Morphology and possible origins of the Perm anomaly in the lowermost mantle of Earth. Issue 1 (29th March 2021) - He, YuMei
Abstract: We have constrained a small‐scale, dome‐shaped low‐velocity structure near the core‐mantle boundary (CMB) of Earth beneath Perm (the Perm anomaly) using travel‐time analysis and three‐dimensional (3‐D) forward waveform modeling of seismic data sampling of the mantle. The best‐fitting dome‐shaped model centers at 60.0°E, 50.5°N, and has a height of 400 km and a radius that increases from 200 km at the top to 450 km at the CMB. Its velocity reduction varies from 0% at the top to –3.0% at 240km above the CMB to –3.5% at the CMB. A surrounding 240‐km‐thick high‐velocity D'' structure has also been detected. The Perm anomaly may represent a stable small‐scale chemical pile in the lowermost mantle, although the hypothesis of a developing mantle plume cannot be ruled out. Key Points: The detailed morphology and velocity structure of the Perm anomaly near the core‐mantle boundary of Earth is reassessed. Travel‐time analysis and three‐dimensional forward waveform modeling suggest that the anomaly is dome‐shaped with a maximum velocity reduction of –3.5% at the core‐mantle boundary. This anomaly may represent a stable small‐scale chemical pile in the lowermost mantle.