逆散射级数法预测层间多次波的算法改进及其策略

波动方程预测层间多次波有两类算法.一是由Berkhout和Verschuur（1998）提出的基于CFP（共聚焦点）延拓的算法,另一是由Weglein（1997）等人提出的基于逆散射级数法的算法.ISS（逆散射级数）算法具有不依赖速度模型的优点,但是其计算成本很高.本文改进了Weglein提出的1-D预测公式,提高了计算效率.从理论方面,改进算法的计算速度提高了大约12倍.实际结果表明其计算速度更快,提高近80倍左右,主要原因在于后者的空间复杂度小.此外,由于时间-空间域比伪深度-波数域的层间多次波预测有更多的优点,本文推导了1.5-D时间-空间域ISS层间多次波预测算法,该算法有计算速度快、预测噪音小、适应观测系统能力强和不依赖地震子波等优点.在实际应用中,计算成本高是ISS预测层间多次波算法的主要障碍.因此,本文还讨论了预测层间多次波的策略.结合本文提出的改进算法和应用策略,能够在实际地震资料处理中较好地应用ISS预测层间多次波.     

中心取样空心螺旋钻进法

中心取样空心螺旋钻进法是新发展起来的钻进工艺,阐述了螺旋钻进法的应用与发展.并论述了各种中心取样空心螺旋钻进法的钻具结构与施工方法.包括内钻杆柱式中心取样钻具、绳索升降式中心取样钻具.摩斯取样系统以及詹姆科绳索回收取样装置.     

Effects of scattering and resonance on energy dissipation of an internal tide in a narrow shelf

The effects of scattering and resonance on the energy dissipation of an internal tide were investigated using a two-dimensional model which is a reassembled version of the theoretical generation model devised by Rattray et al. (1969) for internal tide. The basic character of the scattering process at the step bottom was first investigated with a wide shelf model. When the internal wave incited from a deep region (Region II) into the shallow shelf region (Region I), a passing wave into the shallow region, a reflected wave into the deep region, and a beam-like wave, i.e. a scattered wave (SW), emanated at the step bottom. The SW, which consists of the superposition of numerous internal modes, propagated upward/downward into both regions. The general properties of the SW were well expressed around the shelf edge, even in the present model with viscosity effect. The amplitude of the SW decreased dramatically when the depth of the velocity maximum of the incident internal wave in Region II corresponded with the depth of the shelf edge. In the narrow shelf model, where the decay distance of the internal wave in Region I is longer than the shelf width, the incident internal wave reflected at the coast to form a standing wave. When the internal wave in Region I is enhanced by the resonance, the energy of the SW in Region II is also intensified. Furthermore, the energy of the modes in Region II predominated when the velocity maximum is identical to that of the dominant mode in Region I. These results suggest that the spatial scale of shelf region is a very important factor governing the energy dissipation of the internal tide through reflection and scattering in a narrow shelf.     

Internal generation of waves: Delta source function method and source term addition method

In this study, we investigate two internal wave generation methods in numerical modeling of time-dependent equations for water wave propagation, i.e., delta source function method and source term addition method, the latter of which has been called the line source method in literatures. We derive delta source functions for the Boussinesq-type equations and extended mild-slope equations. By applying the fractional step splitting method, we show that the delta source function method is equivalent to the source term addition method employing the energy velocity. This suggests that the energy velocity should be used rather than the phase velocity for the transport of incident wave energy in the source term addition method. Finally, the performance of the delta source function method is verified by accurately generating nonlinear cnoidal waves as well as linear waves for horizontally one-dimensional cases.     

山西定襄七岩泉新旧测氡仪水氡测值稳定性及映震分析

2014年山西定襄七岩泉新增BHC-336智能定标器,对新、旧2套测氡仪的水氡测值,就稳定性、数据一致性、内在质量等进行对比分析,结果显示,因存在系统误差,2台测氡仪水氡测值稳定性均值存在差异,测量精度和性能具有一致性;与新测氡仪相比,旧测氡仪水氡测值相对偏差和均值标准误差更小,精度更高,数据相关程度较高,数据稳定性更好。定襄水氡对华北5级以上地震具有较好的映震能力,新测氡仪对2016年4月7日原平4.6级地震映震效能比旧测氡仪灵敏。     

船舶海平面气压观测资料质量控制

随着数值预报模式不断发展,各类观测资料在数值模式中发挥着越来越重要的作用,船舶观测资料是海上3类观测系统 (卫星、飞机、船舶) 资料之一。为了保障船舶观测资料质量并有效地应用于数值模式,该文依据船舶观测资料的时空分布特征,以及2011年1月和7月T639分析场与观测资料对比分析结果,建立了一套船舶海平面气压资料质量控制方案,包括要素极值范围检查、缺测和冗余资料剔除、背景场一致性检查、测站黑名单建立等,并将该方案应用于2011年2月、6月、8月的观测资料。结果表明:船舶观测资料在时间上不连续且空间分布不均匀,会影响时间一致性检查和空间一致性检查质量控制效果;船舶海平面气压观测资料在所有观测要素中资料量最大,但其缺测和冗余资料量约占50%;黑名单资料的质量控制方案能够有效识别和剔除黑名单资料,且有利于对各测站的检查与维修工作;由于五大湖和大奴湖地区地形高度的影响,在背景场一致性检查过程中需对这些区域的背景场资料进行订正。     

A framework for the evaluation of ground motion selection and modification procedures

This study develops a framework to evaluate ground motion selection and modification (GMSM) procedures. The context is probabilistic seismic demand analysis, where response history analyses of a given structure, using ground motions determined by a GMSM procedure, are performed in order to estimate the seismic demand hazard curve (SDHC) for the structure at a given site. Currently, a GMSM procedure is evaluated in this context by comparing several resulting estimates of the SDHC, each derived from a different definition of the conditioning intensity measure (IM). Using a simple case study, we demonstrate that conclusions from such an approach are not always definitive; therefore, an alternative approach is desirable. In the alternative proposed herein, all estimates of the SDHC from GMSM procedures are compared against a benchmark SDHC, under a common set of ground motion information. This benchmark SDHC is determined by incorporating a prediction model for the seismic demand into the probabilistic seismic hazard analysis calculations. To develop an understanding of why one GMSM procedure may provide more accurate estimates of the SDHC than another procedure, we identify the role of ‘IM sufficiency’ in the relationship between (i) bias in the SDHC estimate and (ii) ‘hazard consistency’ of the corresponding ground motions obtained from a GMSM procedure. Finally, we provide examples of how misleading conclusions may potentially be obtained from erroneous implementations of the proposed framework. Copyright © 2014 John Wiley & Sons, Ltd.     

一种移动视频与地理场景的融合方法

快速准确地了解灾害现场状况是救灾过程中的重中之重。通常发生灾害都会使用无人机进行现场勘察,但是无人机视频难以与实际的地理场景关联起来,为此本文提出了一种移动视频与地理场景的融合方法。该方法首先采用具有仿射不变性的ASIFT算法检测特征点,将匹配后的特征点采用RANSAC算法进行迭代剔除噪点,计算视频与地理场景最优的透视变换矩阵模型参数;然后将计算得到的透视变换参数应用到视频数据,恢复视频角点坐标;最后通过内插得出所有视频帧的角点坐标,实现视频与DOM的精确融合。试验结果表明,对视频数据匹配的间隔帧越短,其整体融合精度越高,通过本文方法进行视频与地理场景融合的误差标准差低于10 m。     

Solution of dynamic Green׳s function for unsaturated soil under internal excitation

The closed form three-dimensional Green׳s function of a semi-infinite unsaturated poroelastic medium subjected to an arbitrary internal harmonic loading is derived, with consideration of capillary pressure and dynamic shear modulus varying with saturation. By applying the Fourier expansion techniques and Hankel integral transforms to the circumferential and radial coordinates, respectively, the general solution for the governing partial differential equations is obtained in the transformed domain. A corresponding boundary value problem is formulated. The integral solutions for the induced displacements, pore pressure and net stress are then determined considering the continuity conditions. The formulas are compared with the degenerated solution of saturated soils and confirmed. Numerical results reveal that the response of the unsaturated half-space depends significantly on the saturation by altering dynamic shear modulus to account for the effects of matric suction on soil stiffness. Slight differences between the results occur if only the saturation is taken into account. Moreover, a large source-depth results in a pronounced contribution to the reduction of surface displacement amplitudes. The analytical solutions concluded in the study offer a broader application to dynamic response associated with axi-symmetric and asymmetric conditions.