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1.
大地电磁测深二维反演方法求解复杂电性结构问题的适应性研究 总被引：3，自引：1，他引：2
为探讨二维反演方法在三维电性结构中的适应性问题,本研究中设计了一系列的二维/三维正演模型进行实验计算,分析了三维高阻/低阻异常体对模型响应的畸变作用,并从反演模式选择和数据旋转方向两个方面进行模型二维反演的对比分析,与三维反演的结果进行了比较,最后采用了实测数据进一步进行了二维和三维反演的比较实验.实验和研究结果表明,在剖面选择方面,在剖面方向与垂直主构造方向相差不大的情况下,截取剖面方向,将电性主轴旋转到垂直剖面方向的二维反演结果与垂直主构造方向的反演结果都可以较好地还原正演模型,在大的构造的反映上并无太大差异.在地下为二维或近三维条件时,正演模型的主要结构都可以较好地被二维和三维反演解析出来.二维的反演结果可能甚至会比三维的反演结果的边界更清晰,更精确.然而,对于具有较强的三维结构的模型而言,其二维反演结果与原始模型可能仍然存在较大差异,其中TM+TP或TM模式的二维反演结果相对更接近原始模型,而TE模式的结果往往会有较大误差,需要在解释时特别注意以免得出错误结论. 相似文献
2.
In this paper, I introduce a new approach based on truncated singular value decomposition (TSVD) analysis for improving implementation of grid-based Euler deconvolution with constraints of quasi 2D magnetic sources. I will show that by using TSVD analysis of the gradient matrix of magnetic field anomaly (reduced to pole) for data points located within a square window centered at the maximum of the analytic signal amplitude, we are able to estimate the strike direction and dip angle of 2D structures from the acquired eigenvectors. It is also shown that implementation of the standard grid-based Euler deconvolution can be considerably improved by solving the Euler's homogeneity equation for source location and structural index, simultaneously, using the TSVD method. The dimensionality of the magnetic anomalies can be indicated from the ratio between the smallest and intermediate eigenvalues acquired from the TSVD analysis of the gradient matrix. For 2D magnetic sources, the uncertainty of the estimated source location and structural index is significantly reduced by truncating the smallest eigenvalue.Application of the method is demonstrated on an aeromagnetic data set from the Åsele area in Sweden. The geology of this area is dominated by several dike swarms. For these dolerite dikes, the introduced method has provided useful information of strike directions and dip angles in addition to the estimated source location and structural index. 相似文献
3.
为了深入认识2016年4月15日日本熊本地震破裂的复杂性,利用远场体波资料和同震InSAR资料联合反演了此次地震的震源破裂时空过程. 联合反演结果表明:熊本地震的震源破裂持续时间约为25 s,整个破裂过程释放的总标量矩为6.03×1019 N·m,对应于矩震级MW7.1;同震滑动主要集中分布于浅部,破裂以右旋走滑为主,但在沿倾向0—5 km范围内,破裂呈较强的正断特征;此次地震破裂的最大同震滑动量约为4.9 m,且最大同震位错区位于背离断层走向上、距离起始破裂点约5—10 km的区域;破裂前期（0—7 s）,在倾向上向浅表发生破裂,在走向上向东北和西南两侧扩展;大约7 s后,破裂背离断层走向主要向东北方向扩展. 根据有限断层联合反演结果推测,此次熊本地震破裂可能出露至地表. 相似文献
4.
L. F. Moskovskaya 《Izvestiya Physics of the Solid Earth》2007,43(12):1056-1064
A method is proposed for the inversion of marine vertical electric sounding (VES) data in a tomographic approximation. A 2.5-D inversion is based on the correlational similarity method; this method is a natural stabilizer of the solution and provides the most compact image of an anomaly carrier. The algorithm possesses a high convergence rate. The inversion reduces to the expansion of anomalous stresses in orthogonal reference functions that are spatial focusing coefficients of a VES configuration. The coefficients were calculated with the help of a new method of contracting mappings allowing one to construct efficient algorithms for calculating electromagnetic fields on a dense spatial grid. Results of experimental in situ data inversion refined the morphology of deep-sea polymetallic sulfides of the Logachev-1 orefield in the Atlantic Ocean. 相似文献
5.
偶极声源的辐射特性及仪器的四分量正交采集系统使得偶极横波远探测可在一维井筒中对井外构造进行方位探测.基于反射横波幅度随声源偏振方向呈余弦平方变化这一特征,本文提出一种利用函数拟合快速反演井周构造走向的方法.根据这一规律,该方法仅用4个方位剖面数据即可准确反演井周构造走向,同时得到井周构造的离井距离和倾角.数值模拟和物理实验模拟均验证了幅度随方位的变化以及反演方法的可行性.根据这一方法做的现场实例也进一步证明了该方法的适用性.本文工作为利用四分量偶极数据进行井周构造的反射横波成像提供了实用而有效的处理方法. 相似文献
6.
FOCAL MECHANISM OF THE AUGUST 8, M7.0 SICHUAN JIUZHAIGOU AND AUGUST 9, M6.6 XINJIANG JINGHE EARTHQUAKES OF 2017 
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下载免费PDF全文 The W-phase is a long period phase arriving between the P and S wave phases of a seismic source, theoretically representing the total near-and far-field long-period wave-field. Recent study suggests that the reliable source properties of earthquake with magnitude greater than ~MW4.5 can be rapidly inverted by using the W-phase waveform data. With the advantage of W-phase, most of major earthquake research institutes in the world have adopted the W-phase based inversion method to routinely assess focal mechanism of earthquake, such as the USGS and GFZ. In this study, the focal mechanism of the August 8, 2017 M7.0 Sichuan Jiuzhaigou and August 9, 2017 M6.6 Xinjiang Jinghe earthquakes were investigated by W-phase moment tensor inversion technique using global seismic event waveform recordings provided by Incorporated Research Institutions for Seismology, Data Management Center. To get reliable focal mechanism, we strictly select raw waveform data and carry out inversion in stages. At first, we discard waveform without correct instrument information. Then we carry out an initial inversion using selected waveform data to get primary results. Using the preliminary results as input, we carry out grid-search based inversion to find the final optimal source parameters. The inverted results indicate that the August 8, M7.0 Sichuan Jiuzhaigou shock resulted from rupturing on a NW-trending normal fault with majority of strike-slip movement. The parameters of two nodal planes are strike 152.7°, dip 61.4°, rake -4.8° and strike 245.0°, dip 85.8°, rake -151.3° respectively, and focal depth is 14.0km. The August 9, Xinjiang Jinghe M6.6 shock resulted from rupturing on a south-dipping thrust fault with left-lateral strike-slip. The parameters of two nodal planes are strike 100.6°, dip 27.5°, rake 114.1° and strike 259.3°, dip 65.1°, rake 78.0°, and the focal depth is 16.0km. The direction of two nodal planes is consistent with regional seismotectonic background. 相似文献
7.
In this paper, we describe a non‐linear constrained inversion technique for 2D interpretation of high resolution magnetic field data along flight lines using a simple dike model. We first estimate the strike direction of a quasi 2D structure based on the eigenvector corresponding to the minimum eigenvalue of the pseudogravity gradient tensor derived from gridded, low‐pass filtered magnetic field anomalies, assuming that the magnetization direction is known. Then the measured magnetic field can be transformed into the strike coordinate system and all magnetic dike parameters – horizontal position, depth to the top, dip angle, width and susceptibility contrast – can be estimated by non‐linear least squares inversion of the high resolution magnetic field data along the flight lines. We use the Levenberg‐Marquardt algorithm together with the trust‐region‐reflective method enabling users to define inequality constraints on model parameters such that the estimated parameters are always in a trust region. Assuming that the maximum of the calculated gzz (vertical gradient of the pseudogravity field) is approximately located above the causative body, data points enclosed by a window, along the profile, centred at the maximum of gzz are used in the inversion scheme for estimating the dike parameters. The size of the window is increased until it exceeds a predefined limit. Then the solution corresponding to the minimum data fit error is chosen as the most reliable one. Using synthetic data we study the effect of random noise and interfering sources on the estimated models and we apply our method to a new aeromagnetic data set from the Särna area, west central Sweden including constraints from laboratory measurements on rock samples from the area. 相似文献
8.
On July 3rd, 2015, a MW6.4 earthquake occurred on Pishan County, Xinjiang, located in the front of western Kunlun thrust belt, which is the largest earthquake(MW6.0~7.0)in the past 40 years in this region. In this study, we collected both the near-filed geodetic coseismic deformation observations including 4 GPS sites and one high-resolution ALOS-2 InSAR imagery, and far-field teleseismic P waveforms from 25 stations provided by IRIS/USGS, to invert the fault parameters(strike and dip)and coseismic rupture model of 2015 MW6.4 Pishan earthquake. Using the finite fault theory, a non-linear simulated annealing algorithm was employed to resolve our joint inversion problem. The strike (120°~130°) and dip angle(35°~40°)of optimal models are different from that of some previous studies, and the dip change is strongly constrained by combined data than that of strike. In fixing the geometric parameters of optimal fault model, we also considered data weight(5)(geodetic data/teleseismic P waveforms)and constrained weight from moment and smooth factor(2.5). Clearly, our results indicate that the slip distribution mainly concentrates in the depth range from 9 to 16km and a length range of 20km along the strike direction, which is similar to the spatial distribution of the relocated aftershocks. The maximum slip is~95cm. The seismic moment release is 5.45×1018N·m, corresponding to MW6.42. Compared with the single data set, geodetic data or teleseismic waveform, our joint inversion model could simultaneously constrain the seismic moment and slip distribution well, thus avoiding effectively a lower-resolution rupture distribution determined by teleseismic-only inversion and a bias released moment estimated by the geodetic-only inversion. Importantly, we should consider both the near-field geodetic data and far-field teleseismic data in retrieving the rupture model for accurately describing the seismogenic structure of active fault in western Kunlun region. 相似文献
9.
《Journal of Applied Geophysics》1999,41(1):1-17
In the paper the principles of a new inversion method as well as the results of its application are described by using synthetic and field VES data. The basic idea of the method says that the horizontal changes in the layer thicknesses and the resistivities of the 2-D geological structure can be described by (expanding in series) functions of one variable. The coefficients of the functions are determined from the VES data by simultaneous inversion method using a least-squares technique. The local thicknesses and the resistivities of the geological structure are calculated from the coefficients from point to point along the profile. Using this method, the equivalence can considerably be reduced, and by using the functions chosen on the basis of a priori knowledge, the whole geological model can be determined by this inversion method. In the inversion the local 1-D forward modelling is used and this approximation is often applied in the VES practice. To qualify the results of the inversion, the correlation matrix for the coefficients are calculated and the error values for the local model parameters are introduced. 相似文献
10.
S. A. Greenhalgh L. Marescot B. Zhou M. Greenhalgh T. Wiese 《Pure and Applied Geophysics》2009,166(4):673-699
In this paper we develop analytic solutions for the electric potential, current density and Fréchet derivatives at any interior
point within a 3-D transversely isotropic medium having a tilted axis of symmetry. The current electrode is assumed to be
on the surface of the Earth and the plane of stratification given arbitrary strike and dip. Profiles can be computed for any
azimuth. The equipotentials exhibit an elliptical pattern and are not orthogonal to the current density vectors, which are
strongly angle dependent. Current density reaches its maximum value in a direction parallel to the longitudinal conductivity
direction. Illustrative examples of the Fréchet derivatives are given for the 2.5-D problem, in which the profile is taken
perpendicular to strike. All three derivatives of the Green’s function with respect to longitudinal conductivity, transverse
resistivity and dip angle of the symmetry axis (dG/dσl, dG/dσt, dG/dθ0) show a strongly asymmetric pattern compared to the isotropic case. The patterns are aligned in the direction of the tilt
angle. Such sensitivity patterns are useful in real-time experimental design as well as in the fast inversion of resistivity
data collected over an anisotropic earth. 相似文献
11.
基于大地电磁阻抗张量分解技术,本文提出了两种电性主轴方位的统计描述图像：随频率变化的统计分布成像（频率分布云图）和随测点序列变化的统计分布成像（测点分布云图）.这两种图像与传统的统计玫瑰图一起,较全面地描述了最佳主轴的分布特征.在进行构造维性分析过程中,通过定义二维有效因子e2d,来压制一维结构和三维结构、突出纯二维结构的影响.e2d被用于电性主轴的统计加权,有效地起到了滤波的作用;同时,统计成像中还考虑了数据质量的影响.为了得到稳定、高质量的区域阻抗张量数据,提出并实现了共主轴的多测点-多频点阻抗张量分解新算法.最终,完成了以上各项处理手段的可视化实现.本文通过两个理论模型和一个实测算例,以共轭阻抗法（CCZ法）为基础,展示了这一新技术的有效性. 相似文献
12.
利用双差定位方法对西藏比如MS6.1地震序列141次ML≥2.0地震进行重新定位,采用CAP波形反演方法获得主震的震源机制解,并运用最小空间旋转角方法比较不同机构发布的震源机制解的差异。重新定位后主震震中位置为(31.924°N,92.824°E),靠近余震区中心,震源深度为12.8 km;余震分布沿NE向展布,长约18 km。沿NE向深度剖面结果显示,在主震右上方存在5 km×10 km的近椭圆形地震破裂空区。主震的震源机制解为正断兼走滑型,最佳矩心深度为9.3 km,矩震级为5.98。结合重新定位后余震分布、主震与历史地震震源机制解及地质构造背景等分析,认为具有左旋运动性质的安多南缘断裂可能是该次地震序列的主要发震构造。 相似文献
13.
S. N. Bhattacharya 《Pure and Applied Geophysics》2007,164(5):909-928
We consider nine earthquakes in the Koyna-Warna reservoir region on the western side of the Peninsular India. The deviatoric
moment tensors of these earthquakes have been evaluated by minimizing the least-squares misfit between observed and synthetic
seismograms. We use broadband seismograms of observatories at KARD and PUNE which are at distances of nearly 50 and 150 km,
respectively, from the epicenters. Both surface wave inversion and the difference between the arrival times of SH and SV show
the presence of an anisotropic crust. However, we have obtained an equivalent isotropic structure by improving the published
crustal structures of this area through inversion of surface wave group velocity data. The deviatoric moment tensors of the
earthquakes are decomposed into two components: double-couple and compensated linear vector dipoles (CLVD). The double-couple
components of all the nine earthquakes show normal faulting with minor strike slip; the T axis is consistently subhorizontal
with an average azimuth of 260.6° and the P axis is nearly vertical. The fault planes of six events give average strike direction
and dip, respectively as 194.0° and 51.8° and are associated with the main fault of the area. The other three events lie in
the southern part of this area and have strike direction between SSE and SE which is parallel to the tectonic features in
this part. The CLVD component is generally within 20 percent of the total moment tensor. Recent studies show that anisotropy
can produce source mechanism with CLVD up to 30 percent and can also cause high pore fluid pressure leading to fault instability
more rapidly compared to conventional mechanism in an isotropic medium. It appears that the anisotropic crust, noted in the
present work, is generating the CLVD component and also gives the proper environment to trigger earthquakes by reservoirs
through pore fluid pressure. 相似文献
14.
2015年7月3日09时07分,在新疆皮山县发生M_(S)6.5地震,震源深度约10 km,主震后一段时间内陆续发生一系列大小不等的余震。使用新疆测震台网原始波形数据和中国地震台网编目数据库震相数据,采用CAP方法反演皮山M_(S)6.5地震及M_(S)3.5以上余震序列震源机制解,得到震源机制解参数,其中:节面Ⅰ走向为136°,倾角为34°,滑动角为94°;节面Ⅱ走向为311°,倾角为56°,滑动角为87°;最佳震源深度为21.3 km;矩震级为M_(W)6.3。据皮山地区地质构造和余震序列展布,基本确定节面Ⅰ为发震断层面;通过震源球判定本次地震的断层活动主要表现为逆冲型特征,破裂优势方向SE,倾角以20°—40°居多,滑动角以70°—120°居多。 相似文献
15.
1997年11月8日西藏玛尼Mw75级地震是干涉雷达技术应用于地震观测以来的一次重要事件.Peltzer等认为该形变场体现了地壳的非线性弹性形变响应，挤压象限和拉张象限的杨氏模量比值为2.相同的情形并没有在其他地震同震形变场中发现，通常用线弹性理论就能够很好地解释观测数据.考虑到他们所用断层模型的简化程度和纯走滑约束等，本研究认为非线性弹性解释是牵强的.应用广泛使用的Okada线弹性位错模型，采用卫星观测得到的地表断层位置，去除倾滑为零的约束，基于非线性优化反演方法寻求拟合雷达观测的最佳断层几何参数和均匀滑动参数.结果表明，线弹性模型能够满意解释观测数据.断层在朝阳湖以东的段落最深达到165 km，随着断层向两侧延伸，深度逐渐减小；反演得到的断层倾 相似文献
16.
本文应用ISOLA近震全波形方法,以2017年1月4日西藏仲巴4.7级地震为例,反演稀疏台网记录的中小地震震源机制解。该地震反演所得最佳双偶机制参数为：节面Ⅰ的走向109°/倾角85°/滑动角-177°,节面Ⅱ的走向19°/倾角88°/滑动角-4°,最佳矩心位置为30.590°N、83.784°E,最佳质心深度为6km,矩震级MW4.6。震源机制反演结果表明此次地震是一次走滑型为主的事件,其与震源区域附近历史地震震源机制解具有相同性质。本文还应用CSPS初动扫描法,利用P波初动资料和近震波形联合约束反演此次地震的震源机制,并与ISOLA近震全波形反演结果进行比较,结果表明,联合少量台站的的三分量波形数据,能够定量地判断最佳震源机制解,降低了P波初动反演结果的非唯一性,同时也约束了由于少量台站参与全波形反演引起的解的不稳定性。本文研究为中小地震震源参数测定提供了一种简单有效的方法,具有较高的稳定性和可靠性。 相似文献
17.
利用黑龙江、吉林、内蒙古三省数字地震台网的三分量宽频带波形资料对2018年5月28日吉林省松原市宁江区发生的MS5.7地震进行了全波形矩张量反演,获取了此次地震的震源机制解和矩心位置;并使用震源-矩心方法讨论了该地震的发震断层。研究结果显示:松原MS5.7地震的矩震级为MW5.2,矩心位置为（45.225°N,124.685°E）,矩心深度为7 km。震源机制解参数显示:该地震为走滑型;节面Ⅰ的走向、倾角和滑动角分别为217°,82°和164°;节面Ⅱ的走向、倾角和滑动角分别为309°,74°和8°;双力偶成分占96.4%,方差减少为93%。震源?矩心图显示震源更接近节面Ⅰ,与北东向的扶余—肇东断裂走向及倾角一致,因此,推测扶余—肇东断裂为发震断层。 相似文献
18.
2006年7月4日,在距离北京100 km左右的文安地区,发生了Mw=5.1级地震,引起了北京地区的强烈震感.为了更好的认识区域构造,我们利用近震及远震波形反演的方法得到了此次文安地震的震源机制.选择了北京数字地震台网的9个地震台,震中距小于600 km,台站的方位角覆盖较好.为了更好地利用信号相对较弱的P波信号,对于一个地震记录,本文分别截取出P波和面波两个部分,分别给予不同的权重进行反演,结合格点搜索的方法,得到了与记录P波及面波三分量对应较好的地震的方位角、倾角和滑移角.同时考虑到北京西北地区地壳较厚,本文在利用F-K方法计算近震理论波形的时候,对不同的方位角,采用了不同的地壳速度模型.随后结合远震信号中的直达P、pP、sP波形得到了分辨率较高的地震震源深度.反演结果表明,此次文安地震是一个较为典型的走滑型地震,方位角为210°,倾角80°,滑移角-150°,地震的深度为14~15 km,地震的震级为(Mw=5.1).反演结果与断层的几何分布、余震分布及北京地区北北东向应力场有很好的一致性. 相似文献
19.
Gülçin Özürlan M. Emin Candansayar M. Hüdavendigar &#;ahin 《Geophysical Prospecting》2006,54(2):187-197
Within the framework of the National Marine Geological and Geophysical Program, we re‐examined deep vertical electrical sounding (VES) data. The data, measured in 1968 by the General Directorate of Mineral Research and Exploration (MTA) of Turkey with the aim of exploring the deep resistivity structure of the Dikili–Bergama region, focus on the geothermal potential. The geoelectrical resistivity survey was conducted using a Schlumberger array with a maximum electrode half‐spacing of 4.5 km. The two‐dimensional (2D) inversion was utilized to interpret the VES data that were collected along 15‐ to 30‐km profiles. The 2D resistivity–depth cross‐sections obtained show very low resistivity values near the Dikili and Kaynarca hot springs. The 2D inversion results also indicate the presence of fault zones striking nearly N–S and E–W, and fault‐bounded graben‐horst structures that show promising potential for geothermal field resources. The 2D gravity model, which is in good agreement with the density variation of the region, supports the resistivity structure revealed by 2D inversion. The lithology information obtained from the borehole near Kaynarca also confirms the results of the resistivity interpretation and the density model. 相似文献
20.
用近震源波形资料拟合反演地震的震源破裂过程,所包含的一些不确定因素将对反演结果的精度及可靠性产生影响,文中的数值实验分析了所假定的反演断层模型参数的某些不确定性对反演结果的影响程度,并对观测波形的截取长度对反演精度的影响进行了讨论．结果表明：(1)近震源地震波形资料能较好地分辨断层浅部的破裂过程.然而对断层深部的位错分布的约束和反演能力较差．联合使用近、远场地震波资料进行反演,能反演出一个更为完全的整个断层破裂过程的图像.(2)用近震源地震波资料反演时,反演结果对所假定的反演断层的走向和倾角非常敏感.断层走向偏离真实值2°或倾角偏离真实值5°都会导致一个虚假的反演结果.(3)反演中所使用的介质速度结构模型的不确定性,也会对反演结果产生影响. 相似文献