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排序方式: 共有149条查询结果,搜索用时 234 毫秒
41.
根据哈萨克斯坦萨特地震台、中国新疆乌什地震台的地震资料分别作出单台小地震平均机制解,研究了1990年11月12日阿拉木图附近的巴依沙隆6.7级地震前后小区域应力场的变化.同时利用乌鲁木齐地震台的资料研究了该区在强震前后小地震平均机制解的变化.研究表明:天山地区强震前单台小地震平均机制解有P轴转向、初动符号矛盾比下降等征兆反应。对将单台小地震平均机制解用于地震预报等问题进行了讨论. 相似文献
42.
普查1990~2003年河南寒潮资料,筛选出发生在11月上旬的全省性寒潮天气过程,对过程发生前5~10天的候图进行位势高度梯度分析及合成分析,从梯度场和合成图中找出秋季寒潮爆发前5~10天的特征。 相似文献
43.
关于网外地震的定位问题--利用福建区域数字地震台网资料测定台湾地震震源位置 总被引:1,自引:2,他引:1
针对地壳内部的网外地震震源的定位问题,由震相组合成不同的方程组,利用均值寻查定位法迭代求解。在选取地球物理参数模型时,考虑了台湾地震部门定位时所用的模型和华南地区地震走时表等。利用福建数字地震台网记录到的绕射波Pn、Sn的到时资料,通过定位程序测定了134个位于台湾区域的壳内地震的震源位置。测定结果与台湾地震部门在其网址上公布的结果进行比对.平均震中位詈相差9km.震源深度相差8km. 相似文献
44.
This paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the Karst Feature Database (KFD) of Minnesota. Nearest neighbor analysis (NNA) was extended to include different orders of NNA, different scales of concentrated zones of sinkholes, and directions to the nearest sinkholes. The statistical results, along with the sinkhole density distribution, indicate that sinkholes tend to form in highly concentrated zones instead of scattered individuals. The pattern changes from clustered to random to regular as the scale of the analysis decreases from 10–100 km2 to 5–30 km2 to 2–10 km2. Hypotheses that may explain this phenomenon are: (1) areas in the highly concentrated zones of sinkholes have similar geologic and topographical settings that favor sinkhole formation; (2) existing sinkholes change the hydraulic gradient in the surrounding area and increase the solution and erosional processes that eventually form more new sinkholes. 相似文献
45.
本文利用近震、地方震的各种震相的走时方程,经过变换,取得相应的二次型目标函数。对目标函数用一维寻查法、均值寻查法求出其零值点的自变量,即求得各个方程的解;再用均值寻查法求得各个方程的共解,即得震源位置。随机地处理了自2000~2003年6月福建数字地震遥测台网记录到的本省及周边地区的205个地震,定位结果显示走时残差的平均值为0.25s。在可供比较的前提下,将159个地震数据的奇异值分解法的结果与本文的结果进行对比,前者的平均走时残差为0.72s,后者为0.25s,且后者的每一个地震的走时残差都比前者小。 相似文献
46.
基于震源断层面的空间取向和滑动方向,写出力轴张量在地理坐标系中的表达式,进而给出计算平均力轴张量及主值的方法,即通过求解相应的本征方程得到。对使用多个震源机制解中T,B,P轴参数计算平均应力场的正确性,以许忠淮用滑动方向拟合法反演富蕴、唐山地区平均应力场数据进行计算和验证。选择具有地震构造意义地块或地震带内大量地震的震源机制解研究区域平均应力场。根据福建东南沿海地区47次主要地震的震源机制解,给出了该区应力张量的定量分析结果。该方法物理意义明确,使由大量地震震源机制解资料分析构造应力场的方法走向定量化,并为定量探索区域应力场的整体动态变化成为可能。 相似文献
47.
48.
我国地面太阳辐射量的时空变化研究 总被引:30,自引:1,他引:30
在分析我国到达地面太阳辐射量(1957 ̄1992年)时空变化分布规律基础上,阐述了火山爆发产生的气溶胶和城市发展带来的人工气溶胶对太阳辐射量变化的影响,以及大气中气溶胶增加和地面太阳总辐射量的减少在环境研究中的问题。 相似文献
49.
Spatial statistical techniques for aggregating point objects extracted from high spatial resolution remotely sensed imagery 总被引:3,自引:0,他引:3
Trisalyn Nelson K. Olaf Niemann Michael A. Wulder 《Journal of Geographical Systems》2002,4(4):423-433
Using a local maximum filter, individual trees were extracted from a 1 m spatial resolution IKONOS image and represented
as points. The spatial pattern of individual trees was determined to represent forest age (a surrogate for forest structure).
Point attributes, based on the spatial pattern of trees, were generated via nearest neighbour statistics and used as the basis
for aggregating points into forest structure units. The forest structure units allowed for the mapping of a forested area
into one of three age categories: young (1–20 years), intermediate (21–120 years), and mature (>120 years). This research
indicates a new approach to image processing, where objects generated from the processing of image data (rather than pixels
or spectral values) are subjected to spatial statistical analysis to estimate an attribute relating an aspect of forest structure.
Received: 22 April 2002 / Accepted: 23 November 2002 相似文献
50.
Two piston cores, one located far from the continents (The North Pacific Ocean: ES core), and another located comparatively closer to the continents (The Bering Sea: BOW-8a core) were investigated to reconstruct environmental changes on source land areas. The results show significant contribution of terrestrial organic matter to sediments in both cores. The δ13C values of n-C27, n-C29, and n-C31 alkanes in sediments from the North Pacific ES core show significant glacial to interglacial variation whereas those from the Bering Sea core do not. Variations of δ13C values of land plant n-alkanes are related to the environmental or vegetational changes in the source land areas. Environmental changes, especially, aridity, rainfall, and pCO2 during glacial/interglacial transitional periods can affect vegetation, and therefore C3 / C4 plant ratios, resulting in δ13C changes in the preserved land plant biomarkers. Maximum values of δ13C as well as maximum average chain length values of long chain n-alkanes in the ES core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and/or ability of C4 plants to adapt for a longer period before being replaced by C3 plants when subjected to gradual climatic changes. Irregular variations with no clear glacial to interglacial trends in the BOW-8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the Bering Sea catchments. In addition, terrestrial organic matter entering the Bering Sea could originate from multiple pathways including eolian, riverine, and ice rafted debris, and possibly be disturbed by turbidity and other local currents which can induce re-suspension and re-sedimentation causing an obliterated time relation in the Bering Sea biomarker records. 相似文献