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澜沧—耿马地震发震构造初步研究 总被引：2，自引：0，他引：2
本文根据澜沧—耿马地震形变带、极震区及余震序列分布特征,分析了7.6和7.2级地震的发震构造,认为北北西向旱母坝断层是7.2级地震的发震构造,7.6级地震的发震构造不是一条单一的断层,北西向木嘎断裂和北北西向澜沧—勐海断裂均有明显破裂表现,这一特点与震区复杂的地质构造背景有密切联系。 相似文献
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2017年8月8日四川省九寨沟县发生了7.0级地震，中国大陆构造环境网络与北斗地基增强系统的GNSS连续观测共同监测到了此次地震的同震位移（坐标：东向为正，北向为正），结果显示：3个站点记录到了明显的同震位移，距离震中43 km的九寨沟台站（SCJZ）在东西向的位移为-9.8±1.5 mm，在南北向的位移为3.3±0.7 mm；距离震中65 km的松潘站（SCSP）在东西向的位移为-1.8±0.7 mm，在南北向的位移为-7.7±0.6 mm；距离震中77 km的舟曲站（GSZQ）在东西向的位移为0.4±1.2 mm，在南北向的位移为3.6±0.8 mm.通过同震位移分布特征，可以推测此次地震为一次左旋走滑型事件，引起水平向同震位移大致不超过150 km范围，地震对东南侧的龙门山断裂带影响非常小，对北侧的塔藏断裂和西侧的岷江断裂处引起的同震位移为厘米级.同震位移的反演结果显示：断层面上滑动量主要集中在7 km深度，最大量值约为0.4 m，平均滑动角为-15°，利用滑动分布计算的相应矩震级为MW6.4，与地震波反演结果相当.结合同震滑动分布、同震主应变分布、余震分布和震源机制解等特征，推测此次地震破裂极值区累积的能量得到较充分释放，进一步分析得出此次地震在塔藏断裂、岷江断裂和虎牙断裂处产生了一定的应力变化，值得持续关注. 相似文献
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1573年甘肃岷县地震史料考证与发震构造探讨 总被引：1，自引：0，他引：1
通过对1573年甘肃岷县地震的历史资料考证和发震构造的综合研究表明:在1573年岷县地震中遭受破坏最为严重的地区位于如今的岷县县城一带(当时为岷州府所在地)。综合各种资料确定1573年甘肃岷县地震震级为621,极震区烈度为Ⅷ~Ⅸ度,震中位于北纬34.4°,东经104.0°,震中精度为2类,震中位置偏差小于或等于25km。该地区构造上位于东昆仑断裂带和西秦岭北缘断裂带的应变传递和构造转换的中间过渡区,其中的临潭-宕昌断裂带活动特性差异明显,只有部分地段表现出全新世活动特征,地震极震区一带分布有不同程度的滑坡和基岩崩塌等。综合分析认为,临潭-宕昌断裂带的岷县-宕昌段是甘肃岷县1573年621级地震的发震构造。 相似文献
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由于逆断层作用，2013年芦山MS 7.0地震诱发的崩滑地质灾害分布表现出了明显的上盘效应与方向效应。在震后应急科考中未发现发震断层的地表破裂带，然而灾区大量出现的地震诱发滑坡、崩塌，加之密集的余震分布、地震烈度调查结果等，提供了确定芦山地震宏观震中、地震动错动方向以及研究地震发震构造等的诸多线索。 统计结果表明，芦山地震诱发的滑坡、崩塌具有明显的优势滑动方向（135°～144°），该方向揭示了地震断层的错动方向，与震源机制解反映的一致，大体垂直于发震断层的走向；从地震诱发崩塌、滑坡灾害点的分布与密度判断，宏观震中位于宝盛乡北，在仪器记录震中东北约3.6km处；从余震群分布、地震诱发滑坡分布特点及地震等烈度线等，结合以往强震如汶川地震等的调查经验，推测当震级足够大时，发震断层地表破裂带可能通过地质灾害、余震密集区东侧的边缘地带，总体平行于双石-大川断裂。另外，通过分析地层岩性与崩滑地形条件之间的关联性，发现崩滑灾害在某些地层岩性中易发，灾害点呈线性排列的原因是不同地层岩性之间抗风化能力的差异性，造成在地层分界线上形成线性陡崖或高坡度地带，使之在强震作用下容易发生崩塌、滑坡。 相似文献
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利用冷龙岭—托莱山断裂及其附近震前和震后GNSS观测资料，处理获取了2022年门源MS6.9地震同震位移场，并以此为约束反演获取了地震同震破裂滑动分布图像，基于上述结果探讨了本次地震发震断层形变破裂特征，对比了区域震间与同震变形特征，结果表明：(1)此次地震在距震中约90 km范围内产生了10 mm及以上的同震永久变形，距震中160～200 km的GNSS连续站记录到的同震变形则十分微弱，总体在毫米级以下；(2)同震位移图像呈现典型的左旋走滑型同震变形模式.在距震中约3 km破裂带南侧的测站，其同震位移为近东向，大小445.9±3.3 mm,而在破裂带远场则呈现出典型的与左旋走滑型地震匹配的“四象限”对称分布的挤压或拉张尾端变形特征；(3)同震位移量以冷龙岭断裂—托莱山断裂为界，南北两盘具有明显的非对称性，南盘变形运动大于北盘；(4)托莱山断裂西段同震位移总体表现出随震中距减小而增大的“弹性回跳”现象，但其跨断层近场测站却并不服从上述同震变形特征，指示其并未参与此次地震破裂，考虑到托莱山断裂西段显著的左旋剪切应变能积累背景，其未来强震危险性值得关注. 相似文献
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1879年武都南8级大地震断层面参数和滑动性质的厘定 总被引：1，自引：0，他引：1
1879年武都南8级大震发生在高山峻岭之间,由于受自然环境和交通条件所限,一直难以进行详细的实地考察。到目前为止,关于此次地震的发震构造的研究较少且观点不一。依据成丛小震发生在大震断层面附近的原则以及参考前人给出的极震区长轴形态,我们采用1985—2009年发生在该地震破裂区的精定位地震目录,选定了一个长条状研究区域,将模拟退火算法和高斯-牛顿算法结合,给出了1879年武都南8.0级地震震源断层是一条长约30km、埋深2～23km的NNE走向、高倾角并在NNW-SSE向压应力作用下发生右旋走向滑动的断层。该区域地壳深部(H>24km)至今没有地震发生,推测震源断层没有扩展到地壳深部。震源断层位置在文县高楼山(33.01°N,104.74°E)和梨坪(33.22°N,104.90°E)之间。另外,我们发现在极震区以西的雄黄山地区小震成丛发生,但野外调查并未发现明显的断面,这些小震应该与1879年武都南8级地震没有关系。 相似文献
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《中国科学:地球科学(英文版)》2014,(12)
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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《中国科学:地球科学(英文版)》2014,(9)
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 相似文献
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In natural waters arsenic concentrations up to a few milligrams per litre were measured. The natural content of arsenic found in soils varies between 0.01 mg/kg and a few hundred milligrams per kilogram. Anthropogenic sources of arsenic in the environment are the smelting of ores, the burning of coal, and the use of arsenic compounds in many products and production processes in the past. A lot of arsenic compounds are toxic and cause acute and chronic poisoning. In aqueous environment the inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are the most abundant species. The mobility of these species is influenced by the pH value, the redox potential, and the presence of adsorbents such as oxides and hydroxides of Fe(III), Al(III), Mn(III/IV), humic substances, and clay minerals. 相似文献
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Due to deleterious effects on non-target organisms, the use of organotin compounds on boat hulls of small vessels (<25 m) has been widely prohibited. The International Maritime Organisation (IMO) resolved that the complete prohibition on organotin compounds acting as biocides in antifouling systems should commence in 2008. As a result of restrictions on the use of organotin based paints, other antifouling formulations containing organic biocides have been utilised. This survey was conducted to assess the contamination of replacement biocides in the marine environment following the ban of TBT-based paints. Surface sediments samples were collected in the major ports and marinas along the France Mediterranean coastline (Cote d’Azur) and analysed for organotin compounds, Irgarol 1051, Sea-nine 211TM, Chlorothalonil, Dichlofluanid and Folpet. Every port and marina exhibited high levels of organotin compounds, with concentrations in sediments ranging from 37 ng Sn g−1dry wt in Menton Garavan to over 4000 ng Sn g−1dry wt close to the ship chandler within the port of Villefranche-sur-Mer. TBT degradation indexes suggested that fresh inputs are still made. Among the other antifoulants monitored, only Irgarol 1051 exhibited measurable concentrations in almost every port, with concentrations ranging from 40 ng g−1dry wt (Cannes) to almost 700 ng g−1dry wt (Villefranche-sur-Mer, ship chandler). 相似文献
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Ian R. Falconer 《洁净——土壤、空气、水》2005,33(1):64-71
Microcystins are cyclic heptapeptide toxins produced by a range of cyanobacterial genera. These cyanobacteria occur naturally in drinking water reservoirs subject to eutrophication, and in rivers and natural lakes. Because of the diversity of organisms, the toxins occur, from oligo‐mesotrophic lakes in North Temperate latitudes, to hypertrophic tropical ponds. The toxins are responsible for numerous cases of injury and death of domestic animals, and human poisoning from drinking water. The initial poisoning includes hepatic cell death. This leads to secondary effects from liver deficiency, including jaundice and photosensitisation. The toxic effects are largely due to inhibition of phosphatase enzymes, acting to regulate protein phosphorylation. The consequences include structural damage, apoptosis and, at lower concentrations, cell cycle effects and tumour promotion. As there is no clear evidence for direct carcinogenesis by microcystins, they are classed as non‐carcinogenic toxins in drinking water. Guideline Values for safe drinking water are derived from data for subchronic rodent toxicity, using the No Observed Adverse Effect Level (the highest dose giving no toxicity). To this dose are applied uncertainty factors, to calculate a Tolerable Daily Intake. On the basis of a standard bodyweight and water consumption the Guideline Value is determined for drinking water. For microcystin‐LR the WHO have set a provisional Guideline Value of 1 μg/L for drinking water. 相似文献
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The geomagnetic field and secular variation exhibit asymmetrical spatial features which are possibly originating from an heterogeneous thermal control of the Earth's lower mantle on the core. The identification of this control in magnetic data is subject to several difficulties, some of which can be alleviated by the use of core surface flow models. Using numerical dynamos driven by heterogeneous boundary heat flux, we confirm that within the parameter space accessible to simulations, time average surface flows obey a simple thermal wind equilibrium between the Coriolis and buoyancy forces, the Lorentz, inertial and viscous forces playing only a secondary role, even for Elsasser numbers significantly larger than 1. Furthermore, we average the models over the duration of three vortex turnovers, and correlate them with a longer time average which fully reveals the signature of boundary heterogeneity. This allows us to quantify the possibility of observing mantle control in core surface flows averaged over a short time period. A scaling analysis is performed in order to apply the results to the Earth's core. We find that three vortex turnovers could represent between 100 and 360 years of Earth time, and that the heat flux heterogeneity at the core-mantle boundary could be large enough to yield an observable signature of thermal mantle control in a time average core surface flow within reach of the available geomagnetic data. 相似文献
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Richard McCreary John McGaughey Yves Potvin Dave Ecobichon Marty Hudyma Harald Kanduth Alain Coulombe 《Pure and Applied Geophysics》1992,139(3-4):349-373
Located in northern Québec, the Lac Shortt Mine was a small gold mine consisting of a thin subvertical orebody which was mined in three main phases. High stress and rockbursting conditions were experienced when ore was extracted in the upper zone between the surface and a depth of 500 metres during the first two phases of mining. Severe rockbursts were experienced in late 1989 near the shaft and in the footwall development following a deepening of the mine shaft to a depth of 830 m and partial development of footwall drift access for the third phase of mining (the mining of the lower zone starting at a depth of 830 m moving upward toward a depth of 500 m). A 16-channel Electrolab MP250 microseismic system, with a Queen's University Full-Waveform piggy-back system, was installed underground at the site due to these problems.It was expected that the thinning sill would be subjected to an ever-increasing load as the thickness of the 500 m sill pillar decreased in the face of the mining excavation from below. A monitoring program consisting of the microseismic monitoring system, a range of conventional geomechanics monitoring tools as well as the undertaking of periodic seismic tomography surveys to assess the ongoing state of stress and rock mass condition within the sill was therefore warranted.The anomalously high-magnitude stress field and the brittle rockmass created a situation in which rockmass failure was common and violent. In the creation and thinning of the sill pillar, the location of banded microseismic activity was crucial in tracing rockmass failure and the associated ground control problems. Reliable source-location determination enabled the identification of areas of stress increase. The movement of the rockmass failure front could be followed, and was responsible for stope dilution, footwall and orebody development deterioration, and caving.Source-mechanism analyses gave accurate double-couple solutions for approximately forty percent of these events having at least ten recognizable polarities. Results suggested movement along vertical north-south striking or vertical east-west striking features. Underground observation of damaged access points showed that vertical north-south striking joints were experiencing failure.The microseismic activity, which was consistently concentrated close to the southwest and northeast corners of current production stopes, could be explained by a stress field oriented obliquely to the strike of the orebody, as measured prior to shrinkage of the sill pillar byin situ stress measurements and observed borehole overbreaks. The orientations of theP andT axes for the microseismic activity further confirmed that the stress field oriented obliquely to strike.While an increase in compressional-wave velocity of 2.3 percent, corresponding to a measured stress increase of approximately 10 MPa could be measured by repeated tomographic surveys, it was relatively small and only a factor of two or so above the velocity measured uncertainty. The relative insensitivity of thein situ rock mass modulus to the applied stress is believed to be largely due to the rockmass discontinuities being relatively closed prior to stress increase, as substantiated by the small deformations seen by the extensometer and borehole camera. This situation existed because of the very high pre-mining stress level.The experimental demonstration that the rock could not absorb substantially increased load through the mechanism of discontinuity closure or tightening (which would be reflected in the modulus) may be evidence in itself of potentially burst-prone ground, such as encountered at Lac Shortt. 相似文献
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《水文科学杂志》2013,58(4):704-712
Abstract The upper Niger and Volta rivers exhibit a great and highly contrasting variability of inter-annual runoff. The Bani River, the largest tributary to the Niger River in Mali, shows a dramatic decrease in runoff after the 1970s, with the result that many boreholes in the region have dried up since the drought began. In contrast, the Nakambe River (Upper Volta basin, in Burkina Faso) shows an increase in runoff for the same period, leading to unexpected flood peaks that damaged infrastructures. The contribution that the groundwater and its variability make to surface runoff variability is assessed in this study by comparing the data of the national groundwater monitoring networks of Mali and Burkina Faso to surface runoff. Several variables are compared at the basin scale: the date of the maximum level of the water table, the annual rainfall, discharge, low flows and depletion coefficients. Variability in the low flows of the Bani River is well correlated to a decrease in the water table. Since 1970, the greater decrease in runoff in comparison to the rainfall decrease is due to a reduction in the baseflow, related to the cumulated rainfall deficit. Concerning the Nakambe River, the runoff increase is not supported by a water table increase, but is due to the increase in runoff coefficient related to land degradation. 相似文献
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The inability to detect the presence of viable Helicobacter pylori bacteria in environmental waters has hindered the public health community in assessing the role water may play in the transmission of this pathogen. This work describes a cultural enrichment method coupled with an H. pylori‐specific PCR to identify these bacteria in water. While far from perfected at the present time, this represents an exciting new approach to studying the significance of water as a transmission mechanism for H. pylori. Evidence is presented that indicates culturable H. pylori bacteria were found using this enrichment/PCR method in a local groundwater source. 相似文献