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活动断层运动的重力场反演 总被引：4，自引：0，他引：4
阐述了断层错动引起地表地表重力变化的基本原理,给出了弹性半无限空间点源位错到矩形位错引起的重力变化的基本解析式,并将结论推广到多个断层,介绍了利用重力变化反演断层运动的基本思路。以滇西实验场作为实用实例,对１９９６年２月丽江７．１级地震发生前后场区内的活动断层运动进行了演算,给出了断层位位移解,并与已有资料相比较,结果基本一致,但误差分析结果表明本文错模型还有待于改善。 相似文献
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重力资料在确定震源破裂模型以及寻找地震前兆信息都发挥着不可或缺的作用。为分析地震错动在地表导致的重力变化,根据Okubo位错理论公式,首先计算分析典型断层滑动(走滑、倾滑)在地表的重力变化特征：(1)垂直走滑断层引起的重力变化总体呈现出四象限对称分布,且在震中的同一方位上重力变化大小随着远离断层而逐渐缩小;相同破裂尺度和滑动量的垂直走滑断层,深度越深,震中附近的重力变化幅度越小,而自震中向远处的重力变化幅度的衰减越慢。(2)倾滑断层上盘重力变化的数值总体上比下盘重力变化的数值小;对于相同破裂尺度和滑动量的倾滑断层,破裂中心深度越深,远处的重力变化最大值越小。为分析2022年门源地震产生的重力变化,根据该地震的同震破裂模型,按照子破裂产生的重力变化叠加的方式计算震中周围的重力变化,得到：门源地震震中东北和西南方向重力降低,最大变化达-8.82μgal;而震中西北和东南方向的重力增加,最大变化达28.28μgal,重力增加的区域范围要比重力减小的区域范围小。震中附近的门源台重力增加3.40μgal,能够被重力仪器监测到,而震中周围的其他的前兆台的重力变化不足1μgal。在监测和分析该地区长... 相似文献
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介绍了北京大灰厂试验场（简称京西试验场）的概况，对１９９３年３月以来重力重复观测资料进行了处理。计算了各期重力观测精度，结果显示１９９３年３月￣１９９５年５月京西试验场存在一定重力变化，采用给定的模型反演了八宝山断层介质的密度变化，认为断层破碎带介质密度的变化可能是引起地表重力变化的主要因素。 相似文献
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断层错动是否会对工程造成影响是工程建设无法避开的问题,实验研究是解决这一问题的有效途径之一.常重力模型实验是指在自然环境1g条件下的模型实验,被普遍应用在模拟不同类型断层错动产生的地表变形破裂研究中,并获得了较为丰富的研究成果.文中系统地梳理了常重力模型实验在模拟断层上覆土体破裂研究方面的应用历史与现状,研究了不同因素... 相似文献
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南口—孙河断裂和南口山前断裂北段断层活动参数的重力反演 总被引：1，自引：0，他引：1
理论和观测实践表明,断层位错滑动会引起断层周围的局部重力场变化,利用局部重力异常可以反演断层地质活动参数.重复重力测量能获取局部重力场的动态变化,利用其测量结果反演断层的活动参数(走滑、倾滑、引张),定量化研究断层的现今运动过程,为强震孕育过程、机理研究探寻新的理论依据. 相似文献
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根据点源位错引起的地表重力变化和形变的理论公式,应用数值算法求得半无限空间任意产状断层位错在地表的重力变化和形变．计算结果表明,产状和位错方式是决定断层的地表重力和形变效应的基本因素．铲式断层活动的地表重力和形变效应与矩形断层相比有显著差异．断层位错引起的重力变化、垂直形变、视垂直形变的图象特征相似．根据重力变化和形变的特殊图象特征,有可能从观测资料中提取断层活动引起的重力变化和形变信息,判识和估计发震断层的几何学和运动学特征． 相似文献
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断层活动方式与地震地表变形分布特征研究 总被引：2，自引：0，他引：2
基于断层弹性位错理论及断层滑动非均匀模型,用三维有限元方法计算了发震断层逆断、正断和水平走滑三种不同活动方式下的地表变形,探讨了断层不同活动方式下的地震应变与位移的分布规律及震级、断层倾角对地震地表变形分布的影响。研究结果表明,地震地表变形影响因素很多,如地质构造条件、岩性介质特征、断层活动强度、断层产状和区域构造应力场等,但分布形态最终决定于断层活动方式,变形大小则决定于断层活动强度,其它均为局地因素,只影响分布形态的局部扭曲。断层不同活动方式下的地震地表变形分布各有其自身的规律和特点,这些分布特征可作为地震研究及近活动断层建筑工程抗震设计或加固防护参考。 相似文献
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使用布格重力资料对郯庐断裂带的中段部分（沂沭断裂带）进行了研究. 结果表明, 郯庐断裂带莫霍面及地壳内界面均发生错断,断裂带两侧地壳各界面起伏平缓. 该结果与前人的郯庐断裂带是切穿地壳的深大断裂的认识相一致. 在郯庐断裂带两侧,地壳结构明显不同,西侧沉积层较薄,平均在5 km以下;东侧多数在6 km以上;在断裂带中央沉积物最薄,大约为3～4 km. 断裂带东侧莫霍面埋深浅,大约为33～34 km;西侧莫霍面埋深明显增加,达到36～38 km．反映了莫霍面深度在断裂带附近整体是向西增加的. 郯庐断裂带在重力场分布中则表现为一条宽度较大的线性布格重力异常梯度带. 相似文献
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文中通过多源数据融合、模型构建、数据试验、二维离散小波变换和功率谱分析等方法获取了大别造山带东段深、浅部场源布格异常及其场源似深度,并结合地壳结构、地质构造、岩石圈有效弹性厚度和地震活动等资料,讨论了地壳深、浅部的结构特征及地震活动构造背景。结果表明,低频布格异常显示大别造山带东段与华北地块间深部构造缝合带在东部应位于青山-晓天断裂前缘,在落儿岭-土地岭断裂和商城-麻城断裂之间向N偏移至梅山-龙河口断裂之下,造山带南侧与扬子地块间深部构造缝合带位于襄樊-广济断裂以北约20km,造山带东侧与扬子地块间的深部构造转换带位于郯庐断裂带之下,造山带东段腹地显著的低频布格异常低值表明对应部位的莫霍面存在明显下凹,造山带内部的布格异常高梯度带表明其深部结构不完整;高频布格异常揭示肥中断裂、六安-合肥断裂、肥西-韩摆渡断裂和郯庐断裂带等主要断裂对地壳中上部密度结构的影响明显,落儿岭-土地岭断裂对地壳中上部密度结构的影响范围向N延伸至肥西-韩摆渡断裂前缘。结合地震活动资料进一步分析认为,大别造山带东段与华北地块在青山-晓天断裂前缘附近接触和相互作用,且大别造山带东段地壳深、浅部结构均不完整,不利于应力积累,趋向于在断裂交错的脆弱部位频繁释放应力,是霍山地区小地震活动频繁的主要原因。 相似文献
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观测断层气体的动态,研究它的异常变化与地震的相关性,是一种新的短临预报方法。1990年青海茫崖6.7级地震、共和6.9级地震前,断层气Rn、Hg的异常变化特点是临震突变幅度大、异常反应范围广。 相似文献
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ANALYSIS ON STRUCTURAL FEATURES:INSIGHTS FROM SATELLITE-DERIVED GRAVITY MODEL AND SEISMIC PATTERN 
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下载免费PDF全文 In this paper, based on a large number of cumulative observational data from the seismic monitoring network in China, we grid the research area to calculate the density values at each grid node and convert the qualitative earthquake epicenter distribution to quantitative seismic pattern. Minimum magnitude of completeness(MC)is determined by magnitude-rank analysis, which provides lower limit earthquake and original time. New satellite-derived gravity model v23.1, which is based on satellites CryoSat-2 and Jason-1 data, is used to determine the Bouguer gravity anomaly derived from free-air gravity anomaly and elevation database sets SRTM30, and ultimately, the complete Bouguer correction is obtained. In this paper, the Xingtai earthquake zone and Tanlu fault zone (Anhui segment) are selected for case study. Bouguer gravity anomaly presents a NE-trending U-shaped narrow strip in the Xingtai earthquake zone, and its location is consistent with Shulu Fault Basin. Grid density value contours are restricted by the U-shaped strip, and the extreme value of seismic activity density lies in the bottom of the U-shaped strip as shown in the cross section. The results of Bouguer gravity anomaly and upward continuations to the different heights show good linearity and gradient in the Tanlu fault zone (Anhui segment); and both long-axis direction of seismic pattern and nodal plane strike of seismogenic fault from focal mechanism solutions trend NNE. In short, the Tanlu fault zone(Anhui segment)is a large deep-seated fault that still has the ability to control seismic activity along it. Based on the measured gravity and magmatic data, using the edge detection TDX method to interpret the concealed boundary of the Anqing M4.8 earthquake near the Tanlu fault, and combining with the results from deep seismic reflection profiles of the study area, we discussed the causative fault of the Anqing earthquake. 相似文献
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研究龙门山及邻区地壳密度结构对于认识该地区地震活动性具有重要意义.根据龙门山及邻区( 100°～105°E,28°～33°N)的布格重力异常资料,选取了跨越龙门山断裂带的6条重力测线,在深地震测深资料约束下,使用Geosoft软件分别反演出了龙门山地区地下的沉积层、康拉德界面和莫霍面的深度分布.研究结果表明:龙门山断裂带两侧的地壳结构明显不同,西面高原地区沉积层较薄,大部分为基岩出露;而东边盆地沉积层明显较厚,多在6km以上.莫霍面和康拉德面在两侧均相对平缓,康拉德面从东部的大约24km增加到青藏高原山区的35km左右;莫霍面深度从东部盆地的大约42km增加到西部青藏高原的67km左右.龙门山断裂带整体表现为一条近SN向的陡变重力梯度带,并在其地壳内各界面均发生错断,莫霍面和康拉德面错断距离分别达6 ～ 7km和3～ 5km.该区地壳的这种陡变和不均匀性是导致地震活动性强烈的主要原因之一. 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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基于EGM2008重力场模型计算获得了渭河盆地及邻区布格重力异常。采用小波多尺度分解方法对布格重力异常进行了4阶小波逼近和小波细节分解,同时基于平均径向对数功率谱方法定量化地计算出1~4阶小波细节和小波逼近所对应的场源平均埋深。结合区域地质和地震资料,对获得的重力场结果进行分析,得到如下结论:①鄂尔多斯地块、渭河盆地、秦岭造山带3个一级构造单元的布格重力异常之间存在明显差异;构造区内部重力异常也存在横向的显著差异。布格重力异常的走向、规模、分布特征与二级构造区及主要的断裂具有一定的对应关系。②渭河盆地及邻区布格重力异常1~4阶细节对应4~23 km不同深度的场源信息,鄂尔多斯地块南缘东、西部的地壳结构存在明显的差异;渭河盆地凹陷、凸起构造区边界清晰,断裂边界与重力异常边界具有较好的一致性;秦岭造山带重力异常连贯性不好,东、西部重力异常变化特征表现出明显的差异。③渭河盆地及邻区布格重力异常分布与莫霍面埋深具有非常明显的镜像关系。渭河盆地及邻区地震主要分布在六盘山—陇县—宝鸡断裂带、渭河断裂与渭南塬前断裂交汇处、韩城断裂与双泉—临猗断裂交汇处。渭河盆地及邻区重力异常主要由中上地壳剩余密度体所影响,这可能是该区地震以浅源地震为主的主要原因。 相似文献
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A method is described to locate secondary faults, which can be difficult to identify on the Bouguer gravity map. The method is based on cross-correlation between the theoretical anomaly due to a vertical step and the second vertical derivative of the Bouguer anomaly. Faults are located from the closed maxima and minima on the cross-correlation contour map calculated for two perpendicular directions. One-dimensional model computations show that the magnitude of the extremum of the cross-correlation is related to the depth to the top of the hanging wall and the throw of the fault. Application of the method to the Bouguer gravity map of the former mouth of the Yellow River in the Shengli Oilfield area near the Bo Hai Sea shows the effectiveness of the method. 相似文献
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Gravity anomaly and crustal density structure in Jilantai rift zone and its adjacent region 下载免费PDF全文
下载免费PDF全文 This paper deals with the interpretation of Bouguer gravity anomalies measured along a 250 km long Suhaitu-Etuokeqi gravity profile located at the transitional zone of the Alxa and Ordos blocks where geophysical characteristics are very complex. The analysis is carried out in terms of the ratio of elevation and Bouguer gravity anomaly, the normalized full gradient of a section of the Bouguer gravity anomaly (G h ) and the crustal density structure reveal that (1) the ratio of highs and lows of elevation and Bouguer gravity anomaly is large between Zhengyiguan fault (F4) and Helandonglu fault (F6), which can be explained due to crustal inhomogeneities related to the uplift of the Qinghai-Tibet block in the northeast; (2) the main active faults correspond to the G h contour strip or cut the local region, and generally show strong deformation characteristics, for example the Bayanwulashan mountain front fault (F1) or the southeast boundary of Alxa block is in accord with the western change belt of G h , a belt about 10 km wide that extends to about 30 km; (3) Yinchuan-Pingluo fault (F8) is the seismogenic structure of the Pingluo M earthquake, and its focal depth is about 15 km; (4) the Moho depth trend and Bouguer gravity anomaly variation indicates that the regional gravity field is strongly correlated with the Moho discontinuity. 相似文献