Ductile Crustal Flow Facilitates Intraplate Volcanism: Seismic Evidence From Tengchong, China

The mechanisms and processes driving intraplate volcanism remain incompletely understood despite significant advances in recent decades. Here, we use high-resolution multiparameter full-waveform inversion to image the three-dimensional seismic structure beneath the Tengchong volcanic region in southwestern China. Our model reveals a pronounced low-velocity anomaly and elevated Poisson's ratio in the uppermost mantle, consistent with a deep-seated magma reservoir. Significantly, we resolve a laterally extensive mid-to-lower crustal channel characterized by low velocity, high Poisson's ratio, and positive radial anisotropy (V_SH > V_SV) extending from the southeastern Tibetan Plateau toward Tengchong. This feature is interpreted as ductile crustal flow, which ascends beneath Tengchong and interacts with the overlying crustal magma system. Our findings provide the first seismic evidence that deep crustal flow can dynamically couple with mantle-derived magmatism to facilitate intraplate volcanism. These results offer new insights into crust-mantle interactions and the generation of volcanism in continental interiors.