2.5-D DC Resistivity Modeling Considering Flexibility and Accuracy

We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved...     

PROTEM-37瞬变电磁测深系统及应用实例

PROTEM - 37仪器具有分辨率高、动态范围大、抗干扰能力强、探测深度较大等优良性能。简要介绍了该仪器的测深原理、工作装置、野外施工步骤以及资料的处理解释。对TEM和MT资料的联合反演作了有益的尝试。介绍了该仪器在探测地下洞穴、勘察金属矿以及煤田水文地质调查等方面     

A double-differenced cycle slip detection and repair method for GNSS CORS network

The difficulty to detect and repair cycle slip of carrier phase measurements is a key limit for continuously high accuracy of GNSS positioning and navigation services. We propose an automated cycle slip detection and repair method for data preprocessing of a CORS network. The method jointly uses double-differenced (DD) geometry-free (GF) combination and ionospheric-free observation corrected for the computed geometrical distance (IF-OMC) to estimate the cycle slips in dual-frequency observations. The DD GF combination, which is only affected by the ionospheric residual, can be used to detect cycle slips with high reliability except for special pairs such as (77, 60) on GPS L1/L2 frequencies. The detection principle of the IF-OMC observable is such that there is a large discontinuity related to the previous epoch when cycle slips occur at the present epoch. The disadvantages of these two combinations can be overcome employing the proposed detection method. The cycle slip pair (77, 60) has no effect on the GF combination, while a change of 14.65 m is derived from GPS L1/L2 observations using the IF-OMC algorithm. Using pre-determined station coordinates as precise values, we found that the accuracy of the DD IF-OMC combination was 18 mm for a 200-km CORS baseline. Therefore, cycle slips in dual-frequency observations can be correctly and uniquely determined using DD GF and IF-OMC equations. The proposed method was verified by adding simulated cycle slips in observations collected from the CORS network under a quiet ionosphere and shown to be effective. Moreover, the method was assessed with observations made during intense ionospheric activity, which generated extensive cycle slips. The results show that the algorithm can detect and repair all cycle slips apart from two exceptions relating to long data gaps.     

SAR image despeckling with a multilayer perceptron neural network

Speckle noise in synthetic-aperture radar (SAR) images severely hinders remote sensing applications; therefore, the appropriate removal of speckle noise is crucial. This paper elaborates on the multilayer perceptron (MLP) neural-network model for SAR image despeckling by using a time series of SAR images. Unlike other filtering methods that use only a single radar intensity image to derive their parameters and filter that single image, this method can be trained using archived images over an area of interest to self-learn the intensity characteristics of image patches and then adaptively determine the weights and thresholds by using a neural network for image despeckling. Several hidden layers are designed for feedforward network training, and back-propagation stochastic gradient descent is adopted to reduce the error between the target output and neural-network output. The parameters in the network are automatically updated in the training process. The greatest advantage of MLP is that once the despeckling parameters are determined, they can be used to process not only new images in the same area but also images in completely different locations. Tests with images from TerraSAR-X in selected areas indicated that MLP shows satisfactory performance with respect to noise reduction and edge preservation. The overall image quality obtained using MLP was markedly higher than that obtained using numerous other filters. In comparison with other recently developed filters, this method yields a slightly higher image quality, and it demonstrates the powerful capabilities of computer learning using SAR images, which indicate the promising prospect of applying MLP to SAR image despeckling.     

准噶尔盆地玛湖凹陷三叠系源上砂砾岩扇—断—压三控大面积成藏模式

准噶尔盆地玛湖富烃凹陷下三叠统百口泉组新近发现了我国首个源上大面积连续型砂砾岩油藏群,是对全球"连续型"油气藏研究的新补充,但其成藏机理和模式并不很清楚。为加强对其的理论认识,并为下步勘探提供参考,基于油气生、储、盖、圈、运、保等基础石油地质条件,并结合油气藏特征,进行了成藏条件与成藏模式的综合研究。结果表明,优质充足的下二叠统风城组碱湖油气来源、规模有效的扇三角洲前缘砂砾岩储层、多重组合的扇三角洲平原致密砾岩、泥岩和断裂封盖保存、沟通良好的高角度断裂输导体系、平缓连续的构造背景奠定了大面积连续成藏的地质基础。在此背景下,高成熟的风城组所生成油气,在切穿烃源灶和储层的高角度压扭性断裂沟通下,优先充注物性相对好的扇三角洲前缘水下河道砂岩和砂质细砾岩,并且在地层异常高压促进下,控制着油气富集程度,使得油气成藏表现为大型缓坡浅水扇三角洲沉积控制下的源上扇-断-压三控大面积"连续型"。百口泉组油气藏具有的油质轻且含气、微裂缝广泛发育,以及异常高压等,决定了砾岩储层虽总体低孔低渗,但依旧能够高产。在油源断裂沟通的斜坡区上倾方向,叠合地层异常高压以及扇三角洲前缘水下河道砂砾岩的区域是下步有利勘探方向。     

兰州倾斜固体潮潮汐参数的观测研究

本文介绍了兰州形变台FSQ—水管倾斜仪1987—1989年期间观测资料的调和分析结果,讨论了潮汐因子的重复性及其对非潮汐变化的监测能力,分析了气象因素对周日波的影响,並将实测潮汐因子与G—B地球模型理论值进行了比较。     

敏感性分析在烃源岩成熟度史模拟中的应用——以川东北地区普光5井古生界海相烃源岩为例

通过分析输人模型的参数对输出结果的影响,可以确定影响烃源岩成熟度史模拟的敏感性参数.本文应用Easy% Ro化学动力学模型,以普光5井为例,对川东北地区各期构造运动剥蚀厚度、古地表温度和古地温梯度进行了相关的敏感性分析.分析结果表明:研究区下寒武统、下志留统、下二叠统和上二叠统烃源岩现今成熟度状态完全受控于燕山运动晚幕...     

羌塘盆地毕洛错地区古油藏地球化学特征与油源对比

羌塘盆地是一个大型中生代海相沉积盆地,盆地内发育多套烃源岩,并发现多处古油藏和油气显示,确定古油藏油源对油气勘探至关重要.为明确古油藏油源,对古油藏和烃源岩样品进行地球化学分析.研究表明古油藏可分为2类:Ⅰ类古油藏整体处于成熟-高成熟阶段,C₂₄四环萜烷丰度较高,三环萜烷丰度低,C₂₉规则甾烷占有一定优势,C₂₉藿烷含量较高,体现出以陆源有机质贡献为主的特征.Ⅱ类古油藏整体处于低成熟-成熟阶段,以C₂₃三环萜烷为主峰,低丰度C₂₄四环萜烷,C₂₇规则甾烷占优势,表明母质来源以低等水生生物为主.油源对比表明,两类古油藏来源于不同的烃源岩,Ⅰ类油藏来自于上三叠统扎那组烃源岩,Ⅱ类油藏主要为下侏罗统曲色组烃源岩的贡献.      

中更新世以来西菲律宾海上层水体结构演化特征——来自钙质超微化石Florisphaeraprofunda的证据

MD06-3050岩芯位于西菲律宾海吕宋岛以东本哈姆高原,利用钙质超微化石下透光带种属Florisphaera profunda占总颗石的相对丰度,恢复了中更新世以来该海区的上层水体结构演化特征。结果显示,西菲律宾海区自1040ka以来,温跃层/营养跃层经历了由浅—深—浅—深的长周期变动,可能是由于全球碳库的长周期变化对气候系统的大规模调整所致; 同时温跃层/营养跃层也具有明显的冰期-间冰期旋回性特征。温跃层变动的另一个重要特征是在中布容事件前后呈现出相反的冰期-间冰期变化趋势,认为可能是由东亚冬、夏季风强度变化引起。     

The first near real-time inverted echo sounder observation in the South China Sea

正We report the first near real-time inverted echo sounder (IES) observation in the South China Sea (Fig.1).Although the first IES observation in the South China Sea was in 2005,and the near real-time IES observation module was first developed in 2012(http://www.po.gso.uri.edu/dynamics/IES/hist.html),the real-time IES has never been deployed in the South China Sea until the reporting of observations in this study.IES is a bottom-mounted mooring that records the round-trip acoustic travel time from the bottom to the surface and back (τ),