A rapid method for hydraulic profiling in unconsolidated formations

Information on vertical variations in hydraulic conductivity ( K ) can often shed much light on how a contaminant will move in the subsurface. The direct-push injection logger has been developed to rapidly obtain such information in shallow unconsolidated settings. This small-diameter tool consists of a short screen located just behind a drive point. The tool is advanced into the subsurface while water is injected through the screen to keep it clear. Upon reaching a depth at which information about K is desired, advancement ceases and the injection rate and pressure are measured on the land surface. The rate and pressure values are used in a ratio that serves as a proxy for K . A vertical profile of this ratio can be transformed into a K profile through regressions with K estimates determined using other techniques. The viability of the approach was assessed at an extensively studied field site in eastern Germany. The assessment demonstrated that this tool can rapidly identify zones that may serve as conduits for or barriers to contaminant movement.     

Hydraulic tomography for detecting fracture zone connectivity

Fracture zones and their connectivity in geologic media are of great importance to ground water resources management as well as ground water contamination prevention and remediation. In this paper, we applied a recently developed hydraulic tomography (HT) technique and an analysis algorithm (sequential successive linear estimator) to synthetic fractured media. The application aims to explore the potential utility of the technique and the algorithm for characterizing fracture zone distribution and their connectivity. Results of this investigation showed that using HT with a limited number of wells, the fracture zone distribution and its connectivity (general pattern) can be mapped satisfactorily although estimated hydraulic property fields are smooth. As the number of wells and monitoring ports increases, the fracture zone distribution and connectivity become vivid and the estimated hydraulic properties approach true values. We hope that the success of this application may promote the development and application of the new generations of technology (i.e., hydraulic, tracer, pneumatic tomographic surveys) for mapping fractures and other features in geologic media.     

天然气水合物存在的流体特征——以印度西部大陆边缘为例

印度西部大陆边缘的多道地震反射资料揭示了流体排驱是否与天然气水合物相关。在地震剖面上没有典型的似海底反射存在,为了在确定天然气水合物的存在,我们在印度西部大陆边缘的一个小水道找到其它地震反射证据。我们研究了通过海底的排气通道、麻坑、海底滑坡以及反映流体运移通道的断层、清楚的含气沉积、弱振幅、底辟和泥火山等,地震剖面上所有这些流体逸散特征预示着在天然气水合物稳定域内天然气水合物的可能存在。     

机器学习发现地震数据中的隐藏信号

正2018年5月,美国哥伦比亚大学的研究人员在Science Advances发表文章指出,在对加州间歇泉地热区的研究中,他们用机器学习算法从3年的地震记录中发现了不同类型的地震。在这一区域,地震的重复模式似乎与水流入地下热岩的季节性上升和下降相一致,由此说明,水的运移与引起岩石滑动或破裂的机械过程相关,进而引发地震。研究人员汇编了含有46 000次地震的地震目录,每个都以能量波形在震动图中表     

区域地震滑坡体积优化模型

求取滑坡体积在当前是一个难题,原因是其为三维分量,并且部分滑面往往在地下。本文提出了3个区域地震滑坡体积优化模型来计算2008年中国汶川M W7.9地震触发滑坡的体积。本文首先基于20m分辨率的震前和震后SPOT 5卫星影像提取到的数字高程模型(DEM)数据,结合少数滑坡的剖面图,获得了1 415处汶川地震滑坡堆积区体积,作为地震滑坡体积模型训练样本。在常规区域滑坡"体积—面积"模型基础上,提出了3个优化模型。分别利用数据的对数化线性拟合与直接非线性拟合方法对1个常规模型和3个优化模型进行拟合。结果表明,采用直接非线性拟合方法并考虑了滑坡长、宽、高、岩性、坡度和峰值地动加速度后,坡向的优化模型标准误差最小,回归得到的滑坡总体积与滑坡真实总体积也非常接近。将这一模型应用于所有汶川地震滑坡,分别得到每个滑坡的体积。最终结果表明,汶川地震滑坡相对密集分布区内的196 007处滑坡的堆积物体积约为1.2×1010 m~3,源区体积约为1×1010 m~3。根据前人"地震震级—滑坡总体积"经验公式得到的结果仅仅是本文结果的7.5%~9%,这提醒我们有必要基于更多的单次地震触发滑坡总体体积数据对"地震震级—滑坡总体积"的关系进行更新。同时,文中的优化模型对同类研究也有显著的参考价值。     

基于计算智能技术的巴基斯坦北部地区地震活动性预测

本文针对巴基斯坦北部地区进行了地震预测研究。研究方法包含了地震学和计算智能技术领域不同学科的交叉融合。针对历史地震活动计算了8种地震学参数。通过计算它们的信息增益来评估这8种参数的预测效能,进而选择了其中6种应用于预测试验。基于这6种参数发展了多个计算智能模型用于预测试验。这些模型包括前馈神经网络、循环神经网络、随机森林、多层感知、径向基神经网络和支持向量机。本文评估了每一种模型的效能,同时利用McNemar统计检验方法来研究计算方法的统计显著性。前馈神经网络模型在巴基斯坦北部地区可表现出统计显著性为75%准确率和78%正确预报的预测结果。     

Crustal deformation revealed by GPS in Kumaun Himalaya,India

The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust(MCT).Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT.Our study,based on the campaign mode GPS survey during 2003- 2006,reveals that the area between north of North Almora Thrust(NAT) and at the base of Great Himalaya registers maximum strain rate,which is lowered towards the Trans Himadri Fault(THF).The GAMIT-GLOBK processed campaign data of the area show that currently,the Himalayan Frontal Fault(HFF) and Main Boundary Thrust(MBT) are locked with the Indian plate,and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India.     

汶川—芦山地震之间地震空区及邻区的微震时空分布特征及指示意义

在龙门山西南段,汶川和芦山两次地震之间地震空区产生的物理机制及其未来的地震活动性仍然是亟需进一步研究的问题。现有研究结果也无法完全解释地震空区挤压应变/应力的调节模式。我们使用Match and Locate方法获取了2015年5月至12月时段内空区及邻区的详细的背景地震目录,完备性震级为M_c=0.2,微震的时空分布特征凸显了小震级事件的丛集(簇)特征。在深度域上,微震在空区两端的优势深度存在明显差异,南端深于北端,表明空区作为汶川和芦山两次地震破裂的转换带。我们的微震探测结果表明空区存在明显的微震"亏空",否定了其通过微地震释放累积应力的调节模式。我们发现该区域内,不同震级范围内的背景地震活动性都与降雨变化率存在明显的反相关关系。在夏、秋季节,地震活动性极值滞后于降水极值1～2个月,库仑模型计算表明增强的地震活动性很可能被浅地表含水量的减少所触发,季节性降水在一定程度上调节了背景地震活动性。相较于震级大于3.0的背景地震,背景微震对降水的变化具有更敏感的响应,这可能由其更短的起始周期所致。     

四维高分辨率活动构造研究

自野外调查的开创性论文发表以来,活动构造学已有100多年的历史,但它仍然是构造地质学中一个相对年轻的分支学科。该学科主要研究板块构造运动引起的应变积累和通过发生地震(或其他事件)对应变的释放。也就是说,活动构造旨在描述板块构造的过程。确定地震年代、断层滑动速率和其他常见的活动构造研究目标,极大地加深了我们对断层力学和地壳流变学等方面的理解。地震危险性评估和风险缓解方面的需求进一步推动了对大地震和潜在破坏性地震复发特征的研究。活动构造研究中的主要数据来源是地表和浅层地下断裂作用痕迹,两者分别通过地形地貌和地层资料显示。大约在40年前,地质学家开始通过对活动断层错断地层、地貌标志物的野外观察和航空照片解译,建立了地震复发的端元模型。自那以后,特别是在最近20年内,技术的发展极大地提高了地形数据的丰富性和分辨率,增强了对地层单元和地貌面进行定年的能力,这为我们建立更合理的地震复发概念模型奠定了基础。本文对近年来促进活动构造研究不断发展的高分辨率地形数据和测年方法进行了综述。     

Assessing temporal variation of coloured dissolved organic matter in the coastal waters of South Eastern Arabian Sea

Coloured dissolved organic matter （CDOM） plays a major role in marine photochemical and biological processes and its optical properties are known to affect the underwater light penetration. This paper highlights in situ optical estimation and satellite retrieval of CDOM in deciphering its temporal variations in coastal waters of the South Eastern Arabian Sea. The study accentuated the source of CDOM as terrigenous origin during monsoon, of in situ productions during pre-monsoon and during post-monsoon of autochthonous-allocthonous origin. The matchup analysis for in situ and MODIS Aqua retrieved A_dg443 exhibited bias which decreased by incorporating the seasonal component. The study also identified degrading bloom of Noctiluca scintillans as the source for exceptionally high CDOM in the area during January and February. The study demands to incorporate seasonal components and phytoplankton abundance while assessing the performance of CDOM algorithms in optically complex coastal waters.