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91.
92.
Earthquake induced liquefaction features found in the Karewas of Kashmir Valley are potential tools for estimating energy center, magnitude and peak ground acceleration of the paleoearthquakes. Size, pattern and spatial distribution of liquefaction features and in-situ geotechnical data were collected at the paleoliquefaction sites to assess the magnitude and peak ground acceleration of the paleoearthquake. The magnitude of paleoearthquakes was estimated to be of the order of (Mw = 6.2) using “Magnitude bound method” and “In-situ testing of geotechnical properties and assessment of liquefaction potential of liquefied beds (source stratum) using cyclic stress method”. The peak ground acceleration computed were in the range of 0.27 g to 0.83 g using cyclic stress method and 0.30 g using attenuation equation NDMA [21]. 相似文献
93.
对常用的Waples、Middleton及Easy%Ro模型,通过蒙特卡罗方法,得到了相应的简化模型.所有简化模型均表明镜质体反射率(Ro)主要受控于最高温度(Tmax),并且与最高温度附近的温度变化率(Hr)有关.通过对简化模型的比较发现:(1)相对于Easy%Ro模型而言,Waples、Middleton模型对Hr的变化更为敏感;(2)总的来讲,达到相同的Ro值Middleton模型需要的温度最高,Easy%Ro模型其次,Waples模型需要的温度最低.在一定条件下,根据简化模型,利用实测的lnRo-H数据可以求取地层经历的最高温度及相应的地温梯度、热流和时间.实例分析表明岩石热导率等数据的准确性直接影响Ro解释的结果,但这种影响容易分析,而Hr的不确定性则导致多解性. 相似文献
94.
Stephen C. Kuehn Duane G. Froese Franklin F. Foit Jr. Peter Rotheisler 《Quaternary Research》2009,71(2):201-47
The Glacier Peak tephra beds are among the most widespread and arguably some of the most important late Pleistocene chronostratigraphic markers in western North America. These beds represent a series of closely-spaced Plinian and sub-Plinian eruptions from Glacier Peak, Washington. The two most widespread beds, Glacier Peak ‘G’ and ‘B’, are reliably distinguished by their glass major and trace element abundances. These beds are also more broadly distributed than previously considered, covering at least 550,000 and 260,000 km2, respectively. A third bed, the Irvine bed, known only from southern Alberta, is similar in its major-element composition to the Glacier Peak G bed, but it shows considerable differences in trace element concentrations. The Irvine bed is likely considerably older than the G and B tephras and probably records an additional Plinian eruption, perhaps also from Glacier Peak but from a different magma than G through B. A review of the published radiocarbon ages, new ages in this study, and consideration in a Bayesian framework suggest that the widespread G and B beds are several hundred years older than widely assumed. Our revised age is about 11,600 14C yr BP or a calibrated age (at 2 sigma) of 13,710-13,410 cal yr BP. 相似文献
95.
High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhomogeneities along the seismic ray path are the main causes of S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of the medium. The peak delay time of an S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify S-wave envelope broadening. 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by the S-wave envelope broadening algorithm. The results show that S-wave envelope broadening in the Changbaishan Tianchi volcano is obvious,and that the peak delay time of S-wave has a positive correlation with the hypocenter distance and frequency of the S-wave. The relationships between the S-wave peak delay time and the hypocenter distance for different frequency bands were obtained using the statistics method. The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region. 相似文献
96.
97.
Numerical issues in computing inundation areas over natural terrains using Savage-Hutter theory 总被引:1,自引:0,他引:1
Bin Yu Keith Dalbey Amy Webb Marcus Bursik Abani Patra E. Bruce Pitman Camil Nichita 《Natural Hazards》2009,50(2):249-267
When characterizing geologic natural hazards, specifically granular flows including pyroclastic flows, debris avalanches and
debris flows, perhaps the most important factor to consider is the area of inundation. One of the key parameters demarcating
the leading edge of inundation is the run-out distance. To define the run-out distance, it is necessary to know when the flow
stops. Numerical experiments are presented for determining a stopping criterion and exploring the suitability of the Savage-Hutter
theory for computing inundation areas of granular flows. The stopping criterion is a function of dimensionless average velocity,
pile aspect ratio and internal and bed friction angle and can be implemented on either a global (entire flow) or local (small
areas of the flow) level. Slumping piles on a horizontal surface, and geophysical flows over complex topography were simulated.
Mountainous areas, such as Colima volcano, Mexico; Casita, Nicaragua; Little Tahoma Peak, USA, and the San Bernardino Mountains,
USA, were used as test regions. These areas have combinations of steep, open slopes and sinuous channels. Because of differences
in topography and physical scaling, slumping piles in the laboratory and geophysical flows in natural terrain must be scaled
differently to determine a reasonable dimensionless relationship for the stopping criterion. 相似文献
98.
基于反射峰面积的水体叶绿素遥感反演模拟研究 总被引:1,自引:0,他引:1
叶绿素浓度是水体富营养化状态的重要指标,也是水色遥感反演的水质参数之一。水体中叶绿素浓度的遥感反演主要是建立实测光谱和实测水质参数二者之间的关系模型,利用遥感影像进行叶绿素浓度的信息提取。传统的叶绿素浓度遥感反演受区域性和季节性的影响,反演精度不高,而且反演模型不具普适性,需对叶绿素光谱特征进行分析,建立高精度的反演模型。本文采用Hydrolight数据模拟了不同叶绿素浓度(1~200 µg·L-1)的水体在可见光近红外的反射波谱曲线,通过分析叶绿素的光谱特征选取了特征波段或波段组合,并建立了叶绿素浓度反演模型。研究表明,除反射峰波长模型外,反射峰面积模型、三波段模型、红光线高度模型等均能较好地反演叶绿素浓度。在不同叶绿素反演模型中,除红光线模型外,最优的是反射峰面积模型,其决定系数为0.9689,反演误差为25.25 µg·L-1;其次是三波段模型,其决定系数为0.9637,反演误差为10.66 µg·L-1。究其原因,三波段模型考虑了水体中非色素悬浮物、黄色物质及水体后向散射对叶绿素浓度反演造成的影响;反射峰面积模型除此之外还综合考虑了叶绿素散射效率的影响。 相似文献
99.
100.
Rainfall and runoff were monitored simultaneously for one year from a residential road, a car park, nine sections of road draining to individual gullies, two house roofs, two garage roofs, and three types of factory roof. The sites, which included an automatic weather station, were in Redbourn, Hertfordshire on Flood Studies Report Soil Type 1. The 2906 quality controlled ‘station-storms’ represented 193 rain storms and involved 57.2 per cent of the annual rainfall. 1732 storms were of less than 1.4mm of rain, whilst 77 had over 10mm. The percentage runoff averaged 11.4 per cent for roads and 56.9 per cent for roofs (28.3 per cent and 90.4 per cent respectively for rainfalls >5mm). Percentage runoff from the roads was cyclic with a peak during the summer months but there was a marked variation in monthly percentage runoff within and between sites. Regression analysis to explain percentage runoff was undertaken with various subsets of data for: each site; roads; and roofs. The regression analysis considered all storms; >1 percent runoff events; >5mm rainfalls; and events with > = 4 mm rain and > = 5 per cent runoff. The variable values in percentage runoff could not be explained satisfactorily with statistical methods. Only eight of the 72 equations explained more than 57 per cent of the variance. The most important explanatory variables for roads were short term rainfall intensity and rainfall amount, the former was the most important for roofs. ‘Seasonal’ variables had a positive relation ship for roads which shows that the percentage runoff from roads is higher in summer than winter. The antecedent variables showed that percentage runoff from roads and roofs is increased by antecedent rainfall. Seasonal factors and evaporation were unimportant for the percentage runoff from roofs. Depression storage, assessed by examining rainfalls that did and did not produce runoff, showed a diversity of monthly values. The depression storages derived by the regression intercept method were usually smaller. There were no relationships between depression storage and catchment or roof slope. The mean values for roofs and roads respectively were 0.52 mm and 1.23 mm for the classification method and 0.42 mm and 0.6mm with the regression approach. Peak runoff from the roads showed an attenuation to 12.8 per cent for 1 minute rainfall intensities and 24.2 per cent for 5 minute intensities. For roofs the attenuation averaged 36.8 per cent for 1 minute intensities and 92.6 for 5 minute intensities. Regression for peak runoff coefficients from roofs and roads explained negligible amounts of the variance except when events with 1 minute rainfall intensities of over 30 mm hr?1 over the roads were analysed. Total rainfall was an important explanatory variable as was the slope of the road. There was evidence that peak coefficients for roads are greater during the summer. 相似文献