2011年日本东北大地震特低频地磁信号的分形标度特征研究

本文选择2011年3月11日M9.0日本东北大地震震中附近三个地磁台站16个月(2010/01/01—2011/04/30)的特低频地磁观测资料,采用去倾扰动分析方法,得到了这三个台站地磁记录的非均匀标度特征随时间的变化,提出了一种能反映地磁三分量非均匀标度特征同步变化的指标,并据此探讨了特低频地磁信号分形标度特征变化与日本东北大地震之间的可能关联性,初步结果表明,这三个台站的特低频地磁信号分形标度特征指标在日本东北大地震前25~50天左右呈现出同步的异常增加,基于磁静日观测资料的随机合成地磁数据的统计检验结果可知前述异常并非随机异常,而是一种具有统计显著性的异常,可能反映了日本东北大地震对周边地磁信号内在的非线性系统特征产生了有统计意义的影响.     

地表点电流对地电阻率观测的影响

将地电阻率台站地下介质简化为水平层状均匀介质模型,以点电流模拟地表干扰电流源,针对对称四极观测装置,计算干扰源电流增减及位置变化对地电阻率观测的影响。结果表明,地电阻率的受干扰程度取决于地表干扰点电流的大小、在测区的方位及距中心点的距离。     

巢湖水体漫衰减系数空间差异及其遥感反演

根据2009年6月巢湖32个样点的实测数据,分析巢湖水体漫衰减系数光谱特征、主导因子、空间分布规律以及400-700nm各波段Kd与Kd(490)之间的关系,并在此基础上,建立了Kd的遥感反演模型.结果表明:巢湖水体Kd具有一致的光谱特征,400-600nm之间Kd随波长的增加呈指数衰减趋势,在600-700nm之间的...     

Coseismic Slip from the 6 October 2008, M w6.3 Damxung Earthquake, Tibetan Plateau, Constrained by InSAR Observations

Coseismic deformation fields of the 6 October 2008 M _w6.3 Damxung earthquake were obtained from interferometric synthetic aperture radar by using three descending and two ascending Envisat images. Significant coseismic surface deformation occurred within 20?km?×?20?km of the epicenter with a maximum displacement of ~0.3?m along the satellite line of sight. We model a linear elastic dislocation in a homogeneous half space and use a nonlinear constraint optimized algorithm to estimate the fault location, geometry and slip distribution. The results indicate a moment magnitude M _w6.3, and the earthquake is dominated by oblique normal and right-lateral slip with a maximum slip of 2.86?m at depth of 8?km. The rupture plane is about 15?km?×?14?km with strike S190°W and dip 55° to NW, located at a secondary fault of the Southeastern Piedmont of the Nyainqentanglha Mountains. Slip on normal faults in the Tibetan Plateau contributes to the rift evolution.     

三峡水库水体漫衰减系数光学特性及其遥感反演

根据2009年8月22-24 日实测的三峡水库水体的光谱数据以及水质参数,对三峡水库漫衰减系数的光学特性及影响因子进行分析研究,构建了490nm处漫衰减系数的Kd(490)反演模型,并利用环境一号卫星CCD数据对2009年7月21日的三峡水库Kd(490)进行反演.结果表明:由于水体中非色素颗粒物的含量较高,使得研究区...     

PBL剪力键破坏形态及极限承载力试验研究

根据已有试验结果,总结了有贯穿钢筋类PBL剪力键（perfobond rib shear connector）的3种破坏形态,其中充分发挥承载力的破坏形态为贯穿钢筋剪切破坏。为了研究PBL剪力键的极限承载力,对4组21个试件进行了静载破坏试验,结合文献[10]的试验结果,研究了各种因素对PBL剪力键极限承载力的影响,提出了有贯穿钢筋类PBL剪力键极限承载力计算公式。结果表明：有贯穿钢筋类PBL剪力键的极限承载力主要与贯穿钢筋面积及强度有关,与混凝土强度、混凝土榫面积无关,横向钢筋面积及强度对其的影响较以前试验所得结果小。     

Modeling the Yellow River sediment flux and its deposition patterns under climatological conditions

A numerical sediment transport model was embedded into a coupled wave-tide-circulation model to quantitatively estimate the suspended sediment fluxes (SSF) and distribution in different areas for the Yellow River derived sediment. The model is validated by comparing model simulated sediment deposition rates with those from observations. Simulated results show that the SSF of the Yellow River across two major sections (the Bohai Strait and the 37° N section) are highest during September and October, whereas for the 32° N section the flux is negligibly small (less than 0.1 kg/s). We demonstrate that the sediment flux is primarily driven by the buoyancy forcing of the Yellow River freshwater discharge and modulated by the wind-driven surface wave and circulation patterns in this region. The SSF across the Bohai Strait is about 30 % of the Yellow River discharge, while across the 37° N section it is 15.8 %. Therefore, about 70 % of the total discharged Yellow River sediments are deposited in the Bohai Sea, 14.1 % in the North Yellow Sea, and 13.9 % in the South Yellow Sea. There are two deposition branches in the Yellow Sea. The primary one is located off the eastern tip of the Shandong Peninsula and extends to the southwest off the coastline, which is consistent with the observed “Ω”-shape deposition pattern. This simulated tongue shape deposition pattern is isolated from the north by the strong resuspension off the eastern tip of Shandong Peninsula. The secondary branch extends to the middle of the South Yellow Sea and has been strengthened by resuspension process. The two deposition branches are separated by the wintertime Yellow Sea Warm Current in the bottom layer.     

中国地震大地测量——半个世纪的历程与科学贡献

自1966年邢台地震以来,中国尝试用大地测量手段监测地震变形,至1976年唐山地震,变形监测到达高潮,但受地面技术局限,20余年可以用于分析震源的震例寥寥。自20世纪90年代初全面进入空间观测时代以来,境内或边邻6级以上强震大多数有相应的近场变形观测和破裂模型研究,这其中又以2001年昆仑山口西、2008年汶川和2015年廓尔喀3次特大地震的变形资料相对完整、破裂特征清晰、理论成果丰富,成为近期大陆内部最引人注目的大震事件。近30年来,对包括中国台湾在内的60余次强震变形的系统研究丰富了人们对区域地震活动性及危险性的认识,也为青藏高原构造演化研究提供了观测依据与理论参考。半个世纪积累的经验、夯实的基础以及未解的难题更为未来的地震大地测量提供了历史借鉴、前进动力和发展方向。     

老挝万象省爬立山(PHaLek)铁矿磁异常特征及找矿评价

老挝万象省爬立山铁矿床位于长山褶皱带北西端,是长山成矿带内与岩浆作用有关的一个大型铁矿床.矿床类型以矽卡岩型为主,其次为热液型,成矿作用与花岗岩类侵入作用有关,矿区内发育致密块状磁铁矿、孔洞状赤铁矿、砂砾土状铁矿.该区地球物理工作研究程度较低,仅有部分航磁资料,难以准确控制矿化异常;老挝热带雨林气候植被覆盖严重,地表露头难寻,圈定矿体规模和划分地层界线难度较大.为了获得该区铁矿体地表规模及深部延展,笔者在该区开展了1:10000地面高精度磁法测量,运用解析延拓、水平总梯度模、垂向导数、2.5D人机交互反演等方法有效克服了低纬度地区磁异常化极不稳定形成假异常的问题,解译了爬立山矿区磁异常特征,提高了磁异常的解译分辨率,更加准确的控制了爬立山铁矿区铁矿体的范围、深部延展.后期钻探验证结果表明,在老挝地质勘查程度低、覆盖严重的爬立山地区开展高精度磁法是控制该地区铁矿的有效地球物理方法.     

Azimuthal cement evaluation with an acoustic phased-arc array transmitter: numerical simulations and field tests

We developed a novel cement evaluation logging tool, named the azimuthally acoustic bond tool (AABT), which uses a phased-arc array transmitter with azimuthal detection capability. We combined numerical simulations and field tests to verify the AABT tool. The numerical simulation results showed that the radiation direction of the subarray corresponding to the maximum amplitude of the first arrival matches the azimuth of the channeling when it is behind the casing. With larger channeling size in the circumferential direction, the amplitude difference of the casing wave at different azimuths becomes more evident. The test results showed that the AABT can accurately locate the casing collars and evaluate the cement bond quality with azimuthal resolution at the casing—cement interface, and can visualize the size, depth, and azimuth of channeling. In the case of good casing—cement bonding, the AABT can further evaluate the cement bond quality at the cement—formation interface with azimuthal resolution by using the amplitude map and the velocity of the formation wave.