共查询到20条相似文献，搜索用时 62 毫秒
1.
大震前显示的地震震源机制趋于一致的变化 总被引：3，自引：0，他引：3
在构造应力场的制约下强震孕育过程中特定阶段, 震源区中小地震震源机制与构造应力场的方向大体一致, 根据这一特点, 定义各个震源机制解的P轴, B轴, T轴和构造应力场的3个应力主轴在3维空间的夹角之和为一致性参数a, 研究强震前应力场变化特征。 对2006年11月15日千岛岛弧MW8.3地震和2001年6月23日秘鲁MW8.4地震研究表明, 大震发生前孕震区一致性参数a比较低, 震源机制与构造应力场的差异较小, 说明这些前震受到了震源区应力场的统一作用, 而主震发生之后震源机制解的一致性参数比较高, 说明后续发生的地震的震源机制散乱, 表明背景应力场的控制作用开始减弱。 相似文献
2.
山西地区震源机制一致性参数时空特征分析 总被引：10，自引：0，他引：10
利用山西数字地震台网记录到的中小地震波形资料,采用层状介质中点源位错模型的广义透射系数的快速算法和理论地震图拟合直达波最大振幅比来求取小震震源机制解的方法,计算了2001年—2012年山西地区281个中小地震震源机制解,根据优势分布得到山西地区现今平均构造应力场分布,计算震源机制解应力主轴与相应的区域构造应力场主轴之间的震源机制一致性参数,分析一致性参数时空分布与中等地震活动的关系。结果显示,2001年以来山西5次ML≥5.0地震前均有震源机制趋于一致性现象,震中分布在一致性参数低值附近或高低值过渡区域。 相似文献
3.
4.
滇中地区震源机制一致性参数时空分布与强震活动 总被引：1，自引：0，他引：1
利用云南数字地震台网记录到的地震直达波Pg、Sg振幅资料,采用层状介质中点源位错模型的广义透射系数的快速算法,计算理论地震图的Pg、Sg最大振幅比值,将其与观测值拟合,反演得到1999年至2009年11月14日滇中地区206个中小地震的震源机制解,计算震源机制解应力主轴与相应的区域构造应力场主轴之间的一致性参数,分析震源机制一致性参数时空分布与强震活动的关系.分析表明,强震发生前3年至数月,强震震源区附近出现多个震源释放应力场与区域应力场一致或接近的中小地震,强震就发生在中小震震源机制一致性参数低值分布区内或其边缘附近. 相似文献
5.
6.
地震矩张量反演在地震观测报告中的应用 总被引：3，自引：0，他引：3
针对我国地震工作的实际需要,从１９９５年起,《中国地震台网目录和地震矩张量解》刊登了国内较大地震和全球大震的地震矩张量解和震源机制解。同时在《中国地震年报》上也刊登国内及邻区较大地震的地震长张量解和震源机制解。为了方便用户使用,本文对有关参数进行了说明。 相似文献
7.
以伤口愈合理论为基础的地震矩比成像算法,把每次大震的能量按照一定的原则在其周围分配,分析地震矩比R值随时空变化的特征,从而找出地震矩比R值与强震的对应关系.本文以中国地震目录分别作分区、震源深度分析和记录完整性分析,应用调整了参数的地震矩比成像算法,分析了1966年以来中国不同地区7.0级以上地震前,震中及其周围R值对应的异常演化过程,发现通过分析R值异常的时空变化,能够定量化确定未来大震的空间范围和时间迫近程度.结果显示,R值的时空变化能够定量反映大震发生的时空要素,而且R值的变化特征能够反映介质破裂的规律. 相似文献
8.
9.
文中给出了根据地震释放的总地震矩求解平均应力场的方法,并使用加入随机误差的人工合成震源机制解数据和唐山余震区震源机制解数据对其进行检验。由检验结果可知,该方法可以应用于区域平均应力场的求解。使用的震源机制解资料越多,所得结果越稳定,且更接近真实的区域应力场。该方法的优点是: 用每个地震的震级作为权重,能够较好地反映出大小地震在应力场反演中的不同贡献; 并且在计算过程中不需要知道震源机制解2个节面中哪个节面为地震断层面。 相似文献
10.
利用区域地震台网数字波形资料，对2017年9月23日朝鲜ML3.4地震进行地震矩张量反演计算与参数稳定性评估，获得了此次地震的震源机制解.结果表明，地震矩心深度为3 km，标量地震矩为1.34×1014 N·m，矩震级为MW3.4.地震矩张量结果分解后，双力偶分量（DC）为96.4%，补偿线性矢量偶极分量（CLVD）为-0.8%，震源体体积变化的各向同性分量（ISO）为-2.8%.主压应力P轴方位角为144°，倾角为74°，主张应力T轴方位角为341°，倾角为15°.其中一个节面的参数为：走向248°，倾向60°，滑动角-94°.地震震源体积变化分量很小，震源机制类型属于典型的由断层剪切位错引起的正断层型地震事件，且主张应力T轴方向与区域近地表应变率场方向一致.由于朝鲜2017年9月3日核试验释放的能量对局部区域应力场进行了扰动，致使核试验场附近地壳岩体处于破裂的临界状态，2017年9月23日朝鲜ML3.4地震事件可能是区域应力场作用下的一次山体滑动事件. 相似文献
11.
12.
13.
14.
15.
《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
16.
《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
17.
Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
18.
Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored. 相似文献
19.
《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
20.
K.-G. Malle 《洁净——土壤、空气、水》1992,20(4):196-204
Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m3 zinc. Apart from civilization air contains 1–10 ng zinc per m3. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters. 相似文献