the original direction. Combining with the numerical simulation results of nubukik., it can be found that the fracture pattern is formed by the preexisting fracture distribution, the direction of the regional main stress and the rupture expansion. 210 displacement data distributed along the fault are reconstructed from 2m to 249.8m according to the landmarks on both sides of the fault, which includes the same earthquake displacement of the 1997 earthquake and the cumulative displacement of the ancient earthquake. The minimum displacement along the fault and the result of the same earthquake displacement distribution obtained by InSAR have been found. It is found that the displacement distribution obtained by the two methods is consistent. The distribution of the same earthquake displacement of the earthquake in 1997 is the standard. Compared with the displacement distribution of the ancient earthquake, it can be found that the characteristic displacement of the fault activity is about 7 meters maximum. It can be estimated that the long-term sliding rate of the MalG tea card break is about 8mm/a, which is slightly lower than the other parts of the East Kunlun fault, possibly due to some deformation distribution to the whale Lake section of the north side, and the maximum displacement of about 7 m in combination with the mani earthquake. The recurrence period of the mani earthquake was 850~900a. based on high resolution remote sensing images combined with field investigation. It was found that the Yushu earthquake produced a surface rupture of about 65km in total length in 2010, from the west of Zha Xi Zhan Ren's home (96.43863 e, 33.22611 n) from the west to the East to the eastern basqu East Bank Temple (97.04354 [97.04354], 3.94768 n). The overall strike is about 300 degrees, which is an earthquake event with the main left spin, a slight thrust component, and the maximum left rotation displacement of 2.4 meters. Along the fault, the fracture patterns such as shear rupture, tensile shear rupture, compression shear rupture, tensioning rupture, earthquake drums and plateau permafrost regions are formed, and the surface rupture zone of the Yushu earthquake is on the whole The subsurface rupture zone and the subsurface rupture zone of the long approximately 15km are divided into 31km and about 15km, and the maximum left slip displacement is 2.4m and 0.66M, and the no surface rupture segment is about 17km, which corresponds to the two secondary earthquakes of Mw6.9 and Mw6.4, which together with the pattern of seismic displacement distribution and the use of InSAR. The results of the seismic fracture process are consistent with the results obtained. Three river terrace fault geomorphology studies in Gan Da Village, Yushu county and Shiqu County, full of river terraces show that the long-term sliding rate of the Yushu section of Ganzi Yushu fault is about 9.7mm/a, which is consistent with the sliding rate of the other sections of the north boundary of the Sichuan Yunnan block and the reaction in the slots. The record of the ancient earthquake events: recorded to the four paleo earthquake events of 9.5~9.1ka, 7.5~5.3ka, 4.8~3.9ka and 2.7ka, and the magnitude of the earthquake changed. The recurrence behavior of the Yushu section of the Ganzi Yushu fault is conjectured to be closer to the displacement variable model, that is, the slip rate along the fault direction is consistent, but the displacement of each earthquake is not consistent, which may be due to the fact that the displacement of each earthquake is not consistent. This may be due to the fact that the displacement of the earthquake is inconsistent. The regional tectonic background is complicated and the trigger factors are caused by many factors. However, in view of the limited data on the distribution of ancient seismic displacement, it is preliminarily estimated that the recurrence behavior is more close to the variable displacement model.

【学位授予单位】：中国地震局地质研究所
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P315.2

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