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51.
地下流体短临地震信息的特殊意义 总被引:1,自引:1,他引:0
根据华南地区10次5级以上震例分析结果,得到了与理论分析一致的认识,即地下流体能灵敏地显示短临地震信息,特别是地震发生的时间信息,但不能较好地显示震中方位信息。然而,短临地震时间信息对于地震短临综合预报及防震减灾决策具有重要意义。 相似文献
52.
张北—尚义地震前地下流体异常特征分析 总被引:8,自引:4,他引:4
分析了华北北部地区(3~42°N,110~120°E)张北-尚义地震前出现的地下流体各测项异常。研究结果表明:异常数量多,可靠异常达36项,且流体物理异常多于化学异常;异常形态复杂,地震地下流体异常各种形态均有所表现,并以水位的趋势上升异常占优势;中长期、中期和短期异常多,临震异常不突出,震时异常显著;异常时空演化过程中,总体上呈现出异常数量由外围向震中区,由中长期向短期逐渐发展的趋势,但同时也表现出空间分布上此起彼伏,时间进程上时起时落的特征。对沿着NW向构造带出现的一批1994年同步转向上升的长趋势水位异常和水氧上升、下降长趋势异常是否完全由本次张北-尚义地震所引起,还有待进一步研究。 相似文献
53.
Shallow landslide hazard assessment using a physically based model and digital elevation data 总被引:6,自引:1,他引:5
A model for the analysis of topographic influence on shallow landslide initiation is applied to an experimental mountain
basin where high-resolution digital elevation data are available: the Cordon catchment (5 km2) located in northern Italy. The model delineates those areas most prone to shallow landsliding due to surface topographic
effects on hydrologic response. The model is composed of two parts: a steady-state model for shallow sub-surface runoff and
an infinite-slope Coulomb failure model which assumes that the soil is cohesionless at failure. An inventory of landslide
scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide
locations with model predictions. The model reproduces the observed distribution of landslide locations in a consistent way,
although spatial variations in soil strength and transmissivity, which are not accounted for in the model, influence specific
distribution of landslide areas within regions of similar topographic control.
Received: 15 October 1996 · Accepted: 25 June 1997 相似文献
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地下流体尤其是地壳深部的地下水 ,当它们形成具有一定封闭条件的承压系统时 ,能灵敏地反映地壳的应力应变状态 ,这种深部承压系统近似一“天然应变仪”,从这个角度出发 ,研究地下水的动态变化与地壳应力应变的关系 ,利用相关斜率分析法 ,探讨相关斜率 K值时空演变序列与地震间的关系 ,得出相关斜率具有较好的映震能力 ,且有短期预报效应 相似文献
57.
The study integrates petrographical and lithological data from deep exploration wells and outcrops in northern Iraq to better understand the sedimentary environments present in the basin and to evaluate the depositional evolution of the Paleozoic rocks in Iraq. The studied Paleozoic successions are represented by five sedimentary cycles of intracratonic sequences. These are dominated mainly by siliciclastic and mixed sedimentary packages, and are separated by major and minor unconformity surfaces. These cycles are as follow: the Ordovician cycle, represented by the Khabour Formation; the Silurian cycle, represented by the Akkas Formation; the Middle-Late Devonian to Early Carboniferous cycle, represented by the Chalki, Pirispiki, Kaista, Ora and Harur formations; the Permian–Carboniferous cycle, represented by the Ga’ara Formation and late Permian cycle, represented by the Chia Zairi Formation. Generally, the cycles are characterized by siliciclastic and mixed carbonate–clastic facies with abrupt changes during Late Paleozoic reflecting the environmental and tectonic events during this period. The Ordovician Khabour Formation is suggested to be of shallow marine environment of deposition with stacked transgressive and regressive cycles that are eustatically controlled. The shale of Silurian Akkas Formation was deposited in open-marine environment. Depositional regimes in the Late Devonian to Early Carboniferous are considered as a continuation of deposition in the subsiding basin with a wide geographic distribution that reflect the epicontinental or epeiric seas in a homoclinic ramp setting. The Permo-Carboniferous Ga’ara Formation was deposited in continental to paralic environment while the Late Permian Chia Zairi Formation represents the carbonate platform deposition. The study revealed that potential source rocks may include some shale beds of the Khabour Formation, hot shales of Akkas Formation and the shales of Ora Formation. The sandstones of the Khabour, Akkas and Kaista formations have good reservoir potential. The Late Permian carbonates of Chia Zairi Formation may be self-sourcing and contain multiple reservoirs. The occurrence of shale as source rocks and limestone as reservoir rocks and some evaporates as sealing horizons make the formation as a reservoir in its own right. 相似文献
58.
Borehole temperatures, climate change and the pre-observational surface air temperature mean: allowance for hydraulic conditions 总被引:1,自引:0,他引:1
Joint analysis of surface air temperature series recorded at weather stations together with the inversion of the temperature-depth profiles logged in the near-by boreholes enables an estimate of the conditions existing prior to the beginning of the meteorological observation, the so-called pre-observational mean (POM) temperature.Such analysis is based on the presumption of pure diffusive conditions in the underground. However, in real cases a certain subsurface fluid movement cannot be excluded and the measured temperature logs may contain an advective component. The paper addresses the correction for the hydraulic conditions, which may have perturbed the climate signal penetrating from the surface into the underground. The method accounts for vertical conductive and vertical advective heat transport in a 1-D horizontally layered stratum and provides a simultaneous evaluation of the POM-temperature together with the estimate of the Darcy fluid velocity. The correction strategy is illustrated on a synthetic example and its use is demonstrated on temperature logs measured in four closely spaced boreholes drilled near Tachlovice (located about 15 km SW of Prague, Czech Republic). The results revealed that in a case of moderately advectively affected subsurface conditions (fluid velocities about 10−9 m/s), the difference between POM-values assessed for a pure conductive approach and for combined vertical conductive/advective approach may amount up to 0.3–0.5 K, the value comparable with the amount usually ascribed to the 20th century climate warming. 相似文献
59.
汕头台地下流体正常动态与地震短临异常 总被引:1,自引:1,他引:0
地震前兆观测异常信息识别是前兆研究的基础.分析了汕头观测站地下流体各测项如水位、水温、气氡和气汞等观测资料,对其正常动态和短临异常信息进行了讨论.结果表明,上述各测项能够较有效地反映出某些中等地震前兆的短临异常信息. 相似文献
60.
依据地下流体存在趋势性异常和短临异常的基本观测事实, 提出“应力-应变效应说与水诱发异常说并重”的地下流体地震预报研究的科学思路。按照这一思路, 对地震地下流体观测的布网与选井原则提出了新的补充意见; 认为降水及其相关的地表水、地下水及大范围抽水等是地形变、地应变、地应力、水化及地电阻率等多种前兆异常产生的调制与诱发因素, 因而需要对原来的干扰因素的内涵作修正; 对地下流体前兆异常做了新定义及主要特征的归纳; 对于今后的工作, 提出了加强对地下流体短临前兆异常重现性的研究、加强对浅层地下流体的调制与诱发作用的研究以及积极促进地震地下流体学与其他相关学科的交叉与融合等建议。 相似文献