In order to investigate the small-scale scattering heterogeneities underneath the northern Tien Shan, we analyze the P wavefield from teleseismic events. By using the teleseismic fluctuation method, we separate the total wavefield into coherent and fluctuating parts in the frequency band of 0.1–8.0 Hz. Subsequently, we investigate the scattering characteristics by analyzing the frequency-dependent intensities of the coherent and fluctuating wavefield between 0.3 and 2.5 Hz. We further constrain the velocity perturbations and correlation lengths by modeling the P-wave coda envelope with the Monte Carlo simulation. Strong scattering heterogeneities are revealed beneath the northern Tien Shan. The preferred scattering model can be described as a ~ 55- to 130-km-thick randomly heterogeneous layer with velocity perturbations of 6–9% and correlation lengths on the order of 0.4 km. We attribute these small-scale scatterers to isolated melt pockets from the upwelling hot mantle materials.

中文翻译：

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从远震P波场看天山北部小尺度散射不均匀性

为了研究北天山下方的小尺度散射不均匀性，我们分析了远震事件的 P 波场。通过使用远震波动法，我们将总波场在 0.1-8.0 Hz 频带内分为相干部分和波动部分。随后，我们通过分析 0.3 和 2.5 Hz 之间相干和波动波场的频率相关强度来研究散射特性。我们通过使用蒙特卡罗模拟对 P 波尾波包络进行建模来进一步限制速度扰动和相关长度。在北天山下方揭示了强烈的散射异质性。优选的散射模型可以描述为约 55 至 130 公里厚的随机异质层，速度扰动为 6-9%，相关长度约为 0.4 公里。我们将这些小规模散射体归因于与上涌热地幔材料隔离的熔穴。