InSAR约束下的2008年汶川地震同震和震后形变分析

2008年5月12日,青藏高原东缘的龙门山断裂带上发生了M_w7.9级汶川地震.本文通过分析覆盖汶川地震震中区域的ALOS/PALSAR像对的方位向偏移量来选择无明显电离层扰动影响的像对进行干涉处理,获取了高精度、连续的InSAR地表形变场.在此基础上,结合高精度GPS同震形变数据,采用同震、黏弹性松弛震后形变联合反演模型同时确定了汶川地震的同震滑动分布和龙门山地区的流变结构参数.研究结果表明,汶川地震是一个断层破裂非常复杂的地震事件,其中,北川段、岳家山段、虹口段和汉旺段的滑动以逆冲为主,而青川段以右旋走滑为主.滑动主要发生在10 km深度以上的区域,最大滑动量位于虹口段的东北端,达10.7 m.地震释放的总能量为9.28×10²⁰ N·m（M_w7.91）,与地震学的结果一致.联合反演模型确定的龙门山地区中下地壳的黏性系数为2×10¹⁸ Pa·s,为青藏高原东部地区的黏性系数提供了一个可靠的下限值.如果有更长时间的震后形变观测时间序列,将为该区域提供更为可靠的流变结构.     

Appraisal of a new 1D weighted joint inversion of ground based and helicopter‐borne electromagnetic data

In order to couple spatial data from frequency‐domain helicopter‐borne electromagnetics with electromagnetic measurements from ground geophysics (transient electromagnetics and radiomagnetotellurics), a common 1D weighted joint inversion algorithm for helicopter‐borne electromagnetics, transient electromagnetics and radiomagnetotellurics data has been developed. The depth of investigation of helicopter‐borne electromagnetics data is rather limited compared to time‐domain electromagnetics sounding methods on the ground. In order to improve the accuracy of model parameters of shallow depth as well as of greater depth, the helicopter‐borne electromagnetics, transient electromagnetics, and radiomagnetotellurics measurements can be combined by using a joint inversion methodology. The 1D joint inversion algorithm is tested for synthetic data of helicopter‐borne electromagnetics, transient electromagnetics and radiomagnetotellurics. The proposed concept of the joint inversion takes advantage of each method, thus providing the capability to resolve near surface (radiomagnetotellurics) and deeper electrical conductivity structures (transient electromagnetics) in combination with valuable spatial information (helicopter‐borne electromagnetics). Furthermore, the joint inversion has been applied on the field data (helicopter‐borne electromagnetics and transient electromagnetics) measured in the Cuxhaven area, Germany. In order to avoid the lessening of the resolution capacities of one data type, and thus balancing the use of inherent and ideally complementary information content, a parameter reweighting scheme that is based on the exploration depth ranges of the specific methods is proposed. A comparison of the conventional joint inversion algorithm, proposed by Jupp and Vozoff ( 1975 ), and of the newly developed algorithm is presented. The new algorithm employs the weighting on different model parameters differently. It is inferred from the synthetic and field data examples that the weighted joint inversion is more successful in explaining the subsurface than the classical joint inversion approach. In addition to this, the data fittings in weighted joint inversion are also improved.     

A parallel dynamic programming algorithm for multi-reservoir system optimization

This paper develops a parallel dynamic programming algorithm to optimize the joint operation of a multi-reservoir system. First, a multi-dimensional dynamic programming (DP) model is formulated for a multi-reservoir system. Second, the DP algorithm is parallelized using a peer-to-peer parallel paradigm. The parallelization is based on the distributed memory architecture and the message passing interface (MPI) protocol. We consider both the distributed computing and distributed computer memory in the parallelization. The parallel paradigm aims at reducing the computation time as well as alleviating the computer memory requirement associated with running a multi-dimensional DP model. Next, we test the parallel DP algorithm on the classic, benchmark four-reservoir problem on a high-performance computing (HPC) system with up to 350 cores. Results indicate that the parallel DP algorithm exhibits good performance in parallel efficiency; the parallel DP algorithm is scalable and will not be restricted by the number of cores. Finally, the parallel DP algorithm is applied to a real-world, five-reservoir system in China. The results demonstrate the parallel efficiency and practical utility of the proposed methodology.     

瞬变电磁场资料的联合时-频分析解释

本文充分利用瞬变电磁（TEM）信号包含的信息,采用联合时-频分析方法解释了TEM资料。文章选取了Wigner-Ville分布和Gabor展开的联合时-频分布（或表示）,将一维时间域信号拓展到时-频二维平面上,不仅将不同地电断面的响应成功地分开来,而且所显示的信号特征与地层电性结构之间有着明确的物理意义,从时间和频率两个方面同时描述了瞬变涡流场在地层中的激发和衰减的过程。利用时间窗数据和频率窗数据所进行的联合时-频反演,缩小了拟合差,提高了定量解释精度。     

JRC-JCS模型抗剪强度估算的平均斜率法

结构面对工程岩体的稳定性有着决定性的影响,结构面的抗剪强度参数是分析岩体稳定的关键的参数。本文回顾了结构面抗剪强度估算的JRC-JCS模型及其估算方法,提出了可快速估算结构面抗剪强度参数的平均斜率法,并通过对比分析阐明平均斜率法的优越性。     

Combining TEM/resistivity joint inversion and magnetic data for groundwater exploration: application to the northeastern part of Greater Cairo,Egypt

This paper presents the combination of two complementary methods, magnetic and joint inversion of resistivity/TEM data, as an effective approach to characterize groundwater reservoirs. Twenty stations of transient electromagnetic (TEM) and vertical electrical soundings (VES) were measured and interpreted using a joint inversion technique to evaluate the subsurface low resistivity zones connected to the groundwater reservoir. A complementary survey including 871 land magnetic stations was carried out at the same area to detect the upper surface of the basaltic sheet, which represents the bottom of the Miocene aquifer in the study area. The geological log from one borehole drilled in the zone was used to partially calibrate the calculated models. The results revealed that the study area consists of five different geological units with ages ranging from Paleogene (Oligocene) to Quaternary. The methodology provides good results at a very low cost when compared with drilling boreholes.     

VSP上下行反射波联合成像方法研究

VSP资料上下行波场发育丰富.本文在分析VSP直达波、上行反射波、下行反射波传播路径及其照明范围的基础上,指出了常规VSP波动方程偏移方法缺陷,进而通过修改波场延拓方式,提出了上下行反射波联合成像方法,并在高频近似下分析了该方法的成像原理.该方法不需要进行VSP上下行反射波场分离,能够同时对VSP资料中的一次反射波、自由表面多次波、层间多次波进行成像,比常规成像剖面具有更宽的成像范围和更好的成像效果.该方法能够对下行一次反射波进行成像,从而可以实现常规偏移方法难以处理的高陡倾角构造成像.模拟资料和实际资料处理证明了本文方法的正确性.     

新丰江库区上地壳三维细结构层析成像

在新丰江库区布设一个范围约50 km×40 km、由50个地震临时台站组成的观测台阵,接收来自不同方位的人工震源产生的莫霍界面反射波;台阵中的20个台站和5个区域固定台还对2009年3月至2010年5月发生在库区的地方震进行了观测.本文联合利用人工地震莫霍面反射波走时和天然地震直达波走时,采用连续模型反演技术重建了库区上地壳P波、S波慢度扰动和V_p/V_s扰动分布图像.研究结果表明:新丰江库区东、西部地区上地壳结构存在明显的差异.库区东部地区构造复杂,多条断裂在该区呈交叉状分布.北西向的石角-新港-白田断裂带在库区段内具有复杂的岩性和构造特征,该断裂带在新港至双塘一线可能延伸至地下8 km左右;近北东向的断裂带切割地壳较深.峡谷区及大坝以东附近地区存在上、下贯通的波速比高值区,尤其是大坝以西的深水峡谷区,存在一条顺河走向的陡倾角断层裂隙带,为库水渗透提供了良好通道.库区西部地区为相对稳定构造区,完整坚硬的花岗岩体透水性能较差,受库水渗透影响很小.新丰江水库诱发地震的形成与深部构造环境密切相关.峡谷区及大坝以东附近地区上地壳介质性质呈现明显的横向不均匀性,微震分布在介质物性结构的特定部位,"软"、"硬"交错的介质环境是倾滑正断层型微小震产生的可能原因.     

Determination of gravity anomaly at sea level from inversion of satellite gravity gradiometric data

Gravity gradients can be used to determine the local gravity field of the Earth. This paper investigates downward continuation of all elements of the disturbing gravitational tensor at satellite level using the second-order partial derivatives of the extended Stokes formula in the local-north oriented frame to determine the gravity anomaly at sea level. It considers the inversion of each gradient separately as well as their joint inversion. Numerical studies show that the gradients T_zz, T_xx, T_yy and T_xz have similar capability of being continued downward to sea level in the presence of white noise, while the gradient T_yz is considerably worse than the others. The bias-corrected joint inversion process shows the possibility of recovering the gravity anomaly with 1 mGal accuracy. Variance component estimation is also tested to update the observation weights in the joint inversion.     

基于广义的炮偏移方法实现地表多次波和一次波联合成像

多次波是地下反射层的多次波反射,也蕴含了地下反射界面的信息,因此并不是绝对地只能被当做噪音来处理.为实现对地下构造的准确成像,本文基于广义概念上的炮偏移成像算法,对常规一次波偏移方法从用于向下延拓的上、下行场以及成像条件方面进行了改进,将同时含有表层多次波的炮记录与脉冲震源之和作为下行延拓的震源波场,将同时含有表层多次...