Seismic image and origin of the Changbai intraplate volcano in East Asia: Role of big mantle wedge above the stagnant Pacific slab

We determined P-wave tomography of the crust and upper mantle under the Changbai volcanic area in Northeast Asia by using 289,318 arrival-time data from 4802 local earthquakes and 9599 teleseismic events. A prominent low-velocity anomaly is clearly imaged in the crust and upper mantle down to about 410 km depth beneath the Changbai volcano. A broad high-velocity anomaly is revealed in the mantle transition zone and deep earthquakes occurred actively there, suggesting that the subducting Pacific slab is stagnating in the mantle transition zone under East Asia. Our results suggest that the formation of the Changbai and other intraplate volcanoes in Northeast Asia is related to the upwelling of hot and wet asthenospheric materials in the big mantle wedge above the stagnant Pacific slab. Hence the active intraplate volcanoes in Northeast Asia are not hotspots related to deep mantle plumes but are caused by plate tectonic processes in the upper mantle.