电磁脉冲数值异常初探

用ＤＷＭＪ－８９Ａ型电磁波记录仪记录的异常与地震３要素的关系，讨论了判别电磁波脉冲数值异常的方法与地震预报的问题。     

Ion Dynamics and Distribution At the Quasiperpendicular Collisionless Shock Front

Collisionless shocks are well-known to be very efficient energizers of ions. At the first step of energization relatively low energy suprathermal ion distributions are formed in the vicinity of the quasiperpendicular collisionless shock front during ion reflection and direct transmission. These distributions are formed promptly and at the scale of the shock width mainly due to the ion interaction with the quasistationary electromagnetic structure of the front itself. Their features are intimately related to the fine structure of the shock front in the sense that they depend not only on the bulk shock parameters, such as Mach number, but also on the details of the distribution of the fields, in particular, shock width. Therefore, studies of these distributions may provide valuable information about the shock structure itself. We review the observational data collected during in situ measurements (mainly at the Earth bow shock) and compare it to the numerical simulations and theoretical developments. The developed theory of the ion dynamics in the stationary shock front relates the ion reflection and heating to the insufficient deceleration of the ions in the ramp by the cross-shock potential, as compared to the expected downstream drift velocity, required by the Rankine-Hugoniot relations. As a result, the direct flow energy it transferred into the gyration energy, leading to the gyration of the ion distribution as a whole and enhanced spread in the velocity space, that is, effective collisionless heating. Anisotropy and nongyrotropy are typical features of ion distributions at both low and high-Mach number shocks, which is confirmed by observations. Time-dependent fields, which are not considered in the stationary shock model, are thought to provide subsequent smoothing and isotropization of the ion distributions. These processes occur at scales substantially larger than the shock width.     

Research Progress in Cenozoic N-S Striking Rifts in Tibetan Plateau

The formation of the Cenozoic N-S striking rifts in the Tibetan Plateau is the consequence of continuous contraction after the India-Asia collision. Its formation and evolution are of great significance for understanding the growth of the Tibetan Plateau. In recent years, geochronology, structural geology, geochemistry and geophysical exploration have been used to study the onset timing, mechanism and evolution process of the N-S striking rifts, and the N-S striking rifts are related to the deep dynamics in Tibet. However, it is still difficult to reach a consensus on the understanding of the N-S striking rifts in the Tibetan Plateau. This paper summarized the research status and existing problems on the onset timing, mechanism and their relationship with the deep layer of the plateau: the main extension period of the N-S striking rifts is Miocene; mechanisms controlling its formation are complex and may be various in different periods; the N-S striking rifts have a close genetic relationship with potassium and ultrapotassic rocks in the plateau, and their distribution may be affected by high-conductivity and low-velocity bodies. Based on existing knowledge, more precise geochronological constraints, deep process detection, and numerical modeling will be the future development trends in the study of N-S striking rifts.     

The movement age of hidden fault and analysis on width of its effect zone from shallow seismic sounding and drilling data

Field experimental seismic sounding permitted us to obtain optimal shallow seismic reflection sounding parameters. In process of data processing, we obtained a high-qualitative shallow seismic reflection sounding profile by using the techniques such as filtering, edition surgical blanking, prediction deconvolution, fitting static correlation of first arrival time, and velocity analysis. Comprehensive analysis on the information of reflection wave groups along the seismic sounding profile and the stratigraphic and neogeochronological data obtained from many drills near the sounding line reveals that the upper termination of the detected fault zone is located at depth of 75–80 m, in the Middle Pleistocene deposits dated to be about 220 ka BP. The continuity, discontinuity, increasing and decreasing amount of reflection wave groups and change of their configurations, in combination with geological columns of drills, permitted us to know that the width of upper termination of the fault zone is 100 m. It can be inferred from the variation of number of reflection wave groups along the profile that the scarp of hidden fault is 200 m wide and the fault is a synsedimentary active fault in the Early Pleistocene and the early stage of Middle Pleistocene. No tectonic movement, which offset the covering deposits, had occurred since the late stage of Middle Pleistocene. Foundation item: A High-new Technique Project by State Development and Planning Commission of China (2001977).     

Enregistrement de la dernière remontée du niveau marin dans l'architecture interne d'une vallée incisée : le pertuis Breton (Charente-Maritime)

Recent very high-resolution seismic profiles ground-truthed by vibrocores allow us to evidence an atypical incised valley fill in a drowned valley segment, the ‘Pertuis Breton’ (Bay of Biscay, France). The sedimentary valley-fill architecture mainly includes five superimposed progradational wedges composed by marine sands. Sandbodies show a landward migration of their depocentres upward and are topped by almost flat unconformities extended by submarine terraces. This sedimentary infill pattern is similar to backstepping wedges, described on continental shelfs. It suggests that this valley fill records sea-level rise during the last transgression. To cite this article: N. Weber et al., C. R. Geoscience 336 (2004).     

Filtrate Quality from Different Filter Operations

A brief review of the literature on filtrate quality obtained in constant and variable declining rate operation systems is presented, with the general conclusion that both systems usually produce filtrate of similar quality, assuming the flow‐rate controllers in the constant flow rate system operate properly. A mathematical model of CR (constant rate) filters and VDR (variable declining rate) filters based on the model by Mackie and Zhao (1999) has been described and used to investigate filtrate quality under different operating conditions. A similar quality of filtrate was achieved in computations carried out for both modes of operation, while the total head loss was much lower in the VDR mode. For the same time of filter runs slightly better filtration quality resulted from CR operation, but for different filter runs resulting from the same head loss of flow just before a backwash, the VDR control system produced lower turbidity filtrate.     

南海东北部海陆联测与海底地震仪探测

利用三分量海底地震仪、陆上便携式地震仪和海上气枪震源在南海东北部首次进行了海陆联合的深地震探测,测线呈北北西-南南东方向,垂直于区域构造走向,总长达500km,所获得的数据质量好,深部信息丰富,可分辨出Pg、Pn、PmP等地震相,为南海东北部深部地壳结构及油气盆地形成演化的研究提供了重要的基础数据。     

汪清7.2级深震与黑龙江省及其临近地区地震活动趋势分析

20世纪以来，东北地区7级以上强深震与东北地区浅源中强地震活动在时间上表现出很强的相关性。认为汪清7．2级强深震后，黑龙江省及邻区发生5级以上中强震的危险性增大。