二维阵列线圈核磁共振地下水探测理论研究

核磁共振法(Magnetic Resonance Sounding,MRS)是一种直接探测地下水的地球物理方法,目前只能对水平层状的含水层进行一维测深,对于尺寸小于线圈直径的二维或三维含水构造成像时,其灵敏度和横向分辨率很低.本文从研究二维阵列线圈核磁共振地下水探测方式的可行性出发,推导了地面发射线圈产生的椭圆极化激发...     

渤海湾地区壳幔结构重磁综合研究

渤海湾盆地是华北克拉通破坏的中心,其东部渤海海域深部结构研究对认识华北克拉通破坏范围及动力学过程具有重要意义.为此,本文选取自河北新城经天津静海沿东南方向进入渤海海域的剖面进行重磁反演,研究其地壳结构特征.通过对该地区文献调研及2010年渤海海陆联测初步结果建立初始模型,结合本地区密度、磁化率特征进行二度半体重磁异常反...     

菲律宾及其邻近地区的地磁场模型研究

根据2001～2007年期间在菲律宾境内测量的74个点的地磁场数据,利用球冠谐和、泰勒多项式两种方法建立了2005.0菲律宾及周边地区地磁基本场模型,得到了菲律宾地区X、y、Z、D、I、H、F七个分量的分布.两种模型反映的同一地区的地磁场分布形态基本类似,只在拐点的舒缓度、等值线平滑度等方面存在区别.在8°N左右,X、...     

地磁台站的城市轨道交通干扰的小波抑制方法研究——以天津轨道交通干扰为例

我国地磁台站观测环境日益受到轨道交通干扰影响,导致地磁观测数据质量下降,制约地磁观测发展.因此,开展干扰抑制的数据处理方法研究,最大限度抑制干扰是提高观测数据质量切实可行的方法.本文提出轨道交通干扰的小波域噪声阈值抑制模型及方法.以天津轨道交通为例,选用受干扰的天津静海地磁台和未受干扰的参考台站河北红山地磁台观测资料,...     

火山岩油气藏重磁电震综合预测方法及应用

通过准噶尔盆地陆东地区数十口钻井资料的对比分析、归纳总结,提出了火山岩油气藏重磁电震综合预测方法.将正则化下延与延拓回返垂直二次导数串联形成了一个新的滤波器,该滤波器相当于首先通过正则化下延将位场曲面延拓至地下目的层段,降低火山岩埋深对磁J异常幅值的影响,然后利用延拓回返垂直二次导数对弱信号进行增强,不仅提高了位场异常...     

基于Laplace法的磁性球体参数确定

解析信号法被广泛应用于磁性目标平面位置确定中,然而,数值计算表明:斜磁化情况下,解析信号模极大值与磁性目标中心平面位置之间存在较大的偏差,最大可达探测深度的30%,从而制约了该方法在航空磁测或水深较深区域的应用.从理论上推导了磁性球体磁异常经拉普拉斯算子运算后信号(简称"拉普拉斯信号")表达式,分析了其具有的物理性质,...     

An integrated geodynamic model of the Nankai subduction zone and neighboring regions from geophysical inversion and modeling

I investigate large-scale deep crustal structures of the Nankai subduction zone and neighboring region using regional magnetic and gravity anomalies, heat flow measurements, and earthquake hypocenters. It is found that ages, dip angles, and geothermal states of the subducting slab have direct influences on mantle wedge serpentinization. The weakest serpentinization observed in the Nankai forearc region is associated with the youngest downgoing plate of the Shikoku Basin. Conspicuous gravity anomalies identified in the forearc region are coincidental spatially with magnetic anomalies after the reduction to the pole, a mathematical procedure that helps relocate magnetic sources and boundaries, and allows us to more easily interpret magnetic data. It is argued that these patches of magnetic and gravity anomalies are caused by the same sources of anomalous density and magnetization, and are linked directly to preexisting structures such as magnetic anomalies and their boundaries in the subducting oceanic crust. Since the gravity and magnetic anomaly patches are found to be closely related to interplate seismogenic behaviors in the Nankai subduction zone, I suggest that major magnetic boundaries in the Shikoku Basin are likely weak places for slab tears that trigger seismic segmentations along the subduction zone.     

History of faulting and magmatism in the Galilee (Israel) and across the Levant continental margin inferred from potential field data

The Galilee study area, northern Israel, is at present an uplifted, steep continental margin that formed mainly during the Jurassic and has a large positive isostatic anomaly. Since the Jurassic, it was modified by several tectonomagmatic events, which this study attempts to define and classify by updating, reprocessing and reinterpreting gravity, aeromagnetic and geological data. The prominent Rehovot-Carmel N–S positive reduced-to-pole (RTP) magnetic anomaly caused by the Gevim Volcanics, as well as the coexisting Helez-Gaash high Bouguer gravity and the Pleshet low Bouguer gravity, represent the deep (>5 km) Permo-Triassic dominant horst and graben structure of Israel. The Jonah Ridge and Beirut high SW–NE RTP magnetic anomalies in the Levant basin delineate the Levant continental edge that is marked by a deeply buried horst covered by a Late Cretaceous volcanic complex. The Asher and Devora Jurassic volcanics appear to be responcible for the Atlit and Galilee negative magnetic anomalies and for significant negative gravity anomalies which became clear after removing gravity effect of the upper (post-Turonian) light density sediments from the observed gravity. The volcanics extend along a SW–NE belt parallel to the strike of the Moho. It is suggested here that the Carmel-Gilboa fault propagated during the Late Cretaceous from the Levant basin across the Galilee area southeastward to form the Azraq-Sirhan graben in Jordan. As such, it forms a right-step, en echelon, dextral strike-slip fault with associated tectonic basins of various shapes. During the Oligocene and before formation of the Dead Sea transform (DST), the reactivation of the Azraq-Sirhan graben was accompanied by tectonic driven rift propagation in the opposite direction, from Azraq-Sirhan to northwest. It dispersed into many faults and terminated ∼10 km west of the present DST. During the Miocene it propagated in the same direction and includes internal volcanic activity. The numerous Miocene-Pliocene volcanic centers on the margins of the DST indicate that the preferred pathway for magmas at that time was not within the deep basins of the DST.     

早更新世以来青藏高原隆升作用在塔里木盆地腹地的响应

自约55Ma印度-欧亚板块碰撞,青藏高原经历持续挤压,发生多次阶段性隆升作用.晚新生代以来强烈隆升作用不仅造就了青藏高原北部强烈的构造变形效应,还引起了大规模的干旱化.位于塔里木盆地腹地(N38° 40.911′,E80°18.484′)的玛扎塔格褶断带东西向延伸约300km,南缘发育出露连续、完全的早更新世地层,岩性主要以灰黄色泥岩、粉砂质泥岩、粉砂岩为主,含有薄层粗砂岩及砾岩.本文延展了原来研究剖面,共采集古地磁样品90块共9个采点.系统热退磁结果揭示出了正反极性,高分辨率的磁性地层学及野外磁化率研究确定研究剖面时代约为2.2～0.1Ma,对玛扎塔格整个剖面地层的年龄控制提供了限定.利用MS2磁化率仪对野外剖面现场测量,采集209米695点数据.通过与深海氧同位素比对分析,说明磁化率结果不仅较好揭示了全球气候变化,还精确记录了约1.8Ma、1.2Ma、0.9Ma、0.65Ma等多期构造活动,并且直接证明年龄约0.05Ma的地层发生了较强构造变形.青藏高原早更新世以来隆升过程具有脉冲特征,约0.9Ma的强烈隆升使主体达到冰冻圈,起到的屏障效应使塔里木盆地开始较快速干旱化,同时为黄土高原提供了更多风尘物质和增强了对粉尘的搬运能力,导致巨厚的粗粒上砂岩层L9形成.     

地面高精度连续磁测在西天山群吉萨依铜矿勘查中的运用

近年来,地面磁法仪器测量精度和读数速度有根本性改变.特别是Overhauser和铯光汞磁力仪的应用,使读数间隔达0.1 s,而带有载波相位的GPS实时定位精度可达分米级.据新疆西天山尼勒克县群吉萨依铜矿区应用实例,展示出地面磁法连续测量比常规点距能够获得更多地磁场信息,提高发现异常能力和定性、定量解释精度.因此,该方法具很高社会效益和实际应用价值.