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1.
In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°～120°E,29°～42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu≥8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions. 相似文献
2.
《中国地震研究》1994,(1)
The earthquake catalog with the minimum completeness magnitude of ML=1.7 during the period from 1970 to 1976 has been used as basic data for the research on seismic quiescence in source area before occurrence of the July 1976 great Tangshan earthquake in China,based on the analyses of the detectability of seismic network,and of relation between earthquake magnitude and frequency in Northern China.The temporal processes of seismicity rate(January 1970-July 1976)before the July 1976 great Tangshan earthquake for four researched sub regions in and around source area(aftershock area)of the mainshock are investigated and compared.It is found that there exist abnormal seismic quiescence with duration of 38 months in the subregion located in western part of aftershock area,which is significant statistically at confidence level of 0.99 and larger by beta-test.In addition,because there were no false alarms except for the above abnormal interval in the west aftershock area,and the Tangshan mainshock and 85% of af 相似文献
3.
Using the earthquake sequences data with MS≥6.5 since 1966 in Sichuan-Yunnan region, we research the charac-teristic of the magnitude difference distribution between main shocks and their strong aftershocks; and then study the spatial distribution characteristic of the strong aftershocks away from their main shocks. The result shows that the magnitude difference distribution obeys intercepted exponential distribution, while the spatial distribution of strong aftershocks obeys normal distribution and the dominated distribution area of strong shocks is 10~39 km away from main shock. Finally the probability density function of the magnitude difference distribution and the spatial distribution of strong aftershocks is deduced. 相似文献
4.
Discovery and preliminary study of the high tungsten and lithium contents in the Dazhuyuan bauxite deposit, Guizhou, China 总被引：1，自引：0，他引：1
WANG DengHong LI PeiGang QU WenJun YIN LiJuan ZHAO Zhi LEI ZhiYuan WEN ShenFu 《中国科学:地球科学(英文版)》2013,(1):145-152
Bauxite in China remains an urgently needed resource largely dependent on imports. Based on the study of the newly-discovered Dazhuyuan bauxite deposit in northeastern Guizhou, we have found new enrichment of tungsten and lithium in bauxite, with the highest WO 3 content up to 0.33% and the highest Li 2 O content up to 0.58%. The present paper reports the initial result, and the spatial distribution feature of W and Li in the ore body (with Li enriched mostly in the north part of the west limb of the Liyuan syncline, whereas W enriched mostly in the central part of the east limb). The results suggest that it is necessary to delineate lithium and tungsten ore body independently, discuss the feasibility of its industrial utilization, and point out the new direction of synthetic appraisal for such kinds of traditional mineral resources, in order to forecast and assess bauxite resources in the region. 相似文献
5.
In the analysis and design of important structures with relatively long life spans, there is a need to generate strong motion data for possible large events. The source of an earthquake is characterized by the spatial distribution of slip on the fault plane. For future events, this is unknown. In this paper, a stochastic earthquake source model is developed to address this issue. Here, 1D and 2D stochastic models for slip distribution developed by Lavallée et al.(2006) are used. The random field associated with the slip distribution is heavy-tailed stable distribution which can be used for large events. Using 236 past rupture models, the spectral scaling parameter and the four stable or Levy's parameters against empirical relationship for known quantities like magnitude or fault length are developed. The model is validated with data from 411 stations of 1999 Chi-Chi earthquake. The simulated response spectrum showed good agreement to actual data. Further the proposed model is used to generate ground motion for the 1993 Killari Earthquake where strong motion data is not available. The simulated mean peak ground velocity was in turn related to the intensity(MSK) and compared against values in the literature. 相似文献
6.
This paper studies the temporal and spatial distribution of great global earthquakes( M W≥8.0) since 1900.We compare the two periods of upsurges of great earthquakes occurring in the middle of last century and beginning of this century.The former period took place between 1950 and 1965 during which 13 great earthquakes( M W≥ 8.0) occurred,including three events with moment magnitude greater than 9.0.The largest magnitude in this period reached 9.6.The latter period starts from the beginning of this century.In less than 12 years,15 great earthquakes have attacked the world with the largest magnitude being M W9.1.On the basis of comparison between these two upsurges of global earthquake activity,we infer that the ongoing high level of earthquake activity may continue for another five years or so.Numerous great earthquakes( M W≥8.0) and many large earthquakes( M W6.0~7.0) will occur globally in these five years.In addition,this paper also discusses the relationships between earthquake activity along the Sumatra segment of the Indian-Australia plate boundary and that in the Bayankala block in the middle of Qinghai-Tibetan plateau as well as in the blocks of the southern plateau.The results indicate that the Qinghai-Tibetan plateau,in particular its middle and southern parts,is a likely place for future earthquakes of magnitude over 7.0. 相似文献
7.
Long-term highly accurate surface soil moisture data of TP(Tibetan Plateau)are important to the research of Asian monsoon and global atmospheric circulation.However,due to the sparse in-situ networks,the lack of soil moisture observations has seriously hindered the progress of climate change researches of TP.Based on the Dual-Channel soil moisture retrieval algorithm and the satellite observation data of AMSR-E(Advanced Microwave Scanning Radiometer for EOS),we have produced the surface soil moisture data of TP from 2003 to 2010 and analyzed the seasonal characteristic of the soil moisture spatial distribution and its multi-year changing trend in area of TP.Compared to the in-situ observations,the accuracy of the soil moisture retrieved by the proposed algorithm is evaluated.The evaluation result shows that the new soil moisture product has a better accuracy in the TP region than the official product of AMSR-E.The spatial distribution of the annual mean values of soil moisture and the seasonal variations of the monthly-averaged soil moisture are analyzed.The results show that the soil moisture variations in space and time are consistent with the precipitation distribution and the water vapor transmission path in TP.Based on the new soil moisture product,we also analyzed the spatial distribution of the changing trend of multi-year soil moisture in TP.From the comparisons with the precipitation changing trend obtained from the meteorological observation sites in TP,we found that the spatial pattern of the changing trend of soil moisture coincides with the precipitation as a whole. 相似文献
8.
The accuracy of b-value is limited by the uncertainty of the magnitude.In order to improvethe accuracy of the b-value,a statistic methodology was used to estimate the number of eventsbased on that there are several magnitude values for one historical event by several methods toestimate the magnitude.The b-value and seismic strain rates were calculated for the threeregions in the North of China.The method proved to be valid for all the regions,especiallyfor the data with large fluctuation.In order to study the stress state,the strain rate tensorand the principal axes of tension and compression were calculated for each of three regions bythe data of the focal mechanism,finally the stress state in each region was discussed. 相似文献
9.
By applying the GL-value, a parameter describing the heterogeneities in temporal and spatial distribution of moderate and small earthquakes prior to strong earthquakes, the following problems have been studied in the present paper: a systematic investigations have been made on the features of spatial distribution and temporal variation of the high value anomalies ( GL ≥1.0) prior to 28 moderately strong earthquakes with Ms ≥5.0 in the North China region; a systematic study has been made on the reasonability of the lower limit of magnitude, the time window and the space window for calculations at various seismicity levels in this region; the parameters taken in the calculation have been optimized and modified; the anomalous variations of GL-value prior to various moderately strong earthquakes in North China region have been investigated and followed, using the total time-space scanning method. The results of the study have shown that for 82 % of the moderately strong earthquakes in the North China region, obvious anomalous region with high GL-values appears near the future epicenter about 1 ～ 3.5 years before the earthquakes. The earthquakes usually occur in the marginal area of the anomalous zone or near it. Temporal variations of the GL-values in the anomalous zone show that the duration of anomalous ranges between 3 ～ 25 months with a predominant interval of 5 ～ 19 months, into which about 70% the total anomalies fall. The predominant interval of earthquake occurrences is 0 ～ 14 months after ending of the anomaly, into which about 83 % of the total anomalies fall. Based on these results the GL-value method is considered to be a rather effective prediction method for moderately strong earthquakes in the North China region. 相似文献
10.
This paper presents the changes of crust thickness and Poissons ratios distribution in the Binchuan region,where the first air-gun transmitting station and its a small dense array were deployed.From September 2011 to January 2014,more than 239 teleseismic events of M≥6.0 were recorded in 16 stations in the Binchuan region.Their P-wave receiver functions were analyzed respectively.The high spatial resolution result shows that the average crust thickness of Binchuan region is 45.3km,it follows the rule of"deeper in the north and east part,shallower in the south and west part."The deepest region is in Xiaoyindian Station;the crust thickness is 47.9km;the shallowest region is in Paiying Station,it has the thickness of 42.1km.It shows that the deeper Moho surface nearby the Chenghai fault and shallower nearby the Honghe fault;the isoline distribution of thickness changes greatly nearby the Chenghai fault and slowly nearby the Honghe fault.From the distribution of Poissons ratios,it is unevenly in the study area with a great difference from the north part to the south part,which shows a characteristic of"lower in the north,higher in the south".The Poissons ratio nearby the Honghe fault is medium too high(0.26≤σ≤0.29);lower nearby the Chenghai fault(σ≤0.26).This paper concludes the possible reason of different characteristic between Poissons ratio and crust thickness is thicker in the upper crust in the Binchuan region. 相似文献
11.
探地雷达数值模拟中,时域有限差分法在时间和空间上一般采用二阶精度的中心差分近似(FDTD(2,2)),其形式简单,但数值色散误差较大,在复杂模型模拟时不能很好地反映模型的精细变化.高阶时域有限差分法能很好地改善数值色散带来的误差,提高模拟精度.本文基于三维高阶时域有限差分法的基本原理实现了探地雷达正演模拟,采用单轴各向异性完全匹配层(UPML)作为吸收边界条件,可以有效地吸收外向传播的电磁波,在大大地提高计算效率的同时,也能很好地改善边界的吸收效果.分析对比正演模拟结果,通过三维高阶时域有限差分正演能获得目标体准确电磁响应信息,并能很好的提高模拟精度. 相似文献
12.
13.
In this work we examine simultaneous observations from the two geosynchronous satellites GOES-5 and GOES-6 located at 282°E and 265°E respectively, and from middle and low latitude ground observatories located within 250°E and 294°E geographic longitude, during isolated substorms of moderate activity. The spatial distribution of our observation points allows us to make a detailed study of the azimuthal expansion of the substorm current wedge. The data analysis shows evidence that the substorm initiation and development mechanism include the cross-tail current diversion/disruption, the substorm current wedge formation and the azimuthal expansion of the inner plasma sheet. The triggering mechanism is initially confined in a longitudinally narrow sector, estimated to be less than 15° and located very close to local midnight to the east or to the west. The current disruption region expands both eastward and westward in the magnetotail, so that the location of major field-aligned currents flowing into the ionosphere shifts successively eastward, and the location of the currents flowing out of the ionosphere shifts successively westward. Evidence was found that the perturbation travels toward the west with velocities greater than those expanding the wedge eastward. The drastic decrease of the velocity with the azimuthal distance from the location of the disturbance initiation, i.e., the onset sector, indicates that the energy release is a very localized phenomenon. Finally, the transient D perturbation observed by the geosynchronous satellites suggests that the field-aligned currents forming the wedge have a longitudunally limited extent. 相似文献
14.
15.
The development of an expansion double spherical seismic isolation (DSSI) bearing by modifying the fixed DSSI bearing is described in this paper.The expansion DSSI bearing is characterized by its good ... 相似文献
16.
We study the geometry of magnetic fluctuations in a CIR observed by Pioneer 10 at 5 AU between days 292 and 295 in 1973. We apply the methodology proposed by Bieber et al. to make a comparison of the relative importance of two geometric arrays of vector propagation of the magnetic field fluctuations: slab and two-dimensional (2D). We found that inside the studied CIR this model is not applicable due to the restrictions imposed on it. Our results are consistent with Alfvenic fluctuations propagating close to the radial direction, confirming Mavromichalaki et al.’s findings. A mixture of isotropic and magnetoacoustic waves in the region before the front shock would be consistent with our results, and a mixture of slab/2D and magnetoacoustic waves in a region after the reverse shock. We base the latter conclusions on the theoretical analysis made by Kunstmann. We discuss the reasons why the composite model can not be applied in the CIR studied although the fluctuations inside it are two dimensional. 相似文献
17.
地震前兆综合预测支持向量机模型研究 总被引：4，自引：0，他引：4
该文介绍了支持向量机算法的原理与回归方法。 采用支持向量机中的非线性回归算法与理论公式产生的多维样本, 对其进行了数值仿真实验。 利用该方法和地震前兆异常建立了最佳地震综合预测模型, 对获得的最佳模型进行了内符检验, 得出最佳模型的预测结果与实际震例的地震震级基本一致。 综合分析认为, 支持向量机无论在学习或者预测精度方面不但具有很大的优越性和具有较强的外推泛化能力, 而且基于支持向量机回归算法建立的地震前兆综合预测模型是可行的, 其获得的知识可较为准确地实现对主震震级的综合预测。 相似文献
18.
Brendon A. Bradley Misko CubrinovskiRajesh P. Dhakal Gregory A. MacRae 《Soil Dynamics and Earthquake Engineering》2009
In this study the efficacy of various ground motion intensity measures for the seismic response of pile foundations embedded in liquefiable and non-liquefiable soils is investigated. A soil-pile-structure model consisting of a two-layer soil deposit with a single pile and a single degree-of-freedom superstructure is used in a parametric study to determine the salient features of the seismic response of the soil-pile-structure system. A suite of ground motion records scaled to various levels of intensity are used to investigate the full range of pile behaviour, from elastic response to failure. Various intensity measures are used to inspect their efficiency in predicting the seismic demand on the pile foundation for a given level of ground motion intensity. It is found that velocity-based intensity measures are the most efficient in predicting the pile response, which is measured in terms of maximum curvature or pile-head displacement. In particular, velocity spectrum intensity (VSI), which represents the integral of the pseudo-velocity spectrum over a wide period range, is found to be the most efficient intensity measure in predicting the seismic demands on the pile foundation. VSI is also found to be a sufficient intensity measure with respect to earthquake magnitude, source-to-site distance, and epsilon, and has a good predictability, thus making it a prime candidate for use in seismic response analysis of pile foundations. 相似文献
19.
龙感湖水体光学特性的观测 总被引：1，自引：0，他引：1
基于2002—2003年秋、夏季原位水下光场巡测及连续定点观测资料分析了龙感湖不同湖区及不同风浪条件下水体的光学特性,探讨了光衰减系数、辐照度比的光谱分布、空间差异及不同风浪条件对水下光场的影响.结果表明,水下光谱在紫光波段衰减最强烈,其次是蓝光,红、绿光衰减最弱,并且向下辐照度衰减系数一般要大于向上辐照度衰减系数.秋季L1-L3点向下辐照度400—700nm波段衰减系数的变化范围分别为0.71—3.60、1.06—3.72、0.78—2.89m-1;光衰减系数的空间分布是位于湖中心的12点要略大于两边的L1、L3点;辐照度比的变化趋势极为一致,最低值出现在短波蓝光波段,最高值出现在550—600nm之间;从小风浪到中风浪、大风浪其PAR衰减系数分别是1.74、2.02、2.45m-1;透明度、衰减系数与悬浮物浓度相关性最好,决定系数在0.7以上,但其变化除受悬浮物影响外还要受制于溶解性有机物和浮游植物;440nm波长衰减系数(Kd(440))与悬浮物(SS)、溶解性有机碳(DOC)、叶绿素a(Chl.a)的多元线性回归方程为:Kd(440)=0.514—0.075SS 0.125DOC 0.100Chl.a(R2=0.87,N=8,P≤0.05) 相似文献
20.
《中国科学D辑(英文版)》2008,(Z2)
Study on characterizing reservoir parameters dynamic variations by time-lapse seismic attributes is the theoretical basis for effectively distinguishing reservoir parameters variations and conducting time-lapse seismic interpretation,and it is also a key step for time-lapse seismic application in real oil fields. Based on the rock physical model of unconsolidated sandstone,the different effects of oil saturation and effective pressure variations on seismic P-wave and S-wave velocities are calculated and analyzed. Using numerical simulation on decoupled wave equations,the responses of seismic amplitude with different offsets to reservoir oil saturation variations are analyzed,pre-stack time-lapse seismic attributes differences for oil saturation and effective pressure variations of P-P wave and P-S converted wave are calculated,and time-lapse seismic AVO (Amplitude Versus Offset) response rules of P-P wave and P-S converted wave to effective pressure and oil saturation variations are compared. The theoretical modeling study shows that it is feasible to distinguish different reservoir parameters dynamic variations by pre-stack time-lapse seismic information,including pre-stack time-lapse seismic attributes and AVO information,which has great potential in improving time-lapse seismic interpreta-tion precision. It also shows that the time-lapse seismic response mechanism study on objective oil fields is especially important in establishing effective time-lapse seismic data process and interpreta-tion scheme. 相似文献