分量式钻孔应变观测耦合系数的计算

根据双衬套钻孔应变观测力学模型,推导出平面应力作用下各分量应变观测中两个耦合系数(A、B)的计算公式,为进一步确定地壳应变场最大、最小主应变的数值及方向提供了必需的前提条件,对当前国内外开展的利用钻孔应变进行地震、火山和板块边界的观测研究具有一定积极意义.研究结果表明,A、B与用双环模型和复变函数法解算出的c(面应变响应因子)、d(剪应变响应因子)之间分别存在2倍的关系(c=2A,d=2B),并且二者绘制的曲线完全一致,c、d的物理含义分别是地壳岩石面应变与剪应变观测的井孔耦合系数.     

超高阶次Legendre函数的跨阶数递推算法

本文引入了Legendre函数的跨阶数递推算法,并利用该算法在双精度数范围内计算了按间隔为1°余纬从1°变化至89°对应的直到完整的20000阶次的归一化连带Legendre函数的值.为验证计算精度,通过多种途径对该算法的计算结果进行检验,结果表明:该算法算得的每个阶次连带Legendre函数的值至少具有10-10这样的绝对精度.此外还对该算法的计算用时进行了统计,结果为该算法的计算用时大约是Legendre函数计算中常用的按阶数递推算法用时的1.6倍.     

Double parameterized regularization inversion method for migration velocity analysis in transversely isotropic media with a vertical symmetry axis

Simultaneous estimation of velocity gradients and anisotropic parameters from seismic reflection data is one of the main challenges in transversely isotropic media with a vertical symmetry axis migration velocity analysis. In migration velocity analysis, we usually construct the objective function using the l₂ norm along with a linear conjugate gradient scheme to solve the inversion problem. Nevertheless, for seismic data this inversion scheme is not stable and may not converge in finite time. In order to ensure the uniform convergence of parameter inversion and improve the efficiency of migration velocity analysis, this paper develops a double parameterized regularization model and gives the corresponding algorithms. The model is based on the combination of the l₂ norm and the non‐smooth l₁ norm. For solving such an inversion problem, the quasi‐Newton method is utilized to make the iterative process stable, which can ensure the positive definiteness of the Hessian matrix. Numerical simulation indicates that this method allows fast convergence to the true model and simultaneously generates inversion results with a higher accuracy. Therefore, our proposed method is very promising for practical migration velocity analysis in anisotropic media.     

双锋面相遇对强龙卷风环境场影响的数值模拟研究

对2009—2016年江苏北部龙卷事件的环境场进行统计与诊断,并对两次典型龙卷过程环境场进行数值模拟,重点探讨近海岸平原地区的江苏北部在春夏季节成为中国强龙卷最高频发生地的特殊性以及环境双锋面系统相遇对龙卷环境场的增强机制。分析结果显示：苏北龙卷发生率占全省58.6%。其中盐城和徐州又是苏北龙卷最高发地区。春夏季节,冷暖干湿气团势力相近,中尺度锋面系统多,易发生双锋面汇集造成局地龙卷强对流。对徐州（2009年）和盐城（2016年）的两次典型龙卷强对流环境场分析显示,徐州龙卷为变形场锋生和海风锋汇合,盐城龙卷为气旋锋面和岸滨锋相遇。WRF模拟结果显示,双锋面系统汇聚以及锋面二级环流相遇,可造成局地水平风速垂直扭转及垂直速度的水平切变,有利于驱动和增强区域正涡度;双锋面二级环流垂直上升支的叠加,可在平坦地区产生强烈的系统性抬升。这将形成有利龙卷类强对流天气发生发展的环境场。而各种常用的强对流指标均具有较强局地性,需要依据局地统计特征进行参考使用。     

State dynamics of a double sandbar system

A 9.3-year dataset of low-tide time-exposure images from Surfers Paradise, Northern Gold Coast, Australia was used to characterise the state dynamics of a double sandbar system. The morphology of the nearshore sandbars was described by means of the sequential bar state classification scheme of Wright and Short [1984. Morphodynamic variability of surf zones and beaches: a synthesis. Marine Geology 56, 93-118]. Besides the two end members (the dissipative (D) and the reflective (R) states) and the four intermediate states (longshore bar and trough (LBT), rhythmic bar and beach (RBB), transverse bar and rip (TBR) and low tide terrace (LTT)), we identified two additional intermediate bar states. The erosive transverse bar and rip (eTBR) state related to the dominant oblique angle of wave incidence at the study site and the rhythmic low tide terrace (rLTT) related to the multiple bar setting. Using the alongshore barline variability and alongshore trough continuity as morphological indicators enabled the objective classification of the inner and outer bar states from the images. The outer bar was mostly in the TBR state and generally advanced sequentially through the states LBT-RBB-TBR-eTBR-LBT, with occasional transitions to the D state. Wave events led to abrupt state transitions of the outer bar, but, in contrast to expectations, did not necessarily correspond to upstate transitions. Instead, upstate (downstate) transitions coincided with angles of wave incidence θ larger (smaller) than 30°. The upstate TBR-eTBR-LBT sequence during high-angle events highlights the role of alongshore currents in bar straightening. The outer bar was found to govern the state of the inner bar to a large extent. Two types of inner bar behaviour were distinguished, based on the outer bar state. For intermediate outer bar states, the alongshore variability of the dominant inner rLTT state (52% in time) mainly related to that of the outer bar, implying some sort of morphological coupling. For dissipative outer bar states, however, the more upstate inner bar frequently separated from the shoreline and persistently developed rip channels as TBR became the most frequent state (60% in time).     

汶川Ms8.0地震及余震序列重新定位

从2008年5月12日汶川8.0级地震发震时刻起到2008年12月31日,四川省及其周边省区布设的区域台网、水库台网以及流动台共记录到10000余次余震序列(M≥2.0).我们采用双差定位法对主震及余震序列进行重新定位,得到7000多个地震的重新定位结果.结果表明,余震分布带长约350 km.在西南部,余震沿龙门山后山...     

清远CINRAD/SA-D型气象雷达天线动态故障解析

CINRAD/SA-D型气象雷达天线动态故障一直困扰着机务人员,由于影响链路组件过多,排查困难,对于时效要求比较高雷达观测业务造成很大困扰。 本文利用清远连州雷达站2017年9月11日-9月13日雷达运行资料分析,详细解析了此次天线动态故障的排查过程和解决故障的过程,总结出一套可以借鉴的CINRAD/SA-D气象雷达天线动态故障排查方法。     

Advance numerical simulation of tunneling by using a double shield TBM

Double shield TBMs are amongst the most technically sophisticated excavation machines in use by tunneling industry. However, using the shielded machine limits access to the walls for observation of ground conditions and presence of shield makes the machine susceptible to entrapment or seizure in weak rocks under high stresses which results in high convergence. To realistically evaluate the possibility of machine seizure in such grounds, the interaction between the rock mass and shields, lining and backfilling need to be understood. This study explains the application of numerical analysis for 3D simulation of mechanized tunneling by using a double shield TBM. For this purpose, a comprehensive numerical simulation is developed to systematically evaluate the potential of excessive ground convergence. Simulation results at five reference points on the tunnel circumference along the tunnel have been examined. The results are including longitudinal displacement profile (LDP) as well as contact force profiles (LFP) on both front and rear shields, frictional forces and required thrust to move the machine, stress history of ground, and estimated loading of the segments. The results also proved that numerical analyses can successfully be used for prediction of loads on the shield during excavation to assess risks of machine entrapment.     

加勒比海东南部温盐阶梯的地震海洋学研究

通过处理EW0404航次的部分测线的多道地震数据,结合历史CTD（Conductivity,Temperature,Depth）数据,在加勒比海东南部发现了大量的温盐阶梯结构,地震剖面上阶梯层的结构和深度与测线附近的CTD,数据中发现的温盐阶梯有着较好的对应关系.分析认为加勒比海域有两种温盐阶梯形态：一种是连续且密集的阶梯层,阶梯层厚度中等,其在地震剖面上表现为大面积的块状密集高强度反射,是该海域主要的温盐阶梯形态;另一种是深度相差较大的阶梯层,阶梯层较厚,中间夹杂有小的阶梯,其在地震剖面上表现为水平延伸的条带状反射带.

     

新疆天山中段地壳和上地幔顶部P波速度结构研究

天山造山带一直以来是研究盆山耦合作用的理想场所, 深入理解这一地区的壳幔结构对认识天山造山带深部动力学过程具有重要意义.本研究基于2009—2020年新疆区域数字地震台网固定台站、震后架设应急流动台站以及部分宽频带流动地震台站记录到的MS≥1.5地震到时资料, 采用双差地震层析成像方法反演获得了新疆天山中段精细的地壳和上地幔顶部三维P波速度结构和地震震源参数.结果显示: 新疆天山中段具有复杂的深浅构造关系, 地壳浅部及上地壳P波速度结构与地表地质构造密切相关, 高速异常区对应于天山造山带, 低速异常区对应于沉积盆地.研究区中东段中地壳和下地壳存在较大范围低速区, 与两侧准噶尔盆地和塔里木盆地上地壳和中地壳低速区相连, 且准噶尔盆地和塔里木盆地下地壳及上地幔顶部双向均向新疆天山中段下方倾斜.结合前人诸多研究成果推测, 在南北向构造挤压作用下, 塔里木盆地与准噶尔盆地双向向天山造山带壳幔岩石圈发生"层间插入与俯冲削减".重定位后地震分布显示, 地震震源深度优势范围为0~25 km, 主要沿断裂带、盆山结合部以及不同块体接触部位分布, 且与壳内低速体有较好的相关性.这些结果可能为研究新疆天山中段地壳和上地幔顶部速度结构和动力学过程提供参考依据.