GPS结果揭示的龙门山断裂带现今形变与受力——与川滇地区其他断裂带的对比研究   总被引：3，自引：2，他引：3       下载免费PDF全文

刘峡  孙东颖  马瑾  吕健  李爱荣  梁福逊  占伟 《地球物理学报》2014,57(4):1091-1100

本文构建川滇地区二维有限元接触模型,采用“块体加载”方法和1999-2007年GPS数据,模拟计算该区主要断裂带的形变运动,对比、分析其运动、受力特征和应力积累差异.结合区域强震研究汶川地震、芦山地震的力学背景.结果显示强震前龙门山断裂带保持低变形,右旋错动不超过1 mm·a^-1,挤压不超过0.5 mm·a^-1,明显低于其他断裂带,但其两侧应力值与其他断裂带相当,主压应力轴与断裂带走向垂直,形成很宽的挤压带,断层面法向挤压应力积累为-333.74 Pa·a^-1,为全区最高.揭示1999年以来,龙门山断裂带及巴颜喀拉块体东部的挤压应力快速增加,致使实际应力可能处于高水平并诱发地震活跃,期间强震呈丛集性,出现汶川、芦山地震接连发生的现象.  相似文献   

利用余震震中分析芦山M_S7.0 地震发震构造          下载免费PDF全文

赵荣涛  安美建  冯梅  张士安  张纪中  侯春堂 《地震学报》2015,37(2):205-217

对2013年4月20日芦山M_S7.0地震主震震中周边29个地震台记录到的震后一年多的微、 小余震,利用Hypo71绝对定位方法进行定位,获得了约1960次地震的震源位置. 结果显示,芦山地震余震在平面上主要沿双石—大川分支断裂及其周边分布,在垂向上主要集中在大约5—20 km深度之间的两条余震交叉带上. 其中一条余震带倾向NW,倾角在12 km左右深度发生变化,浅部倾角较陡,该余震带延伸至地表与双石—大川分支断裂和新开店断裂之间的推测隐伏断裂位置相重合; 另一条余震带倾向SE,其延伸至地表的位置与双石—大川断裂非常接近,但与该断裂倾向相反. 主震震源位置与两条余震带相交的位置接近,且芦山地震主震的两个节面产状与这两条余震带的深部几何形态正好对应, 表明芦山地震主震可能是两条余震带所对应的两条断裂同时活动的结果.   相似文献   

龙门山断裂带中上地壳速度结构的短周期环境噪声成像   总被引：4，自引：2，他引：2       下载免费PDF全文

赵盼盼  陈九辉  刘启元  郭飚  李顺成  李昱 《地球物理学报》2015,58(11):4018-4030

本文利用在龙门山断裂带周边布设的57个台站自2008年11月至2009年11月为期一年的垂直分量连续地震环境噪声数据,通过短周期地震环境噪声成像方法,获得了龙门山断裂带中北段地壳25km深度范围的S波精细速度结构.结果表明:(1)龙门山断裂带周边区域10km以上的速度结构与地表断裂的分布形态具有良好的一致性,速度结构控制了龙门山主要断层的深部延展特征;在15km及以下深度,S波速度结构呈现沿龙门山和沿岷山隆起走向的交叉构造格局,由此造成的速度结构差异可能影响了汶川地震的破裂过程;(2)速度结构随深度的分布特征为龙门山断裂带主要断层的深部延伸形态给出了良好的约束,结果进一步确认了龙门山断裂中段的高角度铲型断裂构造特征;(3)研究区的南端发现了龙门山断裂下方20km以下深度具有与松潘地块中地壳低速层相关的低速结构的迹象,这可能是汶川地震破裂带南段22km左右深度存在脆韧转换带的一个证据.研究结果显示出密集台阵和短周期环境噪声成像方法在地壳浅部精细结构和断层探测研究中具有巨大潜力.  相似文献   

青藏高原东缘龙门山前陆逆冲带复合结构与生长   总被引：1，自引：1，他引：0  

颜丹平  孙铭  巩凌霄  周美夫  邱亮  李书兵  张森  古术航  木红旭 《地质力学学报》2020,26(5):615-633

位于青藏高原东缘的北东向龙门山逆冲带,研究已经证明是中生代与新生代前陆复合扩展和生长的结果。然而,2008年5·12汶川地震地表破裂、余震和滑坡等的单向和分段迁移现象,对龙门山复合逆冲带的结构认识提出了挑战。文章在已有研究成果基础上,针对龙门山复合生长下构建的特殊结构进行了野外调查和构造解析。结果表明,以中生代与新生代两期前陆逆冲带复合生长为基础,龙门山复合逆冲带具有特殊的、主要由前陆逆冲楔叠加后形成的复合结构,而且这种复合逆冲楔具有分级和时序特征;中生代前陆逆冲楔是以逆冲断层-褶皱为特征,并分别组合形成碧口厚皮逆冲推覆体、唐王寨薄皮逆冲推覆体和龙王庙逆冲推覆体,总体从晚三叠世以前开始,至~160 Ma向南递进扩展生长;新生代前陆逆冲楔由逆冲断层和逆冲岩片组成,分为约35~10 Ma和10 Ma以来两个阶段,向南东向递进扩展生长,并可能与川西盆地东侧龙泉山构造相连通。因此,龙门山逆冲带具有前陆逆冲带和生长过程的双重复合结构。   相似文献   

SPATIO-TEMPORAL STRESS FIELD VARIATION IN THE CENTRAL LONGMENSHAN FAULT ZONE AFTER THE 2008 WENCHUAN EARTHQUAKE FROM FOCAL MECHANISM SOLUTIONS OF SMALL EARTHQUAKES          下载免费PDF全文

JIANG Min  CHEN Jiu-hui  Yasuto Kuwahara  Reiken Matsushita 《地震地质》2018,40(2):310-322

We determined the focal mechanism solutions(FMS)of aftershocks of the 2008 Wenchuan earthquake using the waveform data recorded by the Western Sichuan movable seismic array. We further obtained the spatio-temporal variation of the stress field by inverting the stress tensors from these data. The results show that the FMSs of the small earthquakes are primarily reverse faulting with considerable number of normal and strike-slip. The proportion of reverse type earthquakes clearly increases with time, and the spatial distribution of the FMSs is closely related with local geology and the characteristics of the deep faults. The stress tensor inversion results reveal that the orientations of the maximum horizontal compressive stress(S_H)shortly after the mainshock in each area are mainly in EW to NWW-SEE directions, while in the area along Xiaoyudong-to-Lixian aftershock branch it is in NE-SW direction in shallow crust. This implies that the stress field at the early stage after the Wenchuan earthquake is mainly controlled by the dynamic stress change caused by the rupture propagation, and the conspicuous factor determining the S_H direction is the characteristics of the rupture plane. Temporal variations of the stress tensors show that the stress regimes at depth changed from a mixture of reverse and strike-slip faulting to pure reverse, implying that local Coulomb stress caused by the main shock is released through strike-slip faulting and gradually recovers into the background stress field. The change of stress in the shallow subsurface follows that in the deep subsurface with observable time delay.  相似文献   

球坐标解析定位技术在龙门山近震层析中的应用   总被引：1，自引：1，他引：0       下载免费PDF全文

钱辉  James Mechie  于常青 《地球物理学报》2018,61(5):2011-2021

通过对球坐标梯度速度模型的角距离和走时公式的推导,获取了射线参数驱动的可解析计算的全球多震相时距及其对于模型,震中和地表速度的导数表达式.与TAUP软件进行对比发现除了散射震相外,所有震相的时距曲线误差均可忽略,该方法考虑了高程,在性能和应用方面也可以完全取代TAUP相应的模块.在此基础上升级了耦合一维模型的定位系统,并应用到龙门山地区的近震重新定位,通过对远震的局部化处理,增加了近震层析的射线覆盖范围和密度,使下地壳速度模型在中上地壳模型的约束下有所呈现.通过近震层析处理发现松潘地区浅部存在大量的高低速相间分布,四川盆地深部为扬子板块高速物质控制,浅部则以低速为主.龙门山断裂带浅部呈现高速为主的特征,而中地壳广泛存在低速物质的分布,龙门山断裂控制的彭灌杂岩体存在根部,收束在20 km深度中地壳滑脱带上.  相似文献   

THE THREE DIMENSIONAL DENSITY STRUCTURE OF CRUST AND UPPER MANTLE IN THE CENTRAL-SOUTHERN PART OF LONGMENSHAN     

XU Zhi-ping  WANG Fu-yun  JIANG Lei  ZHAO Yan-na  YANG Li-pu  TANG Lin 《地震地质》2019,41(1):84-98

In recent years, strong earthquakes of M_S8.0 Wenchuan and M_S7.0 Lushan occurred in the central-southern part of Longmenshan fault zone. The distance between the two earthquakes is less than 80 kilometers. So if we can obtain the inner structure of the crust and upper mantle, it will benefit us to understand the mechanism of the two earthquakes. Based on the high resolution dataset of Bouguer gravity anomaly data and the initial model constrained by three-dimensional tomography results of P-wave velocity in Sichuan-Yunnan region, with the help of the preconditioned conjugate gradient(PCG)inversion method, we established the three dimensional density structure model of the crust and upper mantle of the central-southern segment of Longmenshan, the spatial interval of which is 10 kilometers along the horizontal direction and 5 kilometers along the depth which is limited to 0~65km, respectively. This model also provides a new geophysical model for studying the crustal structure of western Sichuan plateau and Sichuan Basin. The results show obvious differences in the crustal density structure on both sides(Songpan-Ganzê block and Sichuan Basin)of Longmenshan fault zone which is a boundary fault and controls the inner crustal structure. In Sichuan Basin, the sedimentary layer is represented as low density structure which is about 10km thick. In contrast, the upper crust of Songpan-Ganzê block shows a thinner sedimentary layer and higher density structure where bedrock is exposed. Furthermore, there is a wide scale low density layer in the middle crust of the Songpan-Ganzê block. Based on this, we inferred that the medium intensity of the Songpan-Ganzê block is significantly lower than that of Sichuan Basin. As a result, the eastward movement of material of the Qinghai-Tibet plateau, blocked by the Sichuan Basin, is inevitably impacted, resulting in compressional deformation and uplift, forming the Longmenshan thrust-nappe tectonic belt at the same time. The result also presents that the crustal structure has a distinct segmental feature along the Longmenshan fault zone, which is characterized by obviously discontinuous changes in crustal density. Moreover, a lot of high- and low-density structures appear around the epicenters of Wenchuan and Lushan earthquakes. Combining with the projection of the precise locating earthquake results, it is found that Longmenshan fault zone in the upper crust shows obvious segmentation, both Wenchuan and Lushan earthquake occurred in the high density side of the density gradient zone. Wenchuan earthquake and its aftershocks are mainly distributed in the west of central Longmenshan fault zone. In the south of Maoxian-Beichuan, its aftershocks occurred in high density area and the majority of them are thrust earthquake. In the north of Maoxian-Beichuan, its aftershocks occurred in the low density area and the majority of them are strike-slip earthquake. The Lushan earthquake and its aftershocks are concentrated near the gradient zone of crustal density and tend to the side of the high density zone. The aftershocks of Lushan earthquake ended at the edge of low-density zone which is in EW direction in the north Baoxing. The leading edge of Sichuan Basin, which has high density in the lower crust, expands toward the Qinghai-Tibet Plateau with the increase of depth, and is close to the west of the Longmenshan fault zone at the top of upper mantle. Our results show that there are a lot of low density bodies in the middle and lower crust of Songpan-Ganzê Block. With the increase of the depth, the low density bodies are moving to the south and its direction changed. This phenomenon shows that the depth and surface structure of Songpan-Ganzê Block are not consistent, suggesting that the crust and upper mantle are decoupled. Although a certain scale of low-density bodies are distributed in the middle and lower crust of Songpan-Ganzê, their connectivity is poor. There are some low-density anomalies in the floor plan. It is hard to give clear evidence to prove whether the lower crust flow exists.  相似文献   

龙门山南段大邑地区断裂带活动多期性研究          下载免费PDF全文

陈芊  陈伟  应家梅  杨晓强  王旭 《地质找矿论丛》2020,35(1):85-94

四川省大邑地区地处龙门山南段,是有名的地震多发地区。文章基于现代构造地质学理论,通过地震解释及构造几何分析、断层相关褶皱原理与几何分析方法、运动学正演模拟方法,开展了对大邑地区断裂带活动多期性研究,结果表明大邑地区断裂带活动具有多期性的特点。自印支期以来主要经历了两期三次构造活动:印支晚期的低角度逆冲推覆过程,须家河组四段(T3x4)中上部形成生长地层;喜马拉雅期Ⅰ幕,隐伏断层再次活动,造成侏罗系与下伏三叠系的变形差异;喜马拉雅期Ⅱ幕,龙门山构造带区域应力场向前传递,大邑地区形成高角度逆冲断层,断层沿深部滑脱层在大邑地区向上逆冲直至地表,早期隐伏断层被错断,伴随次级断层、反冲断层产生。  相似文献   

龙门山前山断裂南段强震崩塌与1327年天全地震     

王世元  许冲  刘韶  孔军  王明明 《大地测量与地球动力学》2018,38(6):609-613

具有强震孕育能力的龙门山前山断裂南段附近地区的强震事件仅有以史料记载的1327年天全地震和仪器记载的1970年大邑6.2级、2013年芦山7.0级地震,这些地震均引发大量的崩塌、滑坡。调查对比发现,沿龙门山断裂南段大川-双石断裂沿线的典型地段分布的历史地震崩塌范围和运移距离都大于芦山地震所触发的崩塌,崩塌的方量和粒径表现为南西往北东逐步减少、减小的趋势。崩塌调查、崩塌体埋藏物和表生地衣相对年代学测试结果、史料记载与震例对比和地震有感半径与震级经验公式计算综合表明,1327年天全地震引起的地面震动大于芦山地震,是天全县“大岩崩”地名和双石镇“晒经书”景观形成的主要原因,1327年天全地震的震中可能位于龙门山断裂南段大川-双石断裂附近的天全响水溪一带,震中烈度≥Ⅸ度,震级≥7.0。  相似文献   

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董运洪  陈长云 《大地测量与地球动力学》2009,29(6):28-31

??????8.0????????й?????????????????????????????????????????????201.8 km?????????????35.6 km????????????????????????????????????????1????8.0??????????????????????????????????λ????????????????????λ?????0.064 m???????????????2?????????????????????????????λ???4.711 m?????????????????λ?????5.100 m???????????????3??????????????????????????λ?????2.440 m??4)????????????????λ????????????????????λ?????0.101 m??5???????????????????????????????λ????????1.003 m?????????????????λ?????1.381 m???????????????  相似文献