Small-scale scattering heterogeneities beneath the northern Tien Shan from the teleseismic P wavefield

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.