Lower mantle inhomogeneities inferred from PcP precursors

Abstract

A search of phases arriving between P and PcP, the reflection from the core‐mantle boundary (CMB), was performed in the Bulletins of the International Seismological Center (BISC). The distribution of the turning/reflection points of anomalous waves in the lowermost mantle indicates the areas which are possibly anomalous regions. The regions exhibiting these anomalies cover only a small fraction of the lowermost mantle sampled. The areas which can be associated with anomalous arrivals are the lowermost mantle under the North Pole region, northern Siberia, central Siberia, western Mongolia, Afghanistan, northeastern China/Korea and the North Atlantic Ridge. These are the regions which should be studied in more detail by analyzing the seismograms, i.e., the amplitude and waveform information, at the corresponding stations in addition to the travel time information reported to the ISC.