DISCUSSION ON ATTENUATION CHARACTERISTICS,SITE RESPONSE AND MAGNITUDE DETERMINATION IN SICHUAN

The attenuation characteristics and site response are calculated respectively for each individual tectonic unit in Sichuan (Sichuan Basin,west Sichuan plateau and Panzhihua-Xichang area),using digital waveform data recorded by regional seismic networks and relevant seismic phase data collected from China Seismograph Network.The frequency dependent Q(f) is obtained by the iterative grid-search technique described by Atkinson and Mereu based on trilinear geometrical spreading model.The source spectra are determined by the model of Brune and the site responses of seismic stations are derived by Moya's method using genetic algorithms.Comparison to conventional M_L estimates shows that the network local magnitude bias is quite significant at low and intermediate magnitudes.The bias at the j^th station for the i^th event is defined as ΔM_ij=M_ij-M_i, where ΔM_ij is the station magnitude and M_i the network-average value.For comparison,we mapped the spatial distribution of biases by digital seismograms recorded from 10535 earthquakes of magnitude 2.5≤M_L≤4.9 that occurred in Sichuan from January 1,2009 to June 30,2015.Based on the above data,the attenuation characteristics,site response and their effects on magnitude determination in Sichuan are analyzed.Our results demonstrate that the associated model for regional quality factor for frequencies can be expressed as Q₁(f)=450.6f^{0.513 4} for Sichuan Basin,Q₂(f)=136.6f^{0.581 3} for west Sichuan Plateau and Q₃(f)=101.9f^{0.666 3} for Panzhihua-Xichang area.Site response results indicate that different stations show different amplifications.Maps of biases appear to be different,but with similar dominant spatial distribution.For stations in Sichuan Basin,their greater magnitudes are functions of low attenuation in structure and amplification effects of both seismic stations and basin effects.For stations in west Sichuan Plateau,the possible causes of these lower magnitudes are severe dependence upon source region due to extreme lateral variations in either structure or path effect attenuation.For stations in Panzhihua-Xichang area,broken medium caused by strong tectonic activity or large earthquakes and heat flow up-welling along active faults may be the main reasons of low magnitude values when earthquakes occur in western Sichuan and eastern Tibetan region.And the greater magnitudes for earthquakes along the Longmen Mountains appear to be well correlated with edge effect of sedimentary basin on strong ground motion.In our study,stations magnitude biases appear to be extremely correlated with tectonic structures and different regions when seismic rays passing through,magnitudes are affected significantly by lateral variations in attenuation characters rather than site responses.     

反射定标板污染对典型月球矿物定量分析影响的研究

悬浮月尘存在污染月表就位光谱仪反射定标板的可能。文中工作模拟并分析了近红外光谱仪反射定标板在无污染、受轻度和重度污染情况下对模拟月壤矿物混合物光谱指纹特征及定量分析模型预测精确度的影响。结果表明：以受污定标板为参比的月壤矿物混合物反射光谱在反射率和指纹特征上均异于无污染样品,且污染越重差异越大;用无污染光谱数据建立的偏最小二乘(PLS)定量分析模型,预测受污样品时其预测精确度显著降低;采用受污后光谱数据重建PLS模型会在一定程度上能提高受污样品的预测准确度。该研究和获得的结论,在星表光学载荷的设计、数据校正以及定量分析模型预测能力评估等方面具有一定的指导意义。     

单台测定中强震震级偏差的修正方法

选取淮北地震台（简称淮北台）测定中强震面波震级编目MS4.5及以上震例为样本,以中国地震台网中心（简称CENC）的震级参数为标准震级,新定义＂二维震级修正法＂对淮北台震级进行修正,分析结论显示＂二维震级修正＂效果显著,且易于操作,对提高单台速报和编目震级的准确性具有现实意义。     

格尔木地震台大震速报震级差异分析

选取格尔木地震台2000年7月到2013年5月的680个地震,与中国地震台网中心提供的《国家台网大震速报目录》进行面波震级的对比,得出格尔木地震台的台基校正值、标准误差;通过计算分析,总结出不同方位、震中距、震级大小的地震震级差异性之间的关系。     

点荷载法测试易风化泥质岩强度的可靠性分析

在川南地区在近年的煤炭开发过程中,多数基建矿井在巷道开拓期间大量出现围岩软弱、易风化、节理裂隙发育、变形大、支护难、多次返修等严重困扰矿井正常投产的支护难题,为合理选取支护技术,必须对软岩类型及等级进行划分。首先进行地质工程调查,选择巷道主要分布的厚层黑灰色泥岩为研究对象,在井下采用点荷载测试仪对新鲜不规则岩块进行强度测试。在对可疑数据采用Grubbs准则进行取舍后,采用传统法、ISRM法、工程分级法分别进行点荷载强度计算,所得结果采用F检验法和t检验法对各公式计算结果进行随机误差和系统误差检验,研究各方法的适宜性。研究发现,在对泥岩进行点荷载测试时,传统法和ISRM法较工程分级法所得单轴抗压强度平均值的随机误差和系统误差小,更适宜作为该类岩性进行工程软岩分级评价时的重要指标;点荷载所获泥岩强度值的偏差系数在11%～30%范围内,与一般岩石单轴抗压强度测定值偏差系数接近,具有可靠、快速、方便、费用低的优点,适宜作为围岩取样困难的巷道进行软岩类型评价的测试方法。     

地下工程开挖面空间效应特征研究及应用

地下工程开挖面对围岩变形具有约束作用,在该约束作用下开挖面表现出显著的空间效应。通过开展地下工程开挖面空间效应现场试验,获得了开挖面空间效应特征。根据现场试验结果,提出了描述开挖面空间效应的双曲正切函数经验公式。利用上述经验公式,开展了洞室围岩稳定性控制研究,获得了不同预警等级条件下拱顶沉降值控制标准。研究发现,对某特定断面,空间效应最显著时并非开挖面透过该断面时;地下工程围岩稳定性越差,开挖面空间约束效应越不明显;若采用常规先开挖再监测的方法,不能监测到围岩全部位移,从而影响参数反分析的准确性;利用开挖面空间效应原理可以获得地围岩稳定性位移控制标准。研究结果为深入了解地下工程空间效应和开展地下工程稳定性控制提供了借鉴和参考。     

A sensitivity analysis of lake water level response to changes in climate and river regimes

Lake water level regimes are influenced by climate, hydrology and land use. Intensive land use has led to a decline in lake levels in many regions, with direct impacts on lake hydrology, ecology and ecosystem services. This study examined the role of climate and river flow regime in controlling lake regimes using three different lakes with different hydraulic characteristics (volume-inflow ratio, CIR). The regime changes in the lakes were determined for five different river inflows and five different climate patterns (hot-arid, tropical, moderate, cold-arid, cold-wet), giving 75 different combinations of governing factors in lake hydrology. The input data were scaled to unify them for lake comparisons. By considering the historical lake volume fluctuations, the duration (number of months) of lake volume in different ‘wetness’ regimes from ‘dry’ to ‘wet’ was used to develop a new index for lake regime characterisation, ‘Degree of Lake Wetness’ (DLW). DLW is presented as two indices: DLW₁, providing a measure of lake filling percentage based on observed values and lake geometry, and DLW₂, providing an index for lake regimes based on historical fluctuation patterns. These indices were used to classify lake types based on their historical time series for variable climate and river inflow. The lake response time to changes in hydrology or climate was evaluated. Both DLW₁ and DLW₂ were sensitive to climate and hydrological changes. The results showed that lake level in high CIR systems depends on climate, whereas in systems with low CIR it depends more on river regime.     

粤北地区导线覆冰气象特征与标准厚度推算

利用广东省乐昌高山气象站1972—1978年观冰资料和气候资料,分析了粤北地区导线覆冰的气象特征,建立了导线覆冰标准冰厚的气象推算模型。根据乐昌国家气象站的历史资料,对乐昌高山气象站的气候资料进行订正延长,构建了乐昌高山气象站覆冰年极值长年代序列,并推算出离地不同高度各重现期的标准冰厚值。结果表明,粤北地区导线覆冰主要发生在1月,其次为2月和12月,平均覆冰期在90天左右,最长覆冰期可达131天以上。主导风向、日最低气温、日降水量是影响导线覆冰厚度的主要气象因素。标准冰厚的年极值序列服从极值I型概率分布,历史上的最大导线覆冰值出现在2008年1月26日,2m高度标准冰厚达64.4mm,15m高度标准冰厚达92.7mm,与2008年冰灾实况调查的覆冰厚度(标准冰厚)115mm较为接近。     

一次西南涡路径预报偏差分析及数值模拟

2008年7月21-23日,在川东的西南涡移出后东北上.参考各数值模式对22-23日西南涡路径预报后,河南省气象台于21日发布暴雨预报,出现了落区偏差.为加深对西南涡移动路径机理的认识,利用常规和NCEP资料,从大气环流、热力、动力等方面对这次西南涡移动路径特征进行探讨;对数值预报产品作天气学检验;利用WRF模式对本次过程进行模拟.结果表明:(1)这次西南涡呈现南掉-东北上-东东北再东北上的曲折路径;(2)低涡结构显示了中尺度特征,涡度轴向、K指数等对低涡的移动路径有指示意义;(3)由于过于依赖数值预报,加之对东北南下冷空气影响考虑不足,是造成这次低涡路径预报偏差的主要原因;(4)WRF模式对这次低涡路径有较好的预报能力.     

俯冲带浅壳和上地幔地震水平向位移谱阻尼修正系数模型研究

考虑场地条件的影响,采用固定效应方法对日本K-NET和KiK-Net强震台网获取的6466条浅壳和上地幔地震记录的统计分析,建立水平向位移谱阻尼修正系数模型.该模型基于13个阻尼比和36个谱周期,使用随机效应模型分离出残差及其对应标准差,用来评估地震动参数对模型的影响.研究表明:以阻尼比对数值为自变量的简单二次函数可以...