Teleseismic migration with dual bootstrap stack

S U M M A R Y A recently developed stacking scheme called dual bootstrap stack (DBS) is applied to teleseismic migration, using deep earthquakes in South America as sources and USArray as receivers. Built with statistical tests for signal significance and coherence, DBS can achieve a clean separation of signal and noise, and unlike conventional non-linear stacks such as Nth-root stack (NRS) and phase-weighted stack (PWS), it can recover signals even when the signal-to-noise ratio is lower than unity. Migration results with DBS are compared with those with linear stack, NRS and PWS, and DBS-based migration is shown to be able to detect weak, smallscale scatterers that cannot be imaged by NRS and PWS and cannot be confidently identified by linear stack. Based on migration results reproducible among multiple data sets, a number of small-scale scatterers are suggested to exist in the top 400 km and the bottom 1500 km of the mantle in the study region. Though being time-consuming, teleseismic migration with DBS is suggested to be a promising tool to map out a variety of hitherto undetected small-scale heterogeneities in the mantle.