共查询到18条相似文献,搜索用时 422 毫秒
1.
2.
规则体重力异常余弦变换谱特征及反演 总被引:1,自引:0,他引:1
提出利用余弦变换,研究规则体重力异常谱特征及反演方法。推导出球体、无限长水平圆柱体、无限和有限延伸垂直台阶的重力异常余弦变换谱及反演表达式。球体与无限长水平圆柱体的余弦变换谱相似,无限延伸垂直台阶的变化很尖锐,有限台阶的表现为上、下有规律的跳跃。在模型反演算例中,选择了适当的采样间隔和“趋势镶边”法,反演的圆柱体线密度和轴心深度误差分别为0.25%和3.8%。 相似文献
3.
为了对近直立特厚煤层冲击地压进行防治,采用地面岩柱深孔爆破方法对煤层间岩柱进行预裂爆破,并采用地面EH-4探测法和井下瞬变电磁探测法对爆破前后岩柱体的物理力学结构进行探测,对卸压效果进行分析。EH-4探测表明,深孔爆破后岩柱结构破坏明显,在+550~+650 m水平范围时,岩柱体的电阻率等值线由近直立向近水平发育,视电阻率值主要集中在150~250 Ω·m,明显高于未爆破区域;井下瞬变电磁探测表明,深孔爆破后岩柱裂隙增大,探测区域前方20~90 m,视电阻率值从爆破前的25~86 Ω·m增加到爆破后的84~216 Ω·m,出现高阻异常区域。深孔爆破后岩柱破碎效果较好,岩柱体内积聚的弹性能得到释放,卸压效果明显,有效降低了冲击地压发生的危险性。 相似文献
4.
5.
利用重力归一化总梯度及相位法研究断裂构造 总被引:9,自引:1,他引:8
用波数域的位场转换和快速傅立叶变换理论研究重力归一化总梯度和归一化相位;在波数域向下延拓和导数计算的滤波算子中,分别引入圆滑滤波因子,抑制了向下延拓计算中对噪声干扰的放大作用,增加了计算的稳定性;利用改进的方法,计算并阐述了4种断裂构造GH场等值线和相位曲线的变化特征;别列兹金重力归一化总梯度法中极大值理论在研究断裂构造中具有局限性,对于无限延伸断裂构造,应根据GH场等值线的走向、形状的特点,结合归一化相位曲线的转折点确定断裂空间位置. 相似文献
6.
方向滤波方法是用于区分不同走向的叠加重力异常的一种方法。本文根据地震勘探二维滤波的原理,提出了可任意改变滤波方向的扇形和矩形滤波器的设计,并给出了各种模型上的滤波结果,本方法可用于区分重力异常,提高分辨不同方向场源产生的异常,从而有利于分析研究地区的格造格局。有走向的物体在空间域其异常的等值线是有走向的,在频率域其异常的振幅谱也是有走向的,且与异常走向垂直。可以利用多方位方向滤波方法,提高不同方向场源产生的异常的分辨率,从而有利于区域重力资料的异常分区和分析研究地区的主要构造格局。 相似文献
7.
黑龙江省虎林盆地单元结构的地质-地球物理研究 总被引:3,自引:0,他引:3
采用基于余弦变换的重力异常向上延拓及常密度单界面重力异常反演方法对虎林盆地布格重力异常进行了处理,反演了基底深度。结合穿过盆地的重力和大地电磁测深剖面资料及俄罗斯一侧的阿尔昌盆地的地质资料,分析了虎林盆地地质-地球物理所反映的盆地南部和北部基底结构的差异性。研究结果表明:敦密断裂(由2支断裂组成)中的南支断裂倾向直立,走滑特征明显,控制着其两侧断块的走滑及盆地的形成和演化过程,为主干断裂;以其为分界线,虎林盆地由地质和地球物理性质完全不同的2个盆地(南部盆地和北部盆地)组成,北部盆地为大三江盆地的一部分,南部盆地则属于另外一个独立的盆地体系。 相似文献
8.
重力勘查成果表明,重力异常总体上反映了羊八井盆地总体形态,走向北东,北东侧重力等值线已经封闭,自东向西呈逐渐减低趋势,北侧和南侧重力值明显增高,以二电厂为中心,存在一个面积较大的低重力异常,而其南西相伴存在一个范围较小的高重力异常,它们反映着深部的一些地质特征。 相似文献
9.
10.
本文导出了某些三维规则形体重力异常的希尔伯特变换式。以球体和无限长直立圆柱体为例,利用异常中心剖面中心部位异常数据的转换值,进行反演定量解释,所得结果精度是令人满意的。 相似文献
11.
基于离散余弦变换(DCT)的重力异常垂询二阶导数的计算方法是笔者提出的新方法。以无限长水平圆柱体为例研究了DCT法的计算规律:模型实验证实,该法计算的无限长水平圆柱体重力异常垂向二阶导数的精度与采样闻隔、剩余密度及圆柱体半径大小无关。与圆柱体轴心埋藏深度成正比。通过分析给出了基于DCT的合适的线性滤波方式,滤波后的重力异常垂向二阶导数与理论二阶导数拟合效果好,具有较高的计算精度。 相似文献
12.
13.
利用DCT法计算重力归一化总梯度 总被引:1,自引:0,他引:1
利用重力归一化总梯度方法可以寻找场源位置,通过“两高夹一低”的典型场特征可以检测油气构造,传统的方法主要采用的是别列兹金法(即傅立叶级数法)和傅立叶变换法。利用DCT法计算重力归一化总梯度是最新研究方法。从理论上给出了基于DCT的重力异常转换公式,进而研究了无限长水平圆柱体、三度体非含油气球冠以及储油球冠模型GH场特征。模型实验证实:随着地质体埋深的增大,谐波数会逐渐减小,GH场奇点极大值向下移动,且呈现线性衰减的特征;储油球冠GH场等值线表现出明显的“两高夹一低”的储油气藏典型标志;用DCT法计算的GH场具有优良的稳定性,而且能够增加向下延拓的计算深度。 相似文献
14.
Nurudeen Kolawole Olasunkanmi Olufemi S. Bamigboye Adebayo Aina 《Arabian Journal of Geosciences》2017,10(24):541
This report details the result of geophysical exploration for iron ore; which involved vertical magnetic intensity (?Z) and gravity measurements, to delineate the geometry and depth extent of the deposit and acquiring quantitative and qualitative information for pre-drilling purposes in Agbado-Okudu. It is located about 3 km from Jakura along Lokoja-Jakura marble quarry and within low latitude precambrian basement complex district of Kogi State, Nigeria. A total of 517 magnetic measurement points along 16 traverses and 330 gravity reading along 11 profiles on the deposit in northeast–southwest azimuth were undertaken. The magnetic and gravity data enhancement involved linear regression curve fitting and fast Fourier transform, which were used to construct residual magnetic (RM) and gravity (RG) anomalies, analytic signal amplitude, Euler deconvolution at varying spectral indices (SI), power spectrum, and source parameter image (SPI), using the submenu of Geosoft Oasis Montaj software. Interpretation of the RM and RG anomalies revealed a primary causative body which perfectly correlates the positive anomalies and iron ore deposit, in form of a horizontal or gently dipping dyke with strike length of 600 m and average width of 110–130 m, within the gneiss complex in the north and trending south of the area. A secondary causative body associated with the negative anomalies and inferred as a vertical/near vertical thin sheet striking northeast–southwest coincided with the granitic and quartzitic intrusion. The NW–SE and E–W lineament trend conformed Kibarian and Liberian orogeny cycles of generally known structural trends in Nigeria, which shows that the iron ore deposit is structurally controlled. Depths to sources were estimated within range ≤ 2–24 m and 37.5–60 m, regarded as shallow and relatively deep depths, respectively. Ten vertical boreholes ranging in depth between 50 and 100 m are recommended, five of which require a priority attention to ascertain the thickness of the primary causative body. 相似文献
15.
基于DCT的重力异常数据处理正、反演方法具有较高的精度,计算方法稳定性优良。将基于DCT的重力异常水平一阶导数、垂向一阶导数、常密度单界面异常反演和Euler反褶积等正、反演方法用于大庆探区外围虎林盆地DB1线重力异常数据处理中,综合分析了该线重力场特征。利用基于DCT的Euler反褶积法反演出断层14条,分析了其中7条较深大断裂的性质。根据反演的结晶基底起伏情况和断裂构造剖面轨迹的基本特征,将DB1线划分为两隆两坳的构造格局,其中七虎林河断陷是由古新纪(E)断陷与早白垩纪(K1)残余盆地组成的2个旋回(E+ K1)的叠合盆地,而凯北坳陷为早白垩纪(K1)的残余盆地。把敦密南北支2条断裂确定为虎林盆地控盆断裂,阐述了控盆断裂的动力学特征。 相似文献
16.
The decrease of density contrast with depth in sedimentary basins is approximated by an exponential function. The anomaly
equation, in frequency domain, of a prismatic model with an exponential density function is derived. The method has been extended
to derive the Fourier transforms of the gravity anomalies of the sedimentary basin, wherein the basin is viewed as vertical
prisms placed in juxtaposition. The gravity anomalies of the sedimentary basin are obtained by taking the inverse Fourier
transforms. Filon’s method has been extended for calculating accurate inverse Fourier transforms. The accuracy of the method
has been tested using a synthetic example. A combination of space and frequency domain methods have been developed for inversion
of gravity anomalies over the sedimentary basin. The method has been applied to interpret one synthetic profile and one field
profile over the Godavari basin. The method developed in this paper to calculate the inverse Fourier transforms yields continuous
spectrum with accurate values. The maximum depth deduced from the gravity anomalies is of the same order as the depth encountered
to the basement at the Aswaraopeta borewell. 相似文献
17.
William E. Strange 《Tectonophysics》1979,52(1-4)
Repeat gravity measurements have been carried out over more than 1000 km of level lines in southern California. The initial surveys over a number of these lines were made in 1962. Repeat gravity survey lines are located primarily in the San Joaquin Valley, in the Los Angeles and Palmdale areas and in the Imperial Valley. Secular changes of gravity have been noted in a number of areas. In areas of subsidence, due to groundwater withdrawal, direct correlation between elevation and gravity change is found. In areas of vertical crustal motion along fault zones, such as in the Palmdale area, gravity changes are also noted. However, these are not, in general, directly related to elevation change. Apparently, subsurface mass redistributions are associated with the vertical motions noted in fault-zone areas before and after earthquakes. Several possible models to explain the gravity observations are being explored. 相似文献
18.
G. Ramadass I. Arunkumar S. M. Varaprasada Rao N. L. Mohan N. Sundararajan 《Journal of Earth System Science》1987,96(3):211-219
The auxiliary functions, namely amplitude, phase, envelope and instantaneous frequency of Hilbert transform over gravity anomalies
of 2-D sphere, vertical fault block and horizontal circular cylinder are studied. The characteristics of these functions are
established in locating and identifying the sources. The method is illustrated with a theoretical example in each case and
supported by field data of gravity anomaly over Humble dome and spherical model of the Satak-Mansar area, Nagpur District,
India. 相似文献