Determining surface wave arrival angle anomalies
Determining surface wave arrival angle anomalies
复制标题
确定表面波到达角异常
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
G. Ekström
中科院分区：
文献类型：
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作者：
E. Larson;G. Ekström
[1]本文提出了一种新的测量瑞利波和瑞利波到达角的方法。新方法利用表面波色散的估计来创建相位匹配滤波器，以隔离三分量记录中的Love或Rayleigh波。通过应用Vidale [1986]的复极化方法的变体，在时域中确定滤波波群的极化。粒子运动的取向、线性和椭圆率在几个频带中被估计以确定频率依赖的极化。该方法采用了一种迭代方案，通过该方案，预测的Love波，估计的色散和偏振的基础上，从三个分量的数据减去之前的瑞利波偏振估计，反之亦然。该方法适用于一套广泛的全球地震台网数据，涵盖了1989年至1998年。在9个不同的周期（37至150秒）的基础模式的爱和瑞利波收集4244和15,075测量。测量的不确定性估计使用成对相似路径的观测的统计数据，通常是总信号的15-50%的顺序，取决于周期和波的类型。大的和方位不变的角度异常记录了几个站，是一致的水平地震仪的定向误差。采用两种方案来确定定向误差：（1）在每个台站的方位加权平均，和（2）地震计定向误差和全球非均匀相速度的联合反演。所确定的校正是稳健的，并与早期研究中报道的那些相关性良好。方位角变化的到达角异常定性同意最近的相速度图，解释高达30%的方差在新的测量计算的波折射的预测。
[1] A new method for measuring arrival angles of teleseismic Love and Rayleigh waves is developed. The new method utilizes estimates of surface wave dispersion to create a phase-matched filter to isolate the Love or Rayleigh wave in three-component recordings. The polarization of the filtered wave group is determined in the time domain by application of a variation of the complex polarization method of Vidale [1986]. Orientation, linearity, and ellipticity of particle motion are estimated in several frequency bands to determine the frequency-dependent polarization. The method employs an iterative scheme, by which a predicted Love wave, based on the estimated dispersion and polarization, is subtracted from the three-component data prior to the estimation of Rayleigh wave polarization, and vice versa. The method is applied to an extensive set of Global Seismographic Network data covering the years 1989–1998. Between 4244 and 15,075 measurements are collected for fundamental mode Love and Rayleigh waves at nine different periods (37 to 150 s). Measurement uncertainties are estimated using the statistics of observations for pairwise similar paths and are generally of the order of 15–50% of the total signal, depending on the period and the wave type. Large and azimuthally invariant angle anomalies are documented for several stations and are consistent with misorientation of the horizontal seismometers. Two schemes are employed to determine the misorientations: (1) an azimuthally weighted average at each station, and (2) a joint inversion for seismometer misorientation and globally heterogeneous phase velocities. The determined corrections are robust and correlate well with those reported in earlier studies. Azimuthally varying arrival angle anomalies are shown to agree qualitatively with predictions of wave refraction calculated for recent phase velocity maps, which explain up to 30% of the variance in the new measurements.