Global surface wave phase velocity variations
Global surface wave phase velocity variations
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全球表面波相速度变化
DOI：
10.1029/96jb00167
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发表时间：
1996
影响因子：
--
通讯作者：
T. Lay
中科院分区：
文献类型：
--
作者：
Yu;T. Lay
使用M ≥ 6.0地震的约30，000个地震记录确定了85至250 s的全球洛夫波和瑞利波相速度变化。所使用的相位是G1、R1、G2和R2到达。这些数据来自中国数字地震台网、GEOSCOPE和全球地震台网的档案，时间范围为1980年1月至1992年6月。所有的地震记录都在时间和频率域进行了仔细的质量控制。我们考虑反演阻尼和模型参数化问题，检查数据统计，并假设数据和模型空间中的误差是零均值的高斯随机分布。考虑到我们数据集的路径采样和散射，对于分辨率高于约球谐次数l = 22的模型进行反演是不稳定的，并且低频数据仅保证扩展到约l = 12。我们发现，块模型参数化，其局部基函数，具有较少的文物比高阶球谐反演，必须严重阻尼。然而，球谐函数本质上提供了长波长结构的上级恢复。我们的最终模型涉及混合参数化，其中初始迭代检索用作非球面参考模型的低阶球谐分量，用于执行最终块模型反演。最佳块大小随频率而减小。这种方法利用全局和局部基函数的单独属性来解决异质性的不同分量，允许不同频率的可变分辨率，并提供了一个自然的框架，用于将局部高分辨率区域反演嵌入到全局模型中。我们进行反演有和没有校正地壳浅层结构。在较短的周期，相速度图强烈反映了地表构造，与大陆盾，洋中脊，和构造活动区。构造相关性随着时间的推移逐渐减弱。
Global Love and Rayleigh wave phase velocity variations from 85 to 250 s are determined using about 30,000 seismograms from earthquakes with M ≥ 6.0. The phases used are G1, R1, G2, and R2 arrivals. The data were obtained from the Chinese Digital Seismic Network, GEOSCOPE, and Global Seismic Network archives for the time period January 1980 to June 1992. All seismograms underwent careful quality control in the time and frequency domains. We consider the inversion damping and model parameterization issues, examining the data statistics and assuming that errors in data and model spaces are Gaussian random distributions with zero mean. It is not stable to invert for a model with resolution higher than about spherical harmonic degree, l = 22, given the path sampling and scatter of our data set, and the low frequency data only warrant expansion up to about l = 12. We find that a block model parameterization, with its local basis functions, has fewer artifacts than a high order spherical harmonic inversion which must be heavily damped. However, spherical harmonic functions provide intrinsically superior recovery of the long-wavelength structure. Our final models involve a hybrid parameterization, in which an initial iteration retrieves the low order spherical harmonic components that are used as an aspherical reference model for performing a final block model inversion. The optimal block size decreases with frequency. This approach exploits the separate attributes of global and local basis functions for resolving different components of the heterogeneity, allows for variable resolution for different frequencies, and provides a natural framework for embedding localized high resolution regional inversions into the global model. We perform inversions both with and without corrections for shallow crustal structure. At the shorter periods the phase velocity maps strongly reflect the surface tectonics, correlating with continental shields, mid-ocean ridges, and tectonically active areas. The tectonic correlation diminishes gradually with period.