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1.
铲形正断层特征数值模拟及其与地震机制的研究   总被引:6,自引:0,他引:6  
谢阳  常祖峰 《地震研究》2001,24(4):351-357
铲形正断层是伸展构造区最普遍、最基本的断层构造。本应用近年来先进的LDDA方法对断层的运动效应进行数值模拟,着重探讨了铲形正断层的几何学和运动学特征,并且依据断层带附近剪应力集中的情况,对铲形正断层与地震机制的关系进行了讨论。这些探讨对于深入认识伸展构造区地震的形成机制和动力学环境具有重要的借鉴意义。  相似文献   

2.
龙门山断层地震周期及其动力学过程模拟研究   总被引:1,自引:1,他引:0       下载免费PDF全文
在断层面上引入速率-状态相依摩擦本构关系、考虑铲形逆冲断层几何结构特征、断层下盘和上盘中下地壳及上地幔为黏弹性介质、上盘上地壳为弹塑性介质,本文用二维有限元动力学模型模拟了龙门山断层上大震准周期复发行为、分析了断层上地震孕育位置、地震周期不同阶段的应力/应变场演化特征.不同于近垂直走滑断层上的地震周期行为,大陆铲形逆冲断层上的构造应力的积累和释放过程更复杂、有其独特性.我们得到如下认识:(1)铲形逆冲断层上的地震复发是准周期行为.(2)龙门山断层最大库仑应力位于断层17~20 km深处,应力长期积累和同震释放都在此深度最大,说明地震会在此处孕育、发动.(3)在断层破裂的深部和浅部,同震滑动大小和构造应力释放大小并非同步,而是差异悬殊.(4)地震仅部分释放区域积累的应变能,断层上盘上地壳顶部和底部的褶皱、破裂等永久变形形式也是释放应变能的重要形式.(5)应变能密度增量的演化图像分为:震间、同震、震后期,清晰反应了龙门山断层附近的地震动力学过程.(6)地震发生除释放能量外,同时也对近断层的中地壳和断层底部有很大的应变能加载;这些加载,在震后期可能通过震后滑移、余震或中下地壳乃至上地幔的驰豫形变用几十年时间释放.以上对大陆内铲形逆冲断层上变形特征的了解,有助于我们在其地震周期行为中评估地震危险性.  相似文献   

3.
针对5种模拟库区:库心存在正断层;库心存在逆断层;库边存在正断层,水库蓄水在上盘;库边存在正断层,水库蓄水在下盘;库心存在带内由胶结程度更好的介质所填充的正断层,分别计算了水库蓄水引起的附加应力场、孔压场和形变场,并对它们的分布特征作了综合分析。  相似文献   

4.
华北地区震源断层与深浅构造关系的初步研究   总被引:8,自引:0,他引:8  
使用地震资料(等震线、地表破裂带、地形变、余震平面和剖面分布及震源机制)描述强震震源断层的立体特征。发现震源断层的上界即为由地震测深资料得到的G界面,并与该界面之下的高倾角深断裂吻合,证明地震时深断裂发生了剪切错动。震源断层与G界面之上的铲形正断层构成不连接的两套断裂系统,它们之间存在有对应和无对应的复杂关系。  相似文献   

5.
临潼-长安断裂带的几何结构及形成机理   总被引:1,自引:0,他引:1       下载免费PDF全文
根据野外大量断层露头以及人工地震结果表明,临潼——长安断裂带主要由两条断层组成,即麻街——碾湾断层和胡家沟——首帕张断层. 麻街——碾湾断层, 在灞河右岸的高桥分出一条分支断层,即王家碥——侯家湾断层; 胡家沟——首帕张断层在铜人塬和少陵塬分出一条分支断层,即冢底村——唐家寨断层. 断裂表现为张性倾滑正断层性质,平面上局部范围大致呈平行等间距展布,剖面上向西北呈阶梯状降落,成ldquo;Yrdquo;字型组合。深地震反射结果显示,该断裂深约5——8 km,为基底断裂,深部为铲形正断层. 临潼——长安断裂带是在近南北向引张应力场的作用下形成的典型的伸展断裂系,同时受余下——铁炉子断裂左旋走滑运动的影响,使断裂带从东北向西南呈帚状展布形态.   相似文献   

6.
2008年汶川8级地震的发震构造是高角度铲形逆冲断层,伴随这种类型地震的远近场强地面运动在中国是第1次被记录到。综合汶川地震发震构造、破裂过程和强地面运动峰值加速度的资料,探讨高角度铲形逆冲断裂作用与强地面运动的关系。结果显示,龙门山断裂带内强地面运动峰值加速度明显大于断裂带外的台站,前者可达后者的2倍多。同时,该地震强地面运动具有很大的垂直分量,近断层垂直分量大于水平分量。结合远场资料,发现龙门山断裂带上盘峰值加速度垂直分量总体上大于下盘,上盘垂直分量的衰减比下盘慢。不考虑远场的高值异常,水平分量似乎也存在上盘效应,但目前无证据表明这些异常应该被剔除。另外,远场地面运动特征显示,相对于反方向,沿同震断层扩展方向(NNE)的峰值加速度水平分量衰减较慢,垂直分量的这种方向效应不明显。考虑到汶川地震破裂浅、断面陡和以垂直形变为主这3个显著的同震构造特性,近场和远场地面运动记录反映出位错类型和台站的实际断层距的控制作用。正因为汶川地震高角度铲形逆冲断裂结构的特殊性,导致其地面运动与普通逆断型地震强地面运动的同震效应在某些分量上相同,其他分量存在差异。  相似文献   

7.
对倾向断层中地城的动力学模拟表明,不对称的近源地面运动是由这类断层不对称的几何形态引起的。在初始应力大小相同的情况下,逆(冲)断层引起的地面运动要比正断层 引起的地面运动大2倍或更多。无论是在逆(冲)断层还是正断层引起的地震中,上盘的运动都比下盘的大。地震产生的应力场与地球自由表面的相互作用导致了与时间相关的正应力的立生,从而造成了正断层与逆(冲)断层之间的不对称性。断层上、下两盘的不对称性是由于  相似文献   

8.
掀斜块体滑脱深度的几何学研究   总被引:3,自引:0,他引:3       下载免费PDF全文
侯建军 《地震地质》1991,13(4):377-383
本文从几何学的角度,根据掀斜块体长度、掀斜角、脊的隆起量和边界断层倾角等几何要素,推导出了计算掀斜块体滑脱深度的表达式。结果表明,旋转平面状正断层围限块体的滑脱深度与脆韧性转换带上顶面深度一致,为10—15公里;铲形正断层围限块体的滑脱深度达到或超过脆韧性转换带深度,为20—30公里  相似文献   

9.
基于数值格林函数法的近场强地震动数值模拟方法,以1994年Northridge地震断层面上位错量的不均匀分布模式和该地区的地层剪切波速度结构为震源模型和计算模型,做了两个方面的模拟研究:(1)直立走滑断层(断层倾角为90°)情况下,模拟分析了有限断层单侧破裂模式和双侧破裂模式对强地震动特征——破裂方向性和上盘效应的影响;(2)对于倾斜断层(倾角为45°),模拟分析了正断层、逆断层和走滑断层情况下,单侧破裂模式对其强地震动主要特征——破裂方向性效应和上盘效应的影响.结果表明:断层的破裂方式直接影响着地表地震动峰值和矢量分布;在近场区无论直立断层还是倾斜断层,其地表地震动峰值分布所表达的破裂方向性效应显著,位于破裂传播前方的地震动强度大,反映了波前被压缩的趋势,破裂后方地震强度明显变小;倾斜断层引起的上盘效应明显,NS向分量和竖向分量的地表地震动峰值的最大值出现在上盘靠近断层迹线处,EW向分量的峰值在断层迹线两侧呈不对称分布,且逆断层引起的地震动峰值最大,走滑断层的次之,正断层的最小.  相似文献   

10.
重力构造的力学研究——铲式断层的力学分析   总被引:1,自引:0,他引:1       下载免费PDF全文
本文采用服从抛物线型破坏准则的滑移线场理论,对重力构造的铲式断层进行了力学研究。岩层重力滑动的坡度与岩石强度、滑动系统厚度、孔隙压力以及润滑层有关;铲式正断层自上至下由张性、张剪性、纯剪性过渡到压剪性,铲式逆断层上下一致为压剪性  相似文献   

11.
Based on field observations and mechanic analysis,the authors think that synthetic faults,antithetic faults,and hangingwall cross-faults are formed on the piedmont alluvial-pluvial plain under the action of hangingwall blocks sliding downward and rotating along concave fault planes of the listric normal fault on the southeastern margin of Weihe Basin.The characteristics of different movements and expressions on the surface of these structures may be taken as the main marks for listric normal fault segmentation.  相似文献   

12.
The results from investigation of large quantity of fault outcrops and artificial earthquakes suggest that the Lin-tong-Chang’an fault zone mainly consists of two faults. One is the Majie-Nianwan fault that separates a branch of Wangjiabian-Houjiawan fault on the right bank of the Bahe River; the other is the Hujiagou-Shoupazhang fault that separates a branch of Zhongdicun-Tangjiazhai fault in Tongrenyuan and Shaolingyuan. As tensional dip-slip normal faults, the faults distribute with approximately parallel equal intervals in local regions and the profiles drop in a step-like form to the northwest, presenting a Y-shape combination. The result from deep seismic reflection indicates that the fault is about 5~8 km in depth, which is not only a basement fault, but also a listric normal fault in the deep stratum. The Lintong-Chang’an fault is a typical outstretching rift system under the NS-trending ten-sion stress field. At the same time, affected by the sinistral strike slip of the Yuxia-Tieluzi fault, the fault extends like a broom from the northeast to the southwest.  相似文献   

13.
夏垫断裂浅部特征高分辨反射地震探测研究   总被引:2,自引:0,他引:2  
在夏垫断裂上采用浅层纵、横波相结合的联合探测方法,获得了多条反映不同深度的高质量叠加时间剖面图,这些图像清晰地显示了夏垫断裂的浅部构造特征和地表以下浅至几米的地层结构和断裂特征信息,使得采用人工地震方法探测地表下10m以内的断裂成为可能。本次探测工作中,还在夏垫断裂的南侧发现了1条倾角较缓、呈铲型向下延伸的断裂,表明夏垫断裂是由2条断裂组成的断裂带。  相似文献   

14.
This work presents a structural model for earthquake faulting in the Umbria-Marche Apennines (Central Italy). The model is derived by an integrated analysis of geological, geophysical and seismological data. At regional scale, the distribution and character of the seismicity appear to be mainly controlled by a low-angle east-dipping normal fault (Altotiberina fault, AF). The latter is the lower boundary of an active, continuously deforming hangingwall block moving toward NE. Moderate magnitude earthquakes (4 < M < 6), such as the Norcia 1979 (M = 5.9), the Gubbio 1984 (M = 5.2) and the Colfiorito 1997 (Mmax = 5.9), occur within the active hangingwall block and are related to the activity of major west-dipping normal faults detaching on the AF. The geometry of the deep seismogenic structures is listric (as in the case of Colfiorito) or more complex, because of local reactivation of pre-existing low-angle thrust (e.g. Gubbio) or high-angle strike-slip faults (e.g. Norcia). For all the analysed earthquakes the rupture nucleation is located at the base of the aftershock volumes, near the line of intersection between the SW-dipping normal faults and the east-dipping AF basal detachment. The progressive increase in depth of the earthquake foci from the north–west (e.g. Gubbio, 6–7 km) to the south–east (e.g. Norcia, 11–12 km) appears to be related to the eastward deepening of the basal detachment. These seismotectonic features are relevant for determining the seismogenic potential of the Apennine active faults, which depends not only on the length of the faults, but also on the depth of the detachment zone as well.  相似文献   

15.
Volume 15,Number 275INTRODUCTIONThe Xln抄al eafthquake swarrn occurred In Shulu basin In the western part ofNorih China PlainIncludes Malan M6.8 eafthquake In hn纽M Countyon Marchs,1966,Don驯aug M6.7 and M7.2earthquakes In Ningln County on March 22,1966,Balchekou M6.2 ealthquake In Shulu County onMarch 26,1966,and啊…ac M6.0 earthquake in Juhi County on March 29 1966.They aredlstnbutedin an elliptical area in N35”E direction with long axisd劝out 110 km and short axis o…  相似文献   

16.
IntroductionIn order to gain a clear idea of the deep tectonic environment of Xingtai earthquake area,three wide-angle deep seismic renectionlrefraction profiles have been conducted through the are4they are Yuanshi--Ji'nan profile, Renxian--Wuqing profile and Tat' an--LongyaM inzhou profi I e.The Yuanshi--Ji'nan profile passes through the epicenter of the Ms=7.2 main shock andTat' ~ongyaO--X inzhou profi ie passes through the ep icenter of the Ms=6. 8 earthquake. Duringthe "Eighth Five-…  相似文献   

17.
The results of seismic deep reflection,high resolution refraction and shallow artificial seismic exploration indicate that the fault on the northern bank of the Weihe river is composed of two faults,one is the Yaodian-Zhangjiawan fault and the other is the Chuanzhang-Zuitou fault.The 22 km long Yaodian-Zhangjiawan fault of EW-striking starts from Chenjiagou via Yaodian town,Qianpai village,Bili village,Wujia town and Zhangjiawan to Jiajiatan.The 15 km long Chuanzhang-Zuitou fault striking near EW starts from Chuanzhang via Mabei to Zuitou.The Weihe fault offset the basement and upper crust,the reflecting layers of TQ,TN,TE and Tg are ruptured at depth of about 15 km.In the deep part,the Weihe fault and the secondary fault form a Y-shaped structure or a synthetic low angle intersection.The Weihe fault is a listric normal fault.The fault has obvious structural characteristics of a reversed-drag normal fault and a normal drag normal fault with the depth of 1 000 m,and also has the characteris-tics of syngenetic sediment.The Weihe fault is one of the faults which control the basin sediment,and it is the boundary fault of Xi’an depression and Xianyang salient.The depth of the fault decreases from the west to east gradually,the deep part intersects with the Lintong-Chang’an fault at the intersection part of Weihe River,Jinghe River and Bahe River and the shallow part connects with the Weinan-Jingyang fault.The seismic exploration re-sults indicate that no fault exists on southern bank of the Weihe River.  相似文献   

18.
通过对邢台地震极震区浅层探测、新生代深浅构造运动的分期、地壳上地幔结构特征剖析及其与震源参数的对比等研究,指出邢台地震区控制早第三纪盆岭构造发育的铲形断裂及其下部向东缓倾的滑脱面与邢台地震的发生无关;邢台地震群是在最新构造应力场作用下,受北西向断层或横向障碍体阻隔的不连续“深断裂”依次向上撕裂状破裂扩展、引起相邻斜列状深断裂间应力迁移和加载等三维破裂过程的产物;邢台地震断层是先存地壳“深断裂”向上撕裂状扩展的“新生断层”。  相似文献   

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