Variation of Q value before and after the 1999 Xiuyan, Liaoning Province, M =5.4 earthquake on the basis of analysis on attenuation dispersion of P waves

A method for determining medium quality factor is developed on the basis of analyzing the attenuation dispersion of the arrived first period P wave. In order to enhance signal to noise ratio, improve the resolution in measurement and reduce systematic error we applied the data resampling technique. The group velocity delay of P wave was derived by using an improved multi-filtering method. Based on a linear viscoelastic relaxation model we deduced the medium quality factor Q _m, and associated error with 95% confidence level. Applying the method to the seismic record of the Xiuyan M=5.4 earthquake sequences we obtained the following result: (1) High Q _m started to appear from Nov. 9, 1999. The events giving the deduced high Q _m value clustered in a region with their epicenter distances being between 32 and 46 km to the Yingkou station. This Q _m versus distance observation obviously deviates from the normal trend of Q _m linearly increasing with distance. (2) The average Q _m before the 29 Dec. 1999 M=5.4 earthquake is 460, while the average Q _m between the M=5.4 event and the 12 Jan. 2000 M=5.1 earthquake is 391, and the average Q _m after the M=5.1 event is 204. Foundation item: State Key Project of Science and Technology during the Tenth Five-year Plan (2004BA601B01-03-01).     

高分辨率卫星影像上地物线性特征的自动识别

在高分辨率卫星影像上，地物的线性形状特征信息是丰富的，但同时，由于其过分细节化，再加上阴影，云层等干扰因素的影响，使得同一地物表现出不同的光谱亮度特征，在无疑给相关的地物线性特征的检测与提取带来了一定的复杂性，本文提出基于多重滤波的方法，并根据图像的纹理排列特征，通过设计使用一个高通滤波器的统计滤波器，来实现线性特征的自动检测与识别，其中高通滤波器的主要功能是突出地物的边界特征，统计滤波器则是消除高通滤波后的一些噪音，最后通过边缘检测与跟踪处理，得到描述地物线性特征的矢量图层，实验结果表明，这种方法显著提高了检测结果的精度，同时也表明了从高分辨率卫星影像上自动提取矢量信息图层的可行性，为高分辨率卫星影像的进一步应用提供了要应的技术基础。     

Variation of Q value before and after the 1999 Xiuyan, Liaoning Province, M=5.4 earthquake on the basis of analysis on attenuation dispersion of P waves

Introduction The medium in the Earth is inhomogeneous, anelastic and anisotropic. By studying the at- tenuation of seismic waves we can acquire some information on the component and property of the material, as well as temperature distribution in the Earth. Dispersion of body waves is caused by the anelasticity of the medium (Wuenschel, 1965; Doornbos , 1983). There are two kinds of approach for studying the wave attenuation: amplitude decay and dispersion. Based on wave am- plitude decay me…     

1999年辽宁岫岩5.4级地震前后P波衰减频散特征

发展了一种根据单台垂向记录的地震直达P波的第一个周期信号, 研究地震波传播路径中介质衰减频散特性的方法. 为了更有效地提高P波频散测量的分辨率和信噪比水平,减小系统误差,使用了数据重采样技术. 应用改进的多重滤波方法测定P波群速度延迟. 根据线性滞弹性体松弛模型反演得到了介质品质因子Qm、95%置信水平下的测量误差及相关参数. 对营口台记录的辽宁岫岩震群的研究结果表明:① 1999年11月9日开始出现高Qm值,高Qm值对应的地震集中在距营口台32~46 km, 明显偏离Qm随震中距增加的线性规律;②5.4级地震前平均Qm值为460, 5.4级地震后至2000年1月12日5.1级地震之前Qm值为391, 5.1级地震之后Qm值为204.