长江流域沿江镉异常源追踪与定量评估的方法技术研究:以长江流域安徽段为例

长江全流域性的Cd异常是被中国正在进行的多目标地球化学调查发现的重大生态环境问题。以长江流域安徽段为研究对象,对沿江镉异常源追踪与定量评估的方法技术进行了系统研究。通过对安徽段长江干流及其主要支流悬浮物中元素含量的测量查明:悬浮物是流域内重金属元素大跨度迁移的主要载体;Cd在悬浮物中的富集程度远远大于其他重金属元素,这或许正是Cd可以形成沿江流域性异常的主要原因;长江干流悬浮物中重金属元素含量的变化明显受到沿江支流的影响。安徽段长江干流及其主要支流重金属元素输出通量定量计算结果表明:秋蒲河是安徽段重金属元素输出通量最大的支流,每年在安徽段长江两岸土壤中沉积下约4.45t的Cd。利用悬浮物加密测量、1∶5万土壤测量和岩石测量对顺安河流域Cd异常源追踪结果显示:内生金属矿床特别是铅锌矿是悬浮物中Cd的最大的供应源。采用河漫滩沉积物分层采样技术和同位素测年技术,初步恢复了研究区Cd等重金属元素沉积和污染的地球化学历史,对研究区Cd等重金属元素异常的未来演变趋势进行了预警预测。     

Observations of Giant Pulses of the Crab Pulsar

The Crab Pulsar was observed at 1540 MHz with the 25m radio telescope at Urumqi with a filterbank de-dispersion backend. A total of 2436 giant pulses with pulse energies larger than 4300 Jy μs were detected in two observing sets. All of these giant pulses are located in the main pulse (MP) and inter pulse (IP) windows of the average profile of the Crab Pulsar. The ratio of the numbers of giant pulses detected in the IP and MP windows is about 0.05. Our results show that, at 1540 MHz, the emission in the IP is contributed by giant and normal pulses, while that in the MP is almost dominated by giant pulses. The distribution of energy of the 2436 giant pulses at 1540 MHz can be described by a power-law with index α=3.13±0.09. The intrinsic threshold of giant pulse energy in the MP window is about 1400 Jy μs at 1540 MHz.     

CCD Photometry and Long-Term Optical Variability of 3C 345

This paper presents evidence for long-term optical variability and colour behaviour of the blazar 3C 345 (1641+399, z=0.595). Our results show that the amplitude of the optical variations of 3C 345 has been only about 3 magnitudes from its photometric history; existent significant correlation between brightness and colours is found for 3C 345. Our recent CCD photometry of 3C 345 in May 1996 and May 1997 showed that they are in good agreement with our prediction of the optical variability period of about 10 years (see Zhang et al., 1998; Webb et al., 1988). This revised version was published online in July 2006 with corrections to the Cover Date.     

1D velocity structure of the Po River plain (Northern Italy) assessed by combining strong motion and ambient noise data

Strong ground motions recorded on the sedimentary deposits of the Po River alluvial plain during the Emilia (Northern Italy) Mw 5.7 earthquake of May 29, 2012 are used to assess the vertical profile of shear-wave velocity above the limestone basement. Data were collected by a linear array installed for site effect studies after the Mw 5.9 mainshock of May 20, 2012. The array stations, equipped with both strong and weak motion sensors, are aligned in the South–North direction, at distances ranging from 1 to 26 km from the epicenter. The vertical components of ground motion show very distinctive, large-amplitude, low-frequency dispersive wave trains. Wavelet analysis yields group-velocity dispersion curve in the 0.2–0.7 Hz frequency band. The availability of a long ambient noise record allows estimates of the site resonance frequency along with its stability among stations. The joint inversion of dispersion of surface waves and ellipticity curves derived from ambient noise H/V allows extending investigations down to the sediment-limestone interface, at a depth of about 5,000 m. Our results add new information about the velocity structure at a scale that is intermediate between the local scale already investigated by other authors with small-aperture arrays using ambient noise and the regional scale inferred from modeling of seismogram waveforms recorded at hundreds of kilometers from the source.     

地闪对崇明地震台地球物理观测的干扰

通过对比崇明地区地闪及崇明地震台地球物理观测资料,发现受地闪引起的电磁场变化的直接作用或对仪器元件的间接作用,地磁、地电、电磁扰动和水位观测干扰比例较高,干扰幅度与地闪距离及形成的电流强度有关。具体干扰形态如下：①对电磁扰动干扰表现为单向突跳和测值的整体抬升;②对地磁测项干扰表现为正负方向的单点突跳;③对大地电场干扰表现为大幅震荡;④对水位观测干扰表现为大幅突跳。     

Hybrid continuum–discrete simulation of granular impact dynamics

Acta Geotechnica - Granular impact—the dynamic intrusion of solid objects into granular media—is widespread across scientific and engineering applications including geotechnics....     

一种用于海底类型聚类的新方法

By using sonar imaging, this paper presents a new algorithm for the clustering of seabed types based on the self-organizing feature maps （SOFM） neural network. The theory as well as data processing is studied in detail. Some valuable conclusions and suggestions are given     

2022年6月1日四川芦山MS6.1地震的发震构造与力学机制探讨

2022年6月1日17时00分08秒（北京时间）四川雅安市芦山县发生M_S6.1地震,此次地震是继2008年汶川M_S8.0、2013年芦山M_S7.0地震后发生在龙门山断裂带的又一显著地震,与后者在空间上仅相距9 km.为揭示此次地震的发震构造特征及其与2013年芦山M_S7.0地震的关系,进而理解龙门山断裂带强震孕育动力学过程与地震危险性,本文采用CAP全波形反演方法计算了芦山M_S6.1地震的震源机制解,利用多阶段定位法对2013年芦山M_S7.0地震以来余震区地震进行了精确定位,并基于库仑应力讨论两次地震的应力触发关系.结果显示,芦山M_S6.1地震的震源机制解为：节面Ⅰ的走向、倾角和滑动角分别为221°、40°和105°;节面Ⅱ的参数为22°、52°和78°,矩心深度14 km,震源机制断层面解呈现一组与龙门山断裂带性质接近的节面.反演给出的P轴方位角为120°,倾角为6°,反映了此次地震主要受NWW-SEE向水平挤压应力作用,与龙门山断裂带南段背景构造应力场一致.地震精定位结果显示芦山M_S6.1地震序列发生在2013年芦山M_S7.0地震发震断层北西侧的一条倾向南东的反冲断层上,据此可判断震源机制解的节面Ⅱ为发震断层面.在此基础上,通过指定发震与接收断层,计算获得2013年芦山M_S7.0地震对此次M_S6.1地震所在断层的最大库仑应力加载值可达1.5 MPa,说明前者对后者有显著的触发作用.

     

大别山北缘地质找矿中遥感方法的研究

本项工作着重探讨在植被覆盖、地质背景十分复杂的地区，利用遥感信息寻找金矿及其它多金属矿的方法。即从地层岩系、构造及构造交叉部位、蚀变带这三个方面，进行地质找矿专题信息特征提取方法的研究。最后，通过信息提取及影像综合特征，进行遥感地质制图，圈定找矿有希望的地段。     

Large scale northward expansion of warm water species Skeletonema tropicum (Bacillariophyceae) in China seas

Skeletonema tropicum is regarded as a species with an affinity to warm waters and it has never been reported in seas where temperatures drop below 11°C in winter. Previous studies in China reported that S. tropicum was restricted to subtropical and warm temperate seas (East and South China Seas), but the species was recently found during August cruises of 2009 and 2010 in Jiaozhou Bay, Yellow Sea, located several hundred kilometers to the north. Here, winter water temperatures often drop below 5°C. Identification of S. tropicum was confirmed under light and scanning electronic microscopes and maximum cell abundance in Jiaozhou Bay was estimated as 1.73×10 4 cell/L. This record of S. tropicum in Jiaozhou Bay represents a significant northward expansion in the geographic range of the species. Ship ballast water was identified as a possible carrier of S. tropicum from southern places along Chinese coastline, and in addition, thermal pollution from local power stations and seawater desalination plants may provide suitable conditions for species over-wintering.