2007年宁洱MS6.4地震的地面运动预测

根据普洱、 西双版纳地区6个地震观测台站在2008——2009年获取的5级以上的地震资料, 利用接收函数和面波衰减系数, 反演得到了研究区域的S波速度结构和Qβ结构. 基于该结构模型, 采用随机振动理论方法, 预测了2007年宁洱MS6.4地震发生后, 在震中距为10——300 km范围内引起的地面运动, 并借助获取的强震观测记录检验、 评价了该预测结果. 同时, 将地面运动预测结果与利用回归衰减公式计算得到的结果进行对比, 进而讨论该地震动预测方法在地面运动预测中的可行性． 结果表明, 该预测结果与实测结果吻合．      

高性能原子钟钟差建模及其在精密单点定位中的应用

鉴于当前许多IGS跟踪站均配置有高性能原子钟的现状,本文首先采用修正Allan方差法分析了不同IGS跟踪站的接收机钟随机噪声的时域特性,进而评估了不同类型接收机的短期稳定度及钟差建模的可行性,然后利用IGS站配有氢原子钟的观测数据,在精密单点定位算法中,通过对钟差参数进行短时建模约束接收机钟差的随机变化,进而改进精密单点定位(PPP)的定位性能。试验结果表明钟差建模方法显著降低了高程分量参数、天顶对流层延迟参数与接收机钟差参数之间的相关性,GNSS高程分量的精度可提高50%。该方法对于提升PPP技术在地壳形变监测、低轨卫星定轨、水汽监测及预报等高精度GNSS地学领域的应用水平具有一定意义。     

云南腾冲火山区地壳及岩石圈厚度研究

使用云南腾冲火山监测台网9个宽频带地震台站的远震数据,采用P波和S波接收函数的方法研究了腾冲火山区的地壳厚度、泊松比值以及岩石圈和软流圈分界面(LAB)深度.研究结果表明: 1) 云南腾冲火山区的地壳厚度约在33.5~38.0 km之间; 2) 火山区的泊松比主要集中范围为0.26~0.32,其中6个台站均大于0.29,推测与地壳镁铁质成分的增加有关并且可能存有2个岩浆囊; 3) 火山区的岩石圈厚度在78.2~88.0 km,较周边地区明显隆起且横向差异较大.腾冲火山区岩石圈的明显穹隆,由软流圈上涌(地幔热物质上升)引起岩石圈的拉张与减薄所致.     

GPS软件接收机信号特征分析

介绍了GPS信号的组成及特性,研究了信号的预处理过程,用Matlab实现了采样后的GPS信号的特征的绘制.     

表层声速对多波束测深影响的研究

在多波束测深系统中,表层声速是线型接收换能器基阵对接收波束进行束控的重要参数。表层声速误差会直接造成接收波束的指向误差,也通过归算导致多波束脚印位置误差和回波图像的失真。在分析多波束信号处理流程和接收波束束控原理基础上,探讨表层声速对多波束指向和测深影响规律。     

华北克拉通东部地壳和上地幔结构的接收函数研究

利用北京大学和早期中国科学院地质与地球物理研究所在华北克拉通东部地区布设的共34台宽频带地震仪记录的远震体波资料,获取P波接收函数和S波接收函数,再分别通过偏移成像和共转换点叠加(CCP)和倾斜叠加得到了华北克拉通东部横跨郯庐断裂带地区沿剖面的地壳和上地幔速度间断面分布.研究结果表明,鲁西隆起下方的莫霍面的深度要比华北盆地和青岛地区浅约5 km,形成类似屋顶状的莫霍面隆起.郯庐断裂带和聊考断裂带下方的莫霍面有明显的错断.岩石圈与软流圈的分界面(以下简称LAB)的深度从太行山山前的约100 km深度上升到鲁西隆起下方约60 km深,向东在青岛地区下方LAB深度进一步变浅.我们利用倾斜叠加计算台站下方波速比得到地壳内的泊松比变化,结果显示鲁西隆起泊松比值分布相对均匀,而青岛地区内泊松比变化剧烈,可能反应了该地区作为苏鲁大别超高压变质带的北缘经历了较为复杂的地质演化过程.     

Morphology of a ‘superfast’ Mid-Ocean Ridge crest and flanks: The East Pacific Rise, 7°–9° S

Detailed bathymetric data from a Hydrosweep multibeam sonar survey of a 250 km-long portion of the superfast-spreading southern East Pacific Rise crest and flanks show that the along-axis variation in morphology and axial depth differs significantly from that observed at the fast-spreading northern East Pacific Rise. While the deep mantle upwelling pattern is similar under the northern and southern East Pacific Rise, our observations require that the connectivity of the shallow, subcrestal plumbing system be more efficient beneath the super-fast spreading southern East Pacific Rise than beneath the slower spreading northern East Pacific Rise.     

水运工程多波束测深作业要求的研究

对水运工程多波束测深作业要求中一系列的技术问题进行了深入研究.以满足波束脚印无缝衔接和探寻水底目标物为约束,分别给出了测船最大限速的计算式.通过数值分析探讨了目前几种常用多波束仪器测线布设的理论宽深比和实际宽深比.对影响多波束测深精度的五个重要参数:横摇偏角、纵摇偏角、艏摇偏角、时延、声速剖面等分别做了详细介绍,并且给...     

Evidence for underthrusting beneath the Queen Charlotte Margin, British Columbia, from teleseismic receiver function analysis

The Queen Charlotte Fault zone is the transpressive boundary between the North America and Pacific Plates along the northwestern margin of British Columbia. Two models have been suggested for the accommodation of the ∼20 mm yr⁻¹ of convergence along the fault boundary: (1) underthrusting; (2) internal crustal deformation. Strong evidence supporting an underthrusting model is provided by a detailed teleseismic receiver function analysis that defines the underthrusting slab. Forward and inverse modelling techniques were applied to receiver function data calculated at two permanent and four temporary seismic stations within the Queen Charlotte Islands. The modelling reveals a ∼10 km thick low-velocity zone dipping eastward at 28° interpreted to be underthrusting oceanic crust. The oceanic crust is located beneath a thin (28 km) eastward thickening (10°) continental crust.     

Fine S wave velocity structure beneath Iwate volcano, northeastern Japan, as derived from receiver functions and travel times

A genetic algorithm inversion of receiver functions derived from a dense seismic network around Iwate volcano, northeastern Japan, provides the fine S wave velocity structure of the crust and uppermost mantle. Since receiver functions are insensitive to an absolute velocity, travel times of P and S waves propagating vertically from earthquakes in the subducting slab beneath the volcano are involved in the inversion. The distribution of velocity perturbations in relation to the hypocenters of the low-frequency (LF) earthquakes helps our understanding of deep magmatism beneath Iwate volcano. A high-velocity region (dV_S/V_S=10%) exists around the volcano at depths of 2–15 km, with the bottom depth decreasing to 11 km beneath the volcano’s summit. Just beneath the thinning high-velocity region, a low-velocity region (dV_S/V_S=−10%) exists at depths of 11–20 km. Intermediate-depth LF (ILF) events are distributed vertically in the high-velocity region down to the top of the low-velocity region. This distribution suggests that a magma reservoir situated in the low-velocity region supplies magma to a narrow conduit that is detectable by the hypocenters of LF earthquakes. Another broad low-velocity region (dV_S/V_S=−5 to −10%) occurs at depths of 17–35 km. Additional clusters of deep LF (DLF) events exist at depths of 32–37 km in the broad low-velocity zone. The DLF and ILF events are the manifestations of magma movement near the Moho discontinuity and in the conduit just beneath the volcano, respectively.