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利用祁连山主动源连续激发台站记录资料,通过不同时间段的多次激发数据叠加处理,可以获取各个地震台的Pg和Sg震相走时变化数据.对震相走时变化数据分析发现,在2015年11月23日祁连5.3级和2016年1月21日门源6.4级地震发生前后震源区附近台站存在明显的震相走时变化,推测导致这种异常变化的原因是震源区的速度发生了改变.这一观测结果说明主动源方法可能成为地震预测的一种新途径. 相似文献
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基于2021年5月21日漾濞M_S6.4地震震中附近50 km范围内15个地震观测台站记录的2020年11月1日—2021年5月30日的气枪震源信号,采用互相关时延检测技术提取这15个台站各自稳定震相(Sg震相)的走时变化时间序列,并对漾濞M_S6.4地震前后各台站的走时变化特征进行分析。结果表明:(1)漾濞M_S6.4地震前10天左右,有4个台站走时开始出现异常,其中,Ey211和Ey213台走时呈"V"型变化结构,Ey210和CHT台走时呈上升趋势。(2)漾濞M_S6.4地震后短期内,大部分台站走时出现了明显的趋势性变化,以维西—乔后—巍山断裂为界,断裂带两侧台站走时变化趋势存在明显差异,断裂以东的EYA、HDQ、YSW09台走时呈上升趋势,变化最为显著的为HDQ台,走时差变化量为0.067 s;而断裂带以西的所有台站在漾濞M_S6.4地震当天(或震后1～2天)开始出现明显趋势性下降,走时下降持续时间在4～9天间,走时差变化量在-0.053～-0.201 s间,其中走时差下降量最大为53 285台,最小为CHT台。 相似文献
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采用叠加、互相关、插值拟合等方法对祁连山气枪主动源台网数据进行处理，针对2016年1月21日青海门源6.4级地震前后气枪激发地震P波、S波震相的走时变化特征进行了分析，结果表明，地震前约6个月时，震中附近3个台站的相对走时出现下降变化（走时减少），至震前约3个月时低值异常恢复正常，之后再次出现走时下降变化，地震即发生于走时变化恢复过程中。S波走时变化最大下降幅度达18ms，震后走时变化逐渐恢复正常，且3个台站变化趋势较为一致，其中，距震中最近的台站的S波走时变化最明显（ZDY38台），较远台站的走时变化幅度较小，其变化特征与震源区位置有关。走时缩短意味着速度增加，可能与区域应力积累间存在一定的关系。 相似文献
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以2017年3月27日漾濞5.1级地震为例，根据区域特性和信噪比要求，选取数据较为完整的6个台站记录的2017年1月1日～6月6日期间的宾川地震信号发射台气枪震源波形资料，采用互相关检测技术提取6个台站各自稳定震相的走时数据，并对漾濞5.1级地震前后走时数据的变化情况进行分析。结果表明，漾濞5.1级地震前后6个台站各自稳定震相存在较为明显的走时变化，且短期内走时变化具有较好的同步性，相关台站异常幅度大小和异常出现时间存在细小差异。地震发生前，6个台站走时低值异常过程明显，以YUL台最为显著。地震发生前后走时变化形态特征为双“V”型，漾濞5.1级地震发生在第1个“V”型末端。地震发生后，不同方位相关台站受地震的影响程度不同，走时波动大小存在差异。 相似文献
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宾川气枪地震信号发射台以水库大容量非调制气枪阵列为震源,可以连续不断地激发重复性极高的地震信号。本文利用其2013年的数据,对地下介质进行了观测。由于水库水位的变化对震源波形及远处台站接收到的地震波形会产生影响,因此,为了区分介质变化与震源变化,研究了陆上水库环境下激发气枪震源所产生的地震波形的特征和合适的处理流程。结果表明:1水库水位变化较大时,同一台站记录的地震波形之间的互相关系数过小,不能直接进行叠加处理,需进行震源聚类分析,而震源聚类受水位变化量的控制;2为消除水位的影响,进行了反褶积处理,当震中距小于10km时,对不同水位激发的信号进行叠加再进行反褶积的效果优于直接进行叠加的效果;3通过互相关计算和信噪比分析发现,4个台站的波形变化可能是由地下介质变化引起的。 相似文献
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《地球物理学进展》2016,(盈江双震)
2014云南盈江区域5月下旬接连发生了M_S5.6和M_S6.1级两个地震(双震),双差定位结果显示这次的盈江双震及其余震序列呈明显的时空聚集分布特征.本文基于波形互相关计算方法,挑选了盈江双震期间研究区内的重复地震事件,利用尾波干涉技术,分析地震序列持续期间地壳介质的物性变化.结果显示,在距离震源区较近的台站发现了盈江地震期间走时延迟的变化特征,随着流逝时间的不同,走时延迟变化复杂不一,这种变化可能源于不同路径上散射体的不同变化.其中,S波早期的尾波部分呈现明显的线性变化,可能是震源区附近地壳介质的波速变化所引起.研究发现,在两个主震之间和第二个主震之后走时延迟变化的特点不同,可能表示因不同地壳应力变化导致的介质性质变化. 相似文献
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针对2021年5月21日云南漾濞M_S6.4地震,采用滑动相关性方法和地电场优势方位角方法,开展震中周围200 km范围内地电场台站地震异常的统计特征分析和优势方位角的回溯性研究,发现:(1)通过对漾濞M_S6.4震中周围历史地震事件的统计分析,认为该区域地电场地震异常现象通常在震前约20(±5)天开始出现,如弥渡、祥云和洱源台;(2)漾濞M_S6.4地震前,洱源和祥云台地电场优势方位角在震前约15天或更早时间开始出现异常变化现象;(3)当地电场台站与地震事件处于同一发震断层(或断裂带)时,其观测到地震异常的可能性更大。此外,结合研究区域已有大地电磁测深结果,对地震反映敏感的地电场台站测区下方电性结构特征进行了初步探索,认为当测区位于电阻率边界上时,更易观测到地震地电场异常变化现象,相关研究结论将有望为地电场台站的选址建设、地震异常分析等工作提供技术支撑。 相似文献
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震源到接收台站之间的地层响应函数能够反映地下介质信息。对地震波传播过程中的卷积模型进行推导:记录信号是众多震源子波经过时移加权叠加的结果;通过反卷积方法可去除震源子波信息,提取震源到接收台站之间的地层响应函数;地层响应函数中第一个突跳值对应的时间即为P波走时。在河北赤城—张北地区进行人工震源实验,通过反卷积计算得到该地区地层响应函数剖面图,得出P波波速约6 km/s。利用人工震源系统还可以对地下介质波速变化进行长期动态监测,对地震预测具有一定意义。 相似文献
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《地震研究》2021,44(4)
利用2017年1月31日—2019年12月1日云南数字地震台网的宽频带连续波形资料,基于背景噪声互相关方法,提取了14个台站对当天经验格林函数与参考经验格林函数的直达瑞利波走时偏移来研究2018年通海5.0级、墨江5.9级地震震源区的波速变化特征。结果表明,通海5.0级和墨江5.9级地震都在一定程度上造成了震源区地壳介质速度的变化。地震发生前后,穿过地震震中和震中附近的部分台站对的瑞利波走时偏移在地震发生前的20余天表现出明显的异常特征,且短期内走时变化具有较好的同步性,但异常幅度大小和异常持续时间存在一定差异,异常台站对走时偏移变化形态为"V"或双"V"型结构,两次地震都发生在了第1个"V"型的前端。多台站对组合的平均走时偏移结果显示,两次地震造成的震源区波速的异常持续时间大概都为260 d(通海地震略长于墨江地震),但墨江地震造成的最初的走时偏移变化量和持续时间均高于通海地震。 相似文献
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《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
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《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
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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
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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
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《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
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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