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Paper reference: Y. LeStunff, C. Wicks and B. Romanowicz, 1995, P'P' Precursors Under Africa - Evidence for mid-mantle reflectors, Science, 270, 74-77

Observations of precursors to P'P' from a recent exceptionally large deep earthquake in the Fiji Islands (moment magnitude = 7.6) at an array of broadband stations in California revealed mid-mantle reflectors near depths of 785 kilometers and 1200 kilometers under the southern African rift. Such observations, previously reported primarily in subduction zones, suggest that these reflectors may have a global character. Our analysis, which also indicated a sharp, uplifted 670-kilometer discontinuity, demonstrates the power of sparse regional broadband arrays for the study of weak, frequency-dependent features in deep-Earth structure.