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基于活动块体的基本概念,综合对研究区内活动断裂带空间展布、地震活动性等资料的分析将巴颜喀拉块体东部及邻区划分为巴颜喀拉块体（I）、华南块体（Ⅱ）、川滇块体（Ⅲ）和西秦岭块体（IV）等4个一级块体.利用GPS形变场、地球物理场等资料结合F检验法,将巴颜喀拉块体划分为阿坝（I1）、马尔康（I2）和龙门山（I3）3个次级块体,将西秦岭块体划分为岷县（IV1）和礼县（IV2） 2个次级块体.利用分布在各个块体内部的GPS测站,计算各活动块体及块体边界断裂带的运动变形特征.结果表明：各活动块体的整体运动包括平移和旋转运动;东昆仑断裂带、甘孜—玉树断裂带和鲜水河断裂带的滑动速率明显高于龙门山断裂带的滑动速率;巴颜喀拉块体东部走向北西或北西西的边界断裂表现出左旋拉张的特性;走向北东的边界断裂带,除成县—太白断裂带外,均表现出右旋走滑兼挤压的活动特征.巴颜喀拉块体的东向运动存在自西向东的速度衰减,衰减主要被龙日坝断裂带和岷江断裂带分解吸收,其中龙日坝断裂带的水平右旋分解非常明显,约为~4.8±1.6 mm/a,岷江断裂带的水平分解较弱.龙门山断裂带被马尔康、龙门山和岷县等次级块体分成南、中、北三段,龙门山断裂带中段上的主压应变率要明显小于龙门山断裂带南段上的应变率,其北西侧变形幅度从远离断裂带较大到靠近断裂带逐渐减小,表明其在震前已经积累了较高的应变能,有利于发生破裂滑动.汶川地震后,地表破裂带和余震分布揭示的断裂带运动性质自南西向北东由以逆冲运动为主,逐渐转为逆冲兼走滑的特征可能与龙门山断裂带中段所受主压应力方向自南西向北东的变化有关.马尔康、龙门山和岷县3个次级块体与华南块体之间较低的相对运动速度以及龙门山断裂带低应变率、强闭锁的特征都决定了汶川地震前龙门山断裂带低滑动速率的运动特征. 相似文献
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利用1999-2007和2009-2011年中国大陆GPS水平速度场数据, 采用DEFNODE(反演计算弹性岩石圈块体旋转、 应变和块体边界断层闭锁或同震滑动的Fortran程序)负位错反演程序估算了芦山地震前龙门山断裂带的三维闭锁程度, 并结合剖面结果分析了断层深浅部变形特征. GPS反演结果表明, 1999-2007年, 龙门山断裂中北段(闭锁比例为0.99)处于强闭锁(本文将闭锁比例大于0.97的称为强闭锁)状态; 龙门山断裂南段地表以下深度16 km内为强闭锁, 深度16-21 km处闭锁比例降低为0.62, 深度21-24 km处整条断裂逐渐转变为蠕滑状态. 2009-2011年, 即汶川地震后, 龙门山断裂中北段处于震后蠕滑状态; 龙门山断裂南段深度16-21 km处闭锁比例降低为0.45, 其它位置闭锁程度保持不变. GPS剖面结果显示, 2009-2011年, 即汶川地震后, 龙门山断裂中北段为逆冲兼右旋走滑运动; 而南段断层不能自由滑动、 变形宽度较大. 综合分析认为, 汶川地震时, 龙门山断裂南段并没有发生破裂, 一直处于较强的闭锁状态, 汶川地震的发生又加速了芦山地震的孕育进程; 由于龙门山断裂带南段的闭锁深度较中北段浅, 因此芦山地震较汶川地震强度低、 震级小、 破裂范围窄. 相似文献
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芦山—康定地区是川滇块体、松潘—甘孜块体和华南块体三个块体过渡的"Y"型交汇区,构造变形十分强烈.本文对EGM2008计算的布格重力异常进行1~5阶离散小波变换,得到三方向分量平方和的平方根(HVDM)图像;利用实测剖面布格重力异常数据,得到剖面的布格重力异常归一化总梯度(NFG)图像.结果分析表明:(1)垂直于龙门山断裂带南段剖面的NFG图像显示推覆构造体前端切割较浅、后端逐步变深至中地壳,说明松潘—甘孜块体在深约10~30km之间存在滑脱构造,在青藏高原东向挤出和四川盆地的阻挡作用下,造成深、浅部构造差异性运动,形成逆冲推覆的龙门山构造带;(2)HVDM图像和剖面的NFG图像均显示龙门山断裂带西南段与中段和东北段不同,松潘—甘孜块体对四川盆地的逆冲推覆作用沿北东方向具有分段性;(3)雅江—洪雅剖面NFG图像显示鲜水河断裂带和龙门山断裂之间存在高梯度变化带,在鲜水河断裂带下方强变形带不仅在20km左右东倾至龙门山断裂带前缘,且逐渐近垂直向下伸入至少到下地壳,反映了两大断裂带交汇区域变形作用较强.川滇块体内部和四川盆地内部则显示低值,说明其变形作用较弱.强烈左旋剪切的鲜水河断裂带对芦山—康定地区构造活动具有主要的控制作用. 相似文献
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利用1999—2007期GPS水平速度场数据,采用Defnode负位错反演程序估算了龙门山断裂在汶川地震前的闭锁程度和滑动亏损分布,结合龙门山断裂带附近地表水平应变率场结果,综合分析了震前地壳变形特征.反演结果表明,震前龙门山断裂中北段处于完全闭锁状态,闭锁深度达到21 km(闭锁比例0.99)左右,垂直断层方向的挤压滑动亏损速率约为2.2 mm/a,平行断层方向的右旋滑动亏损速率约为4.6 mm/a.龙门山断裂南段只有地表以下12 km闭锁程度较高(闭锁比例0.99),垂直断层方向滑动亏损速率约为1.4 mm/a,平行断层方向滑动亏损速率约为4.6 mm/a;在12~16 km处闭锁比例约为0.83,垂直断层方向滑动亏损速率约为1.2 mm/a,平行断层方向滑动亏损速率约为3.8 mm/a;在16~21 km处闭锁比例约为0.75,垂直断层方向滑动亏损速率约为1.1 mm/a,平行断层方向滑动亏损速率约为3.5 mm/a.在21~24 km处整条断裂均逐步转变为蠕滑.上述反演结果与区域应变计算获得的龙门山断裂带中北段整体应变积累速率较低、南段应变积累速率较高相一致,均表明中北段闭锁程度高、南段闭锁程度稍低,该特征可以较好地解释汶川地震时从震中向北东向单向破裂现象. 相似文献
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基于1999—2016年GPS数据和1980—2010年区域精密水准数据,获取了东昆仑断裂带东部及其邻区主要断裂的滑动速率和区域构造变形特征。结果表示:东昆仑断裂带自西向东的走滑速率衰减非常明显,走滑速率从西大滩—东大滩和阿拉克湖段的约10 mm/a向东到塔藏段衰减至约2 mm/a,速率自西向东每100 km下降梯度约1 mm/a;东昆仑断裂带阿拉克湖段、托索湖段、下大武段和塔藏段均表现出一定的弱挤压特征。跨岷江断裂剖面显示区域挤压变形自西向东由龙日坝断裂至龙门山断裂带有逐渐减弱的特征。区域最大主应变方向为E-NEE向,最大剪切应变高值区位于阿拉克湖段和托索湖段交汇区域以及巴颜喀拉块体的龙日坝断裂中段区域。分析东昆仑断裂带东部及其邻区主要断裂间的构造转换关系认为,岷山地区的隆起变形主要是因为巴颜喀拉块体自西向东的运动受到了华南块体的阻挡,而非东昆仑断裂带向东延展引起的构造转换。 相似文献
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巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义 总被引：27，自引：0，他引：27
在青藏高原东缘NE向龙门山断裂带西北侧约200km的巴颜喀拉地块东部,由GPS复测发现存在一条宽阔的NE向右旋剪变带,变形速率达4-6mm／a．卫星影像解译和野外考察表明：这一右旋剪切带对应了以往被忽略的、新生的NE向龙日坝断裂带．龙日坝断裂带北东段由走向N54°±5°E、相距约30km的两条平行分支断层组成．这两条分支断层沿线晚第四纪断错地貌发育,北支龙日曲断层具有较大的逆冲分量,南支毛尔盖断层为纯右旋走滑断层．依据矢量合成原理可知,龙日坝断裂带北东段晚更新世以来平均右旋滑动速率为（5．4±2．0）mm／a,垂直滑动速率约0．7mm／a,地壳缩短率约0．55mm／a．龙日坝断裂带的存在和发现可以很好地解释青藏高原东缘的大地构造与动力学特征：以龙日坝断裂带为界,巴颜喀拉地块分为西部阿坝和东部龙门山两个次级块体;龙门山次级块体的整体缩短和隆升反映出从龙门山断裂带到龙日坝断裂带是巴颜喀拉地块南东向运移过程中由于受到华南地块的强烈阻挡而形成的后展式推覆构造系统,并成为青藏高原东缘承载新生代晚期至今地壳变形的一种活动地块边界构造类型．龙日坝断裂带正是这一系统中晚第四纪新生的活动断裂带． 相似文献
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本文简要分析了2008年5月12日汶川8．0级地震前川青块体及邻区的地震活动性特征。结果表明,汶川地震发生的龙门山断裂本身历史地震活动水平不高,其周边的鲜水河断裂、岷江断裂、虎牙断裂等历史上强震多发;汶川8．0级地震前龙门山断裂带3级以上中小地震活动增强或平静异常现象不明显,地震活动参数值均在正常变化区间内;4级以上地震异常平静,形成了地震空区;2007年底到2008年初位于龙门山断裂带及其附近台站的0．1级以上小震月频度增强明显。 相似文献
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2008年5月12日四川龙门山断裂带发生了汶川8.0级地震,之后四川境内发生了两次7.0级地震(其中一个是芦山地震),为了研究汶川地震之后龙门山断裂带及周边区域的地震活动性,本研究收集了国家地震台网和四川区域地震台网2010年1月1日—2017年12月31日四川地区发生的17次M≥5.0地震以及120多次5.0>M≥4.0地震的波形资料,利用波形拟合法反演了震源机制解及区域应力场.反演结果显示,位于龙门山断裂带上的地震,震源机制以逆冲型为主,鲜水河断裂带地震震源机制以走滑型为主,而川滇块体西南部的理塘断裂、金沙江断裂附近,震源机制解以正断层为主.根据震源机制解反演得到的龙门山地区、鲜水河地区的主压应力场方向为WNW、近EW向.川滇块体的巴塘、理塘等地区,其主压应力轴方向为12°左右,接近SN向,且仰角接近40°左右.本研究利用面波振幅谱特征对震源深度进行了精确定位,定位结果与中国地震台网中心(CENC),美国地震调查局(USGS),国际地震中心(ISC)等机构地震目录进行了对比.结果显示,四川地区强震震源深度主要分布在20km以上的中上地壳.龙门山地区震源优势分布在10～20km,鲜水河断裂地震震源深度在10km左右,川滇块体西南部的理塘断裂,巴塘断裂,金沙江断裂等地区,震源深度一般在5～10km范围. 相似文献
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在野外考察的基础上 ,结合所采集的各条断裂之上的覆盖物或断层带物质的热释光 (TL)或电子自旋共振 (ESR)样品年龄 ,对龙门山断裂带北段的晚第四纪活动性进行了分析 ,认为 :后山断裂在第四纪早 -中期曾有过活动 ,晚更新世以来已不再活动 ;中央断裂早更新世或前第四纪是活动的 ;前山断裂在白龙江以北变成一些小的、零星分布的断裂 ,它们在第四纪早期以前有过活动。而已有研究表明龙门山断裂带中段和西南段晚第四纪以来仍在活动。造成龙门山断裂带不同段落新活动时代不同的主要原因 ,可能是区域应力场的变化所导致的活动地块边界的变化。龙门山断裂带的北段现在已不构成活动块体的边界 ,加之岷山隆起对龙门山断裂带东北段的屏障作用 ,使得龙门山断裂带北段活动减弱。而龙门山推覆构造带中南段和岷山隆起构造带共同成为块体持续挤压作用的东界。这为研究青藏高原的运动学及动力学等问题提供了重要信息 相似文献
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通过对汶川地震前观测的碌曲—若尔盖—北川—中江大地电磁剖面的数据处理和反演解释,揭示了沿剖面的松潘—甘孜地块、川西前陆盆地、龙门山构造带及秦岭构造带50 km深度的电性结构特征及相互关系,表明青藏高原东缘向东挤压,迫使向东流动的地壳物质沿高原东缘堆积,并向扬子陆块逆冲推覆.龙门山恰好位于松潘—甘孜地块与扬子陆块对挤部位,主要受松潘—甘孜地块壳内高导层滑脱和四川盆地基底高阻体阻挡的约束,地壳深部存在着西倾且连续展布的壳内低阻层,表明龙门山深部确实存在着逆冲推覆构造,其逆冲断裂系中的三条断裂不仅以不同的倾角向西北倾斜,并且向深部逐渐汇集,但茂县—汶川断裂可能在深部与北川—映秀断裂是分离的.龙门山两翼的四川盆地和松潘甘孜褶皱带的电性结构既具有明显差异性,又具有一定的相关性.四川盆地显示巨厚的低阻沉积盖层和连续稳定的高阻基底的二元电性结构,而松潘—甘孜地块则表现为反向二元结构,即上部大套高阻褶皱带,下部整体为低阻的变化带,龙门山逆冲构造带本身又表现为松潘地块逆冲上覆在四川盆地之上,构成上部高阻褶皱带、中部低阻逆冲断裂带和底部盆地高阻基底的三层电性结构.对比龙门山逆冲构造断裂带的西倾延伸上下盘两侧的两个反对称的二元电性结构,松潘区块深部推断的结晶基底与龙门山断裂带下盘推断的下伏盆地结晶基底又存在某种内在对应关系,推断可能存在一个西延至若尔盖地块的泛扬子陆块.因此,龙门山构造带地壳电性结构研究对于揭示青藏高原东缘陆内造山动力过程,探索汶川大地震的深部生成机理都具有重要意义. 相似文献
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2008年5月12日汶川地震突发在现今并不活动的龙门山断裂带上,该地震发生的动力学机制问题引起广泛关注.文中利用黏弹性接触问题的有限元方法,考虑重力作用,对青藏高原东缘的应力场空间分布及其随时间的演化进行了数值模拟,结果显示应力在空间由分散分布逐渐向龙门山及周边地区转移集中.基于前人的研究成果及计算分析,初步认为汶川地震孕育发生的动力学过程如下：青藏高原的物质东流在向东运动过程中由于受到稳定的四川盆地的阻挡,一部分东流物质在川西地区囤积,造成龙门山隆升;高角度(50°~70°)、犁状的龙门山断层面上的正应力随着川西高原向东运动而不断增大,导致该断层的闭锁性逐步加强,并且分布在断层附近的变质杂岩为存贮高密度弹性应变能提供物质保障.但另一方面随着青藏高原较柔软的下地壳物质的不断向东运动,囤积的东流物质对龙门山断裂带上盘的推挤作用会不断加强,从而导致断裂带上剪应力越来越大;当剪应力超过摩擦强度时,断层解锁产生滑动,发生地震.模拟结果还表明龙门山断层面上的摩擦系数较高,断裂带上地震的平均复发周期约为3163年,这与其他资料结果有一致性. 相似文献
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通过分析中国地壳运动观测网络的GPS数据得到川滇地区地壳水平运动速度场 ,由此划分活动块体并分析其运动特征。结果表明 :相对欧亚板块 ,滇中、雅江和中甸次级块体的顺时针转动速率分别为 0 37°± 0 16°/Ma ,0 84°± 0 39°/Ma和 0 90°± 0 39°/Ma ,造成块体间跨木里弧形断裂带约 3mm/a的SN向挤压、丽江 -大理断裂带约 4mm/a的EW向拉张和理塘断裂带约 6mm/a的近EW向拉张。鲜水河断裂带左旋走滑速率 8～ 10mm/a ,安宁河 -则木河 -小江断裂带左旋走滑 5～6mm/a。龙门山断裂带没有明显的地壳消减 ,而断裂带西北约 15 0km处有一形变速度阶跃带 ,右旋走滑速率 4～ 5mm/a。阶跃带两侧的岷山块体和阿坝地区逆时针转动速率分别为 0 13°± 0 0 8°/Ma和0 5 3°± 0 19°/Ma。鲜水河 -小江断裂带以南、以西地区 ,青藏高原物质的E向挤出和重力滑塌造成川滇块体东移 ,在东部相对稳定的华南地块的阻挡下 ,川滇块体沿鲜水河 -小江断裂带由东转向南运动 ,从而引起川滇块体内部各次级块体的顺时针转动 相似文献
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于慎谔 《地震学报(英文版)》2004,17(4):417-425
Introduction Shanxi fault depression zone (SFDZ) is one of important Cenozoic fault basin zones and strong earthquake belts in Chinese mainland. Its northern part has aroused wide research interests due to the complicated tectonics and high activity of strong earthquakes there. Early researches on this depression zone were carried out since 60s of last century (DENG, et al, 1973; DENG, YOU, 1985; LU, DING, 1985; XU, 1990; XU, et al, 1996, 2002). In 90s of last century, the geologica… 相似文献
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Using methods of discontinuous deformation analysis and finite element (DDA+FEM), this paper simulates dynamic processes of the Tangshan earthquake of 1976, which occurred in the northern North China where its internal blocks apparently interacted. Studies focus upon both the movement and deformation of the blocks, in particular, the Ordos block, and variations of stress states on the boundary faults. The Tangshan earthquake was composed of three events: slipping motions of NNE-striking major fault, NE-striking fault near the northeastern end of the NNE-striking fault, and NW-striking fault on the southeastern side of the NNE-striking fault. Compared with previous studies, our model yields a result that is more agreeable with the configuration of aftershock distributions. A number of data are presented, such as the principle stress field during the earthquake, contours of the maximum shear stress, the strike-slip deformation between blocks near the earthquake focus, time-dependent variations of slips of earthquake-triggered faulting, the maximum slip distance, and stress drops. These results are in accord with the earthquake source mechanism, basic parameters from earthquake wave study, macro-isoseismic line, observed horizontal displacement vectors, etc. The Tangshan earthquake exerted different influences on the adjacent blocks and boundary faults between them, thus resulting in differential movement and deformation. The Ordos block seems to have experienced the small-scale counterclockwise rotation and deformation, but its northeast part, bounded on the east by the Taihangshan and on the north by the Yanshan and Yinshan belts, underwent relatively stronger deformation. The Tangshan earthquake also changed the stress state of boundary faults of the North China, leading to an increase in shear stress and a decrease in normal stress in the NW-trending Zhangjiakou-Penglai fault through Tangshan City and the northern border faults of the Ordos block, and therefore raises the potential risk of earthquake occurrence. This result is supported by the facts that a series of Ms≥ 6 earthquakes took place at the northern margin of the Ordos block after the Tangshan earthquake. 相似文献
16.
Using methods of discontinuous deformation analysis and finite element (DDA+FEM), this paper simulates dynamic processes of the Tangshan earthquake of 1976, which occurred in the northern North China where its internal blocks apparently interacted. Studies focus upon both the movement and deformation of the blocks, in particular, the Ordos block, and variations of stress states on the boundary faults. The Tangshan earthquake was composed of three events: slipping motions of NNE-striking major fault, NE-striking fault near the northeastern end of the NNE-striking fault, and NW-striking fault on the southeastern side of the NNE-striking fault. Compared with previous studies, our model yields a result that is more agreeable with the configuration of aftershock distributions. A number of data are presented, such as the principle stress field during the earthquake, contours of the maximum shear stress, the strike-slip deformation between blocks near the earthquake focus, time-dependent variations of slips of earthquake-triggered faulting, the maximum slip distance, and stress drops. These results are in accord with the earthquake source mechanism, basic parameters from earthquake wave study, macro-isoseismic line, observed horizontal displacement vectors, etc. The Tangshan earthquake exerted different influences on the adjacent blocks and boundary faults between them, thus resulting in differential movement and deformation. The Ordos block seems to have experienced the small-scale counterclockwise rotation and deformation, but its northeast part, bounded on the east by the Taihangshan and on the north by the Yanshan and Yinshan belts, underwent relatively stronger deformation. The Tangshan earthquake also changed the stress state of boundary faults of the North China, leading to an increase in shear stress and a decrease in normal stress in the NW-trending Zhangjiakou-Penglai fault through Tangshan City and the northern border faults of the Ordos block, and therefore raises the potential risk of earthquake occurrence. This result is supported by the facts that a series of Ms ≥ 6 earthquakes took place at the northern margin of the Ordos block after the Tangshan earthquake. 相似文献
17.
THE RELATIONSHIP BETWEEN REGIONAL SEISMIC ENERGY RELEASE AND RELATIVE MOTION BETWEEN BLOCKS ON BOTH SIDES OF YISHU FAULT ZONE 
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下载免费PDF全文 Following the 11 March 2011 Japan MW9.0 earthquake, frequent moderate and small events occurred on the Yishu fault zone and its either side. Using continuous GPS data and a sliding block model, this work studies the relationship between the energy release of these shocks and the block relative motion of either side of the Yishu fault zone. The results show that(1)the equivalent magnitude M from released energy and the two blocks' relative motion are well correlated when earthquakes are selected in a retrieval circle(whose center is the midpoint of the Yishu fault zone)with a radius of 250~500km and using a sliding time window of 3~10 months. The best correlation coefficient between M and the two blocks' relative motion is 0.74 and the T test shows a significant linear correlation between them.(2)Spatial distribution of the correlation coefficients shows that the relative motion of the blocks on both sides affects the energy release in the area from the north part of Yishu fault zone to the Jiaodong Peninsula area and southwest Shandong-Henan border area obviously.(3)Since June 2014, the relative motion of the two blocks on both sides of the Yishu fault zone presents a wave of change, which may be an expression of the accumulation of seismic strain energy in the Yishu fault zone and its two sides. The linear relationship between the equivalent magnitude M from released energy and two blocks' relative motion V can be fitted by linear equation M=0.51*V+3.9, showing that strain energy accumulation could be released by the moderate and small earthquakes in a timely manner, which may favorable to delay the seismic risk in the study area. It also shows, on the other hand, that earthquake energy was not released so completely in the study area since the end of 2015 to 2016, which is likely associated with the Changdao earthquake swarm in 2017. 相似文献
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By using moving average method to separate Bouguer gravity anomaly field in Sichuan-Yunnan region, we got the low-frequency Bouguer gravity anomaly field which reflects the undulating of Moho interface. The initial model is obtained after seismic model transformation and elevation correction. Then, we used Parker method to invert the low-frequency Bouguer gravity anomaly field to obtain the depth of Moho interface and crustal thickness in the area. The results show that the Qinghai-Tibet block in the northwest of the study area deepens and thickens from the edge to the interior, with the depth of Moho interface and the crust thickness of about 52~62km and 54~66km, respectively. The depth of Moho interface in Sichuan Basin is about 38~42km. In Sichuan-Yunnan block, the depth of Moho interface is about 42~62km from southeast to northwest. Beneath the West Yunnan block, west of the Red River fault zone, the Moho depth is about 34~52km from south to north. The Longmen Mountains and Red River fault zone are the gradient zone of the Moho depth change. Along the Red River fault zone, the depth difference of Moho interface is increasing gradually from north to south. No obvious uplift is found on the Moho interface of Panzhihua rift valley. The depth of Moho interface distribution in Sichuan and Yunnan is obviously restricted by the collision between the Indian plate and the Eurasian plate and the lateral subduction of the Indo-China peninsula. The mean square error of the depth of Moho interface is less than 1.7km between the result of divisional density interface inversion and artificial seismic exploration. At the same time, we compared the integral with divisional inversion result. It shows that:in areas where there is obvious difference between the crust velocity and density structure in different tectonic blocks, the use of high resolution seismic exploration data as the constraints to the divisional density interface inversion can effectively improve the reliability of inversion results. 相似文献
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2008年汶川8.0级地震沿龙门山断裂带内的映秀—北川断裂和灌县—安县断裂分别形成约230 km和70 km的地表破裂带.震后地质考察研究表明,伴随地震断层出露地表的滑动面大多沿炭质泥岩和煤层发育.与1∶5万区域地质图进行对照,显示映秀—北川地震破裂带的西南段（虹口—清平段）和灌县—安县地震地表破裂带的展布与龙门山地区上三叠统须家河组煤系地层的出露范围相一致.龙门山地区的上三叠统须家河组地层中的薄煤层、炭质泥岩层以及志留系、寒武系的炭质页岩层是易于产生滑动的柔性岩层,易形成滑脱面或成岩片夹于断层带中.汶川地震产生的复杂地表破裂带是龙门山逆冲推覆构造带沿地表构造层中夹有煤层等柔性岩层的断层产生B型滑动的结果. 相似文献
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LATE QUATERNARY ACTIVITY OF THE CENTRAL SEGMENT OF THE DARI FAULT AND RESTUDY OF THE SURFACE RUPTURE ZONE OF THE 1947 M73/4 DARI EARTHQUAKE,QINGHAI PROVINCE 下载免费PDF全文
下载免费PDF全文 Bayan Hara Block is one of the most representative active blocks resulting from the lateral extrusion of Tibet Plateau since the Cenozoic. Its southern and northern boundary faults are characterized by typical strike-slip shear deformation. Its eastern boundary is blocked by the Yangze block and its horizontal movement is transformed into the vertical movement of the Longmen Shan tectonic belt, leading to the uplift of the Longmen Shan Mountains and forming a grand geomorphic barrier on the eastern margin of the Tibet Plateau. A series of large earthquakes occurred along the boundary faults of the Bayan Hara Block in the past twenty years, which have attracted attention of many scholars. At present, the related studies of active tectonics on Bayan Hara Block are mainly concentrated on the boundary faults, such as Yushu-Ganzi-Xianshuihe Fault, East Kunlun Fault and Longmen Shan Fault. However, there are also some large faults inside the block, which not only have late Quaternary activity, but also have tectonic conditions to produce strong earthquake. These faults divide the Bayan Hara Block into some secondary blocks, and may play important roles in the kinematics and dynamics mechanism of the Bayan Hara Block, or even the eastern margin of the Tibet Plateau. The Dari Fault is one of the left-lateral strike-slip faults in the Bayan Hara Block. The Dari Fault starts at the eastern pass of the Kunlun Mountains, extends eastward through the south of Yalazela, Yeniugou and Keshoutan, the fault strike turns to NNE direction at Angcanggou, then turns to NE direction again at Moba town, Qinghai Province, and the fault ends near Nanmuda town, Sichuan Province, with a total length of more than 500km. The fault has been considered to be a late Quaternary active fault and the 1947 M73/4 Dari earthquake was produced by its middle segment. But studies on the late Quaternary activity of the Dari Fault are still weak. The previous research mainly focused on the investigation of the surface rupture and damages of the 1947 M73/4 Dari earthquake. However, there were different opinions about the scale of the M73/4 earthquake surface rupture zone. Dai Hua-guang(1983)thought that the surface rupture of the earthquake was about 150km long, but Qinghai Earthquake Agency(1984) believed that the length of surface rupture zone was only 58km. Based on interpretation of high-resolution images and field investigations, in this paper, we studied the late Quaternary activity of the Dari Fault and the surface rupture zone of the 1947 Dari earthquake. Late Quaternary activity in the central segment of the Dari Fault is particularly significant. A series of linear tectonic landforms, such as fault trough valley, fault scarps, fault springs and gully offsets, etc. are developed along the Dari Fault. And the surface rupture zone of the 1947 Dari earthquake is still relatively well preserved. We conducted a follow-up field investigation for the surface rupture zone of the 1947 Dari earthquake and found that the surface rupture related to the Dari earthquake starts at Longgen village in Moba town, and ends near the northwest of the Yilonggounao in Jianshe town, with a length of about 70km. The surface rupture is primarily characterized by scarps, compressional ridges, pull-apart basins, landslides, cleavage, and the coseismic offset is about 2~4m determined by a series of offset gullies. The surface rupture zone extends to the northwest of Yilonggounao and becomes ambiguous. It is mainly characterized by a series of linear fault springs along the surface rupture zone. Therefore, we suggest that the surface rupture zone of the 1947 Dari earthquake ends at the northwest of Yilonggounao. In summary, the central segment of the Dari Fault can be characterized by strong late Quaternary activity, and the surface rupture zone of the 1947 Dari earthquake is about 70km long. 相似文献