新疆伽师地区地应力的GPS损伤模拟研究

采用几何损伤理论和方法推导了地壳存在不同方向和大小的断层时的有效应力的公式 ,讨论了利用几何损伤理论来分析和计算地壳中存在不连续断层的理论和方法 ,同时对中国新疆伽师地区的地应力变化用几何损伤理论和方法结合该地区的GPS资料进行了数值计算研究 ,通过比较计算结果与 1 997年 1月至 1 998年 1 2月发生在该地区的MS ≥ 5 .0地震活动可以看出 ,新疆南部的中强地震活动区主要在应力场变化激烈的地区 .     

Remote estimation of surficial seafloor properties through the application Angular Range Analysis to multibeam sonar data

The variation of the backscatter strength with the angle of incidence is an intrinsic property of the seafloor, which can be used in methods for acoustic seafloor characterization. Although multibeam sonars acquire backscatter over a wide range of incidence angles, the angular information is normally neglected during standard backscatter processing and mosaicking. An approach called Angular Range Analysis has been developed to preserve the backscatter angular information, and use it for remote estimation of seafloor properties. Angular Range Analysis starts with the beam-by-beam time-series of acoustic backscatter provided by the multibeam sonar and then corrects the backscatter for seafloor slope, beam pattern, time varying and angle varying gains, and area of insonification. Subsequently a series of parameters are calculated from the stacking of consecutive time series over a spatial scale that approximates half of the swath width. Based on these calculated parameters and the inversion of an acoustic backscatter model, we estimate the acoustic impedance and the roughness of the insonified area on the seafloor. In the process of this inversion, the behavior of the model parameters is constrained by established inter-property relationships. The approach has been tested using a 300 kHz Simrad EM3000 multibeam sonar in Little Bay, NH. Impedance estimates are compared to in situ measurements of sound speed. The comparison shows a very good correlation, indicating the potential of this approach for robust seafloor characterization.     

Strain segmentation and lateral membrane deformation rate of the subducted Ryukyu slab

Abstract Focal mechanisms of intermediate-depth earthquakes within the subducted Ryukyu slab indicate a systematic pattern of down-dip extension in the northern part under Kyushu. These mechanisms switch rapidly around the Tokara channel to down-dip compression in the southern part toward Taiwan. This intriguing pattern of strain segmentation, together with the differences between the slab geometry of the northern and southern parts, has raised the question of whether stress segmentation, as defined possibly by a tear fault, might exist in the slab. However the Ryukyu trench has a concave oceanward shape in the northern segment while it is convex in the southern oceanward part toward Taiwan. The inflection zone is located around the Tokara channel. The concept of Gaussian curvature of a curved surface suggests that the along-arc variation of the geometric configuration of a subducted slab is related to the shape of the trench. This is in order to accommodate the lateral membrane deformation of the slab as the oceanic lithosphere subducts from a spherical shell to the geometry delineated by the Wadati-Benioff zone. The membrane deformation regime of the subducted Ryukyu slab and its relation with the trench geometry was examined by assuming that the subduction be modelled by the flow field of a thin viscous sheet. A projection operator was utilized to compute the membrane strain-rate tensor of an arbitrary non-Euclidean surface. Numerical experiments indicated that the northern segment of the slab was dominated by lateral compression and down-dip extension and the southern part by lateral extension and down-dip compression. This transition is sharply located near the Tokara channel. These patterns were compatible with what had been observed from studies of focal mechanisms, suggesting that the strain segmentation might be controlled, at least in part, by the lateral membrane deformation within the slab due to the trench shape in this subduction zone. The slab geometry was predicted by minimizing the integrated total dissipation power; this revealed distinct features that were consistent with observations. This implies that the slab geometry may also be affected by the membrane deformation in a systematic fashion.     

海斗深渊区十字放炮与POBS精确位置校正

TS03航次创新性地投放了 6台被动源海底地震仪(POBS)到马里亚纳海沟南部"海斗深渊区",实施了万米级水深的天然地震观测,通过十字放炮获得POBS的精确坐底位置是后续研究工作中至关重要的一环.本文首先对POBS的SEG-Y数据进行裁截误差修复,然后采用直达水波走时反演的方法得到这6个POBS的精确坐底位置,并进行精...     

Confidence Evaluation of Medium-and Long-Term Earthquake Prediction by Use of the Analytical Hierarchy Process

This paper offers an approach to the relative confidence level of medium- and long-term earthquake prediction methods by use of the analytical hierarchy process (AHP). We construct the criterion judgment matrices according to the results of an expert questionnaire known as the Delphi scheme. From the matrices we can obtain a scale for the relative preference or priority weight of each factor. The quantitative weights might be applied to make synthetic prediction of earthquake risk areas in the northern part of the North China seismic region.     

均匀充电矩形薄板电场复形调优反演计算

针对充电电场反演计算参数较多以及复形调优算法处理约束条件的直接有效性,作者就均匀充电矩形薄板反演问题编制程序,计算地质体理深、倾角及大小。尽管迭代次数较高,计算结果颇为理想,取得了较好的效果。     

Intensifying Earthquake Prediction in the Light of Action of International Decade for Natural Disaster Reduction

This paper is a review on earthquake prediction and forecast research,progress in earthquake prediction work and pre-estimation of earthquake hazard degree in China in recent years.It indicates that China is the first country,the government of which has promoted and organized the state administration department on reduction of seismic hazards and ensured the socialization of earthquake prediction and forecast in the world.A program of earthquake prevention and protection and hazard reduction based on the results of research on earthquake occurrence regularities and prediction of earthquake preparation trend has been completed,and hence the socialization of results of earthquake prediction and forecast research can be expected to be in practice.The practical seismological works in last 20 years indicate that the earthquakes are not considered to be unpredictable,but it is a challenge remaining to be accepted.We are willing to cooperate with all friends who are engaged in earthquake prediction and forecas     

基于无人机光学图像的海流观测方法研究

海流信息在海上航行、海洋资源勘探等方面有着重要的应用,传统的现场和遥感观测方式不能满足大面积、实时观测海流的要求。基于无人机平台的光学海洋遥感技术具有机动灵活、成本低、分辨率高的特点,近年来在海洋环境监测中得到应用。然而,由于小型无人机容易受飞行姿态、太阳耀斑等因素的影响,目前在海流观测方面还不成熟。本文提出了利用小型无人机获取高分辨率海面流场的方法,并分析不同因素对观测结果的影响。首先,对无人机获取的光学海面图像做预处理,消除几何成像和图像噪声等因素的影响,并通过分析图像灰度值均值的变化,减小太阳耀斑对图像的影响;然后,基于三维傅里叶变换和海浪的频散关系反演海流,并将反演结果与浮标实测的海流数据进行对比,验证了该方法的可靠性。其次,结合实验数据详细分析了不同因素对海流反演的影响:在本文的实验条件下(有效波高0.2～1.5m,波浪主波周期3.8～5.7s),当图像空间分辨率为0.15m、反演子图尺寸在波浪主波波长的2～3倍时,海流的反演误差较小;增加图像幅数和提高时间分辨率也有利于提高海流的反演精度。现场观测实验的结果表明,本文提出的无人机观测海流技术可以有效获取海流信息。     

用DSS资料研究首都圈地区的地壳结构

利用几种不同的一维反演方法对天津-北京-赤城剖面的DSS（deep seismic sounding）数据进行了处理．结果显示：沿剖面基底面北浅南深,但C界面和M界面北深南浅,存在镜像关系：地壳平均速度华北盆地较低,燕山下方较高;燕山隆起和华北盆地的交界处曾多次发生过5．0级以上地震。且在该过渡带上,多条深大断裂成北北东、北东向穿过该剖面,推断首都圈地区地震的发生与莫霍面的局部隆起、速度结构的急剧变化以及深大断裂的存在具有密切关系。     

Local amplification of deep mining induced vibrations Part 1: Experimental evidence for site effects in a coal basin

The work presented in this paper lies under the scope of a research program aiming to assess the impact of deep coal mining induced vibrations on the surface constructions. The concerned section of the program is dedicated to the study of geological site effects and their influence on the mining induced vibrations for which the experimental investigations have been carried out and developed in this paper (Part 1). The empirical methods based on H/V spectral ratios have been applied on data sets provided from mining induced vibrations recorded within private residences above the deep coalmine as well as complementary measurements of ambient noise. The results evidence an amplified zone in the southern part of the Gardanne basin where drilling data confirmed the presence of particularly fractured and soft stratigraphic units. This joint analysis of induced seismicity and ambient noise enabled to validate the method based on H/V ratios applied to the mining context.