Crustal wide-angle reflection imaging along Lianxian-Gangkou profile in Guangdong province,China

A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection (from crystalline basement and Moho) pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.     

Creep behavior of microbiotic crust

The creep behavior of microbiotic crust at room temperature was revealed by the creep bending tests of cantilever beam under constant-load conditions.The variation in the deflection with time can be depicted well by a standard creep curve.Creep rupture is a fundamental failure mechanism of microbiotic crust due to creep.A simple theory was then applied to describe this new me-chanical behavior.The existence of creep phenomenon brings into question the validity of widely used methods for measuring the strength of microbiotic crust.     

Interpretation of Magnetic Anomalies and Estimation of Depth of Magnetic Crust in Slovakia

The magnetic map of Slovakia used in the paper was compiled as part of a project titled Atlas of Geophysical maps and profiles in 2001. The residual magnetic data were analyzed to produce Curie point estimates. To remove distortion of magnetic anomalies caused by the Earth’s magnetic field, reduction to pole transformation was applied to the magnetic anomalies using the magnetization angle of the induced magnetization. Anomalies reduced to the pole tend to be better correlated with tectonic structures. We applied a 3-km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography. The depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area. Such estimates can be indicative of temperatures in the crust, since magnetic minerals lose their spontaneous magnetization according to Curie temperature of the dominant magnetic minerals in the rocks. The computed Curie point depths in the Slovakia region vary between 15.2 km and 20.9 km. Heat flow higher than 100 mWm⁻² occurs at the central volcanics and eastern part of Slovakia, where the Curie point depths values are shallow. The correlation between Curie point depths, heat flow and crust depth was investigated for two E-W cross sections. Heat flow and Curie point depth values are correlated with each other however, these values could not be correlated with crust depth. The Curie point isotherm, which separates magnetic and non-magnetic parts of the crust, is represented in two cross sections.     

Crustal velocity structures and their tectonic implications in different tectonic block regions of the Chinese mainland

In this paper,the typical velocity structures and average velocities of the crust in six different active tectonic block regions are presented on the basis of previous studies and their tectonic implications are discussed. The results show that different tectonic units have different features of crustal velocity structures. In general,there are low velocity distributions in the crust in regions with strong tectonic activities,and the scales of low velocity distributions are related to the tectonic activitie...     

荒漠藓类结皮层中齿肋赤藓形态结构适应性及其原丝体发育特征

 在实验室内通过光镜与扫描电镜相结合的手段观察了新疆古尔班通古特沙漠藓类结皮层的优势物种——齿肋赤藓(Syntrichia caninervis Mitt.)的形态结构特征及其原丝体发育的全过程,并分别从藓类植物生长发育所必经的配子体和原丝体两个阶段对齿肋赤藓形态结构与荒漠干旱的生态环境之间的适应性关系进行了探讨。研究结果表明,①植物体密集丛生;叶片边缘强烈背卷,两面均具马蹄形细疣;中肋粗壮并突出叶尖成白色长毛尖。②原丝体系统的细胞短粗,细胞质高度浓缩,液泡较小,细胞壁较厚;原丝体系统具有短枝群。     

Microbiotic crusts as biomarkers for surface stability and wetness duration in the Negev Desert

Microbiotic crusts play an important role in arid and semi‐arid regions. Yet, very little information exists regarding the factors that impact their development. In an attempt to assess the main factors that may determine their growth, measurements of the amount of fines (silt and clay), rain, moisture content, wetness duration and wind erosion and deposition were carried out along a 12 station transect within a partially crusted dune field in the western Negev Desert and compared to the crust cover and chlorophyll content. Surface stability was the only variable that exhibited significant relationship with crust cover while daylight wetness duration exhibited strong positive relationship (r² = 0·92–0·99) with the crust's chlorophyll content. The data point out that microbiotic crusts may serve as a useful biomarker for surface stability. While wetness duration and wind will control crust cover and the crust chlorophyll content in semi‐stable habitats (with absolute annual change in sand level of 2–3 mm), stable habitats (absolute change <1 mm) will be controlled primarily by moisture, while habitats with low surface stability (absolute change of tens and hundreds of millimeters) will be primarily controlled by wind. Furthermore, owing to the strong positive relationship between daylight wetness duration and the crust's chlorophyll content, the crust may serve as a useful biomarker for the quantification of surface wetness duration. Copyright © 2009 John Wiley & Sons, Ltd.     

形变数字化资料对山西地区地震前兆反应研究

使用张家口、怀来、赤城、宽城、易县和涉县6个地震台站共计43个观测项目的数字化资料,针对2002年至2005年山西地区发生的4次ML≥4．0地震,进行了地震前兆、同震反应及震后效应的系统研究。结果发现．河北省数字化资料对,1次山西4．0级以上地震前兆反应主要以应变为主,包括体应变和线应变,异常形态以固体潮畸变和抖动为主。     

中国地球深部物理学和动力学研究16大重要论点、论据与科学导向

中国地球深部物理学与动力学的研究始于20世纪50年代,半个多世纪以来这一创新性工作取得了重大进展.基于我国大陆陆缘和邻近海域壳、幔结构的分区特征和不均匀性展布,特别是在印度洋板块、太平洋板块和欧亚板块的相互作用下形成了一个破碎镶嵌的块体组合.因为资源、能源、灾害的形成和动力机制均为地球内部物质与能量的交换所致.为此表明:地球内部结构和深层动力过程的研究与探索在成山、成盆、成岩、成矿和成灾过程中有着极为重要的作用.半个多世纪以来我国在该领域中,不论是理论、方法和探测技术诸多方面已有着较丰富的积累,并首先提出了16大论点与论据,它们是重要的科学导向.这不仅促进了我国在20世纪百年里地球科学的发展,而更为重要的是提出了一系列的有待研究和探索的科学问题.在21世纪的进程中,地球物理学必须牢牢地把握国家战略需求和自主创新,方能有所发现和突破.为此我们必须深化对地球本体的认识.     

几内亚红土型铝土矿床地质特征

几内亚铝土矿资源丰富,并具有品位高,富铝、高铁、低硅、易采、易选之特点,属富含三水铝石的红土型铝土矿。硅铝铁风化壳是本区的含矿岩系,主要矿石类型为蜂窝状、土状和块状铝土矿。矿体多赋存于山体顶部和坡度适中的斜坡上,地形平坦地段和沟谷部位矿体质量差或无矿体。几内亚属于湿热多雨和干湿交替的热带气候,为红土型铝土矿的形成提供了有利条件。广泛分布的富铝基性岩石是铝土矿的母岩,也是形成铝土矿的基本前提。     

根据接收函数反演得到的首都圈地壳上地幔三维S波速度结构

利用2002~2003年中国地震局地质研究所台阵实验室以唐山大震区为中心布设的40个流动宽频带地震台站和首都圈数字台网的33个宽频带台站的远震数据,采用接收函数非线性反演方法得到其中72个宽频带台站下方60 km深度范围内的S波速度结构.根据得到的各台站下方地壳上地幔的S波速度结构,并综合刘启元等（1997）用接收函数非线性反演方法得到的延怀盆地15个宽频带流动台站下方的地壳上地幔S波速度结构模型,给出了39°N～41°N,114°E~119.5°E区域内沿不同走向、不同深度S波速度分布.由于综合了利用首都圈数字地震台网的宽频带台站以及流动地震台阵的观测数据,本文给出了较前人同类研究空间分辨率更好的结果.结果表明: (1)研究区的速度结构,特别是怀来以东的速度结构十分复杂.在10~20 km深度范围内,研究区地壳具有高速和低速异常块体的交错结构.研究区中上地壳速度结构主要被与张渤地震带大体重合的NW向高速条带和穿越唐山大震区的NE向高速条带所控制,而其中下地壳的速度结构主要为延怀—三河—唐山地区上地幔隆起所控制.(2)研究区内存在若干壳内S波低速体,它们主要分布在唐山,三河及延怀盆地等地区.在这些地区,壳内低速体伴随着壳幔界面的隆起和上地幔顶部速度结构的横向变化.(3)地表断层分布与地壳速度结构分区有较好的相关性,表明断层对不同块体有明显的控制作用.其中,宝坻断裂,香河断裂和唐山断裂均为超壳断裂.(4)首都圈内大地震的分布与壳内低速体及上地幔顶部的速度结构有密切关系.对于唐山大地震的成因,仅考虑板块作用引起的水平应力场是不够的,有必要充分重视由于上地幔变形引起的地壳垂直变形和上地幔物质侵入造成的热效应.