2-D crustal structure of Changbaishan-Tianchi volcanic region determined by seismic traveltime inversion

2-D velocity structure and tectonics of the crust and upper mantle is revealed by inversion of seismic refraction and wide-angle reflection traveltimes acquired along the profile L1 in the Changbaishan-Tianchi volcanic region. It is used in this study that seismic traveltime inversion for simultaneous determination of 2-D velocity and interface structure of the crust and upper mantle. The result shows that, under Changbaishan-Tianchi crater, there exists a low-velocity body in the shape of an inverted triangle, and the crustal reflecting boundaries and Moho all become lower by a varying margin of 2-6 km, forming a crustal root which is assumed to be the Changbaishan-Tianchi volcanic system. Finally, we make a comparison between our 2-D velocity model and the result from the studies by using trial-and-error forward modeling with SEIS83.

SOLVING THE VELOCITY PARAMETER OF THE 2-D WAVE INVERSE PROBLEMS WITH THE INTEGRATION-CHARACTERISTIC METHOD

For the 2-D wave inverse problems introduced from geophysical exploration, in this paper, the author presents integration-characteristic method to solve the velocity parameter, and then applies it to common shotpoint model data, in noise-free case. The accuracy is quite good.

A Two-step Inverse Method for Quantitative Damage Evaluation of Plate-like Structures Using Vibration Approach

This study presents a novel two-step approach to assess plate-like structural laminar damages,particularly for delamination damage detection of composite structures.Firstly,a 2-D continuous wavelet transform is employed to identify the damage location and sizes from vibration curvature data.An inverse method is subsequently then used to determine the bending stiffness reduction ratio along a specified direction,enabling the quantification of the delamination severity.The method employed in this study is an extension of the one-dimensional inverse method developed in a previous work of the authors.The applicability of the two-step inverse approach is demonstrated in a simulation analysis and by an experimental study on a cantilever composite plate containing a single delamination.The inverse method is shown to have the capacity to reveal the detailed damage information of delamination within a constrained searching space and can be used to determine the effective flexural stiffness of composite plate structures,even in cases of complex delamination damage.

Electronic Absorption Spectra and Third-Order Nonlinear Optical Property of Dinaphtho[2,3-b:2’,3’-d]Thiophene-5,7,12,13- Tetraone (DNTTRA) and Its Phenyldiazenyl Derivatives: DFT Calculations

Third-order nonlinear optical (NLO) materials have broad application prospects in high-density data storage, optical computer, modern laser technology, and other high-tech industries. The structures and frequencies of Dinaphtho[2,3-b:2’,3’-d]thiophene-5,7,12,13-tetraone (DNTTRA) and its 36 derivatives containing azobenzene were calculated by using density functional theory B3LYP and M06-2X methods at 6-311++g(d, p) level, respectively. Besides, the atomic charges of natural bond orbitals (NBO) were analyzed. The frontier orbitals and electron absorption spectra of A-G5 molecule were calculated by TD-DFT (TD-B3LYP/6-311++g(d, p) and TD-M06-2X/6-311++g(d, p)). The NLO properties were calculated by effective finite field FF method and self-compiled program. The results show that 36 molecules of these six series are D-π-A-π-D structures. The third-order NLO coefficients γ (second-order hyperpolarizability) of the D series molecules are the largest among the six series, reaching 107 atomic units (10-33 esu) of order of magnitude, showing good third-order NLO properties. Last, the third-order NLO properties of the azobenzene ring can be improved by introducing strong electron donor groups (e.g. -N(CH3)2 or -NHCH3) in the azobenzene ring, so that the third-order NLO materials with good performance can be obtained.

Interannual variability of carbon cycle implied by a 2-D atmospheric transport model

A 2-dimensional atmospheric transport model is deployed in a simplified CO 2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.

Reconstruction of Temperature Field in 3-D, Absorbing, Emitting, and Anisotropically Scattering Medium

The soft measurement technology of flame temperature field is an efficient method to learn the combustion status in furnace. Generally, it reconstructs the temperature field in furnace through the image of flame, which is a process to solve radiative inverse problem. In this paper, the flame of pulverized coal is considered as 3-D, absorbing, emitting, and anisotropically scattering non-gray medium. Through the study on inverse problem of radiative heat transfer, the temperature field in this kind of medium has been reconstructed. The mechanism of 3-D radiative heat transfer in a rectangular media, which is 2 m×3 m× 5 m and full of CO2, N2 and carbon particles, is studied with Monte Carlo method. The 3-D temperature field in this rectangular space is reconstructed and the influence of particles density profile is discussed.

Comparative analysis of bed density, total phenol content and protein expression pattern in <i>Posidonia oceanica</i>(L.) Delile

Posidonia oceanicameadows are experiencing a progressive decline, and monitoring their status is crucial for the maintenance of theseecosystems. We performed a comparativeanalysis of bed density, total phenol content and protein expression pattern to assess the conservation status ofPosidoniaplants from the S. Marinella (Rome, Italy) meadow. The total phenol content was inversely related to maximum beddensity, confirming the relationship betweenhigh phenol content and stressful conditions. In addition, protein expression pattern profilesshowed that the number of differentially expressed proteins was dramatically reduced in the latest years compared to previous analyses. Our results support the usefulness of integrating solid descriptors, such as phenol content, with novel biochemical/molecular approaches in the monitoring of meadows.

Analysis of Dynamic Variations of Crustal Density in the Longmenshan Area before the Wenchuan M_S8.0 Earthquake

Based on the repeated gravity observation data from 1996 to 2007 from the Longmenshan gravity network, which has been dealt with by adjustment processing, the benchmark interference removal and impact of elevation changes removal, and by using the 3-D inversion method to reflect underground density, we analyze the characteristics of Longmenshan regional dynamic crustal density at depths of 25km, 20km and 15kin. The results show that in the Wenchuan earthquake preparation process, the regional density field showed marked characteristics both in time and space distribution. From the point of time process, the density change trend in the ten years before the earthquake presents a periodic change pattern： steady phase, dramatic stage, slow reducing phase and slow increase phase. The degree of density changes is from large to small, which means that earthquake gestation has reached the final stage. From the point of space distribution, density change distribution has a tendency of ＂dispersion--relative concentration＂, this shows that before the earthquake, the entropy of the underground density field was decreased. In addition, dramatic density changes often occur in the Longmenshan fault zone and western Sichuan plateau. Also, with the increase of depth, the trend of density change is more and more obvious. Through comparative analysis, the influence of density change on gravity is much bigger than that from height change.

Imaging Rock Density Distribution beneath Liwa Fracture Zone in the Southern Part of the Great Sumatran Fault System, Indonesia

We have imaged rock density distribution beneath Liwa fracture zone in the southern part of the the Sumatran Fault Zone by modelling and inverting Bouguer gravity data in two-and three-dimensional environments, respectively. The purpose of this study is aimed to figure out the subsurface distribution of rock densities associated with subsurface basement structure representing the evidence of trans-tensional tectonic product in the SF. In the gravity modeling, to eliminate distortions to the measured gravity values before modelling and inverting the data, Bouguer anomalies obtained in field measurements are reduced to the horizontal plane of z = +800 m as a representation of the average elevation in Liwa. For the inversion, we used algorithm implementing depth-and minimum volume weighting parameters in order to obtain a smooth model with better vertical resolution. The two-dimensional models show clearly surface topography of the basement rocks and the presence of normal faults. The reduced Bouguer anomaly of +800 m elevation shows the presence of structural lineaments extending primarily in a northwest-southeast direction, parallel to Sumatran Fault Zone and older graben faults showing a negative flower structure. From the three-dimensional inversion, the model illustrates an increase of density contrast, lower values being found near the surface and higher values in the deeper parts. The lower density contrast of 0.15 to 0.3 g/cm3 found in the rock groups at depths of 2 km and less is characteristic of relatively homogeneous and poorly compacted rocks. Rocks with moderate to high density contrast (>1.0 g/cm3) are recognized at depths of over 2 km. This model suggests a change of basement morphology as a function of depth, and delineates structural lineaments extending in northwest-southeast direction. This study supports the previous thought that Liwa area is underlain by graben structures, formed by trans-tensional tectonic events. Higher-density Tertiary volcanic breccia and lower-density Quaternary volcanic products of the Ranau Formation form the basement rocks and the overlying younger sediments, respectively.

基于二维高密度电阻率勘探数据的三维反演及应用

针对目前高密度电阻率法所采用的数据处理方法主要是把地质结构体视为二度体进行二维处理,从而二维数据资料处理结果只是一种近似解释,其计算精度与反演效果达不到精确反演的要求,设计一种典型的地质体模型,利用有限单元法进行正演计算,对含有高斯随机误差的各测线二维正演数据分别进行高密度电阻率法二维、三维反演,对比二维和三维的反演结果。最后在广东某场地采用高密度电阻率法对岩层划分,利用二维勘探的数据进行二、三维反演。研究结果表明:三维反演受高斯随机误差的影响更小,反演结果与实际地质模型更接近;三维反演在岩层划分中更能凸显岩层分界面区域,岩层的空间分布及岩层、覆盖层的整体连续性能更真实地体现,与钻探结果吻合程度更好。

1966年邢台6.8级地震的深部结构背景

根据“八五”期间邢台地震区深部地球物理方法的综合探测研究成果，依据P波、S波联合解释和二维密度反演，并结合浅部构造和三维应力场数值模拟计算等资料，进行综合分析研究。以1966年邢台6．8级地震为例，揭示了邢台地震区的孕震发震过程。邢台地震区的深部结构和介质结构：①中、下地壳内分布有北东向高角度深断裂，深断裂两侧出现明显的波速比异常。②中地壳有低速高导层和密度不均匀异常。③上地壳底部有滑脱构造带，浅部为束鹿断凹。

高密度电阻率法多剖面二维勘探数据的三维反演及应用

目前高密度电阻率法所采用的数据资料处理方法主要是把地质结构体视为二度体进行二维处理,而实际的地质结构体大都为三度体或似二度体,从而二维数据资料处理结果只是一种近似解释,其计算精度与反演效果都不佳,对测区多条断面进行综合解释的难度大。然而在实际勘探工作中,受自然条件和工作成本的影响,三维勘探原始数据的获得一般较少,数据勘探仍以二维为主,这样利用二维勘探数据进行三维反演显得尤为重要。本文结合了广东某地高密度电阻率法对岩层划分的工程勘察实例,利用二维勘探的数据进行三维反演,并对二、三维反演结果进行对比,结果表明三维反演在岩层划分中更能凸显岩层分界面区域及岩层的空间分布,而岩层与覆盖层的整体连续性也得以更真实的体现,与钻探结果吻合更好。

高压输电线塔基煤矿采空区的高密度电阻率法探查研究

煤矿采空区的塌陷与变形对高压供电线塔基的稳定构成了极大的威胁.使用高密度电法对塔基附近的地质结构进行了探测,应用二维和准三维反演方法确定了地下电阻率分布形态,以此为基础推断解释了塔基附近煤矿采空区的位置和形态,并对塔基的加固处理提出了建议.

高密度电探法在隧道勘察中的应用

我国碳酸盐岩分布极为广泛,由岩溶引起的地质灾害十分严重。快速、准确地查明地下岩溶等不良地质体在空间的赋存位置和形态,是工程地质勘察中要解决的重要课题之一。在庐山环南山一级公路(隘口—仓房)桃花源隧道地质勘察中,采用高密度电探法与钻探相结合,较准确地查明了沿隧道轴线范围内不同岩性的分界面及地下溶洞的分布情况,取得了良好的地质效果,充分显示了该方法在地质勘察中的优势。

重力异常稳健迭代密度界面反演研究

重力异常界面反演是重力勘探中的一个重要研究课题,它是一个求解第一类Fredholm非线性积分方程问题,目前情况下直接求解比较困难,只能采用拟合法或逐步线性化办法实现反演计算.在计算过程中,由于反演的不适定性,往往不能很好地获得反演解.我们从二度体重力异常正演公式出发,导出地下界面迭代反演的计算公式;然后利用广义似然函数对模型参数进行优化选择,从而获得模型参数修正量迭代计算方法,实现二度体单一密度界面的稳健迭代(最小二乘加权迭代)反演.模型计算表明方法可以很好地反演出地下界面.

高密度电阻率法二维勘探数据的三维反演及其在岩溶探测中的应用

三维高密度电阻率法可以有效地解决二维高密度电阻率法在探测空间形态上的不足。将高密度电阻率法二维勘探数据做三维反演,不仅实现了地下空间结构的三维电阻率成像,还克服了传统三维高密度电阻率法在经济成本上的限制。将此方法应用到岩溶勘探中,利用DUK-2A高密度电法仪系统采集数据;然后,把二维高密度数据拼接转化成三维可反演数据,再将反演得到的结果通过三维成像软件实现任意三维地电切片,从而获得丰富的地电结构信息;最后,结合三维切片与钻孔资料对溶洞进行解释,为工程的顺利施工提供科学依据,从而证明该方法的可行性和有效性。

POTENTIAL INVERSION PROBLEMS FOR COUPLED SYSTEM OF DOWNGOING AND UPCOMING ONE-WAY WAVE EQUATIONS

By using wave splitting method the formulation of the two-dimensional potential inversion problem is set up in terms of the coupled system for downgoing and upcoming wavefields. The boundary counditions on the characteristic surface needed for solving the problem are derived by singularity analysis. Two stability theorems are given for the direct problems of the system treated as Cauchy problems in the direction of depth.

LAYER STRIPPING METHOD FOR POTENTIAL INVERSION

To solve the potential inversion problem of the coupled system for one-way wave equations, the absorbing boundary conditions in the lateral direction are derived. The difference schemes are constructed and a layer stripping method is proposed. Some numerical experiments are presented.

基于C语言的常规电阻率测深法与高密度电阻率法数据转换

在实际生产中,常规电阻率测深法占有相当重要的地位,由其发展而来的高密度电阻率法也已被一线生产单位广泛采用。基于二者的原理可知,常规电阻率测深法所得数据理论上就是高密度电阻率法的一部分,因此将电测深数据按一定的格式进行排列,也可以利用高密度电法的相关软件进行处理。将对如何利用Res2dinv反演常规电测深数据进行探讨,并着重叙述二者之间数据转换的C语言算法。