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121.
I. Lerche 《Pure and Applied Geophysics》1991,136(2-3):191-200
The variability of sedimentary thermal conductivities with increasing temperature are explored for their impact on estimates of present-day heat flux and subsurface temperature gradient. For sand thicknesses less than about 10–20 km, or shale thicknesses less than about 40–80 km, the subsurface temperature is closely linearly proportional to the thermal resistance integral obtained in the absence of the temperature dependence of thermal conductivity. Estimates of heat flux should be increased (decreased) by about 5% for sands and decreased by about 1% for shales. For salt, because of the much shorter temperature range over which its thermal conductivity decreases, effects produced by the temperature dependence are more noticeable: heat flux should be increased by around 13%, salt thicknesses in excess of 5 km will yield major (around 30–100°C) changes in their temperature regimes solely as a consequence of the temperature-dependent thermal conductivity, and the linear increase of temperature with increasing thermal resistance is not an adequate approximation but has to be replaced with a more exact exponential increase.The impact of the variations, particularly in the case of salt, for geologic processes is briefly considered. 相似文献
122.
本文研究了1988年11月6日澜沧、耿马7.6和7.2级地震的水氡异常,认为:1.震前中期、短期及临震各阶段异常均有显示;2.中期异常是趋势性上升的高值异常,它占全部异常的比例,与国内其它几次7级地震相比较略偏低;3.短期异常中有高值和低值异常,位于震中区及北西向腾冲-耿马地震带上的水氡观测点,以氡浓度降低的负异常为主要特征;4.震中周围300公里内未发现临震异常,它多出现在300—500公里范围内,特别集中在小江断裂带上。 相似文献
123.
124.
对1880 ̄1993年新疆及邻区7级以上强震活动特征进行了分析讨论,认为研究时段内7级以上强震活动有明显的活跃与平静交替现象。研究时段内的强震活动经历了5个轮回,每个轮回包括一个平静幕和一个活动幕,每个活动幕都有相对的主体活动区,主体活动区和7级以上单个强震都具有沿西昆仑-南天山-北天山-阿尔泰地震带往返迁移的特征。各地震带6级以上地震活动也具有明显的由西南向北东整体迁移的特征,并且这种时、空、强 相似文献
125.
复杂构造应力扰动场与发震构造识别问题的研究 总被引:7,自引:2,他引:7
在地震短临阶段异常是由局部断层扩展或弱化引起。实验与数值模拟结果曾得到与之相伴的是平均应力扰动场的四象限分布和最大剪应力扰动场的八瓣式分布。为检验此结果的普适性作了进一步的研究。结果表明不论区域构造及其基本应力场如何复杂,这种四象限分布与八瓣式分布型式不变,这为最终判定失稳区提供了依据。与此同时,在复杂构造情况下这种应力扰动场的畸变也不容忽视 相似文献
126.
Reconstructing spatio-temporal patterns of debris-flow activity using dendrogeomorphological methods 总被引:2,自引:0,他引:2
Michelle Bollschweiler Markus Stoffel Melanie Ehmisch Michel Monbaron 《Geomorphology》2007,87(4):337-351
Debris flows are a major threat in many parts of the Alps, where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life. Nonetheless, the spatial behavior of past debris-flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris flows on a forested cone in the Swiss Alps (Bruchji torrent, Blatten, Valais). The analysis of past events was based on a detailed geomorphic map (1:1000) of all forms related to debris flows as well as on tree-ring series from 401 heavily affected trees (Larix decidua Mill. and Picea abies (L.) Karst.) growing in or next to deposits. The samples were analyzed and growth disturbances related to debris-flow activity assessed, such as tangential rows of traumatic resin ducts, the onset of reaction wood or abrupt growth suppression or release.In total, 960 growth disturbances were identified in the samples, belonging to 40 different event years between A.D. 1867 and 2005. In addition, the coupling of tree-ring data with the geomorphic map allowed reconstruction of eleven formerly active channels and spatial representation of individual events. Based on our results we believe that before 1935, debris flows preferentially used those channels located in the western part of the cone, whereas the eastern part of the cone remained widely unaffected. The spatial representation of the 40 events also allowed identification of five different spatial patterns for debris flows at the study site. 相似文献
127.
128.
Seismic rotational displacement of gravity walls by pseudo-dynamic method: Passive case 总被引:8,自引:0,他引:8
Prediction of the seismic rotational displacements of retaining wall under passive condition is an important aspect of design in earthquake prone region. In this paper, the pseudo-dynamic method is used to compute the rotational displacements of rigid retaining wall supporting cohesionless backfill under seismic loading for the passive earth pressure condition. The proposed method considers time, phase difference and effect of amplification in shear and primary waves propagating through both the backfill and the retaining wall. The influence of ground motion characteristics on rotational displacement of the wall is evaluated. Also the effects of variation of parameters like wall friction angle, soil friction angle, amplification factor, shear wave velocity, primary wave velocity, period of lateral shaking, horizontal and vertical seismic accelerations on the rotational displacements are studied. The rotational displacement of the wall increases substantially with increase in amplification of both shear and primary waves, time of input motion, period of lateral shaking and decreases with increase in soil friction angle, wall friction angle. The rotational displacements of the wall also increase when the effect of wall inertia is taken into account. Results are provided in graphical form. 相似文献
129.
John Douglas 《Bulletin of Earthquake Engineering》2007,5(3):363-376
Accurate estimates of the ground motions that occurred during damaging earthquakes are a vital part of many aspects of earthquake
engineering, such as the study of the size and cause of the uncertainties within earthquake risk assessments. This article
compares a number of methods to estimate the ground shaking that occurred on Guadeloupe (French Antilles) during the 21st
November 2004 (M
w
6.3) Les Saintes earthquake, with the aim of providing more accurate shaking estimates for the investigation of the sources
of uncertainties within loss evaluations, based on damage data from this event. The various techniques make differing use
of the available ground-motion recordings of this earthquake and by consequence the estimates obtained by the different approaches
are associated with differing uncertainties. Ground motions on the French Antilles are affected by strong local site effects,
which have been extensively investigated in previous studies. In this article, use is made of these studies in order to improve
the shaking estimates. It is shown that the simple methods neglecting the spatial correlation of earthquake shaking lead to
uncertainties similar to those predicted by empirical ground-motion models and that these are uniform across the whole of
Guadeloupe. In contrast, methods (such as the ShakeMap approach) that take account of the spatial correlation in motions demonstrate
that shaking within roughly 10 km of a recording station (covering a significant portion of the investigated area) can be
defined with reasonable accuracy but that motions at more distant points are not well constrained. 相似文献
130.
我国资源卫星资料应用对空间分辨率的需求 总被引:6,自引:0,他引:6
在简介了我国3种对地遥感卫星的基础上,归纳出我国主要应用领域对遥感图像空间分辨率的需求状况。 相似文献