基于华北区域地震活动性分布的地震危险性评价模型

采用了分布式地震活动性模型. 该模型无需潜在震源区划分,同时简化了地震危险性概率分析方法. 根据破坏性地震目录建立了3个地震活动性模型,利用高斯光滑函数获得了华北区域内的a值分布特征,使用3种典型的衰减模型,分别计算了50年内超越概率10%, 5%和2%的地震动峰值加速度分布. 其分析结果显示了峰值加速度分布特征与我国第四代区划图大体一致,特定地震活动区（太原、 石家庄等地区）的峰值加速度略高于第四代区划图的结果,而这种峰值加速度分布特征与该地区较高的地震活动性特征是一致的. 概率危险性曲线结果表明,唐山、太原和北京等地区的潜在地震危险性比华北区域内其它城市高.      

Exploratory spectral analysis of hydrological times series

Current methods of estimation of the univariate spectral density are reviewed and some improvements are made. It is suggested that spectral analysis may perhaps be best thought of as another exploratory data analysis (EDA) tool which complements, rather than competes with, the popular ARMA model building approach. A new diagnostic check for ARMA model adequacy based on the nonparametric spectral density is introduced. Additionally, two new algorithms for fast computation of the autoregressive spectral density function are presented. For improving interpretation of results, a new style of plotting the spectral density function is suggested. Exploratory spectral analyses of a number of hydrological time series are performed and some interesting periodicities are suggested for further investigation. The application of spectral analysis to determine the possible existence of long memory in natural time series is discussed with respect to long riverflow, treering and mud varve series. Moreover, a comparison of the estimated spectral densities suggests the ARMA models fitted previously to these datasets adequately describe the low frequency component. Finally, the software and data used in this paper are available by anonymous ftp from fisher.stats.uwo.ca.     

半参数回归与模型精化

就一般情况给出了半参数平差的算法,并结合一种特定的情况,讨论了正规化矩阵半正定时的计算方法,给出了相应的公式。最后构造了一个模拟的平差问题,对半参数法和最小二乘法的计算结果进行了比较。计算表明,半参数法能够发现并识别模型误差或观测值中的系统误差     

基于有效邻域波场近似的起伏地表保幅高斯束偏移

随着我国陆上地震勘探向复杂地表探区的转移,高精度、适应性强的地震成像方法在地震资料的处理、解释及后续属性分析、储层预测中具有重要意义.本文基于有效邻域波场近似理论发展了一种成像精度更高且适用于复杂起伏地表条件的叠前保幅高斯束偏移方法.在传统水平地表高斯束偏移的基础上,本文根据中心射线附近有效邻域内高斯束表征的近似波场,导出了起伏地表条件下具有相对振幅保持的高斯束偏移公式,并给出了一种精度更高的旁轴射线传播角度计算方法.同现有的高斯束偏移方法相比,本文方法不仅考虑了起伏地表对高斯束走时的线性影响,而且首次引入了由地表高程差异和近地表速度变化引起的二次时差校正项和振幅校正项,使得成像结果更加准确可靠.两个典型模型算例验证了本文方法的正确性和有效性.     

Annual Frequency of Tropical Cyclones Directly Affecting Guangdong Province:Prediction Based on LSTM-FC

Tropical cyclone(TC) annual frequency forecasting is significant for disaster prevention and mitigation in Guangdong Province. Based on the NCEP-NCAR reanalysis and NOAA Extended Reconstructed global sea surface temperature(SST) V5 data in winter, the TC frequency climatic features and prediction models have been studied.During 1951-2019, 353 TCs directly affected Guangdong with an annual average of about 5.1. TCs have experienced an abrupt change from abundance to deficiency in the mid to late ...     

复杂地表条件下高斯波束叠前深度偏移(英文)

在复杂地表条件的区域,地震数据的采集和处理是一项极大的挑战。虽然可以通过静校正来消除起伏地表的影响,然而当地表高程以及近地表速度剧烈变化时,简单的垂直时移对地震波场造成的畸变会严重降低偏移成像的质量。基于射线的偏移方法可以直接在起伏地表面进行波场的延拓成像,是解决上述问题的有效手段。本文针对复杂地表条件下的高斯波束叠前深度偏移进行研究,对倾斜叠加公式进行修改,使之包含地表高程以及速度的信息,通过直接在复杂地表面进行平面波的合成,得到了一种具有更高成像精度的改进方法。首先简单介绍常规高斯波束偏移的基本原理和计算流程,并以此为基础,给出复杂地表条件下高斯波束偏移原有的实现方法以及本文的改进方法,最后通过模型和实际资料的试算验证本文方法的有效性。     

空间光滑地震活动性模型中光滑函数的比较研究

使用Frankel提出的基于空间光滑地震活动性模型的地震危险性分析方法,选择华南、华北、川滇3个地区的地震记录,比较分析了高斯、幂律和地震分形分布光滑函数3种光滑函数在不同地区的适用性．结果表明,使用交叉验证法可以为高斯光滑函数选取合适的相关距离c值,光滑得到的地震活动性模型能够真实反映研究区域的地震活动特征,根据活动性模型计算得出的峰值加速度(PGA)分布也符合人们对研究区域地震危险性的认识．幂律光滑函数适用于地震活动性较强的地区,且具有容易求取光滑参数的优点．光滑程度较低的幂律光滑函数不适用于地震活动性弱的地区,在该类地区应选择光滑程度较高的高斯光滑函数．地震分形分布光滑函数不适用于地震活动较强且地震活动强度差异较大的地区,其容易过分高估高震级地震对地震危险性的影响,而忽略了低震级地震对地震危险性的贡献．但对于地震活动较弱且地震活动强度差异较小的地区,可使用地震分形分布光滑函数,且同样具有容易求取光滑参数的优点．     

Reverse time migration with Gaussian beams using optimized ray tracing systems in transversely isotropic media

Prestack depth migration is a key technology for imaging complex reservoirs in media with strong lateral velocity variations. Prestack migrations are broadly separated into ray-based and wave-equation-based methods. Because of its efficiency and flexibility, ray-based Kirchhoff migration is popular in the industry. However, it has difficulties in dealing with the multi-arrivals, caustics and shadow zones. On the other hand, wave-equation-based methods produce images superior to that of the ray-based methods, but they are expensive numerically, especially methods based on two-way propagators in imaging large regions. Therefore, reverse time migration algorithms with Gaussian beams have recently been proposed to reduce the cost, as they combine the high computational efficiency of Gaussian beam migration and the high accuracy of reverse time migration. However, this method was based on the assumption that the subsurface is isotropic. As the acquired azimuth and maximum offsets increase, taking into account the influence of anisotropy on seismic migration is becoming more and more crucial. Using anisotropic ray tracing systems in terms of phase velocity, we proposed an anisotropic reverse time migration using the Gaussian beams method. We consider the influence of anisotropy on the propagation direction and calculate the amplitude of Gaussian beams with optimized correlation coefficients in dynamic ray tracing, which simplifies the calculations and improves the applicability of the proposed method. Numerical tests on anisotropic models demonstrate the efficiency and accuracy of the proposed method, which can be used to image complex structures in the presence of anisotropy in the overburden.     

基于误差分布的震源区波速比反演及其应用:乳山震群源区介质性质变化研究

本文利用误差分布和概率统计分析改进了波速比计算方法.对于震源位置相对集中的震群活动,对台站震相到时进行两次差分,通过对差分后的震相数据对进行二维高斯分布拟合,可以稳健地估计震群活动震源区波速比.该方法充分利用了不同台站Pg、Sg到时差的所有信息,其优势是不需要地震事件的震源位置,并且不依赖震源区以外的速度变化,有效消除了震源区到台站的传播路径效应的影响;相对于传统的平均波速比,本文方法得到的震源区波速比,更能真实地反映震源区介质的性质.我们将该方法应用到2013-2016年的乳山震群,结果显示：震源区波速比的变化与震群活动过程密切相关,波速比的变化反映了序列活动的阶段性特征.

     

用L-曲线法确定半参数模型中的平滑因子

提出了一种新的方法——L-曲线法确定平滑因子。通过确定合适的平滑因子，更好地控制了残差部分V^TPV与光滑度部分S^TRS之间的平衡，得到了更准确的参数估值。通过算例，将基于L-曲线法确定平滑因子的半参数模型解算方法和其他方法进行了比较。结果表明，用L-曲线法确定平滑因子后，提高了半参数模型计算结果的精度，可以更好地将观测值中的系统误差分离出来。