Highland Boundary Fault Zone: Tectonic implications of the Aberfoyle earthquake sequence of 2003

The Highland Boundary Fault Zone (HBFZ) is one of the major faulted tectonic boundaries in Great Britain. Historically, seismicity has occurred in this zone around the town of Comrie. But an earthquake sequence that occurred in 2003 near the village of Aberfoyle (M_L 1.3–3.2) was the first significant activity to be recorded in the HBFZ since the installation of modern seismograph networks in the 1970s. This study describes detailed analysis of these data. The waveform signals of the events were almost identical and by applying a cross-correlation technique combined with multiple event location, the alignment of the events was found to be WSW–ENE. This alignment matches one of the nodal planes determined by joint focal mechanism analysis. The fault plane dips to the northwest, and shows oblique sinistral strike–slip with normal movement. The orientation of the event alignment matches the direction and orientation of observed features in the HBFZ. Hence, it is concluded that the WSW–ENE striking nodal plane was the causative fault that is associated with the HBFZ. The orientation of maximum compressional stress is rotated from the regional average expected due to the Mid-Atlantic ridge-push force. This rotation is possibly explained by stresses due to postglacial rebound. Smaller events in the sequence were used as empirical Green's functions and deconvolved from the larger events to determine source time functions. The corresponding corner frequencies matched results from spectral fitting, showing that the events were of relatively low stress drop.     

利用COSMIC掩星资料研究对流层/下平流层大气比湿对ONI指数的响应

本文利用2006年6月至2014年6月COSMIC掩星观测的水汽廓线, 分析了对流层/下平流层(TLS)比湿信号对ENSO的响应.在数据处理中, 将COSMIC掩星水汽廓线计算得到的全球比湿数据内插为1000~30 hPa区间水平分辨率为5°×5°的三维格网, 在各等压面上求取各格网点去除年/月际信号后的比湿月异常值.然后在对比湿月异常时间序列低通滤波的基础上, 进行经验正交分解(EOF)得到比湿主成分, 并对该主成分信号进行二项式平滑; 接下来将平滑后的主成分信号与反映ENSO活动的ONI指数进行相关处理, 得到各等压面主成分信号相对于ONI指数的相关系数及对应的时间延迟.论文分析了包括Niño-3.4的5个代表性区域的TLS比湿异常主成分信号, 结果表明:在各区域, 采用本文先低通滤波再EOF分解的处理方法获得的TLS比湿异常主成分信号与ONI指数均有很强相关性, 对流层相关系数绝对值达0.8以上, 低平流层高于0.7, 在300~200 hPa的上对流层达到峰值; 各等压面上比湿异常主成分信号相对于ONI指数的时间延迟不尽相同, 在对流层中比湿异常主成分信号普遍滞后于ONI指数1~6个月; 在各区域, 比湿异常主成分与ONI指数相关系数绝对值达到最大的等压面都接近250 hPa, 最大相关系数绝对值均达到0.9以上.进一步对全球250 hPa等压面比湿异常主成分与ONI指数相关性的分析表明:两者强相关的区域主要集中在热带; 在这些强相关区域, 比湿异常主成分相对于ONI主要表现为滞后, 且相关系数越大, 相应的时间延迟越短.

     

原位测试及快剪指标的对比与分析以大连长兴岛葫芦山湾海域海相黏性土为例

以大连长兴岛葫芦山湾海域为例, 通过对海相黏性土(Q4m)标贯、十字板及土工试验快剪指标的统计, 提出了该区域海相黏性土的标贯、十字板、土工试验快剪指标特征值, 以按深度分组统计的试验指标平均值为分析指标进行对比分析, 建立了深度及标贯、十字板、土工试验快剪指标之间的经验关系15个。     

芦山7级地震的同震位移估计和震源滑动模型反演尝试

利用自动经验基线校正方法,分析2013年4月20日芦山MS7.0级地震13个近场强震动台的观测资料,以估算同震位移场分布,并据此反演了震源滑动模型.经与GPS结果比较,两种不同方法给出的芦山7级地震的水平近场同震位移场幅度都不超过cm级,均显示为典型的逆冲型地震（兼有少量左旋走滑错动）.强震最大水平和垂直永久位移分别为4.9 cm和4.4 cm,分别出现在51YAM台和51QLY 台.两种资料反演的震源滑动模型虽显示多事件特征,但主要滑动均集中在第一次事件,即初始滑动点两侧的走向长约30 km、倾向长约25 km的相对集中的较小范围内,强震和GPS模型的最大滑动量分别为1.14 m和1.09 m,较为一致.其余子事件滑动量小且分布零散,不能排除其数值效应的因素.反演矩震级均在Mw6.7左右,地表破裂应该不明显.文章还讨论了目前在我国利用近场强震动记录估计Mw6~7级地震同震位移场存在的困难和问题,为今后类似工作提供参考.     

A study of the empirical functions of the height fields over India and their relation with the rainfall

The empirical orthogonal functions have been obtained for the individual summer monsoon (June through September) months using the grid point values of monthly 700 mb geopotential heights over Indian region. The data for 21 summer monsoon months for the years 1958 to 1978 have been used in the present computation. The major variance reduction is due to the first three dominant functions accounting over 80% of the total variance in each month. The variance reduction only due to the first function ranges from 45 to 65%. The first function has in-pbase oscillation throughout the area indicating that the area under study is homogeneous and the centre of the oscillation lies over northwest India. The amplitudes of the first function also show generally quasipers stence in their sign within a season. The second function has two centres of action over the region of monsoon trough which are in phase. The third function has also two centres oriented in the east-west direction but they are in the opposite phase. Fairly large values of correlation coefficients between the patterns of the different monsoon months suggest that the patterns for these months corresponding to the first and the second functions respectively are quite similar. The patterns for these months also evolve with time in a related way. The spectrum analysis to the time series of amplitudes indicates the presence of the quasi-periodicity of 3 years during these monsoon months. The amplitudes corresponding to the dominant functions are found to be significantly related with the rainfall of central and western parts of India     

基于干涉成像的微震定位方法

提出了一种基于光学干涉原理,用地震波代替光波进行地震成像的一种新的成像方法:地震干涉成像方法。用这种方法进行微震定位的特点是不需要进行初至拾取,观测系统也可以使用任意阵列检波器。模拟了一个地下震源的二维时间延迟记录,编制了基于C语言的震源定位程序,对接收的记录使用此方法进行成像。通过程序运行结果验证了此方法的可行性,且定位效果明显。     

Spatial patterns from EOF analysis of soil moisture at a large scale and their dependence on soil,land-use,and topographic properties

We hypothesize that the spatial and temporal variation in large-scale soil moisture patterns can be described by a small number of spatial structures that are related to soil texture, land use, and topography. To test this hypothesis, an empirical orthogonal function (EOF) analysis is conducted using data from the 1997 Southern Great Plains field campaign. When considering the spatial soil moisture anomalies, one spatial structure (EOF) is identified that explains 61% of the variance, and three such structures explain 87% of the variance. The primary EOF is most highly correlated with the percent sand in the soil among the regional characteristics considered, but the correlation with percent clay is largest if only dry days are analyzed. When considering the temporal anomalies, one EOF explains 50% of the variance. This EOF is still most closely related to the percent sand, but the percent clay is unimportant. Characteristics related to land use and topography are less correlated with the spatial and temporal variation of soil moisture in the range of scales considered.     

影响公众地震应急准备因素分析

汶川地震发生后,受桑枣中学案例启发,在中小学开展应急演练受到重视。提高公众地震应急准备能力是提高我国防震减灾能力的重要环节,本研究通过问卷数据分析,描述我国公众地震应急准备现状,分析影响中国公众地震应急准备的因素。研究结果表明,收入、学历、风险感知和政府责任影响公众地震应急准备,并提出做好相关工作的政策建议。     

基于经验正交分析法的暴时热层大气密度时空分布规律

本文选取2002—2006年期间的36个强磁暴为研究对象,对CHAMP卫星加速度仪反演的实测大气密度进行经验正交分解,研究暴时热层大气密度的纬度分布特征,以及大气密度与ap指数、Dst指数的关系.结果表明,大气密度的纬度分布与季节相关,夏季半球的密度大于冬季半球,春秋季节南北半球的大气密度几乎对称分布;春秋季节白天大气密度在低纬地区呈现出赤道密度异常结构,在中高纬地区密度随纬度增加而减小,夜间则呈现抛物线的形状,赤道附近密度值最小.大气密度的纬度分布特征在若干天内具有良好的稳定性,发生时间相近的磁暴事件,纬度分布曲线非常相似,并且暴前与暴时的纬度分布变化不大.相关性分析表明,大气密度滞后ap指数2~6 h,相对Dst指数平均提前0~1 h,对磁暴的响应速度在日照区比在阴影区快,大气密度与ap指数、Dst指数具有较好的相关性.     

用HJ-1B IRS数据反演海表温度的2种辐射传输方程改进算法

针对使用NCEP再分析数据和辐射传输方程法反演SST出现偏差较大的问题,以HJ-1B SST反演为例,从修正大气透过率入手,提出中心点算法和均值点算法2种辐射传输方程改进算法。2种改进算法对大气透过率偏差和HJ SST反演偏差均有明显改善,反演的HJ SST与MODIS SST均呈现显著的一致性。MODIS SST验证表明2种改进算法的平均偏差和均方差在0.5 ℃左右;浮标SST验证表明均值点算法的反演精度较高,其平均偏差为0.55 ℃,而中心点算法的为0.81 ℃。