Low-velocity layer atop the subducting Indian plate beneath the Burmese Arc constrained by guided waves

The Burmese arc, located at the eastern Himalayan syntaxis formed by the collision between the Indian and Eurasian plates, is characterized by intense crustal deformation, active magmatic–metamorphic processes, and frequent seismicity. Imaging the low-velocity layer (LVL) atop the subducting Indian plate is crucial for understanding post-collisional magmatism and lithospheric dynamics in this region, yet its detailed structure remains poorly constrained. Using continuous seismic data recorded by the CMGSMO network between June 2016 and February 2018, we identified 11 intermediate-depth earthquakes within the subducting Indian plate beneath the central Burmese arc that exhibit prominent guided-wave signatures. We conducted two-dimensional finite-difference simulations for a representative event near 22°N and obtained a best-fitting velocity model through systematic comparisons between synthetic and observed seismograms, including waveform characteristics and arrival-time behavior of guided phases. The preferred model reveals a LVL atop the subducting plate, characterized by P-wave velocities of 6.4–6.9 km s⁻¹ and a thickness of 8–14 km. The observed spatial distribution of guided wave events further suggests lateral variability of the LVL, consistent with a localized tear zone in the subducting slab. We interpret the LVL as a partially molten layer generated by the combined effects of Monywa magmatism, thermally driven upwelling associated with slab tearing, and fluid release due to slab dehydration. These results highlight the role of slab tearing in controlling melt generation and transport beneath the Burmese arc and provide new seismic constraints on post-collisional lithospheric processes in the eastern Himalayan region.