三维粘弹性LDDA方法及其在地学中的初步应用

在二维弹性LDDA方法的基础上提出了三维粘弹性LDDA方法，并开发了相应的计算机软件．通过两个三维块体的摩擦滑动数值实验，证明了这个方法的理论和程序是正确和可靠的．用该程序研究了印度板块碰撞引起的东亚地区的现今速度场和沿主要断裂带的相对位移速率．初步结果表明，碰撞边界附近的速度最大，向内部衰减很快．青藏高原向北东方向运动，华北平原向东运动，东南亚向东南运动．在祁连山西南和东北速率变化的衰减梯度分别为0.05和0.007mm/a/km，衰减是非线性的，运动方向由北东转向近东西方向，变化很大．穿过龙门山断裂的速度衰减基本是线性的，其值为0.01 mm/a/km，运动方向为南东．印度板块碰撞对于东经115以东和北纬45以北的区域影响很小．由计算得到的速度场与GPS观测结果基本一致．计算得到的班公湖——怒江——澜沧江断裂带在近1Ma以来的相对滑动速率平均约0.5mm/a；金沙江断裂带相对滑动速率最大，为0.8 mm/a；郯庐断裂带基本不动．理论和计算表明，三维粘弹性LDDA方法可以用于研究具有断层的地球动力学问题．      

Three-dimensional velocity images in Yunnan and its neighboring district

Using the techniques of seismic tomography three-dimensional velocity images at crust and upper mantle in Yunnan province and its adjacent region have been successfully reconstructed. The results of image are: (1) The image of the velocity in the upper crust is closely related to the well-known geological structure of the surface, the Kangdian earth axis is a distinct high velocity area, and a high velocity rock stratum, which appoaching the surface of the earth, has been formed. (2) There is a low-velocity layer between 26°–31°N and 100°–104°E in deep crust, the depth of Moho discontinuity in Sichuan bass in is less than 50 km. (3) The results of seismological tomography not only reveal the lateral heterogeneity in the researched region, but also find approximately the strike of Honghe fault from the image at bottom of crust, and the velocity in both side of the fault are different obviously. (4) There is a low-velocity column within 25 km to 110 km in Tengchong region, which may be occured by upward moving of the basalt in the mantle. (5) In studied area, the thickness of the crust in west part is thicker than in southeast part. (6) From the image at bottom of the crust we can find that earthquakes with magnitude greater than 5 occurred in big velocity gradient zones, especially in transition zone between high and low velocity. There are a few earthquake in the low-velocity area. (7) We can see from Figure 6 that there still clearly exists lateral heterogeneity at 450 depth. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 61–67, 1993.     

Three-dimensional geological modeling and its application in Digital Mine

The 3D geological modeling is the prerequisite and core foundation for Digital Mine. Although this new technology brings new opportunities and motivation for the mineral exploration industry, it still has many difficulties to be solved in this area. Based on the characteristics of mine data and the aim of Digital Mine construction, this paper introduces a theory including multi-source data coupling, multi-modeling methods integration, multi-resolution visualization and detection, and multidimensional data analysis and application. By analyzing problems such as the uncertainty in each step of the modeling process, we designed a novel modeling method that can be applied to the complex geological body modeling, mineral resource/reserve estimation, and the mining exploration engineering. Along with the process of mine exploration, development, and reclamation, 3D modeling undergoes the process of “construction-simulation-revision” during which the 3D model is able to be dynamically updated and gradually improved. Based on the result of practical utilization, it is proven that the methodology introduced by this paper can be used to build an effective 3D model by fully using the mining data under the control of spatial information quality evaluation. Our experiments show that such a 3D model can be used to evaluate the mine resource and provide the scientific evidence to improve mining efficiency during the various stages of evolvement process in mine.     

Depth distribution of Moho and tectonic framework in eastern Asian continent and its adjacent ocean areas

It is the essence of the study on the dynamics of eastern Asian continent to investigate the ef-fects of geophysical field and the process of the deep block boundaries, and furthermore, to estab-lish a geodynamic physical-mathematical model based on the d…     

天山中东段地震层析成像的初步研究

以中国境内天山中东段为研究区域,选定新疆地震台网自2001年以来近10年的P波和S波震相,对研究区域网格化,反演了地壳P波速度结构。结果表明：地壳中成像分辨率较高,高低速分布明显,天山中东段莫霍面埋深在48～60 km内变化,其中,中天山莫霍面最深,北天山莫霍面最浅;莫霍面起伏最大的地方往往位于盆山交汇处。     

地震活动性模拟方法及太原地区地震活动性模拟

本文改进了地震活动性模拟方法,使模型可以使用GPS反演得到的断层滑动速率的结果作为应力加载,进行区域的地震活动性模拟.选取太原地区作为研究区域,模拟并分析太原地区地震活动性.计算太原地区长达20000年的理论地震目录,通过对理论地震目录进行分析发现模拟结果的震级频度关系与实际观测资料具有相似性.太原地区的震级大于6级的模拟地震在时间上表现出很强的随机性,与年平均发生率为0.0129a^-1的Poisson过程对比,当采用卡方检验进行检验时,置信水平达到99.0%;然而,单一断层的强震的时间分布与相应年平均发生率的Poisson分布并不完全相近,部分断层拟合置信水平为90%左右,部分断层置信水平接近为0.这一结果表明,用Poisson过程估计太原地区长期地震发生率是比较合理的,估计单一断层上的地震危险性不是十分合理.地震危险性模拟结果显示,太原盆地地区7级以上地震的复现周期为4000年.

     

变阻尼约束层析成像及其在VSP资料中的应用(英文)

初至波走时层析成像已经取得了广泛的应用,然而,由于观测系统的限制,射线在模型中分布不均匀,导致层析结果的分辨能力不足。变阻尼约束方法应用不均匀的先验信息来匹配不均匀的数据分布,可以减小速度模型校正量与射线覆盖程度的相关性。本文将变阻尼约束方法应用于初至波旅行时层析成像中,并将平滑约束方法加入正则化方程组中来避免单独使用变阻尼约束带来的不稳定性,利用阿尔法滤波器对反演中间迭代结果进行平滑和去噪,采用LSQR算法求解线性方程组来提高收敛速度和压制误差传递。本文应用上述层析成像算法对VSP观测系统进行速度反演,分别应用于检测板速度模型数据和实际VSP资料速度反演中,结果表咀变阻尼约束层析成像可以改善射线不均匀覆盖带来的影响,从而提高速度反演结果的质量;VSP资料检波点附近的速度反演结果可靠性高。     

基于小尺度构造约束的网格层析方法及其在火山岩发育区速度建模中的应用

速度场精度是影响偏移成像质量最为关键的因素,因此,速度模型的建立成为解决复杂地质体成像的核心工作.但在火山岩发育区,由于火山岩岩性、岩相复杂,空间相互叠置、尺度小等原因,导致地震波场复杂,成像难度大.常规基于网格的层析成像技术完全是数据驱动,其要求地震数据具有较高信噪比.而火山岩发育区地震反射杂乱,该方法无法满足精细建模需求.为此本文提出一种基于小尺度构造约束的网格层析速度建模方法.该方法既可以通过偏移距共成像点道集的剩余曲率对全局速度进行更新,也可以利用层位约束进行小尺度速度的局部修饰,即,在基于数据驱动的网格层析基础上通过地质约束提高速度模型精度.通过在渤海M油田的实际应用表明该方法在保证计算效率的同时大幅提高小尺度特殊构造体的反演精度,为后续火山岩发育区地震精确成像奠定坚实的基础.     

Crustal movement and deformation in Taiwan and its coastal area

Introduction Both Taiwan Island and Chinese mainland belong to Eurasian plate in geological structure. And the nearest distance between Taiwan Island and Fujian Province, which is located on the opposite coast, is only 130 km. Although there are high-precision GPS networks in both Taiwan and Fujian Province, joint GPS measurement cannot be made directly because of the inconvenient contact due to the strait between them. However, the GPS networks arranged on b…     

补偿向下延拓方法研究及应用

位场向下延拓是重、磁处理和解释的常用方法,但其不稳定性限制了其在资料处理及反演中的应用.本文基于补偿圆滑滤波思想以及空间域向下延拓迭代法,通过逐次补偿的办法实现位场的稳定向下延拓.同时,在频率域空间给出了该下延方法的频率域响应因子,并讨论了其低通滤波特性,理论模型和实际位场资料试验表明该方法向下延拓稳定性具有较高的延拓精度.将其应用于重力密度界面反演中,改进反演的稳定性,实际莫霍界面反演表明下延因子具备实用性.     

补偿向下延拓方法研究及应用

位场向下延拓是重、磁处理和解释的常用方法,但其不稳定性限制了其在资料处理及反演中的应用.本文基于补偿圆滑滤波思想以及空间域向下延拓迭代法,通过逐次补偿的办法实现位场的稳定向下延拓.同时,在频率域空间给出了该下延方法的频率域响应因子,并讨论了其低通滤波特性,理论模型和实际位场资料试验表明该方法向下延拓稳定性具有较高的延拓精度.将其应用于重力密度界面反演中,改进反演的稳定性,实际莫霍界面反演表明下延因子具备实用性.     

A study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunan region, China

Based on the first arrival P and S data of 4 625 regional earthquakes recorded at 174 stations dispersed in the Yunnan and Sichuan Provinces, the 3-D velocity structure of crust and upper mantle in the region is determined, incorporating with previous deep geophysical data. In the upper crust, a positive anomaly velocity zone exists in the Sichuan basin, whereas a negative anomaly velocity zone exists in the western Sichuan plateau. The boundary between the positive and negative anomaly zones is the Longmenshan fault zone. The images of lower crust and upper mantle in the Longmenshan fault, Xianshuihe fault, Honghe fault and others show the characteristic of tectonic boundary, indicating that the faults likely penetrate the Moho discontinuity. The negative velocity anomalies at the depth of 50 km in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with the temperature and composition variations in the upper mantle. The overall features of the crustal and the upper mantle structures in the Sichuan-Yunnan region are the lower average velocity in both crust and uppermost mantle, the large crustal thickness variations, and the existence of high conductivity layer in the crust or/and upper mantle, and higher geothermal value. All these features are closely related to the collision between the India and the Asia plates. The crustal velocity in the Sichuan-Yunnan rhombic block generally shows normal value or positive anomaly, while the negative anomaly exists in the area along the large strike-slip faults as the block boundary. It is conducive to the crustal block side-pressing out along the faults. In the major seismic zones, the seismicity is relative to the negative anomaly velocity. Most strong earthquakes occurred in the upper-mid crust with positive anomaly or normal velocity, where the negative anomaly zone generally exists below. Foundation item: National Scientific and Technological Development Program (95-973-02-02), the Climb Program (95-S-05-01) of National Scientific and Technological Ministry of China, and the State Natural Sciences Foundation of China (49874021). Contribution No. 02FE2004, Institute of Geophysics, China Seismological Bureau.     

A study on 3-D velocity structure of crust and upper mantle in Sichuan -Yunnan region, China

Many evidences indicate that the collision of two plates deformed strongly the crust of the SYR, and the deformation has been continued up to the present. In addition, the SYR is in the south segment of the South-North Seismic Zone of China, which is one of the regions in the Chinese mainland, where the seismic activity is very high, and the strong earthquakes frequently occurred. Since the 1970s, a series of large earthquakes with magnitude M>7.0 occurred in SYR, such as the 1970 Tongha…     

Regional variations in abrupt-change sequence of georesistivity and its application in earthquake prediction

Based on fracture mechanics, large amount of practically observed data is analyzed in this paper, and it is disclosed that seismically-anomalous earthquake resistivity sudden change sequence can be observed at the earth resistivity stations around the epicenter of a strong event. The maximum sudden change in the sequence tends to shift backward with the increase of epicentral distance, while it shifts forward with the increase of the magnitude of the earthquake. The maximum sudden change also expands from the epicenter to the peripheral areas. Therefore, the authors propose that it might be possible to predict the 3 key elements of a forthcoming earthquake by using the sudden change sequence, the frequency of the sudden change, the expansion velocity of the maximum sudden change and the time-distance product. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 176–185, 1993.     

东亚磁异常及其对中国东北地区地磁场的影响

利用东亚及邻区４９个地磁台１９７０－１９７９年、Ｈ、Ｚ的实测年均值，逐年计算、缓制了蒙古异常的地磁非偶极场等值图，给出了蒙古异常非偶极场Ｚｎ分量的焦点位置和强度变化及其对中国东北地区地磁场的影响量级，计算表明蒙古异常的年变化是该区地磁场年变化的主要成份。     

兴蒙造山带及邻区地壳速度结构特征

兴蒙造山带位于中亚造山带东段, 作为古亚洲构造域的重要组成部分, 由西伯利亚板块与华北板块碰撞拼合而成, 其经历了大陆裂解、洋盆扩张、洋壳俯冲消减和碰撞拼合造山等复杂的构造演化过程.为了利用壳幔结构约束造山带演化的深部过程, 跨越华北地块北缘、松辽—锡林浩特地块、兴安地块以及索伦—西拉木伦缝合带和二连—贺根山缝合带, 实施了一条520 km长的深地震测深剖面, 获得了高质量的人工源大当量的宽角反射和折射地震资料, 并采用地震动力学射线方法获得地壳速度结构.结果显示: (1)研究区地壳平均速度为6.15~6.3 km·s^-1, Pn波速度为7.8~8.2 km·s^-1; (2)地壳厚度约为36.1~42.2 km, 最厚位置(~42.2 km)对应地表大兴安岭主峰, 说明大兴安岭在此位置存在山根; (3)地壳速度在1.5~6.8 km·s^-1范围内, 认为在该区地壳内不存在洋壳物质; (4)主要断裂带或缝合带位于速度等值线变化剧烈的梯度带上; (5)速度结构显示研究区具有明显的横向分区和纵向分层的特点.地壳内速度剧烈变化特征表明兴蒙造山带的地壳物质组成不均匀, 尤其中下地壳, 速度等值线起伏剧烈.这种复杂的地壳速度结构应该与中生代以来多板块汇聚引发的多期区域性伸展和挤压作用有关.

     

一种实时场地校正方法及其在地震预警中的应用

地震预警系统对地震数据处理的实时性要求极高。其系统数据来源除布设在基岩的测震台站外,还有大量非基岩场地的强震动台站和地震烈度仪台站,其场地影响不容忽视。为了考虑震级估算和地震动场预测中的场地影响,需实时对各种场地条件下的地震波形进行校正。目前处理一般使用某个标量来表征场地放大效应。本文采用一种实时的场地校正方法,首先计算目标场地与参考场地的谱比,然后通过最小二乘法、双线性变换将谱比转化为因果递归的无限冲激响应(IIR)时域滤波器,之后可以应用该滤波器进行实时场地校正。该方法考虑了场地放大系数的频率依赖性,相比于标量校正提高了准确度。应用我国四川和日本部分强震动台站记录,验证并讨论了这种实时场地校正方法在地震预警中的应用效果。     

黏弹性介质VSP记录模拟及在估算Q值研究中应用

采用标准线性固体模型,本文建立了黏弹性介质完全匹配层吸收边界的高阶速度-应力交错网格有限差分算法,并对黏弹性介质中的地震波传播进行了数值模拟.基于黏弹性波动方程正演模拟提供的零偏VSP全波场数据,本文进行了质心频移法计算Q值的反演分析.结果表明,反射波、转换波及短程多次波对频谱的影响较大,对Q值反演造成一定误差.本文的结论为实际零偏VSP资料估算地层Q值提供了有益的指导.     

青藏高原冈底斯带及邻区重磁三维反演及岩浆岩特征研究

岩浆岩在青藏高原的大陆动力学研究中有着重要的作用,它既是构造演化的记录,又是重要构造-岩浆-成矿带的指示.本文主要基于冈底斯带及邻区的地面重力和航磁数据,首先进行地质-地球物理先验信息约束下的重磁2.5维交互式反演,再将2.5维反演结果作为参考模型加入到三维反演计算中,得到地下三维密度和磁化率结构.结合岩浆岩密度、磁化率统计资料和岩浆岩地球化学成果,推断研究区基性岩、Ⅰ型花岗岩和S型花岗岩的三维分布图,得到如下结论：S型花岗岩主要分布在冈底斯东带和冈底斯弧背断隆带以北;北冈底斯的西部无明显的岩浆活动,而在其南侧和北侧,发现大量的隐伏基性岩和零散分布的Ⅰ型花岗岩;中生代Ⅰ型花岗岩在南冈底斯和冈底斯弧背断隆带广泛分布,且到新生代才出现大量的S型花岗岩.上述结果为中生代班公湖-怒江洋壳和新特提斯洋壳的双向剪刀式俯冲模式的观点提供了重要佐证,并认为班公湖-怒江洋壳在北冈底斯西部约84°E-88°E的范围内先后存在向北和向南俯冲的可能,北向羌塘地体下俯冲,南向冈底斯地体下俯冲.

     

Primary study on pattern of general circulation of atmosphere before uplift of the Tibetan Plateau in eastern Asia

The Tibetan Plateau is a key factor for the pattern of the general circulation of the atmosphere (GCA) in eastern Asia. The pattern of the GCA after the uplift of the plateau is well known, while the pattern of the GCA before the uplift of the plateau is lack of direct evidences. Based on the knowability of desert, a section recording wind directions across the Cretaceous northern hemisphere mid-low latitude desert belt is measured and the pattern of the GCA in the Cretaceous is revealed. The result shows that the eastern Asia was really controlled by the planetary circulation before the uplift of the plateau, i.e. westerlies in the north and northeast trades in the south. The convert belt between westerlies and trades had drifted northwards and southwards. The possibility of existence of paleo-monsoon is also dealt with and a possibly imposed paleo-monsoon is suggested.