2016年新疆轮台MS 5.3地震序列尾波Qc值分析

基于Sato单次散射模型,利用轮台地震台单台记录,计算并分析2016年1月14日新疆轮台M_S5.3地震及余震序列尾波Q_c值震后变化,拟合得出Q_c值随频率的变化关系为Q_c (f) =（18.0±3.19）f^1.184±0.072。结果表明,Q_c值在序列初期起伏较大,随着强震后能量的释放,Q_c值趋于平缓;低频段的Q_c值在较大余震发生前有显著变化;不同中心频率点的Q_c值变化形态不一致。对Q_c值变化特征的研究,可为地震预报提供参考依据。     

Moment magnitudes of two large Turkish earthquakes on February 6, 2023 from long-period coda

Two large earthquakes (an earthquake doublet) occurred in south-central Turkey on February 6, 2023, causing massive damages and casualties. The magnitudes and the relative sizes of the two mainshocks are essential information for scientific research and public awareness. There are obvious discrepancies among the results that have been reported so far, which may be revised and updated later. Here we applied a novel and reliable long-period coda moment magnitude method to the two large earthquakes. The moment magnitudes (with one standard error) are 7.95±0.013 and 7.86±0.012, respectively, which are larger than all the previous reports. The first mainshock, which matches the largest recorded earthquakes in the Turkish history, is slightly larger than the second one by 0.11±0.035 in magnitude or by 0.04 to 0.18 at 95% confidence level.     

用叠加谱比法研究新疆地区Lg尾波Q值的区域性变化

运用叠加谱比法,对分布于新疆地区的5个台站所记录的51个地震数据进行分析,得出与各射线路径相对应的Lg尾波Q0(Lg尾波在1Hz处的Q)值。结果表明:Q0值呈现出明显的区域性变化特点,与构造活动关系紧密。在较为稳定的塔里木地台,Q0呈现出高值,在350～450之间。在南部构造活动较为激烈的昆仑褶皱系,Q0呈现出较低的值,约为200～250。在构造活动最为激烈的帕米尔地区,Q0值在170～200之间。在北部的天山褶皱系,Q0值约为220～270。准葛尔褶皱系比天山褶皱系的Q0值略高,约为260～290。     

浙江及邻区尾波Q值研究

基于单次散射(Aki)模型,利用2000年至今浙江及安徽台网记录的37次ML3.0以上地震的数字地震波资料,计算了浙江及邻近省区平均尾波Q值,并拟合了Q值对频率的依赖关系数据。结果为:Q(f)=212±33.5f0.62±0.11,与国内其它区域相比,本区域为Q值高值、对频率低依赖性区域。认为本研究区内构造活动弱,地震活动水平低。本文就Q值对频率、尾波窗长等的依赖性特征及影响Q值计算的噪声水平、滤波器、数据采样等因素进行了深入分析。     

Time-domain computation of scattering from a heterogeneous layer

Adopting Born and ray approximations, time-domain synthetic seismograms for P-P and P-S scattering from a plane wave incident on a thin, laterally heterogeneous layer are presented in this paper. The time-domain P coda is a convolution between a structure function and the second-order derivative of the time function of the incident P wave. Examples of synthetic seismograms are given using a time function from a computed short-period seismogram for a point explosive source in a half-space. These show that it is impossible, with realistic values of the parameters involved, to generate significant codas when only single scattering is involved.