Beijing Anomaly

The Beijing Anomaly is a seismic wave anomaly in the Earth's mantle, from ~700–1400 km depth, characterized by relatively high attenuation and decreased sound speed. It is centered beneath northern China, just northwest of Beijing.

The seismic properties of the anomaly are similar to those of the asthenosphere, which contains water absorbed from subducting slabs. The discoverers of the anomaly, Jesse Lawrence of Scripps and Michael E. Wysession of Washington University, propose that it has a similar water content, from subducting lithosphere from the Pacific plate. This would imply that the amount of water in this region of the mantle is comparable to that in the Arctic Ocean (although the water content is no more than 0.1% by volume). Other possible causes of the anomaly include small-scale chemical heterogeity and abnormally small particle size.