天津地区地面沉降及其对地理环境的影响

本文应用现代精密水准资料，结合地质、地震资料对天津及邻近地区地面沉降的发展、演化状况进行了深入研究，从动态观点初步探讨了由于地面沉降所造成的地理环境条件恶化和灾害问题。     

物探在城市工程建设中广东惠州某重点工程的应用

为了给城市重大建设工程设计提供详尽的地质勘查资料,结合前人的相关地质资料分析,采用综合物探技术方法的快捷、低成本特点。针对当地的地质情况分别投入高密度电阻率和浅层地震反射波勘查,查明了地下地质情况,对异常结合钻探验证,满足设计和施工的要求。     

昌马断裂带地震滑坡的展布特征

根据大量的野外地质调查和测量资料分析，讨论了地震滑坡沿昌马断裂带走向和倾向的展布特征。研究认为昌马断裂带地震滑坡主要发生在山坡坡度３０°－５０°的部位和山坡地形高差１００－３００ｍ的部位；地震滑坡规模、数量的分布特征与断裂活动强度的分布变化有密切的关系，这是地震滑坡与降水滑坡、人为滑坡和融冻滑坡的最大区别；最后讨论了地震滑坡最大水平滑距的规律，对地震滑坡灾害预测有很现实的意义。     

地震解释的步骤及解决的地质问题

地震解释工作是开展石油地质研究的基础,一个含油气构造的发现、岩性圈闭的识别以及井位部署都离不开地震解释,甚至连现在的石油开发也需要应用地震资料完成扩边挖潜、技术创新和增储上产,因此开展好地震解释工作至关重要。构造解释是从全三维解释理念出发,严格对三维地震资料进行三度空间的立体解释。利用层位自动追踪,解释系统中的多种显示功能,任意切割测线,生成时间切片,利用垂直断层走向的任意方向测线识别小断层,利用相干数据体技术,研究相邻地震道的反射特征,突出因地质体横向变化而引起的反射特征的变化,可以达到识别小断层并预测地层横向变化的规律的地质目的,能够从点—线—面不同角度认识各反射层的横向变化,从而正确识别地下构造形态。     

表、浅部地震地质条件对地震勘探效果的影响

地震地质条件是决定一个煤田开展地震勘探工作的客观条件,通常可分为表、浅部条件和深部条件。表、浅部地震地质条件是指地表及一定深度的地质和地貌特征,它主要影响地震勘探的施工效率、激发、传播和接收条件以及勘探效果。本文以同一煤田的两个工区为例,论述了不同表、浅部地震地质条件对地震勘探效果的影响。     

高原冻土复杂区二维地震勘探技术浅析——以青海木里煤田聚乎更矿区三露天井田为例

研究区平均海拔在4000m以上,近地表为季节性冻土层,其速度具有时变特点,随气温升高,冻土层融化,速度变低,反之速度升高,冻土层与永久冻土层之间存在溶蚀缝洞或者渗流层。从地质露头可以看出,近地表地层倾角比较陡,高寒、缺氧的自然环境,冻土固化的山前砾石堆积地表,复杂的地质结构,给地震勘探带来极大困难。本文针对研究区特点,结合高原冻土二维地震勘探实例,分析了该类地区地震勘探工程的主要难点,阐述了在资料采集、处理及解释中应采取的技术方法。文章在研究区获得了高品质的地震资料,为今后类似地区的地震勘探及其他物探方法奠定了基础。     

厚层黄土覆盖区地震数据采集方法研究

宁夏固原地区为厚层黄土覆盖的山区,黄土层厚度达270m左右,其浅部干燥的黄土层速度低、厚度大,对地震波的激发和接收极为不利。根据该地区特点,通过大量的试验工作,确定了最佳的地震数据采集方法和参数,取得了较好的地震原始资料,最终查明了主要可采煤层的赋存情况和构造发育情况。为矿井建设、生产提供了可靠的地质资料。     

南极布兰斯菲尔德盆地重力异常研究

１９９１年，“海洋四号”科学考察船在南极布兰斯菲尔德海峡采集了大量的地球物理资料。本文在利用地震调查资料的基础上，根据现有的重力测量数据，研究引起重力异常的各种地质因素，对实测剖面重力异常进行正演拟合，建立了布兰斯菲尔德盆地的密度模型，并推导出该地区莫霍面深度－布格异常关系表达式，绘制出盆地的莫霍面深度图。     

瞬变电磁法在内蒙古自治区阿巴嘎旗那仁宝力格煤田地质勘查中的应用

通过对阿巴嘎旗那仁宝力格煤田地质及地球物理特征的分析,发现勘探区内玄武岩与围岩之间存在着较大的电性差异,而运用三维地震方法无法准确地确定其底板埋深情况。基于此种原因,我们选择了大定源回线瞬变电磁法在目标区域上进行了探测。通过对瞬变电磁数据的分析整理及成图,结合地质及三维地震资料,基本确定了玄武岩底板的埋藏深度、喷发通道及底板界面的展布情况,为煤田工作区下一步工作的布置提供了宝贵的资料。     

深层地震勘探在深埋特长隧道勘察中的应用

以沪蓉国道主干线湖北省高坪一吉心段大水井隧道的工程地质勘察为例，讨论了深层地震勘探在深埋特长隧道勘察中的应用。利用深层地震反射波法可以有效地探测覆盖层、各风化层以及不同基岩界面的埋藏深度，根据波速判断隧道围岩类别、探测不良地质现象(喀斯特、断层、节理裂隙等)等。因此，深层地震勘探可为隧道的设计、施工提供必要的地质依据。     

四川雅安芦山地震灾区次生地质灾害评估及对策建议

2013年4月20日08点02分,四川雅安芦山县发生了7.0级强震。此次地震发生的区域地形条件复杂,地震烈度大,使得震区地质条件进一步恶化,在强降雨等叠加等条件下,次生地质灾害风险显著加剧。本文收集了震区地形、地质、构造断层分布、地震烈度分布、历史灾害、降雨以及卫星影像等资料,对震区的次生地质灾害的危险性从以下3个方面进行了评估:① 地震力触发下震区次生地质灾害空间分布;② 不同降雨触发下震区次生地质灾害空间分布及趋势分析;③ 地震与降雨共同作用下震区次生地质灾害空间分布。在此基础上圈定了震区次生地质灾害高危和需要重点监测防范区域,为灾害救援与重建过程中次生地质灾害的防范提出了对策建议。     

Crustal profiles of active continental collisional belt: Czechoslovak deep seismic reflection profiling in the West Carpathians

Summary. Czechoslovak deep seismic reflection profiles across the West Carpathians, the first in the Alpine-Himalayan belt, and surface geological data, suggest that the passive margin of the Eurasian plate was obliquely overriden by the upper Carpatho-Pannonian plate during the end of the Krosno sea subduction some 17-14 Ma ago. The following period was dominated by slight oblique continental collision (transpression and transtension) of the West Carpathian-East Alpine continental material escaping from the East Alpine collision zone and Eurasian Brunovistulic passive margin. Crustal shortening in the North was accommodated by significant northerly dipping backthrusting and crustal thickening. Backthrusting is clearly observable on deep seismic lines 2T and 3T. Different subsidence features are present on the deep seismic line 3T. There are active pull-apart graben in the Vienna basin, mid-Miocene (16–10 Ma) low-angle normal faulting in the Danube basin, and there is a normal simple shear zone offsetting the Moho boundary beneath the Danube basin.     

青藏高原山地系统动力学数值模拟研究

青藏高原山地系统地壳巨厚，约为正常地壳厚度的两倍，由于第四纪以来高原的急剧隆升而成为全球构造研究的热点，根据山地系统岩石圈运动的主要因素－构造带和断裂带，本文将青藏高原山地系统的地壳演变化简化成一个平面问题和一个典型剖面问题的力学模型，应用变形体模拟构造带，采用摩擦模型模拟断裂带，并根据周边位移情况给出边界条件，应用ABAQUS有限元分析软件和位移加载，变成了青藏高原山地系统岩石圈应力－位移场吻合较好，由此分析和推断了青藏高原山地系统演变的历史和现状。     

3D seismic technology: the geological 'Hubble'

The proliferation of three‐dimensional (3D) seismic technology is one of the most exciting developments in the Earth Sciences over the past century. 3D reflection seismic data provide interpreters with the ability to map structures and stratigraphic features in 3D detail to a resolution of a few tens of metres over thousands of square kilometres. It is a geological ‘Hubble’, whose resolving power has already yielded some fascinating (and surprising) insights and will continue to provide a major stimulus for research into geological processes and products for many decades to come. Academic and other research institutions have a major role to play in the use of this data by exploiting the enormous volume of geological information contained in 3D seismic surveys. This paper reviews some of the recent advances in basin analysis made using the medium of 3D seismic data, focusing on the fields of structural and sedimentary geology, fluid–rock interactions and igneous geology. It is noted that the increased resolution of the 3D seismic method provided the essential catalyst necessary to stimulate novel observations and discover new geological structures such as mud diapir feeders, km‐long gas blow‐out pipes, giant pockmarks and sandstone intrusions, and to capture the spatial variability of diagenetic fronts. The UKs first impact crater was also discovered using 3D seismic data. The potential for future developments in this field of geophysical interpretation is considerable, and we anticipate that new discoveries will be made in many years to come.     

沪蓉高速公路西段线路工程地质遥感解译

沪蓉高速公路西段路线走廊带是我国西南喀斯特生态环境脆弱区，喀斯特发育，存在一些重要的不良地质现象，如喀斯特地面塌陷和滑坡。该区在长期地壳运动发展中，不同时期、不同规模、不同方向的断裂构造体随时间、空间(构造位置及边界条件)和构造运动方式的变化，在各种地应力场的作用下形成了不同性质、不同规模等级的线性构造形迹。在沪蓉高速公路西段勘察中，利用空间图像的光谱特征和几何图形特征，探讨遥感解译过程中对各类线性构造分布及其特征的识别、判别工作方法与流程。     

Joint two-dimensional cross-gradient imaging of magnetotelluric and seismic traveltime data for structural and lithological classification

Collocated magnetotelluric (MT) and seismic profiling is emerging as a necessary combined approach for deep and near-surface imaging but the resulting experimental data are typically interpreted separately since no production programs exist for multidimensional joint inversion of MT and seismic data. We present a joint 2-D inversion approach for imaging collocated MT and seismic refraction data with cross-gradient structural constraints. We describe the main features of the algorithm and first apply it to synthetic data generated for a hypothetical complex geological model. For the synthetic data, we find that the scheme leads to models with remarkable structural resemblance and improved estimates of electrical resistivity and seismic velocity. We apply the scheme to near-surface field data to test the consistency of a previously suggested resistivity–velocity interrelationship and its potential use for subsurface lithofacies discrimination or structural classification. The MT-seismic relationship is found to be in excellent accord with that derived previously for DC resistivity and seismic data set at the test site. Our results suggest that joint MT-seismic cross-gradient imaging leads to improved characterization of heterogeneous geological targets at near-surface to mantle depths.     

Double-planed deep seismic zone and upper-mantle structure in the Northeastern Japan Arc

Summary. The ScSp wave converted from the ScS wave at the boundary between the descending lithospheric slab and the mantle above it was clearly observed from a nearby deep earthquake with magnitude 7.7 at some stations of the seismic network of Tohoku University which covers the Tohoku District, the northeastern part of Honshu, Japan. By applying the three-dimensional seismic-ray tracing method, the location of this boundary was determined from the difference in arrival time between the ScS and ScSp waves. The result shows that the upper boundary of the descending slab lies exactly on the upper plane of the double-planed deep seismic zone found in the Northeastern Japan Arc.
There is an additional evidence that the boundary is located on the upper plane of the double-planed deep seismic zone. The hypocentre distribution of intermediate-depth earthquakes located by the small-scale seismic-array observation is extremely different from that obtained by the relatively large-scale seismic network. The discrepancy in the distribution of hypocentres of the same earthquake independently located is well explained by the inclined lithospheric slab model derived from the difference in arrival time between the ScS and ScSp waves.
The earthquakes with reverse faulting or with down-dip compressional stresses occur at the upper boundary of the descending slab. Within the descending slab, the earthquakes with down-dip extensional stresses also occur in a very narrow zone from 30 to 40 km below the dipping boundary in the depth range from 50 to about 200 km, and these shocks form the lower plane of the double-planed deep seismic zone.     

Heterogeneous structure around the Jemez volcanic field, New Mexico, USA, as inferred from the envelope inversion of active-experiment seismic data

We analyse active-experiment seismic data obtained by the 1993 Jemez Tomography Experiment (JTEX) programme to elucidate the heterogeneous structure of the Jemez volcanic field, which is located at the boundary between the Colorado Plateau and the Rio Grande Rift. Using a single isotropic scattering assumption, we first calculate the envelope Green's functions for the upper and lower crust and the uppermost mantle. By fitting the theoretical envelopes with the observed three-component data, we estimate depth-dependent features of the scattering coefficients around Valles Caldera. We estimate the ratios of scattering coefficients, rather than scattering coefficients themselves, because of the uncertainty of the seismic efficiency of the explosive sources and knowledge of absolute site-amplification factors. The strongest scattering coefficients are observed at a shallow depth beneath the Valles Caldera. This is considered to be related to the complex structure caused by two episodes of caldera formation and the ensuing resurgent uplift in the caldera, etc. The depth-dependent characters of the scattering coefficients for the Colorado Plateau and the Rio Grande Rift are similar to each other: a transparent upper crust and a heterogeneous lower crust (small and large scattering coefficients, respectively). However, the scattering coefficients beneath the Rio Grande Rift are several times larger than those beneath the Colorado Plateau. Depths of the lower crust and the Moho boundary beneath the Rio Grande Rift are shallower than those of the Colorado Plateau. From their geological settings and other geophysical results around the region, we infer that the larger scattering coefficients of the rift are associated with rift formation and volcanic activity, such as magma ascent from the upper mantle to the crust.     

Characterization of the depocenters and the basement structure,below the central Chile Andean Forearc: A 3D geophysical modelling in Santiago Basin area

Since the last century, several geological and geophysical studies have been developed in the Santiago Basin to understand its morphology and tectonic evolution. However, some uncertainties regarding sedimentary fill properties and possible density anomalies below the sediments/basement boundary remain. Considering that this is an area densely populated with more than 6 million inhabitants in a highly active seismotectonic environment, the physical properties of the Santiago Basin are important to study the geological and structural evolution of the Andean forearc and to characterize its seismic response and related seismic hazard. Two and three‐dimensional gravimetric models were developed, based on a database of 797 compiled and 883 newly acquired gravity stations. To produce a well‐constrained basement elevation model, a review of 499 wells and 30 transient electromagnetic soundings were used, which contribute with basement depth or minimum sedimentary thickness information. For the 2‐D modelling, a total of 49 gravimetric profiles were processed considering a homogeneous density contrast and independent regional trends. A strong positive gravity anomaly was observed in the centre of the basin, which complicated the modelling process but was carefully addressed with the available constrains. The resulting basement elevation models show complex basement geometry with, at least, eight recognizable depocenters with maximum sedimentary infill of ~ 500 m. The 3‐D density models show alignments in the basement that correlates well with important intrusive units of the Cenozoic and Mesozoic. Along with interpreted fault zones westwards and eastwards of the basin, the observations suggest a structural control of Santiago basin geometry, where recent deformation associated with the Andean contractional deformation front and old structures developed during the Cenozoic extension are superimposed to the variability of river erosion/deposition processes.     

Upper Mantle Velocity Structure Estimated From Ps-Converted Wave Beneath the North-Eastern Japan Arc

Summary. The upper boundary of the descending oceanic plate is located by using PS -waves (converted from P to S at the boundary) in the Tohoku District, the north-eastern part of Honshu, Japan. the observed PS-P time data are well explained by a two-layered oceanic plate model composed of a thin low-velocity upper layer whose thickness is less than 10 km and a thick high-velocity lower layer; the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle. the estimated location of the upper boundary is just above the upper seismic plane of the double-planed deep seismic zone. This result indicates that events in the upper seismic plane, at least in the depth range from 60 to 150 km, occur within the thin low-velocity layer on the surface of the oceanic plate.