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1.
基于土壤氡气测量识别甘肃北山南缘隐伏断裂 总被引：1，自引：0，他引：1
我国高放废物地质处置库首选预选区位于甘肃北山南缘，区内分布有多条大型非活动断裂构造，这些断裂很可能成为未来放射性核素迁移的主要通道。断裂在向地表延伸过程中，受第四系覆盖等因素影响，造成关键构造部位隐伏地下而难以识别。本文以北山地区新场地段南部红旗山和前红泉断裂为研究对象，采用土壤中氡气测量方法，探讨了大型断裂构造中隐伏段落的识别及其指示的水文地质意义。结果表明：土壤中氡气测量对于识别北山南缘隐伏断裂具有很好的指示意义，是传统地质调查方法的一种重要补充；红旗山和前红泉断裂裂隙系统整体开启性均较差，裂隙系统不发育，影响范围较小，不具备形成较大规模储水空间的可能性。不同断裂带土壤氡浓度背景值差异较大，可根据土壤氡浓度累积频率分布图确定背景值；土壤氡浓度等值线分布图对判断隐伏断裂位置具有一定的指示作用。对于压剪性断裂而言，主断裂多沿氡气高异常与低异常边界分布或表现为氡气中等异常，而两侧的次级断裂表现为氡气高异常。 相似文献
2.
本文是为了确定在卢氏盆地内被第四系覆盖的黄村断裂的位置、断裂性质,分析黄村断裂与其北侧的乔家窑地热异常的关系。断裂构造是深部氡气汇集和迁移的主要通道,氡气沿断裂向上迁移,在地表浅部形成氡异常。土壤氡气异常可揭示隐伏断裂构造的位置、产状和活动性。黄村断裂通过卢氏乔家窑一带,为第四系沉积物所覆盖。沿垂直断裂走向方向布置4条测线。应用瞬时土壤测氡仪进行了野外现场测量,测试了土壤氡气浓度,确定土壤氡气异常,分析黄村断裂位置、产状和活动性。结果表明:黄村断裂带上方土壤氡气具有异常显示,异常位置与断层位置具有较好的一致性。沿QJ12测线,从南向北,土壤氡气异常形态为低-高-较高-较低-低的峰值形态。在断层带上方氡气峰值异常高于背景值的1.5倍以上,异常峰多数为2个测点以上组成。土壤氡气变化特征表明黄村断裂具有较强的活动性。利用土壤氡气异常分析了黄村断裂深部结构特征,给出了主断裂面与次级断裂面产状和位置。结合土壤氡气异常,分析了乔家地热形成机理。初步研究结果表明,豫西基底构造具有多期活动性,活化区域内的压扭性断裂,可转变为局部张性断裂,控制水热、成矿物质的迁移和富集。 相似文献
3.
利用测量土壤中氡气异常来确定隐伏断裂的几何学特征。在缅甸拉泰—其培河段布置的四条测氡剖面中,氡气异常明显,拉泰-芒童段异常值约为本底值的3～8倍,芒童以南部分异常值比本底值高100倍,表明芒童以南地段活动性较强。氡气测量结果很好地控制了恩梅开江断裂在覆盖层之下的延伸展布方向。地表开挖及平硐揭露,很好地验证了测氡结果所推测的断层几何学特征。因此,测定土壤中氡气异常来寻找隐伏断裂的方法是可行的。 相似文献
4.
云南木利锑矿区矿体与断裂关系密切,为解决矿区深边部找矿问题,采用FD-3017 RaA测氡仪,对该区三号背斜进行土壤氡气测量,以寻找隐伏断裂。结果显示,研究区各已知断层和矿体上部均出现明显的氡气异常;因此,可将氡气测量作为寻找隐伏断裂的有效手段,并可作为寻找与断裂构造(包括断层、节理、劈理等)关系密切的隐伏矿床的辅助方法。依据测量结果推测,在三号背斜核部和研究区北东部各存在一条大型隐伏断裂,并发现若干条已知断裂及推测隐伏断裂的次级断裂。最后总结出研究区氡气异常的形成模式。 相似文献
5.
《中国煤炭地质》2015,(10)
煤层采空后容易富集氡气,而上覆岩层裂隙及断层等构造又有利于氡气上移,因此探测氡气异常可以确定采空区。在山西省吕梁地区临县某工作区,利用氡气放射性测量,并结合瞬变电磁方法,有效的解释了该区采空区的范围。该区共布设氡气测线19条,测点634个。经统计计算氡气平均值为8.84,解释异常阈值为12.58。通过介绍已知采空区氡气放射性曲线特征及典型测线瞬变电磁电阻率断面与氡气放射性曲线对比,分析其不同地质条件下氡气解释范围出现的原因。根据该区氡气测量等值线平面图与3号煤顺层视电阻率等值线平面图的解释结果,确定了该区4个采空区的位置及范围,该结果在后来的生产过程中都得到了验证。 相似文献
6.
7.
峨眉山柿子坪热田地表氡气异常特征 总被引：3，自引：0，他引：3
本文通过柿子坪地区地表氡气测量,对热田地表氡气异常特征作了初步分析。该区地表氡气高值异常呈环状产出,并严格受构造控制。同时指出地表氡气测量是热田勘查的有效途径。 相似文献
8.
龙泉山断裂构造带作为龙门山推覆带的前陆隆起,严格控制了成都平原东边界,其活动性历来受到人们的关注。通过对龙泉山断裂带的氡气进行测量,可以有效地判断隐伏断层的位置及其活动性。测量结果显示,龙泉山断裂带北段东坡活动性强于西坡,主断层的活动性明显强于边缘隐伏断层,4条断层的活动性由强到弱依次为合兴场断层红花塘断层龙泉驿断层松林场断层。龙泉山断裂带同一条断层在地表由多个破碎带组成,其氡气异常特征与断层活动性和破碎带特征呈正相关性,即断层活动性越强,氡气异常特征越显著。龙泉山断裂带氡气平均异常浓度是背景值的9.6倍,将各异常带峰值浓度与背景值进行对比分析,大致归纳出了龙泉山地区隐伏断层活动性的相对判别标准。 相似文献
9.
分析了聊城—兰考断裂带形成和地质背景,将断裂带划分为3段,分述各段不同时代构造特征和地震活动等。土壤汞气、氡气测量得出,该区域存在明显的汞气、氡气异常,且异常位置接近,异常区宽度多在90～200m,表明地壳存在着汞气和氡气向上运移通道,证实了隐伏断裂存在,而且具有活动性。 相似文献
10.
利用氡气测量方法对礼贤断裂的位置进行勘查,通过对测量数据的分析,圈定氡气浓度的异常区,从而作为判定礼贤断裂位置的重要依据。 相似文献
11.
Radon concentrations in soil gas,considering radioactive equilibrium conditions with application to estimating fault-zone geometry 总被引：1，自引：0，他引：1
A calculation method for determining the amount of Rn isotopes and daughter products at the start of measurement (CRAS) is
proposed as a more accurate means of estimating the initial Rn concentration in soil gas. The CRAS utilizes the decay law
between 222Rn and 220Rn isotopes and the daughter products 218Po and 216Po, and is applicable to α-scintillation counter measurements. As Rn is both inert and chemically stable, it is useful for
fault investigation based on the soil gas geochemistry. However, the total number of α particles emitted by the decay of Rn
has generally been considered to be proportional to the initial Rn concentration, without considering the gas condition with
respect to radioactive equilibrium. The CRAS method is shown to be effective to derive Rn concentration for soil gases under
both nonequilibrium conditions, in which the total number of decays increases with time, and equilibrium conditions, which
are typical of normal soil under low gas flux. The CRAS method in conjunction with finite difference method simulation is
applied to the analysis of two active fault areas in Japan, and it is demonstrated that this combination could detect the
sharp rises in 222Rn concentrations associated with faults. The method also allows the determination of fault geometry near the surface based
on the asymmetry variation of the Rn concentration distribution when coupled with a numerical simulation of 222Rn transport. The results for the new method as applied to the two case studies are consistent with the data collected from
the geological survey. It implies that the CRAS method is suitable for investigating the fault system and interstitial gas
mobility through fractures. The present analyses have also demonstrated that high Rn concentrations require the recent and
repeated accumulation of 222Rn parents (230Th and 226Ra) in fault gouges through deep gas release during fault movement. 相似文献
12.
玉树Ms7.1级地震甘达村段构造地球化学特征 总被引：1，自引：0，他引：1
为探究地震对断层带气体逸出的影响和震后气体地球化学特征随时间的变化,以及地震动力学特征,利用土壤气地球化学方法,于2010年4月14日青海玉树Ms7.1级地震断层甘达村段测量地表破裂特征和震后断层气氡和汞浓度,发现断层带土壤的气氡和汞浓度的平均值分别为9246 Bq/m3和4.2 ng/m3。破裂带中Rn浓度变化幅度大,而Hg的浓度变化较小。断层主滑面附近Rn浓度相对降低,为地表破裂后断层气逃逸所致。泉水气氡观测发现,震前氡浓度增高,表明地震断层活动性增强。因此巴颜喀拉地块向东不均匀挤压,使深部气体沿地震断裂逃逸至地表,这也是造成断层带气氡、汞浓度的增高的原因。 相似文献
13.
《Applied Geochemistry》2005,20(6):1106-1119
Anomalies have been observed in Rn content in soil gas from 3 boreholes at the Orlica fault in the Krško basin, Slovenia. To distinguish the anomalies caused by environmental parameters (air and soil temperature, barometric pressure, rainfall) from those resulting solely from seismic activity, the following approaches have been used: (i) deviation of Rn concentration from the seasonal average, (ii) correlation between time gradients of Rn concentration and barometric pressure, and (iii) regression trees within a machine learning program. Approach (i) is much less successful in predicting anomalies caused by seismic events than approaches (ii) and (iii) if ±2σ criterion is used and is equally successful if ±1σ is used. Approaches (ii) and (iii) did not fail to observe an anomaly preceding an earthquake, but show false seismic anomalies, the number of which is much lower with (iii) than with (ii). Model trees are shown to outperform other approaches. A model has been built which, in the seismically non-active periods when Rn is presumably influenced only by environmental parameters, predicts the concentration with a correlation of 0.8. This correlation is reduced significantly in the seismically active periods. 相似文献
14.
Radon concentrations in high background radiation areas in the south are higher than those of others in China, especially ^220Rn concentration is significantly high. Therefore, measurements of ^222Rn and ^220Rn concentrations should be carried out there. This paper introduces a large size collector of radon progeny and its applications. The collector is a sheet of polyvinyl chloride fiber with electrostatics of (-500 V)-(-700 V). Its size (60 mm in diameter) is larger than those of others (26 mm in diameter) that work with the same principle. The collector is more effective to adsorb radon progeny than most of others. The equipment of ZnS(Ag) Scintillation Counting System is available for large size collectors to detect radon progeny. Therefore, its sensitivity of measurement is higher than that of others. According to the different half lives of radon progeny, and based on both theory and experiments, a formula for discrimination and calculation of ^222Rn and ^220Rn concentrations is deduced. The ^222Rn and ^220Rn concentrations were surveyed with electrostatic collectors of radon progeny on the campus of commercial school and some other areas in Hainan, southern China. Neither ^222Rn nor ^220Rn concentration was found significantly high. However, several faults underground were delineated. The collector is also used to study radon transportation. Results indicate that radon changes regularly with date when it has transported for a certain distance. Velocities of radon migration in the four media are quite different. Radon migrates more quickly in vertical tube than in the horizontal tube. 相似文献
15.
Soil–gas measurements of different gas species were performed in two distinct areas of the Corinth Gulf Rift (Greece): the Aigion-Neos Erineos-Lambiri (ANEL) fault zone and the Rion-Patras fault zone. Both zones lie in one of the most seismically active areas of the Euro-Mediterranean region, where a fast-opening continental rift is located. In particular, the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological, lithological and structural studies.In this work the applicability of soil–gas geochemistry surveys for the exploration of buried/hidden faults was tested by using various statistical methods. Moreover, a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep-seated gas migration towards the surface. In both investigated areas, the highest 222Rn and CO2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods. This indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas. Furthermore, obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration needed to obtain anomalies of short-lived 222Rn in the soil pores. 相似文献
16.
17.
Groundwater electrical conductivity and soil radon gas monitoring for earthquake precursory studies in Koyna, India 总被引：3，自引：0，他引：3
Hourly monitoring of electrical conductivity (EC) of groundwater along with groundwater levels in the 210 m deep boreholes (specially drilled for pore pressure/earthquake studies) and soil Rn gas at 60 cm below ground level in real time, in the Koyna-Warna region (characterized by basaltic rocks, >1500 m thick, and dotted with several sets of fault systems), western India, provided strong precursory signatures in response to two earthquakes (M 4.7 on 14/11/09, and M 5.1 on 12/12/09) that occurred in the study region. The EC measured in Govare well water showed precursory perturbations about 40 h prior to the M 5.1 earthquake and continued further for about 20 h after the earthquake. In response to the M 4.7 earthquake, there were EC perturbations 8 days after the earthquake. In another well (Koyna) which is located 4 km north of Govare well, no precursory signatures were found for the M 4.7 earthquake, while for M 5.1 earthquake, post-seismic precursors were found 18 days after the earthquake. Increased porosity and reduced pressure head accompanied by mixing of a freshwater component from the top zone due to earthquakes are the suggested mechanisms responsible for the observed anomalies in EC. Another parameter, soil Rn gas showed relatively proportional strength signals corresponding to these two earthquakes. In both the cases, the pre-seismic increase in Rn concentration started about 20 days in advance. The co-seismic drop in Rn levels was less by 30% from its peak value for the M 4.7 earthquake and 50% for the M 5.1 earthquake. The Rn anomalies are attributed to the opening and closing of micro-fractures before and during the earthquake. On line monitoring of these two parameters may be useful to check the entire chemistry change due to earthquake which may help to forecast impending earthquakes. 相似文献
18.
Radon in groundwater as a tracer to assess flow velocities: two test cases from Israel 总被引：1，自引：1，他引：1
U. Kafri 《Environmental Geology》2001,40(3):392-398
Two test cases from Israel are presented herein employing the decay rate of radon along the flow path to assess groundwater
flow velocities. Groundwater flow reaching the fault zone emerges in several places along the rift fault zone as thermal springs
because of deep water confinement. The high water temperature of the surface is indicative of high vertical flow velocities,
which maintains the original high temperatures. Knowing the Rn content at a source point and at a given down-gradient, and
assuming no Rn addition from the water itself or along the flow path, one can calculate the flow velocity based on the Rn
half-life time. The decay of Rn in western Galilee was found to be ∼570–150 pCi/l, and in the Dead Sea area from 5000–2000 pCi/l
along a respective flow path of 1000 and 200 m, Based on the above, the calculated flow velocities were compared with those
obtained from pumping tests in the study area. The method is applicable, because of the short Rn half-life, to cases of high
Rn contents, short distances and high flow velocities.
Received: 18 January 2000 · Accepted: 21 March 2000 相似文献
19.
Integrated geophysics and soil gas profiles as a tool to characterize active faults: the Amer fault example (Pyrenees, NE Spain) 总被引：1，自引：0，他引：1
M. Zarroca R. Linares J. Bach C. Roqué V. Moreno Ll. Font C. Baixeras 《Environmental Earth Sciences》2012,67(3):889-910
The combined use of geophysical and soil gas composition exploration methods allows to rapidly obtain at relative low cost information that might be related to seismic activity conditions. In this study, we carried out geochemical soil gas sampling (222Rn, 220Rn and CO2), electrical resistivity tomography and seismic refraction profiles in two selected zones near the town of Amer in the Spanish Pyrenees, where the presence of recent fractures is evident in the field. Data analysis clearly reveals anomalous values for each gas at specific positions along the electrical imaging transects. Geomorphologic and hydrogeologic data and the integration of geophysical data and soil gas measurements indicate that: (1) endogene gases radon (222Rn) and carbon dioxide (CO2) are released from the meta-sedimentary basement rocks across the main fractured zones with higher permeability values, while lower Cenozoic detrital sedimentary formations act as an impervious boundary; (2) sites with highest radon concentrations (52?kBq?m?3) coincide with the zones in the Amer fault showing more recent geomorphic evidence of activity, and more specifically with those areas covered by thinner surficial formations; (3) the lowest 222Rn values (0.2?C0.4?kBq?m?3) were recorded just on the master active fault plane. This pattern could be explained by a dilution effect resulting from high rates of soil CO2 efflux (267?g?m?2?day?1); (4) soil thoron (220Rn) activity is maximum (143?kBq?m?3) in areas with high surficial fracturing; (5) groundwater pumping may cause important distortions in the natural flow dynamics and in the measured concentrations of gases. The agreement between the different data (geochemical, geophysical, and hydrogeological) and field observations (geology and geomorphology) leads us to propose a preliminary tectonic-gravitational model for the study area. 相似文献