南海中西部地貌单元划分及其特征和成因分析

南海中西部处于南海北部和南部的过渡带,夹持于印支地块和南海海底扩张中心之间,其特殊的地貌对于研究整个南海地质地貌有重要意义。本文基于广州海洋地质调查局在南海中西部海洋地质调查项目获取的水深、底质调查及地震剖面数据,结合该海域以往研究成果,提取了有关地貌的信息,编制了南海中西部地貌图。把研究区划分出陆架、陆坡和深海盆地三个二级地貌单元,以及水下岸坡、水下浅滩、海岭、峡谷、麻坑、阶地、盆地、海台、海山、深海扇、深海平原等众多次级地貌单元。文章详细描述了该海域各地貌单元的特征,提出了断层、火山、构造隆起和浊流等地质作用是本区地貌形成的主要因素。     

基于软件接收机的BDS/MEMS IMU深组合导航性能分析

针对BDS/MEMS IMU深组合导航全物理实验难度较大的问题,提出一种基于软件接收机的BDS/MEMS深组合导航系统仿真分析方法。给出BDS软件接收机结构,介绍深组合导航系统结构设计及滤波算法,最后基于仿真数据进行验证。结果表明,在高动态条件下,就BDS/MEMS IMU导航系统而言,其深组合的导航精度较紧组合有较大提高,位置误差小于1 m,速度误差小于0.01 m/s。     

青藏高原西部班公-怒江缝合带下方地壳结构与地块拼合模式

利用远震接收函数偏移成像方法获得青藏高原西部Hi-Climb项目剖面北段地壳结构转换波成像。结果显示班公-怒江缝合带下方拉萨地体上地壳向N仰冲,下地壳向N俯冲,而羌塘地块上地壳向S仰冲,下地壳向S俯冲,可能意味着青藏高原西部拉萨地块和羌塘地块具有复杂的拼合过程。结合前人的岩石学研究成果,建立了新特提斯北洋盆洋壳S向俯冲、距今60～50Ma印度板块与欧亚板块碰撞后,拉萨地块的下地壳向羌塘地块下俯冲,而后印度板块俯冲到羌塘地块下方的地块拼合模式     

Receiver function imaging in strongly laterally heterogeneous crust: Synthetic modeling of BOLIVAR data

We resolve a large (~20 km) discrepancy in Moho depth determined from PdS receiver functions (RFs) and from active source seismic profiling in the complex Caribbean-South American plate boundary zone in eastern Venezuela. As part of the BOLIVAR experiment 20 broadband stations were deployed along an active source profile to record teleseisms. Using the extremely heterogeneous crustal model obtained from active source data, we generated 2D finite-difference elastic wave synthetics and from them calculated receiver functions and CCP stacks. We compare the observations with synthetic sections that have been spatially sampled at 0.25 km to 40 km. The densely sampled synthetics show that several events in the field data that were originally interpreted as the Moho are multiple reflections within sedimentary basins. Where the Moho has the steepest dip under the plate boundary the CCP stacks fail to image the Moho well, regardless of the density of spatial sampling. A suitable spatial sampling criterion for clearly imaging the lower crust and Moho is to overlap Fresnel zones by 50% at Moho depth, which for the 1 Hz receiver functions examined here, requires an instrument spacing of 15–20 km, with the actual field data density ranging from 20 km to 100 km.     

用接收函数方法研究上海地震台阵下地壳结构

利用上海地震台阵16个台站记录的远震资料,采用接收函数线性反演方法,对台阵下的地壳速度结构进行研究,获得了研究区域内地壳厚度和地壳速度的分布特征。研究结果表明,研究区域Moho面深度约为33±2 km,Moho面深度基本不变,地幔顶部S波速度约4.4 km/s,地壳内没有发现明显的低速层。     

THE RESEARCH OF THE SEISMOGENIC STRUCTURE OF THE LUSHAN EARTHQUAKE BASED ON THE SYNTHESIS OF THE DEEP SEISMIC DATA AND THE SURFACE TECTONIC DEFORMATION

The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.     

BDS/GPS卫星数据质量分析软件开发及应用研究

通过对TEQC数据质量模块相关算法进行分析,实现了支持RINEX2、3 格式的BDS/GPS卫星数据质量分析软件DataQC的开发,其主要参数包括数据完整率、多路径指数、信噪比和周跳等,并增加卫星分布状况以及电离层、接收机硬件延迟偏差估计功能。通过多组数据验证,软件计算指标与TEQC结果具有较高的一致性;在电离层估计方面,与全球电离层格网（global ionosphere maps, GIM）插值计算结果的RMS在3 TECu之内,并可用于接收机硬件延迟偏差稳定性的分析。     

接收机对卫星控制网精度影响研究

介绍了GPS测量的各种主要误差源及其影响;对精度控制问题,主要接收机精度对小型控制网（基线长10—20km）精度的影响。     

四川芦山7.0地震和汶川8.0地震震源区地壳岩石圈变形特征分析

地壳和岩石圈变形特征研究对于深入了解中强地震的深部孕震环境具有重要科学意义.本文联合P和S波远震接收函数偏移成像结果,对发生过芦山7.0地震和汶川8.0地震的龙门山断裂带及附近区域地壳和岩石圈结构进行分析.结果揭示出在青藏高原向四川盆地过渡的龙门山断裂带,Moho面和岩石圈底界面(LAB)呈现出强烈变形,特别是芦山地震和汶川地震震源区下方地壳出现了错断、下凹,岩石圈也呈现下凹变形特征.这种地壳及岩石圈变形所代表的高应力的积累可能是汶川和芦山地震发生的重要深部地球动力学背景.     

中国大陆东南缘地震接收函数与地壳和上地幔结构

从2008-2011年,分别在中国大陆东南缘沿海和内陆两条NE向剖面上进行了宽频地震观测,利用记录到的远震波形资料提取得到1446个远震P波接收函数,用H-κ叠加扫描和CCP偏移叠加方法研究了中国大陆东南缘地壳及上地幔过渡带的结构及其变化特征.结合固定台网25个台站的H-κ结果,获得中国大陆东南缘(福建地区)地壳厚度从内陆到沿海逐渐减薄的图像:地壳从闽西北山区的33 km减薄到厦门沿海一带的29 km以下,平均地壳厚度为31.3 km,具有陆地向洋壳过渡的特征;地壳泊松比从内陆到沿海显示出分带特征,闽中西部内陆地区小于0.26,沿海地带高于0.26,且在断裂带的交汇区域表现为相对异常高值.地壳上地幔顶部(0~200 km)的CCP偏移叠加成像结果显示闽江断裂等NW向断裂深切Moho界面,在断裂两侧Moho面急剧抬升或下沉,产状改变,这些特征向内陆地区逐渐变得不明显.闽江等NW向断裂对研究区地壳厚度、地震等有明显控制作用.上地幔尺度(300~700 km)的CCP偏移叠加成像,未见410 km和660 km速度间断面突变和起伏异常,其绝对深度略大于IASP91模型的,上地幔转换带厚度正常(250±5 km),表明中国大陆东南缘上地幔转换带未受欧亚与菲律宾板块碰撞的明显影响,推断中国大陆东南缘及台湾海峡下方不存在俯冲板块,或俯冲前缘未扰动到410 km的深度.