Structural evidence for large-scale top-to-the-north normal displacement along the Median Tectonic Line in southwest Japan

Abstract   The Median Tectonic Line (MTL) is a first-order tectonic boundary that separates the Sanbagawa and Ryoke Metamorphic Belts. Strike-slip movements on the MTL have been well documented by many workers. New field based structural studies in the Sanbagawa Belt close to the MTL reveal a large number of secondary faults and semibrittle shear bands indicating a top-to-the-north normal sense of displacement. The strikes of these shear zones and their spatial distributions suggest that development of these structures is related to movements on the MTL. These results imply that the MTL has a large-scale normal shear component on a regional scale that can help account for the exhumation of the Sanbagawa Belt. Our proposed history of the MTL can also account for changes in the geometry of folds in the Sanbagawa Belt.     

Quantification of Hydrophone Records of the 2004 Sumatra Tsunami

The 2004 Sumatra-Andaman tsunami was recorded by hydrophones of the International Monitoring System at Site H08 near Diego Garcia, notably in frequency bands extending outside the range of the Shallow Water Approximation. Despite the severe high-pass filtering involved in this instrumentation, we show that the spectral amplitudes recovered around T = 87 s can be successfully explained by generation from the seismic source, in the framework of the normal mode theory of tsunami excitation. At the lower frequencies characteristic of more conventional tsunami waves (800 to 3200 s), the signal is probably present in the hydrophone records, but reliable deconvolution of its spectral amplitude is precluded by the fact that the instrumental filters lowered the tsunami signal to the level of resolution of the instrument digitizer. In the context of distant tsunami warning, hydrophone records could provide useful insight into high-frequency tsunami components, and even at lower, more conventional, frequencies, provided that an unfiltered channel could be recorded routinely.     

基于正常轮廓更新的自适应异常检测方法

根据网络系统发生正常改变的基本特征,提出了确定网络系统正常改变的“三条件”计算方法,其计算结果可作为更新正常轮廓的依据。对正常轮廓的更新问题进行了深入探讨,提出了自适应异常检测的实现机制。并以网络流量分析为例,验证了在异常检测中应用这一方法的可行性。     

GPS高程拟合转换正常高的研究

通过对GPS测高与水准测量理论及其异同分析的基础上,阐述了确定似大地水准面的原理与方法,分析了用数学模型法,用少量GPS与水准重合点将GPS大地高直接转换为具有cm量级正常高的实现方法。实验结合黑龙江省虎林地区的地形特点,提出了用线性内插法、平面模型法和二次曲面模型法等来转GPS高程,证明在黑龙江省虎林地区可以通过少量且分布合理的水准点来直接求出该地区具有cm量级的正常高,且精度可以达到四等水准测量的精度要求,满足一般工程的需要。     

Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data

All variables of several large data sets from regional geochemical and environmental surveys were tested for a normal or lognormal data distribution. As a general rule, almost all variables (up to more than 50 analysed chemical elements per data set) show neither a normal or a lognormal data distribution. Even when different transformation methods are used more than 70 % of all variables in every single data set do not approach a normal distribution. Distributions are usually skewed, have outliers and originate from more than one process. When dealing with regional geochemical or environmental data normal and/or lognormal distributions are an exception and not the rule. This observation has serious consequences for the further statistical treatment of geochemical and environmental data. The most widely used statistical methods are all based on the assumption that the studied data show a normal or lognormal distribution. Neglecting that geochemcial and environmental data show neither a normal or lognormal distribution will lead to biased or faulty results when such techniques are used. Received: 21 June 1999 · Accepted: 14 August 1999     

时移动校正和叠加方法

在水平层状介质假设情况下, 推导了反射波时距曲线的表达式, 指出: 在对水平层状介质情况下, 反射波时距曲线是一时移双曲线.通过对理论模型和实际资料的处理, 表明时移动校正和叠加方法具有高保真、高分辨率和明显的叠加成像效果.同时, 用时移动校正τ₀分析谱计算层速度较以往用Dix公式由叠加速度计算层速度精度要高.这种方法不仅可以用于复杂构造的地震资料的叠加成像, 也可以应用到高分辨率处理的流程中.      

最大有效力矩准则及相关地质构造

摩尔-库伦准则广泛用以说明断裂构造的形成,然而却不能解释自然界广泛分布的大变形。最近提出的岩石变形新理论--最大有效力矩准则,其数学表达式为Meff=0.5(σ1-σ3)L.sin2α.sinα。式中,σ1-σ3代表变形岩石的屈服强度,L为单位长度,α为σ1与变形带间的角度。该准则证明最大有效力矩出现在σ1轴左右54.7°方向,55°±10°区间力矩无显著变化,天然和实验的全部观测值全部位于该区间内。相关地质构造包括:膝褶带、伸展褶劈理、膏盐层中的屈服带、低角正断层、高角逆断层、结晶基底中的菱网状剪切带、地震反射剖面中的鳄鱼嘴构造和前陆盆地中的拆离褶皱等。据该准则可确定有关构造形成时的应力状态和运动学涡度,并扩展说明深俯冲超高压岩石的折返-出露机制。     

正断层断距纵剖面图及其运动学:概念模型与地质实例

断距纵剖面图 （T H图）是指以断层的垂直断距为横轴、以地层或地质年龄为纵轴所绘制的随地层或地质年龄所变化的断距分布图。断距纵剖面图为确定正断层类型、断层形成时间和断层的纵向演化史提供了一个简单迅捷的工具。概念模型表明,断距纵剖面图可以明确无误地区分出简单后沉积型正断层、后沉积拱顶拉张型正断层、同沉积生长型正断层及其复合型正断层。简单后沉积型正断层的断距不随地层年龄的变化而变化, 其断距纵剖面图为一垂直线段。后沉积拱顶拉张型正断层的断距随地层年龄的增大而减小并趋向零值,同沉积生长型正断层的断距随地层年龄的增大而增大,复合型正断层则具其组合型断距纵剖面形态。除简单后沉积型正断层外,断距纵剖面图中的最大断距点代表了该断层的起始形成年代。     

拉斯曼丘陵新生代剥露作用的裂变径迹证据

在西南极和横贯南极山脉地区,新生代裂谷和剥露作用非常普遍。但是,文献中很少记录东南极地区的新生代剥露作用。文中根据东南极普里兹湾拉斯曼丘陵地质样品的磷灰石裂变径迹年龄和热历史的模拟,认为在东南极海岸边缘存在新生代的隆升和伸展作用,其年龄为始于(49.8±12)Ma。该年龄略晚于西南极裂谷系的启动年龄(约60~50Ma)。由于差异隆升作用,在拉斯曼丘陵地区发育了更新的正断层作用--拉斯曼丘陵拆离断层的新活动,其年龄为约5.4Ma。东南极周缘新生代裂谷和伸展作用的普遍存在,是冈瓦纳裂解以来大陆分离和印度洋形成的结果。