Attenuation differences in layer 2A in intermediate- and slow-spreading oceanic crust     

D. Goldberg  Y.F. Sun 《Earth and Planetary Science Letters》1997,150(3-4):221-231

In situ seismic attenuationQ⁻¹logs are derived from borehole velocity profiles and reveal sharp boundaries between morphologies of the extrusive volcanic layers in intermediate- and slow-spreading oceanic crust.Q⁻¹logs are calculated from the scattering attenuation associated with vertical velocity heterogeneity in Ocean Drilling Program Holes 504B and 896A and in Hole 395A, located in 5.9–7.3 Ma crust on the Pacific and Atlantic plates, respectively. Our results strongly tie crustal properties to seismic measurables and observed geological structures: we find that the scattering attenuation can be used to identify the extrusive volcanic sequence because it is closely related to changes in the degree of vertical heterogeneity. We interpret a distinct decrease in the Q⁻¹log at the transition below the extrusive volcanic layer to correspond with the seismic layer 2A/2B boundary. The boundary is located at 465 m depth below the sea floor in both Hole 395A and 504B, although this is likely to be a coincidence of the sediment thickness at these sites. Layer 2A is estimated to be approximately 150 m thick in Hole 504B and > 300 m thick in Hole 395A. Cyclic sequences of high-porosity pillows and low-porosity massive units in the uppermost 100 m of volcanics in Hole 395A result in large velocity heterogeneities which cause > 5 times more attenuation in this layer than in Hole 504B. In Hole 896A, by contrast, fewer pillows, more massive flows, and a greater volume of carbonate veins decrease the velocity heterogeneity and attenuation significantly over only 1 km distance from Hole 504B. We conclude that the attenuation in the extrusive volcanics of the ocean crust is largely controlled by variation in local heterogeneity and morphology as well as by subsequent hydrothermal alteration. The observed differences inQ⁻¹profiles and layer 2A thickness at these sites may be attributed to variations in the volume and duration of volcanic activity at mid-ocean spreading centers for these Pacific and Atlantic ridge segments.  相似文献   

油田中,高含水期小层剩余油研究     

马正  桂峰 《地质科技情报》1997,16(2):57-61

综合利用岩心分析、测井及动态开发资料研究了扶余油田西一、二区北的剩余油分布规律，所研制的油田中、高含水期确定小层剩余油分布图，解决了油田开发中的动态预测小层剩余油分布的难题，并且对１９８２年和１９９２年底的剩余油分布规律作了分析。  相似文献   

高密度电阻率法在地下涵洞勘测中的应用   总被引：1，自引：2，他引：1  

汤洪志  官云鹏 《华东地质学院学报》1997,20(4):343-348

本文介绍的高密度电阻率法是一种新兴的电阻率方法，与常规电阻率方法相比，高密度电阻率法具有成本低，效率高，测点密集，反映地电信息更丰富，更直观以及资料解释简单方便等特点。本文运用高密度电阻率法勘测地下涵洞，实践证明，高密度电阻率法获得的图形，质量高，解释误差小，是一种方便实用，效果良好，能广泛应用于工程勘测的物探方法。  相似文献   

吉林省地质灾害类型及防治对策探讨     

腾继奎 《吉林地质》1997,16(2):62-64

本文针对吉林省的地质灾害类型及各类地质灾害的成因，分布及其危害进行了论述。对其防治对策进行了探讨，提出了切合本省实际的五项防治措施。  相似文献   

中强震与江苏新沂地震台地电阻率异常的关系研究   总被引：1，自引：0，他引：1  

李飞  孙雷 《山西地震》2004,(4):19-22,30

运用速率法、滑动富氏法对江苏省新沂地震台1990年至1999年地电阻率观测资料进行了分析，研究了电阻率异常与江苏省及其邻近地区的中强震的关系。结果表明．从1994年到1997年之间发生的中强震，新沂地震台地电阻率3个测向有不同程度的异常与之对应。研究结果表明．资料异常呈现出的各向异性和其对应性与地球自转加速年份、孕震期的应力状态、震区构造、介质结栖有关。  相似文献   

地壳介质弹性和电性各向异性研究的新进展   总被引：3，自引：2，他引：3       下载免费PDF全文

李清河  阮爱国  范小平  金淑梅 《地震工程学报》2004,26(1):10-17

分析了地壳介质各向异性研究的现状，指出了弹性和电性各向异性研究中存在的问题，提出了联合利用弹性和电性各向异性研究地球介质特征及提取物性参数的正反演方法．理论研究和地震过程的实际资料表明，将弹性和电性结合起来研究地壳介质各向异性具有清晰明确的物理意义，是各向异性研究的一个非常有发展前景的新领域。  相似文献   

测井技术在灰岩地区隧道深孔勘探中的应用     

申建平  何红生 《中国煤田地质》2004,16(3):57-60

鄂西地区完整灰岩地层的视电阻率、密度、声波、自然伽马等曲线形态受灰岩胶结物质成份和泥质含量影响并具有一定的规律性，当灰岩地层受到构造、溶蚀作用产生破碎带、岩溶、裂隙等不良地质体或存在地下含水体时，各测井物理参数发生变化并在曲线形态上呈现异常反映，据此可以对不良地质体的位置、规模、类型进行准确判断。测井技术在鄂西地区灰岩地区隧道深孔勘探中的应用，补充、验证了钻探资料，为隧道设计、施工提供了可靠的依据。  相似文献   

高密度电阻率法在探测煤层露头中的应用     

杨永明 《中国煤田地质》2004,16(Z1):96-97

新 疆 含 煤 地 层 具 有 地 层 倾 角 大 、煤 层 厚 度 较 大 、上 覆 第 四 系 厚 度 薄 等 特 点 ,适 宜 用 高 密 度 电 阻 率 法 追 踪 煤层 露 头 。新 疆 煤 田 地 质 局 物 测 队 使 用 复 合 对 称 四 极 剖 面 法 、联 合 剖 面 法 和 中 间 梯 度 法 等 方 法 ,在 拜 城 县 梅 斯 布 拉 克矿 区 探 测 煤 层 露 头 的 隐 伏 位 置 ,收 到 了 很 好 的 效 果 。  相似文献   

Optimizing a layered and laterally constrained 2D inversion of resistivity data using Broyden's update and 1D derivatives     

Anders V. Christiansen  Esben Auken   《Journal of Applied Geophysics》2004,56(4):247

Dense profile-oriented resistivity data allows for 2D and 3D inversions. However, huge amounts of data make it practically impossible to do full 2D or 3D inversions on a routine basis. Therefore, a number of approximations have been suggested over the years to speed up computations. We suggest using a combination of Broyden's update on the Jacobian matrix with derivatives calculated using a 1D formulation on a parameterized 2D model of locally 1D layered models. The approximations bring down the effective number of 2D forward responses to a minimum, which again gives us the ability to invert very large sections. Broyden's update is not as useful with a parameterized problem as is the case with a smooth minimum structure problem that has been the usual application. 1D derivatives, however, seem to be very effective when initiating a full 2D solution with Broyden's update. We compare the different methods using two different kinds of data on two synthetic models and on two field examples. The most effective and reliable optimization combines 1D derivatives with a full 2D solution and Broyden's update. When using Broyden's update the Jacobian matrix needs to be reset every once in a while. We do this whenever the difference in data residual from the previous iteration is less than 5%. This combined inversion method reduces the computation time approximately a factor of 3 without losing model resolution.  相似文献   

用测井方法确定深部隐伏构造的实例一则     

张德权  贺颢  张彦林  陈韶 《物探与化探》2004,28(4):298-299,319

通过1个实例,说明应用测井方法并结合区域地质资料进行综合对比分析,可了解区域范围内地下隐伏构造和不同层系的地层岩性在空间上的展布,找出赋存地下水的有利地段。  相似文献