In traditional seismic reflection exploration, geological structures are characterized only by interpreting reflection wave events from wave impedance interfaces and then obtaining information of stratigraphic interfaces and structures. Herein, we present a method used to rapidly invert velocities of seismic waves reflected from strata layers. We have named this method “Seismic Reflective Ground Penetrating Mirroring (SRGPM)”. This method consists of three steps, which are: (1) adaptive extraction of respective reflection signals, (2) automatic selection of root mean square velocity, and (3) fast inversion of layer velocity. The validity of the proposed method was verified with field data. The layer velocities and structures of strata can be quickly acquired by SRGPM. Combining this data with prior geological information, the inverted layer velocities can be converted into the uniaxial compressive strengths of the soil layers, providing basic data for evaluation of urban foundations.

Identifying faults and structural features from seismic wavefields is a pivotal approach in hydrocarbon reservoir prediction. Although seismic attributes and edge detection techniques are widely used in reservoir prediction, they are often inadequate for effectively delineating complex structures, particularly deep carbonate reservoirs exhibiting karst cave characteristics. Based on the stochastic process theory, we have introduced a new algorithm that applies spectral moments and statistical invariants to analyze the amplitude variations in the seismic wavefield. and the covariance of seismic data within a calculation window in different directions. Statistical invariants are derived from second-order spectral moments, including the scratch coefficient designed to capture finer details within lower-amplitude anomalies. We develop a new scratch coefficient, termed the seismic scratch, which accurately captures the structural geom-etry of karst cave bodies. A comparative evaluation is conducted among the root mean square (rms) attribute, coherence, curva-ture, edge detection technology, and the seismic scratch method. The study reveals that (1) the seismic scratch method surpassed the rms amplitude attribute in detecting reservoirs with weak amplitudes; (2) coherence and curvature can only predict faults, whereas the seismic scratch method more accurately character-ized the geometry and structure of karst cave reservoirs; and (3) the seismic scratch method outperformed edge detection technology in depicting carbonate reservoir features and pre-serving amplitude variations. The application of this method in the Tazhong region demonstrates its efficacy in accurately mapping fracture-cave units and enhancing predictive accuracy for oil and gas well locations.

During the early Cenozoic, the collision and convergence between India and Eurasia resulted in the uplift of the Tibetan Plateau and continuous northward compression, forming the Circum‐Tibetan Plateau Basin and Orogen System (CTPBOS). The Tarim Basin, located between the Tibetan Plateau and the Tianshan Mountains, plays a crucial role for studying the convergence‐driving strain propagation mechanism intra‐Asian continent during the growth processes of the Tibetan Plateau. Owing to the lack of accurate geophysical information on the deep structure of the Tarim crust，the mechanism of Cenozoic deformation in the Tarim Basin has been under debate. In this paper, the teleseismic data acquired by the broadband seismic profile across the Tarim Basin from south to north and the S‐wave receiver function method were used to obtain the depth of the Moho and the discontinuities in the lithosphere beneath the Tarim Basin. The SRF result shows that the Moho geometry has an abrupt relief under the Bachu Uplift, and Moho offset under the fault zone between the Kalashayi Fault and the Tumuxiuke Fault. The regional dip of the Moho under the Bachu area can be explained by the root of the Bachu basement‐involved uplift cutting across the whole crust and locally penetrating into the mantle lithosphere. The Bachu Uplift, located in the central Tarim terrane, has a relatively weak lithosphere. In the process of forming the Tarim large igneous province during the early Permian, the crust beneath the Bachu area was weakened and thinned by the thermo‐mechanical erosion from upwelling mantle plume. As the collision and convergence of India and Eurasia since the early Cenozoic, the convergence‐driving strain was propagated into the Tarim Basin. The pre‐existing weak Bachu Uplift was reactivated. The Tarim Basin absorbs Cenozoic compressional deformation through the crustal shortening and Moho offset of the Bachu Uplift.

Groundwater is a potentially significant resource for agricultural and industrial uses in Tarim Basin, the largest arid endorheic basin in China. Hydrogeochemical and hydrogeologic researches have provided detailed information of groundwater chemical type, composition, ion content and flow. However, there is lacking in quantitative estimation of groundwater in whole basin scale subject to the limits of samples as well as the unclear underground structure. To address the problem, 3-D electrical resistivity model constructed from inversion of magnetotelluric (MT) data was used to calculate the Total Dissolved Solids (TDS) of groundwater based on previous experimental studies and empirical equations. The TDS model shows relatively high value in the east of the study area and in deep, primarily controlled by depth, flow direction, stratigraphy, and water table gradient. Groundwater can be classified into five categories in terms of TDS range in Standard for Groundwater Quality. Finally, the volume of each type and average available quantity of Classes I similar to III (TDS < 1 g/L) per person were estimated by taking account of population distribution. Mapping groundwater TDS and volume reveals that human activities also play a role in groundwater salinity. The evaluation of groundwater quality and volume based on TDS provides a basis for future urban construction and development as well.

Using high-quality seismic data collected from a large number of local seismic stations, we have achieved high-resolution imaging of the three-dimensional velocity structure of the crust and upper mantle in the Qinghai-Tibetan Plateau with an accuracy of 0.5°×0.5°×10 km, which revealed in great detail the crustal and upper mantle structure of the Qinghai-Tibetan Plateau and provided new evidence for understanding the dynamics of continental collision and plateau evolution. Then, based on the 3D seismic P-wave velocity data, a 3D depth map of the lithosphere-asthenosphere boundary beneath the Qinghai-Tibetan Plateau is obtained. It is found that there are fundamental differences in geological attributes between the eastern and western parts of the plateau: The eastern part is dominated by thick lithosphere with high wave velocity, high resistivity and density, and a thickness range of 150-180 km; whereas the west is dominated by thin lithosphere with low wave velocity, low resistivity and density, and thickness ranging between 130-155 km. Furthermore, there is no large-scale asthenospheric upwelling in the eastern part whereas ～20-30 km upwelling has occurred in the west. The coordinates of the two endpoints of the east-west boundary are（20°N, 85°E） and（40°N, 98°E） respectively. According to the paleomagnetic data, the eastern massif in the Qinghai-Tibetan Plateau is a stress transition zone situated between the western continent-continent subduction zone and Southeast Asia ocean-continent subduction zone since 40 Ma.

应用三维地球物理成像技术可以揭示陆域地壳的流体分布.在青藏高原,高分辨率的地震波速度三维图像是揭示高原地壳流体层分布的主要方法.从取得的三维波速、密度和电阻率图象可见,低波速、低密度和低电阻率异常指示了地壳流体层的位置和范围.同时,高波速高密度异常也揭示上方发育的屏蔽盖层.据此,划分出高原地壳的多个流体发育层的分布范围.根据地壳高分辨率地震层析成像的结果还发现,青藏高原地壳流体发育层分布,与其下面的软流圈上涌有密切关联.

Syncontractional extension is prominent in present-day Tibet, but its origin remains vigorously debated. Several deep-seated geodynamic processes (e.g., Indian underthrusting, horizontal flow, and mantle upwelling) have been linked to Tibetan rifting. Indian underthrusting is a good candidate because it can well explain why surface rifts are more prominent south of the Bangong-Nujiang suture; however, how Indian underthrusting causes extension is not well understood and lacks observational constraints. Seismic anisotropy, measured by exploiting the birefringence effect of shear waves, can be indicative of the deformation styles within the crust. Here, we unveil the dominant convergence-parallel alignment of anisotropic fabrics in the deep crust of the southern Tibetan rifts using seismic recordings collected from our recently deployed and existing seismic stations. This finding suggests that the strong north-directed shearing exerted by the underthrusting Indian plate is key to enabling present-day extension in southern Tibet.

地球物理调查和地质资料的综合分析表明,现今蒙古高原的地壳构造主要是由于古亚洲洋和蒙古-鄂霍茨克洋两次大洋闭合和拼合造山作用形成的.其中古亚洲洋闭合作用主要发生在蒙古高原的西部和南部,造成阿尔泰碰撞造山带地壳隆升、乌布斯-巴彦洪戈尔地壳沉降,也牵连到杭爱山地块发生次级的地壳隆升.蒙古高原的东部,中生代古蒙-鄂洋封闭时没有发生强烈的碰撞,上、下阿穆尔地体和锡林浩特地体就完全拼合成陆地.这种类型的拼合造山,速度缓慢的陆-陆俯冲起主要作用.当然,速度缓慢的陆-陆俯冲作用同样会造成众多的地壳变形和岩浆侵入,使大陆增生.蒙-鄂洋的闭合没有发生明显的地壳缩短加厚,而是发生大规模幔源岩浆侵入,使地壳熔解和结晶基底快速克拉通化.在蒙古下方的上地幔,有反映上地幔羽毛状热流体上涌的痕迹残留.

The key to seismic data processing is to extract the wavefield information related to the subsurface geological targets. In this paper, we first introduce the low-rank signal priority and the strong energy signal priority characteristics of the Singular Value Decomposition (SVD) method. By analyzing the characteristics of the second-order difference spectrum of typical seismic data, we find two indicative parameters to adaptively select the singular value threshold for extracting reflection and diffraction events. Our proposed Adaptive Local Singular Value Decomposition (ALSVD) method takes advantage of the local analysis, and can effectively extract the weak signals in the seismic data. It is a robust method with good resolution and separation integrity, which is beneficial to seismic migration, seismic imaging, and evaluation of Oil and gas traps. Synthetic examples and field examples demonstrate the effectiveness of this method.

位于扬子克拉通内部的长江中下游构造带是一个特别的岩石圈构造带,它的成因一直是个谜.前人认为这与晚侏罗世伊佐奈琦洋向亚欧大陆的俯冲有关,但是为什么伊佐奈琦洋俯冲只在长江中下游构造带局部形成深入内陆的铁铜和多金属成矿带?为了解这个问题,必须从华南地区的地球物理数据来分析研究区的岩石圈和软流圈的属性特征,并进行类似构造的全球对比.根据地球物理调查结果可知,长江中下游构造带的地壳主要体现地堑的特征;岩石圈呈现低S波速与高密度,此类浅地幔动力学构造系统与洋中脊向大陆的俯冲模式接近.根据太平洋区域侏罗纪—白垩纪大洋磁异常条带与古地磁研究可以推测,长江中下游构造带与铁铜多金属成矿带的形成原因,应该是伊佐奈琦洋的洋中脊与洋脊三叉连向下扬子克拉通地幔的俯冲.当然,证明这个推测还需要更多的调查数据.

In this work, an extended multiphase hybrid-stress finite element method (X-MHSFEM) is developed to investigate the stress intensity factor, kinking angle, and propagation path of an interface crack. Further, we have simulated the propagation of the interface crack by using the X-MHSFEM. Several types of element models containing the interface and matrix cracks are introduced in the propagation process of the interface crack. The derivation of the functional of the element containing the two materials, one interface, and all types of cracks, is performed. Stress functions are enriched by the asymptotic singular items that accounts for the oscillatory behavior to describe the stress concentration in the vicinity of the interface crack-tip, and the stress concentration near the matrix crack-tip are also captured by inserting certain singular stress terms of Williams expansion into the physical field of whole model. The stress intensity factors of the tips of the interface and matrix cracks are calculated by the least square method. The maximum and relative maximum circumferential stress criterion are employed as the fracture criteria for predicting the interface crack propagation along the interface or the deflection into layers. Further, the matrix crack propagation angle within the layers is determined by the maximum energy release rate criterion. A remeshing algorithm is employed to implement the propagation of the interface and matrix cracks. The effectiveness and accuracy of the present method are validated by comparing the results, obtained by the new method, with the experimental observation and other numerical results. Therefore, the extended multiphase hybrid-stress finite element method can provide an effective medium to deal with the interface crack fracture problems.

Background: Edge enhancement plays an important role in potential field data processing and interpretation, which facilitate regional tectonic studies, mineral and energy exploration. This is because edges on potential field often indicate linear geological structures such as fractures, edges of geological bodies and so on. With the development of meticulous edge enhancement on potential field, the phenomenon of false edges caused by the associated anomalies when detect ing edges from magnetic field cannot be ignored. Methods: Aiming at this problem, we proposes a modified magnetic edge detection method (SP Mag) based on the second order spectral moment. This method has been tested on both synthetic and field data. The synthetic test show that SP Mag cannot only balanced edges no matter from strong or weak anomalies, but also eliminates those false edges caused by the associated anomalies in magnetic field, which provide more effective information for subsequent interpretation. Results: We apply this new method to the RTP aero magnetic field and gravity field of Rizhao Lianyungang area. The lineaments recognized by the SP Mag method correspond well with geologic structures through comparing with geological maps. Discussion: The results illustrate the usefulness of the method for potential field interpretation. Furthermore, more geological and geophysical data should be still combined for comprehensive interpretation in the actual interpretation, though the SP Mag method can recognize lineaments effectively.

本文对西太平洋的洋—陆转换作用进行探讨.西太平洋洋—陆转换带在中国东部可分为华南、华北—黄海和东北3个区段.东北地区中—新生代洋—陆转换作用涉及古今太平洋板块和蒙古—鄂霍茨克洋板块两方面俯冲作用的影响,产生大面积中基性岩浆和火山活动,从侏罗纪一直延伸到现在.不同于东北和华南地区,华北—黄海有克拉通型的岩石圈,在晚侏罗世—新近纪因为太平洋板块的大角度旋转造成软流圈低黏度物质上涌,和地壳拉张与幔源岩浆的底侵,造成上地壳裂谷型沉积盆地.燕山地区在侏罗纪与东北地区类似,有强烈的软流圈上涌和岩石圈岩石部分熔融,产生强烈岩浆活动.在白垩纪到新生代,因为蒙古—鄂霍茨克洋闭合和太平洋板块大角度旋转,发生沿蒙古—鄂霍茨克洋的转换断层的拉张,产生从南蒙古过锡林浩特的NW向玄武质岩浆和火山带.洋—陆转换带不同区段有不同的动力学作用演化过程,与先期岩石圈的性质、大洋板块俯冲带的分布、方向变化和俯冲持续时间、以及后期俯冲带后撤作用都有密切关系.洋—陆转换作用的统一后果是大陆的增生,但是不同区段大陆增生和物质运动的模式是不一样的.

采用快速行进法正演计算了西藏西部地区的远震P波理论走时,随后基于该地区台阵提取到的相对到时残差利用子空间迭代算法反演得到该地区的地壳上地幔速度相对分布.层析成像结果显示:西藏西部地区在下地壳深度显示高速异常,上地幔深度该地区内部的高速异常范围从西往东逐渐减小,且研究区域东部存在高低速异常相间分布.据此认为印度板块在青藏高原内部近水平俯冲,西部俯冲范围较大,且俯冲过程中存在板块撕裂现象,撕裂的印度板块拆沉进入上地幔,而撕裂产生的间隙由于应力释放导致了西藏西部地区新生代裂谷的形成.

Faults, fractures, karst caves, and other small-scale geological targets are critical for carbonate oil and gas exploration. However, seismic responses of these small-scale geological targets are low-energy diffractions and it is difficult for traditional method to image them with high resolution. To identify these targets, the diffraction separation is a key technology. Based on the difference of diffractions and reflections in both kinematic and dynamic properties, the singular value decomposition (SVD) method can separate diffractions and reflections effectively. However, how to select the appropriate singular value sequence for diffractions and reflections is a key issue in the application. Based on the analysis of the singular value spectrum characteristics, we propose a second-order difference spectrum strategy to improve the SVD method. The improved SVD method can separate the diffractions and reflections with minimal error. It is stable when seismic data contain Gaussian noise. Reverse time migration (RTM) method is used in the diffraction imaging because it can keep the true shape of subsurface scatterers when diffractions information is complete. Synthetic examples demonstrate the effectiveness of this method.

Several models were proposed to account for the tectonic evolution of Tibetan Plateau, among which delamination of the Tibetan lithosphere is suggested to be a leading process. However, direct evidence for the removed Tibetan lithosphere in the deep mantle remains highly lacking. Here we image the mantle transition zone (MTZ) structure beneath western Tibet and Himalaya by common conversion point stacking of 25254 receiver functions (RFs) with unprecedented clarity. One striking feature is the significant depression (15–20 km) of 660‐km discontinuity beneath Himalaya, which indicates the presence of the detached Lhasa lithospheric mantle (∼26 Ma) at the bottom of the MTZ. Our results also show ∼15 km uplift of 410‐km discontinuity (d410) and small d410 amplitude beneath western Tibet, which we ascribe to the more recently delaminated Qiangtang lithosphere (∼15 Ma). Furthermore, the small dependence of d410 amplitude on frequency indicates that the MTZ is anhydrous in the study area.

Full waveform inversion is often troubled by falling into a local minimum due to cycle-skipping problem when missing low-frequency seismic data. According to the dynamics of seismic waves, the travel-time information will not change due to the variation in the frequency band of seismic data, which is the working mechanism of travel-time inversion. However, the current travel-time inversion method often requires various assumptions for the convenience of calculation, resulting in limited inversion effects. We present a novel velocity building method based on travel-time information. First, we use the sparse-constrained deconvolution (SCD) to convert travel-time information of seismic data into reflection sequences, which greatly reduces the complexity of the travel-time inversion. Then, the phase-independent characteristic of the envelope is introduced into the SCD to deal with the phase shift of the seismic wave. The combination of SCD and envelope greatly improves the reconstruction accuracy of the reflection sequences. Finally, the reconstructed reflection sequences are convolved with the full-band source wavelet to obtain full-band seismic data, and thus, the envelope-based SCD (E-SCD) inversion method is proposed. The results of numerical experiments on the partial basic tracking (BP) model and SEG/EAGE overthrust model verify the performance of the E-SCD inversion method. The limitations of the method and the direction of future development are also briefly discussed.

The quantitative analysis of the urban-rural integration development (URID) level and its driving factors is of great significance for the new-type urbanization of urban agglomerations. This study constructed a multidimensional framework in the perspective of a population–space–economy–society–ecology framework to measure the URID level from 2000 to 2020 and further explored the driving mechanism of the URID changes by a geographical detector model in the Hangzhou Bay urban agglomeration (HBUA). The results showed that the land-use change in the HBUA from 2000 to 2020 showed a typical characteristic of the transition between cultivated and construction land. The URID level in the HBUA improved from 0.294 in 2000 to 0.563 in 2020, and the year 2005 may have been the inflection point of URID in the HBUA. The URID level showed a significant spatial aggregation with high values. Hangzhou, Jiaxing, and Ningbo were hot spots since 2015, and the cold spots were Huzhou and Shaoxing. The population and spatial integration had more important impacts on URID levels in 2000, 2005, and 2020, while economic and social integration had more significant impacts on URID levels in 2010 and 2015. This study provided a deeper understanding of the evolution of URID in an urban agglomeration and could be used as a reference for decision makers.

Applying the scratch recognition method to regional gravity fields, we defined the ridge and edge coefficient for delineation of the deformation belts and the tectonic boundaries, which are able to recognize characteristic parameters about crustal scratches contained in regional gravity field. The tests on theoretical models prove that our method is correct and applicable. After performing this procedure to Bouguer gravity field of Chinese continent, we obtain the resulting scratch maps for locating the crustal deformation belts. Finally, by comparing the known deformation belts in Chinese continent with these crustal scratches, we try to find the correlation between these scratches and the Phanerozoic crustal deformation belts. Comparison between the calculated crustal scratches and different types of deformation belts in Chinese continent shows that the strong and long scratches are correlated with most of mature plate collisional zones, strike-slip fault zones and large crustal detachments in Phanerozoic, which have been found by Chinese geologists. Thus, the scratch procedure is meaningful for recognizing the crustal deformation belts and useful for locating tectonic boundaries. However, young and active deformation faults are usually correlated with rather weak scratches as they are not mature enough.

浙江地区基岩为大面积的中生代火山岩覆盖,对了解地壳深部的组成结构造成困难.本文通过对布格重力异常和航磁异常数据进行小波多尺度分解,深入地了解浙江省不同深度的地壳结构,结合地震和大地电磁资料,取得地壳构造的三维信息.根据浙江地区位场的多尺度分解结果,可以将浙江省上地壳细分为六个构造单元:下扬子南部浙北陆沿带、江山绍兴古陆块碰撞拼合带、古华夏陆块北沿带、丽水余姚早古生代陆缘俯冲带、浙东侏罗纪白垩纪火山岩带和杭嘉地块.在上地壳的六个构造单元中,江山-绍兴古陆块碰撞拼合带、浙东火山岩带和杭嘉地块具有高密度强磁性的属性;而下扬子南部浙北陆沿带、古华夏陆块北沿带和丽水余姚早古生代陆缘俯冲带具有低密度的属性,与它们在古生代受安第斯型大洋俯冲作用有关.浙江省下地壳只有西—西南部低密度区、中部杭州嵊州苍南中密度带和杭嘉舟山群岛滨海高密度带三个构造区.东部的中生代陆缘火山弧和杭嘉地块在中下地壳连为一体;江山-绍兴古陆块碰撞拼合带和古华夏陆块北沿带也连为一体.浙江省中下地壳的格局主要受西太平洋俯冲带向东后撤的影响.