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991.
根据室内岩石变形声发射实验结果,计算了声发射序列的地震非均匀度GL值,并以此探讨了岩石破裂失稳的可预测性。在双轴压缩、等速率加载条件下,含障碍体断层、挤压雁列断层和Ⅲ型剪切断层等非连续岩石标本在临近滑动失稳前,声发射活动均出现了显著的均匀—非均匀的状态变化,表现为GL值出现持续大于1的异常变化,GL值异常的位置与破裂成核部位相重合,并与断层走向一致;改变统计窗长、窗内分割数及能级统计下限计算声发射序列的GL值,结果表明,GL值计算结果具有一定的稳定性。综合分析认为,地震非均匀度(GL值)可以较好地刻画岩石失稳前夕因破裂成核导致的声发射活动在时间分布上的状态变化,GL值持续异常是岩石失稳的显著性标志,对预测岩石失稳具有较好的指示意义。 相似文献
992.
对云南地区4个地震序列,分别为2000年姚安6.5级地震、2001年施甸5级震群、2001年永胜6.0级地震和2003年大姚6.2、6.1级震群,利用垂直向数字地震尾波分别计算地震序列周边台站3个频率段的Qc-1值,分析对比其时间演化趋势。发现对于主-余震型序列,主震后Qc-1值整体上变化幅度不大,趋于稳定。而对于震群(或双震)型序列,在第一个主震后,Qc-1值表现出上升-下降趋势,持续一段时间后强震发生。这些变化在序列周围的台站和三个频率段的变化整体趋势是一致的,但变化幅度不一致,可能与孕震区的位置和孕震应力的演变过程有关。上述研究为强余震的预报提供一个新的方法。 相似文献
993.
Wang Xinling 《中国地震研究》2006,20(1):37-49
The Yao'an Ms6.5 earthquake occurred on Jan. 15, 2000 and the Yongsheng Ms6.0 earthquake occurred on Oct. 27, 2001 in Yunnan Province, China. They are both located in the middle of the Dian block. Their epicenters are close to each other, the tectonic and strain characters of the earthquakes were similar, and there were many aftershocks after the two main shocks. In order to further study the spatial-temporal distributions and fault rupture characters of the main shocks and aftershocks, the latter are located using the Geiger earthquake location algorithm (Geiger) and the double difference earthquake location algorithm (DD) based on the seismic phase data of the two earthquake sequences. They were recorded by two Near Source Digital Seismic Networks (YNSSN and YSNSSN) deployed by the Yunnan Seismological Bureau (YNSB). Then, two main shock parameters were relocated using DD based on the data of larger magnitude aftershocks and the two main shocks that were recorded by the Kunming Regional Digital Seismic Network (KMSN). Combining the spatial- temporal distributions of the two earthquake sequences, the tectonic and strain characters of earthquakes, the rupture processes of the two aftershock sequences along faults are analyzed and discussed contrastively. 相似文献
994.
An earthquake with magnitude of 5.7 took place on Aug. 18, 2003 in the Nyingchi Region, Tibet. The macroseismic epicenter was located in the unpopniated high mountain area, 13 km south of Zhamo town, Bond County. The seismic intensity in the meizoseismal region was Ⅶ degree. The Ⅶ and Ⅵ areas were 2000 km^2 and 11000 km^2 , respectively. This seismic event is related to the movements of the Lhari fault trending in the NW direction and the ZhamoManiweng fault trending in the NE direction. As a result of this earthquakes, the buildings in the areas were badly damaged. 相似文献
995.
Amr Z. Hamouda 《Acta Geophysica》2006,54(2):165-176
Earthquake hazard parameters such as maximum magnitude, annual mean seismic activity rate, and the Gutenberg-Richter parameter,
have been evaluated for the Hellenic and Cyprean Arc regions of the Eastern Mediterranean. The applied maximum likelihood
procedure permits the combination of both historical and instrumental data. The collected data from different sources cover
earthquakes with magnitude ≥ 3.5 throughout the last two centuries. The historical part of the catalogue only contains the
strongest events, whereas the complete part can be divided into several subcatalogues, each assumed complete above a specific
threshold of magnitude.
The hazard parameters assessment is performed for the two study regions. The Hellenic Arc region was found to be of higher
seismicity level than the Cyprean Arc region. The number of annually expected earthquakes with magnitude ≥ 3.5 is much larger
in the Hellenic Arc (56±2) than in the Cyprean Arc (35±2). The maximum magnitude calculated in the Hellenic Arc zone is 7.8±0.4
for the time period equal to the length of the catalogue, i.e., 210 years. For the Cyprean Arc zone, the maximum possible
magnitude is 6.8±0.4 for the time span of 330 years. 相似文献
996.
Y. E-A. Mohamedzein J. A. Abdalla A. Abdelwahab 《Bulletin of Earthquake Engineering》2006,4(3):277-293
Khartoum, the capital of Sudan, is located at the confluence of White and Blue Niles. The city is heavily populated. Central Khartoum with its high-rise buildings is the center of governmental and business activities and is located on a strip adjacent to the Blue Nile. Geological and geotechnical data indicate that the subsoil conditions at Central Khartoum are characterized by alluvial deposits underlain by Nubian Sandstone at a depth of 25 m. The alluvial deposits, locally known as Gezira formations, consist of clays grading into silt and sand with depth. Macro seismic zonation of Sudan and its vicinities, developed by the authors, gave the ground acceleration at the bedrock surface. The effect of alluvial deposits in Central Khartoum on propagation of seismic motion parameters to the ground surface is investigated in this study. Correlations are proposed for pertinent cyclic soil properties such as shear modulus, damping, and shear wave velocity. The Equivalent-Linear Earthquake Response Analyses (EERA) Model was used to study the effect of local soil conditions on ground-motion parameters. In the absence of strong-motion records in Khartoum, available worldwide strong-motion records are used. Plots showing the time histories of ground motion parameters at the ground surface are obtained. The results indicate amplification of ground motion of up to 4.93. The predicted fundamental period of soils is about 0.5 s which is typical for these types of soils. The maximum spectral acceleration varied from 0.76 to 0.95 g. For design purposes, a response spectrum curve is proposed. 相似文献
997.
Ezio Faccioli 《Bulletin of Earthquake Engineering》2006,4(4):341-364
The main features of the Risk-UE project approach to assessing the ground-shaking (and related hazards) distribution within urban areas are described, as a basis for developing seismic damage scenarios for European cities. Emphasis was placed in the project on adoption of homogeneous criteria in the quantitative treatment of seismicity and in constructing the ground-shaking scenarios, despite wide differences in amount and quality of data available for the cities involved. The initial steps of the approach include treatment of the regional seismotectonic setting and the geotechnical zonation of the urban area, while the hazard assessment itself takes the form of both a deterministic analysis, and of a probabilistic, constant-hazard spectra analysis. Systematic 1D site response analyses were used, mostly in the softer soil zones, to modify (when needed) the obtained ground motion maps. Earthquake induced hazard effects, such as liquefaction and landsliding, are also briefly dealt with at the end. 相似文献
998.
Chih-Chiang Lu Chu-Hui Chen Tian-Chyi J. Yeh Cheng-Mau Wu I-Fang Yau 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):6-22
Typhoons and storms have often brought heavy rainfalls and induced floods that have frequently caused severe damage and loss
of life in Taiwan. Our ability to predict sewer discharge and forecast floods in advance during storm seasons plays an important
role in flood warning and flood hazard mitigation. In this paper, we develop an integrated model (TFMBPN) for forecasting
sewer discharge that combines two traditional models: a transfer function model and a back propagation neural network. We
evaluated the integrated model and the two traditional models by applying them to a sewer system of Taipei metropolis during
three past typhoon events (NARI, SINLAKU, and NAKR). The performances of the models were evaluated by using predictions of
a total of 6 h of sewer flow stages, and six different evaluation indices of the predictions. Finally, an overall performance
index was determined to assess the overall performance of each model. Based on these evaluation indices, our analysis shows
that TFMBNP yields accurate results that surpass the two traditional models. Thus, TFMBNP appears to be a promising tool for
flood forecasting for the Taipei metropolis sewer system.
For publication in Stochastic Environmental Research and Risk Analysis. 相似文献
999.
This paper focuses on interpreting the different spatial relationships between NDVI and T
s, a triangular or a trapezoid, and on analyzing transformation conditions, the physical and ecological meanings of the vegetation
index-surface temperature space as well. Further, we use the Temperature-Vegetation Dryness Index (TVDI) to explain the existent
meaning of a triangular space after NDVI reaches its saturated state by employing the relationships between NDVI, LAI and
evapotranspiration. The specific relations between NDVI and T
s are useful for describing, validating and updating land surface models. 相似文献
1000.