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本文收集了1976—2017年滇缅活动地块98个MW 4.8—7.0地震的震源机制解，分析震源机制解和震源深度的空间分布特征，探讨了其构造动力学背景。结果表明:①滇缅活动地块震源深度优势分布范围为10—30km，90%以上的地震震源深度小于30km，结合研究区统计时段内地震震源深度、优势度、众数等参数，推断滇缅活动地块及周边震源深度的下界为30km，脆性多震层位于10—30km，且主要位于15km附近；②滇缅活动块体不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解，在空间上存在着明显的分区性特征，揭示出位于青藏高原东南缘的滇缅活动块体及周边地区应力场的非均匀性；③滇缅活动地块区域构造应力场明显受周边板块作用的控制，活动地块内部由于构造格局及其运动的差异，应力状态具有明显的区域特征。根据研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征，可以将滇缅活动地块初步分为3个应力区。 相似文献
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利用目前国际上较为流行和普遍接受的基于P波初动符号和振幅比HASH方法，研究给出川滇地区2003年1月1日-2012年12月31日1 893次M3.0以上地震震源机制解。选择1 651个可靠的中小地震震源机制解，采用基于中小地震震源机制解的Hardebeck和Michael的阻尼区域应力场反演方法，研究区域的水平最大主压应力方向。结果表明：川滇菱形块体南段红河断裂带尾部左右两侧应力方向相同，水平最大主压应力NW-SE向；川滇菱形块体内部以丽江—小金河为界呈现出不同的应力状态，位于分界线以南的滇中块体水平最大主压应力NW-SE向，而在分界线以北取向基本上沿NS方向；从青藏高原内部到川滇菱形块体东边界应力方向整体有一定的顺时针旋转趋势；块体东边界从北部的NNE-SWW向逐渐过度到南部的NW-SE向。滇西及滇西南水平最大主压应力方向与构造方向基本平行，为近SWW-NEE向。 相似文献
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利用目前国际上较为流行和普遍接受的基于P波初动符号和振幅比HASH方法，研究给出川滇地区2003年1月1日-2012年12月31日1 893次M3.0以上地震震源机制解。选择1 651个可靠的中小地震震源机制解，采用基于中小地震震源机制解的Hardebeck和Michael的阻尼区域应力场反演方法，研究区域的水平最大主压应力方向。结果表明：川滇菱形块体南段红河断裂带尾部左右两侧应力方向相同，水平最大主压应力NW-SE向；川滇菱形块体内部以丽江—小金河为界呈现出不同的应力状态，位于分界线以南的滇中块体水平最大主压应力NW-SE向，而在分界线以北取向基本上沿NS方向；从青藏高原内部到川滇菱形块体东边界应力方向整体有一定的顺时针旋转趋势；块体东边界从北部的NNE-SWW向逐渐过度到南部的NW-SE向。滇西及滇西南水平最大主压应力方向与构造方向基本平行，为近SWW-NEE向。 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20 km以上的中上地壳.龙门山地区震源优势分布在10~20 km，鲜水河断裂地震震源深度在10 km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5~10 km范围. 相似文献
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以位错理论为依据探讨了地震分类的理论基础,利用美国哈佛大学1977—2008年的震源机制解资料,采用地震三角形分类法,研究了中国川滇及邻近地区震源机制解124例,从地壳脆性变形的角度分析了川滇次级块体的变形形式。结果表明:整体上川滇及邻区的走滑断层、逆冲断层和正断层具有明显的分区性特征,受青藏高原SE方向的挤压,沿着鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带产生了大的剪切位移和变形带;同时,受缅甸弧挤压和四川盆地的阻挡,在缅甸弧前端和龙门山断裂带等地形成了强烈的挤压区,在云南大部分区域形成了扇形剪切应力变形区;而沿鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带所产生的大的剪切位移和变形直接作用在红河断裂带上,造成红河断裂带呈右旋向SE方向错动,引起其后延金沙江断裂至丽江-小金河断裂之间形成大的应力拉张区,构成了现今川滇及邻区地壳变形的最新格局 相似文献
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川滇地区中小震重新定位与速度结构的联合反演研究 总被引：8，自引：0，他引：8
通过震源与速度结构联合反演,利用2000年4月至2006年3月云南和四川区域地震台网给出的P波初至走时资料,确定了川滇地区的三维速度结构,同时获得了川滇地区6 642次中小地震的重新定位结果。结果表明:①川滇地区地震震源平均深度随震级增大而加深的特征明显,地震震级越大,震源深度越深,但震源下界不超过25 km;②在瑞丽-龙陵、丽江-小金河以及龙门山等断裂带以西地区,震源深度偏浅,大多在15 km以上,15 km深度以下地震稀少;③川滇地区中小地震分布具有与强震相同的地壳深部介质背景,震源大多分布于正、负异常过渡区的速度相对较高一侧,而其下方主要为低速异常分布。 相似文献
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文中选取金沙江下游水库区溪洛渡—乌东德段为研究区,采用CAP和GPAT方法获得区域内2016—2017年2. 0级以上地震的震源机制解,分析各分区震源机制解的空间分布特征,探究地震活动与区域构造的关系。研究结果表明:1)溪洛渡大坝及邻区的地震震源机制解以逆冲型为主,其次为走滑型,主要分布在峨边-金阳断裂带中段附近。节面走向在NNW—NE范围内的地震与区域断裂带的分布特征相符,且一些较大地震的发生受区域构造控制。2)尚未蓄水的白鹤滩、乌东德大坝及邻区的地震震源机制解的空间分布较为一致,其中左旋走滑型地震与小江断裂带和普渡河-西山断裂的活动性质相符。区域内存在多组断裂的交会部位,震源机制解的节面走向离散分布,孕震环境较为复杂。3)鲁甸地震余震区的震源机制解以逆冲型和走滑型为主,呈"L"形分布,其中长轴近EW向,短轴近NNW向。大量余震震源机制解结果显示,可能存在近EW向的隐伏构造,不同类型的断层共同控制该地区的地震活动,发震构造十分复杂。4)各分区的地震矩心深度集中在5～15km范围内,推断研究区孕震层在深度为5～15km的中上地壳内。 相似文献
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本文用三维非连续变形与有限元相结合（DDA+FEM）的方法，在青藏川滇地区三维构造块体相互制约的大背景中，通过用GPS资料做位移速率边界约束和震源机制约束，计算得到研究区的初始位移场和应力场与该地区GPS测量结果和震源机制分布结果基本一致.在此基础上进一步数值模拟1997年玛尼7.9级大震的发生过程，研究大震引起研究区各块体边界断层应力状态变化的特征.（1）发震断层两侧发生左旋走滑错动，最大水平位错大约7 m；（2）深部位错面上位错分布与用地震波资料震源反演的结果类似；（3）最大差应力变化等值线图与由星载D\|INSAR技术获取的地表形变场图像相似；（4）地表垂直位移表明地震断层面略向北逆冲.计算模拟得到了玛尼地震发生引起青藏川滇地区构造块体系统各边界断层上库仑破裂应力变化的分布，表明玛尼大震的发生除了使其发震断层的两端库仑破裂应力增大，应力进一步集中外，位于上地壳层上东昆仑断裂中段的2001年昆仑山8.1大震（H=11 km）发震断层段的库仑破裂应力增加约2 MPa，位于中地壳层上喀拉昆仑断裂带中的2008年改则6.9级地震（H=30 km）发震断层段的库仑破裂应力也增加约0.7 MPa，可见这两个已接近破裂强度地段的失稳对发生大震起了一定促进作用.研究结果也表明：作者发展的三维DDA+FEM方法能有效地用于大震活动与各构造块体相互作用关系的研究. 相似文献
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基于CAP方法, 使用地震波形资料, 计算得到了2009年1月~2017年8月期间南北地震带及周边区域466个3.5级以上地震震源机制解。 在补充收集1976年1月~2017年8月GCMT公布的259个4.5级以上地震震源机制解的基础上, 分析了南北地震带地震震源机制解和应力特征。 震源机制空间分布显示, 不同断裂带、 块体间表现出不同的震源机制空间分布特征, 该特征与南北地震带不同段落活动构造性质基本吻合。 作为青藏高原东边界的南北地震带, 由于动力环境复杂, 其内部P轴方向具有明显的差异性。 这种差异主要表现为: 南北地震带北段P轴呈NE向分布; 龙门山断裂带及周边除NE段P轴取向为NW—NNW向外, 其他地段P轴近EW向; 川滇菱形块体内部P轴呈NNW向, 而其西边界以西呈NNE向, 东边界以东呈NW向, 应力方向转换带的与川滇菱形块体边界基本一致。 整体而言, 南北地震带及近邻P轴方向由北到南发生了顺时针转动。 相似文献
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QI Yu-ping ZHANG Zhi-wei LONG Feng XIAO Ben-fu LIANG Ming-jian LU Qian JIANG Peng 《地震地质》2018,40(2):377-395
The Daliangshan sub-block is a boundary region among the Bayan Har block, the Sichuan-Yunnan block and the South China block. It hosts four major fault systems:The southwest to south trending Xianshuihe-Zemuhe Fault zone in the west, the Longmenshan fault zone is the northern boundary, the Zhaotong-Lianfeng fault zone in the south, and the NS-trending Mabian-Yanjin fault zone in the east. This study focused on focal mechanisms and the regional stress field of the Daliangshan sub-block to help understand the earthquake preparation process, tectonic deformation and seismic stress interaction in this area. We collected broadband waveform records from the Sichuan Seismic Network and used multiple 1-D velocity models to determine the focal mechanisms of moderate and large earthquakes(ML ≥ 3.5)in the Daliangshan sub-block by using the CAP method. Results for 276 earthquakes from Jan 2010 to Aug 2016 show that the earthquakes are dominated by strike-slip and trust faulting, very few events have normal faulting and the mixed type. We then derived the regional distribution of the stress field through a damp linear inversion(DRSSI)using the focal mechanisms obtained in this study. Inversion results for the spatial pattern of the stress field in the block suggest that the entire region is predominantly under strike-slip and trust faulting regimes, largely consistent with the focal mechanisms. The direction of maximum compression axes is NW-NWW, and part of the area is slightly rotated, which is consistent with the GPS velocity field. Combining geodynamic background, this work suggests that because the Sichuan-Yunnan block is moving to SE and the Tibetan plateau to SE-E along major strike-slip faults, the stress field of the Daliangshan sub-block and its adjacent regions is controlled jointly by the Bayan Har block, the Sichuan-Yunnan block and the South China block. 相似文献
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We select the Xiluodu-Wudongde reservoir area in the downstream of Jinsha River as the research area, and use the CAP and GPAT method to obtain focal mechanisms of ML ≥ 2.0 earthquakes from 2016 to 2017 in this region. Then, we analyze the spatial distribution characteristics of focal mechanism solutions in each local region and investigate the relationship between seismicity and regional structures. According to 414 focal mechanism solutions we get following conclusions:1)The Xiluodu dam began to impound water on May 4, 2013, and seismicity increased significantly after impoundment. We get 49 focal mechanisms in the Xiluodu dam and its adjacent area which are dominated by thrust faulting and next by strike-slip faulting, which are mainly distributed near the middle section of the Ebian-Jinyang fault zone. The distribution of nodal planes striking in NNW to NE direction is consistent with that of regional faults, and some large earthquakes are controlled by regional structures. 2)There are 39 and 24 focal mechanisms obtained in the unimpounded Baihetan and Wudongde dams and adjacent areas, and the spatial distribution of focal mechanism solutions are relatively consistent, dominated by strike-slip faulting with a small amount of thrust and normal faulting. The sinistral strike-slip earthquakes are consistent with the activity of Xiaojiang fault zone and Puduhe-Xishan Fault. The strikes of the nodal planes are distributed discretely, and many groups of faults intersect with each other in the area, suggesting that the seismogenic environment is relatively complex. 3)The seismicity in Ludian continues to be active after the Ludian M6.5 earthquake. By the end of 2017, we got 260 focal mechanism solutions in the aftershock area of the Ludian MS6.5 earthquake of Aug 3rd, 2014, which show an "L-shape" in distribution and are dominated by thrust and strike-slip faulting. The long axis is distributed in EW direction, and the short axis is distributed in near NNW direction. The strikes of nodal planes are mainly near EW and near NE, and the nodal planes in the NW direction are less. According to characteristics of a large number of focal mechanism solutions, we deduce that there may exist a buried structure in the EW direction, the seismicity is controlled by different types of faults and the seismogenic structure is very complex. 4)The centroid depth in each region is concentrated in the range of 5~15km, indicating that the seismogenic layer in the study area is 5~15km deep in the middle and upper crust. 相似文献
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CHARACTERISTICS OF FOCAL MECHANISMS AND STRESS FIELD IN THE EASTERN BOUNDARY OF SICHUAN-YUNNAN BLOCK AND ITS ADJACENT AREA 
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下载免费PDF全文 This study is devoted to a systematic analysis of the stress state of the eastern boundary area of Sichuan-Yunnan block based on focal mechanisms of 319 earthquakes with magnitudes between M3.0 and M6.9, occurring from January 2009 to May 2018. We firstly determined the mechanism solutions of 234 earthquakes by the CAP method, using the broadband waveforms recorded by Chinese regional permanent networks, and collected 85 centroid moment tensor solutions from the GCMT. Then we investigated the regional stress regime through a damp linear inversion. Our results show that:1)the focal mechanisms of moderate earthquakes are regionally specific with three principal types of focal mechanisms:the strike-slip faulting type, the thrust faulting type and the normal faulting type. The strike-slip faulting type is significant in the eastern boundary area of Sichuan-Yunnan block along the Xianshuihe-Xiaojiang Fault, the Daliangshan Fault, and the Zhaotong-Lianfeng Fault. The thrust faulting type and the combined thrust/strike-slip faulting type are significant along the Mabian-Yanjin Fault, Ebian-Yanfeng Fault and the eastern section of Lianfeng Fault; 2)The most robust feature of the regional stress regime is that, the azimuth of principal compressive stress axis rotates clockwise from NWW to NW along the eastern boundary of Sichuan-Yunnan Block, and the clockwise rotation angle is about 50 degrees. Meanwhile, the angels between the principal compressive axis and the trend of eastern boundary of Sichuan-Yunnan Block remain unchanged, which implies a stable coefficient of fault friction in the eastern boundary fault zone of Sichuan-Yunnan Block. The movement of the upper crust in the southeastern Tibetan plateau is a relatively rigid clockwise rotation. On the whole, the Xianshuihe-Xiaojiang Fault is a small arc on the earth, and its Euler pole axis is at(21°N, 88°E). The Daliangshan Fault is surrounded by the Anninghe-Zemuhe Fault, which formed a closed diamond shape. When the Sichuan-Yunnan block rotates clockwise, the Daliangshan Fault locates in the outer of the arc, while the Anninghe-Zemuhe Fault is in the inward of the arc, and from the mechanical point of view, left-lateral sliding movement is more likely to occur on the Daliangshan Fault. Our results can be the evidence for the study on the "cut-off" function of the Daliangshan Fault based on the stress field background; 3)The regional stress regime of the eastern boundary faults zone of the Sichuan-Yunnan Block is the same as the south section of the Dalianshan Fault, and the focal mechanism results also reveal that the Dalianshan Fault is keeping left-lateral strike-slip. There may be the same tectonic stress field that controls the earthquake activities in the southern section of Daliangshan Fault and Zhaotong-Lianfeng Fault. The regional stress regime of Zhaodong-Lianfeng Fault is also the same with the Sichuan-Yunnan Block, which implies that the control effect of the SE movement of the Sichuan-Yunnan block may extend to Weining. 相似文献
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SEISMOGENIC STRUCTURE OF THE M4.9 AND M5.1 LITANG EARTHQUAKES ON 23 SEPTEMBER 2016 IN SOUTHWESTERN CHINA 下载免费PDF全文
下载免费PDF全文 YI Gui-xi LONG Feng LIANG Ming-jian ZHANG Zhi-wei ZHAO Min QI Yu-ping GONG Yue QIAO Hui-zhen WANG Zhi WANG Si-wei SHUAI Li-rong 《地震地质》2017,39(5):949-963
On 23 September 2016, two earthquakes with magnitude of M4.9 and M5.1 occurred successively near Litang city in Sichuan Province, southwestern China. These two events are located between two large-scale fault zones, i.e., the Jinshajiang and Litang faults, in the northwest of the Sichuan-Yuannan active block, eastern Tibetan plateau. Based on the phase data and waveform data from the Sichuan regional seismic network, the M4.9 and M5.0 mainshocks and 390 aftershocks have been relocated using the multi-step locating method, and the focal mechanism solutions and centroid depths for the two mainshocks were calculated by the CAP waveform inversion method. From the spatial distribution of the relocated aftershocks and fault plane solutions of the two mainshocks, combining with the seismic intensity map and tectonic setting, we suggested that the two earthquakes were generated by the E-W trending northward dipping Hagala fault. The nodal plane consistent with the strike and dip of the Hagala fault is interpreted as the coseismic rupture plane with a dip angle of 44° for both the M4.9 and M5.1 earthquakes. And we inferred that the M4.9 and M5.1 earthquakes may be resulted from the nearly E-W striking Hagala normal faulting in the upper crust between the Litang and Batang regions due to the continuous eastward extrusion of the material of the Qiangtang block in the west. 相似文献
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使用小震机制解资料 ,分析了 1975年海城 7 3级和 1976年唐山 7 8级强震及 1983年菏泽 5 9级和 1995年苍山 5 2级中强震前 ,震源区及其周围不同构造部位应力场的时、空变化 ,证实震前震源区附近应力场曾有某些异常改变 ,如唐山强震前震源区周围出现长达 4a多的小震机制解主应力轴一致性取向的现象 ,菏泽地震前小震机制解P轴“集中—转向” ,苍山地震前P轴偏转且一致性增强。同时还发现 ,唐山地震前应力场异常变化开始时间可能早于 1972年 ;震源区内的陡河台与源外区的昌黎台小震综合机制解反映出震前的受力差异 ;震源断层附近不同应力区内震源机制解和地震活动有时空动态差异。这些现象一定程度上提供了不同构造条件和应力背景下 ,中、强震前震源区不同构造部位力学状态的改变或地震孕育过程的信息 ,对研究不同地震的孕震过程及差异有一定意义。 相似文献
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STUDY ON THE SEISMOGENIC FAULT AND DYNAMICS PARAME-TERS OF THE 2014 MS6.6 JINGGU EARTHQUAKE IN YUNNAN 下载免费PDF全文
下载免费PDF全文 On October 17, 2014, a MS6.6 earthquake occurred in Jinggu, Yunnan. The epicenter was located in the western branch of Wuliang Mountain, the northwest extension line of Puwen Fault. There are 2 faults in the surrounding area, one is a sinistral strike-slip and the other is the dextral. Two faults have mutual intersection with conjugate joints property to form a checkerboard faulting structure. The structure of the area of the focal region is complex. The present-day tectonic movement is strong, and the aftershock distribution indicates the faulting surface trending NNW. There is no obvious surface rupture related to the known fault in the epicenter, and there is a certain distance from the surface of the Puwen fault zone. Regional seismic activity is strong. In 1941, there were two over magnitude 7.0 earthquakes in the south of the epicenter of Jinggu County and Mengzhe Town. In 1988, two mainshock-aftershock type earthquakes occurred in Canglan-Gengma Counties, the principal stress axes of the whole seismic area is in the direction of NNE. Geological method can be adopted to clarify the distribution of surficial fracture caused by active faults, and high-precision seismic positioning and spatial distribution characteristics of seismic sequences can contribute to understand deep seismogenic faults and geometric features. Thus, we can better analyze the three-dimensional spatial distribution characteristics of seismotectonics and the deep and shallow tectonic relationship. The focal mechanism reveals the property and faulting process to a certain extent, which can help us understand not only the active property of faults, but also the important basis for deep tectonic stress and seismogenic mechanism. In order to study the fault characteristic of the Jinggu earthquake, the stress field characteristics of the source area and the geometric parameters of the fault plane, this paper firstly uses the 15 days aftershock data of the Jingsuo MS6.6 earthquake, to precisely locate the main shock and aftershock sequences using double-difference location method. The results show that the aftershock sequences have clustering characteristics along the NW direction, with a depth mainly of 5~15km. Based on the precise location, calculations are made to the focal mechanisms of a total of 46 earthquakes including the main shock and aftershocks with ML ≥ 3.0 of the Jinggu earthquake. The double-couple(DC)component of the focal mechanism of the main shock shows that nodal plane Ⅰ:The strike is 239°, the dip 81°, and the rake -22°; nodal plane Ⅱ, the strike is 333°, the dip 68°, and the rake -170.31°. According to focal mechanism solutions, there are 42 earthquakes with a focal mechanism of strike-slip type, accounting for 91.3%. According to the distribution of the aftershock sequence, it can be inferred that the nodal plane Ⅱ is the seismogenic fault. The obtained focal mechanism is used to invert the stress field in the source region. The distribution of horizontal maximum principal stress orienation is concentrated. The main features of the regional tectonic stress field are under the NNE-SSW compression(P axis)and the NW-SE extension(T axis)and are also affected by NNW direction stress fields in the central region of Yunnan, which indicates that Jinggu earthquake fault, like Gengma earthquake, is a new NW-trending fault which is under domination of large-scale tectonic stress and effected by local tectonic stress environment. In order to define more accurately the occurrence of the fault plane of the Jinggu earthquake, with the precise location results and the stress field in the source region, the global optimal solution of the fault plane parameters and its error are obtained by using both global searching simulated annealing algorithm and local searching Gauss-Newton method. Since the parameters of the fault plane fitting process use the stress parameters obtained by the focal mechanism inversion, the data obtained by the fault plane fitting is more representative of the rupture plane, that is, the strike 332.75°, the dip 89.53°, and the rake -167.12°. The buried depth of the rupture plane is 2.746km, indicating that the source fault has not cut through the surface. Based on the stress field characteristics and the inversion results of the fault plane, it is preliminarily believed that the seismogenic structure of the Jinggu earthquake is a newly generated nearly vertical right-lateral strike-slip fault with normal component. The rupture plane length is about 17.2km, which does not extend to the Puwen fault zone. Jinggu earthquake occurred in Simao-Puer seismic region in the south of Sichuan-Yunnan plate. Its focal mechanism solution is similar to that of the three sub-events of the Gengma earthquake in November 1988. The seismogenic structure of both of them is NW-trending and the principal stress is NE-SW. The rupture plane of the Jinggu main shock(NW direction)is significantly different from the known near NS direction Lancang Fault and the near NE direction Jinggu Fault in the study area. It is preliminarily inferred that the seismogenic structure of this earthquake has a neogenetic feature. 相似文献
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利用福建地震台网记录的数字地震波形,采用基于P波初动和S/P振幅比(HASH)方法,反演了2010年8月至2014年12月间发生在福建仙游地区ML2.0级以上地震的震源机制解。结果表明,仙游地震序列中小地震震源机制解一致性较好,其节面走向、倾角及滑动角以及P、T轴优势分布十分明显。节面走向优势方向为北西向,与该区域沙县—南日岛断裂走向一致,震源破裂类型为近直立右旋走滑型。序列的发生主要受控于近南北向主压应力,与福建地区背景应力场方向存在一定差异。分析认为,仙游地震序列的发生主要受控于仙游地区小尺度区域的构造应力场,金钟水库水位变化与序列显著地震活动存在一定相关性,但对仙游地区构造应力场影响不明显。 相似文献
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丁青地区地震重定位、震源机制及其发震构造初步分析 总被引：1，自引：0，他引：1
文中利用青海省地震台网的宽频带数字记录,通过CAP反演等方法获取了西藏丁青8次MS≥3.0地震的震源机制解(1次地震的震源机制解来自USGS)。结果显示,7次地震以正断破裂为主,兼具少量右旋走滑分量,断层优势走向为NNE,P轴的优势方位为SWW,T轴的优势方位为SEE。同时,利用双差相对定位法获得了217个地震的重定位结果。重定位后,余震沿NE-SW向展布,与震源机制解的走向基本吻合,但与区域内主要走滑型断裂近EW的走向不一致。2015—2018年发生的地震主要分布在5~15km深度范围,2018—2020年震源深度范围缩小至7~12km,2018年以后震源深度的分布范围明显收窄。丁青地震发生在羌塘块体中部,域内既受到SN向印度洋板块与亚欧板块的强烈碰撞挤压作用,也存在EW向伸展构造活动。综合分析重定位、震源机制结果及地质构造背景等资料,认为2016年MS5.5、2020年MS5.1地震的发震构造可能是同一条NE走向的正断型断裂,发震断层面可能为节面I,即走向、倾角和滑动角分别为12°、58°、-103°与9°、57°、-101°的节面。由于丁青地区地质资料匮乏,无法明确具体的发震断裂。 相似文献
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PRELIMINARY APPLICATION OF FOCAL MECHANISM SOLUTIONS OF SMALL AND MEDIUM-SIZE EARTHQUAKES TO FAULT STABILITY ANALYSIS IN THE SOUTHEASTERN TIBETAN PLATEAU 下载免费PDF全文
下载免费PDF全文 Analysis of stress state of faults is helpful to understand crustal mechanical properties and seismicity. In the paper, we invert the horizontal crustal stress field in the southeastern Tibetan plateau using focal mechanism solutions of small and medium-size earthquakes, and apply them to estimate the stability of regional major faults.
Firstly, we collect focal mechanism solutions of small and medium-sized earthquakes in the southeastern Tibetan plateau. The dataset includes more than 1 000 focal mechanism solutions in the past twenty years. Magnitudes of these earthquakes vary from M3.0 to M6.0. Most of the focal mechanism solutions were determined using waveform inversion technique. Although most of focal mechanism solutions in the southeastern Tibetan plateau are strike-slip faulting, their spatial pattern is different in sub-regions. Normal faulting earthquakes mainly occurred in the western Sichuan region, reverse faulting earthquakes mainly occurred in the boundary zone between the Tibetan plateau and the South China craton, and strike-slip faulting earthquakes mainly occurred in the central and southern Yunnan region.
Next, we settle on a mesh with grid spacing of 0.5° in longitude and latitude in the region and invert the horizontal crustal stress field at each grid point. Spatial variation of the maximum principal stress axis in the southeastern Tibetan plateau shows a clockwise rotation around the eastern Himalaya syntax. The azimuth of maximum compressional stress axis is about 88.1° in the western Sichuan region, about 124.6° in the South China craton, and about 21.6° in the western and southern Yunnan region. The azimuth of regional maximum compressional stress is nearly parallel to the direction of terrain elevation gradient, and that of the minimum compressional stress is nearly parallel to the tangential direction of the topographic elevation contours. The spatial pattern reflects the control role of gravity spreading of the Tibetan plateau on the regional horizontal stress field.
Finally, we analyzed regional fault stability based on these collected focal mechanism solutions. The fault instability parameter (I) is defined based on the Mohr-Coulomb criterion and indicates the degree of fault approximating to rupture. The instability parameters on fourteen major faults in the southeastern Tibetan plateau were calculated. Our results show that the stability of the Lianfeng-Zhaotong Fault is the lowest before 2014 in the region, which indicates the fault zone is close to rupture at that time. Our results provide a new useful tool to assess regional seismic potential using dense focal mechanism solutions. 相似文献