板内和板间区域构造与地震

讨论会的第三个专题为板内和板间区域构造与地震.该专题共收到46篇论文摘要,其中来自俄罗斯、越南、印度、日本、中国、美国、伊朗、尼泊尔、泰国的学者在大会上宣读了28篇论文,中国、吉尔吉斯斯坦、印度、日本、俄罗斯、孟加拉国的学者展示了12篇张贴报告.     

1989年魁北克昂加瓦地震：一次复杂的板内事件

1989年12月25日在昂加瓦半岛发生了一次6.3级地震,这是魁北克北部地区至少60年来最大的一次事件,是北美东部历史地震中唯一被证实产生了地表破裂的地震。野外观测表明,该地震为逆断层和走滑断层运动的组合。波形模拟表明这次地震由两个子事件组成,开始是沿东北—西南走向的逆断层事件、随后是一次更大一点的沿北北东—南南西走向的走滑子事件。面波等效双力偶矩1.3×10~(25)dyne-cm(ldyn=10~(-5)N),两个子事件的矩比单个子事件矩几乎大一倍。子事件的深度都是3km,时间上相差0.9s,第二个子事件位于第一个子事件西南5.2km。波形模拟测定的震源参数和由地面观测导出的结果大体符合,但子事件断错上有些差别,如果走滑运动分布在破裂西南端的几条小规模断层上,或者没有发现完整的地面破裂,也许差别就不存在了。由断层面解推测的应力方向与加拿大北部地区大多数地震机制一致。昂加瓦地震和其他大陆板内地震一样,震源浅而复杂,且发生在早先尚未破裂的断层上。     

用地震反射法对玉溪盆地普渡河断裂的探测

通过在玉溪盆地用地震反射法探测普渡河隐伏断裂的实例, 阐述了在覆盖层很厚、 人口密集、 环境干扰强条件下的地震勘探方法技术. 本次勘探针对场地条件使用了大型可控震源和小检波距、 长排列、 高覆盖次数的观测系统. 获得的高信噪比时间剖面清晰地揭示了玉溪盆地内普渡河断裂的产状和规模. 勘探结果表明, 玉溪盆地覆盖层(N+Q)最大厚度超过820 m; 基岩面西陡东缓, 呈北北东走向的箕状分布; 普渡河断裂分两支穿过玉溪盆地西部, 主断裂为正断性质, 走向约N20°E, 倾向东, 视倾角75°—80°; 断裂规模由南向北逐渐变大, 基岩断距在盆地南部的大营街附近为40 m, 而在盆地北部的九龙池东部, 基岩断距增加到280 m左右, 穿过玉溪盆地西部的普渡河断裂错断了新近系上新统中上部地层.     

板内地震复发间隔对断层长度的标度关系研究及应用探索

虽然关于一些重要参数值仍然存在显著的不确定性，地学家们一致认为断层分布遵从幂律标度关系。本文我们把这些标度关系和地震分布的幂律标度关系结合起来获得了区域板内地震复发间隔对断层长度的标度关系式，再对其进行局部校准进而得到某一具体小地方的地震危险估计方法。小断层（未跨越孕震层与断４层）的标度资料表明地震复发间隔和断层长度的负幂成比例变化。由于最近认识到了大震标度中参数的不确定性，对于大断层（跨越孕震层的断层），其地震复发间隔是和断层长度的负幂还是和正幂成比例变化的问题是不确定的，这个问题对地震危险估计是至关重要的。     

层状断层与地震关系初探

通过讨论层状断层的性质、特点以及与正断层、逆断层和走滑断层的相互关系,探讨了大陆板内地震的发震机制,指出许多地震的震源位于层状断层面上,有些地震在地表找不到相应的地震构造的原因是由层间滑动所引起。     

板内逆断层地震破裂的基本特征及分段标志研究

通过对１６ 个板内逆断层地震的基本类型、构造环境、地震地表破裂尺度、几何形态、运动学特征及余震分布图像的研究分析,较系统地归纳了板内逆断层地震破裂的基本特征及分段标志．研究表明：（１） 逆断层破裂往往沿走向延伸较短,常表现为二维面状分布形态;（２） 地震断层未出露地表或仅有部分出露地表;（３） 逆断层地震破裂较走滑断层和正断层产生的地震破裂更为复杂,不仅表现在构成整体破裂带的各个单条破裂的力学性质差异方面,而且表现在几何结构方面．     

隐伏活动断层的多层次综合探测——以银川隐伏活动断层为例

以银川活动断层试验探测为例,介绍了第四纪巨厚沉积区隐伏断层多手段、多层次探测的步骤与方法。在对前人资料综合分析的基础上,选择银川市兴庆区新渠梢村为综合探测试验场。首先,分层次布施道间距10m、5m和1m的浅层人工地震勘探,由深至浅将银川隐伏断层主断层逐步控制在可以布施浅钻勘探的程度。然后,实施钻孔联合剖面探测,确定了断层的准确位置和倾角,获得了由钻探资料可分辨的断层上断点埋深8.3m的信息。最后,通过大型探槽开挖,查明了断层实际上断点埋深1.5m和5期古地震活动事件。结合地层年龄的初步测定,得出了银川隐伏断层主断层中—晚全新世活动的结论     

隐伏活断层探测中的精定位技术——以银川盆地芦花台断裂为例

以银川盆地芦花台断裂为例,探讨隐伏活动断层精定位技术。经浅层地震勘探查明,芦花台断层总体走向NNE,倾向SEE,倾角73°~78°。根据取自钻孔的地层样品沉积年龄测定,又将主断层分为南段和北段。芦花台隐伏断层南段中更新世活动,而北段全新世活动。通过对浅层地震勘探断层上断点上延伸计算,使其与钻探得到的断层上断点埋深相匹配。通过断层的精确定位,得到了芦花台隐伏断层在浅表的几何分布、产状及活动性分段特征的认识。所得成果为石嘴山市城市辖区内的建设提供了重要参考依据。     

ANALYSIS OF THE CONFIDENCE INTERVAL OF THE COMPOSITE FAULT PLANE SOLUTION OBTAINED FROM THE GRID SEARCH METHOD: AN EXAMPLE OF SOUTHERN JIANGXI PROVINCE

In order to quantitatively analyze the reliability of the composite fault plane solution of small earthquakes, the Bootstrap sampling technique is introduced into the grid search method, and the ideas and methods for calculating the confidence interval from the grid search method are proposed initially. There are two sample sets that can represent the characteristics of the composite fault plane solution. One sample set is the optional solutions obtained by the grid search method and the other is obtained by the Bootstrap sampling technique. Then, we calculate the confidence intervals of the two sample sets (P, B and T axis). The research results of tectonic stress field in southern Jiangxi Province are relatively few. In view of such situation, we use the focal mechanism solutions of small earthquakes to calculate and analyze the composite fault plane solution and the confidence interval. This study shows that the confidence interval of the principal stress axis can be obtained well by both of the sample methods. The reliability of the results and the confidence range of the principal stress axis can be better represented by the confidence intervals. The middle principal stress in southern Jiangxi Province is nearly vertical, and the maximum and minimum principal stresses are nearly horizontal. The direction of maximum principal stress is NWW-SEE and that of the minimum principal stress is NNE-SSW. And, the area is in a strike-slip stress regime. The results are consistent with previous studies, and the stress directions obtained by previous researchers are within the confidence interval calculated by this paper.     

中国东部城市地区隐伏断裂上断点与最新活动时代关系的初步分析——以邢台、唐山地震区为例

中国东部城市地区大多为较厚第四系松散物覆盖区,许多城市附近发育了具有相当规模的隐伏断裂。在这些第四系较厚覆盖区发育的隐伏断裂的上断点是否代表了断裂的最新活动时代?文中通过对邢台、唐山等发生过强震的中国东部城市附近地区地质、地球物理、地震活动、地形变等资料的综合分析,来讨论这些较厚第四系覆盖区隐伏断裂的上断点与断裂的最新活动年代的关系问题。初步分析表明,作为邢台地震和唐山地震发震断裂的新河断裂和唐山断裂带,并不象其上断点显示的为晚更新世不活动断裂或者为局部活动段,而均为大型活动断裂。由此认为,在中国东部沉积层较厚地区,不能完全根据断裂断错的最新地层确定断裂的最新活动时代。对于一条穿过新沉积较厚地区的断裂,其最新活动时代应根据构造背景、断裂对新地层的控制作用、断错最新地层、新地层沉积厚度、构造地貌、地震活动、地形变、现今构造应力场等综合判定     

姚安、大姚中强震区地震构造初析

对2009年7月9日云南姚安6.0级地震烈度考察和现场流动数字地震观测资料,以及自2000年以来在该地区发生的其它3次6级地震序列空间展布、震源机制、烈度分布资料的分析表明,该地区4次6级地震在震源深度、等震线长轴、序列优势空间分布等方面都具有各自的特点。结合石油部门提供的地震勘探资料综合分析认为,该地区地震构造背景十分复杂,突出表现为多方向地震构造的交织,且可能存在不同深度层次断裂构造的耦合     

地史时期地震事件的岩石学证据——以四川峨眉晚侏罗世湖泊沉积中的震积岩为例

震积岩(物)是地史时期地震事件的岩石学记录,其震积层序自下而上由微型递变断裂层、微褶皱层、碎块层和液化均一层组成。震积岩可作为古地震计,以了解地史时期地震的时空分布、地震强度和迁移规律。以作者发现的峨眉震积岩为例,描述了震积层序中的各种特征,总结了认识和辨别震积岩的标志     

地震-电成像联合探测试验——以淄博市活断层探测为例

在城市浅部活断层探测中,地震和电成像是2种主要的地球物理勘探手段。它们既可独立开展工作,也可在地质构造复杂地段进行联合探测,以更合理地解释探测区域的地质构造。文中利用电阻率和地震纵波速度之间的简单关系,进行了地震-电成像联合反演的初步探索。结果表明,通过参考电成像图像的电阻率分布,可获得合理的准二维地震波叠加速度模型,最终获得探测区域合理的地震时/深剖面,深化对地质构造的认识和提供合理的解释     

On the role of buoyancy force in the ore genesis of SEDEX deposits: Example from Northern Australia

Finite element modeling on a highly conceptualized 2-D model of fluid flow and heat transport is un-dertaken to simulate the paleo-hydrological system as if the Mount Isa deposits were being formed in the Mount Isa basin, Northern Australia, and to evaluate the potential of buoyancy force in driving ba-sin-scale fluid flow for the formation of sedimentary-exhalative (SEDEX) deposits. Our numerical case studies indicate that buoyancy-driven fluid flow is controlled mainly by the fault penetration depth and i...     

COMPARISON OF METHODS FOR DISTINGUISHING DIFFERENT GRADES OF GEOMORPHOLOGIC SURFACES BASED ON SEDIMENT PARTICLE SIZE FEATURES: TAKING THE QINGYIJIANG RIVER BASIN AS AN EXAMPLE

When using river geomorphology to study tectonic deformation, it is often difficult to distinguish the same level geomorphology in areas with severe weathering. In this paper, we take the geomorphologic surfaces of the Qingyijiang river basin as an example and try to distinguish the geomorphic surfaces by the sediment features that make up them. In order to distinguish different geomorphic surfaces, the traditional particle-size analysis method, SOFM network method and system clustering analysis method are taken to classify 29 samples from different geomorphic surfaces. The classification results of the three methods are different to a certain extent. We analyzed and compared the classification results of the three methods in detail. The results show that the traditional particle size analysis method, SOFM network method and cluster analysis method all can distinguish the geomorphic surface of different genesis, besides, they also can distinguish low-level terraces(T₁, T₂)and high-level terraces(T₃, T₄)for different grades of river terraces. Furthermore, the results also show that SOFM network method and cluster analysis method can make a certain distinction for the low-level terraces(T₁, T₂), while the traditional particle size analysis method is difficult to distinguish them. In addition, we analyzed and compared the three methods from the classification results, the results presentation, the operation process, and the error transmission. The results suggest that the advantages and disadvantages of the three methods are obvious. From the perspective of the classification results, the three methods all can distinguish the river terraces and alluvial fans and can make certain discrimination for different levels of river terraces. From the presentation of the results, the result of SOFM network is simple and clear. From the operation process, the traditional particle-size analysis method is relatively cumbersome, and the SOFM network method and the cluster analysis method are relatively simple to operate. From the perspective of error transmission, the traditional particle-size analysis method calculates the partial particle size feature value of the sample, which has a certain loss for the particle size distribution information of the whole sample. The error of the clustering analysis method has cumulative features and the influence exists consistently. The classification results of the SOFM network are independent of each other, which effectively avoids the problem of such error transmission of clustering analysis method. Overall, the classification results of the SOFM network method are simple and clear, the operation is simple, and the error is small. It has stronger adaptability to identifying different levels of different geomorphic surfaces. The results of this study will provide a simple and effective means for distinguishing different levels of geomorphic surfaces.     

川滇地区应力场演化与强震间相互作用的三维有限元模拟

针对川滇地区，在大量搜集、总结前人资料和结果的基础上，建立了包括上地壳、下地壳(两层)、上地幔等4层结构的三维有限元模型. 通过反复调试，确定了其边界条件，并且计算了川滇地区背景应力场、断层蠕动产生的应力场和强震触发的应力场，以及它们的动态变化. 结果表明:后续地震大多发生在前面地震引发的库仑破裂应力正值区，前一地震对后续地震有一定的触发作用，强震是在较高的应力背景下成组发生的. 这对判断、识别地震异常，提高地震预测水平有着很大的意义.