Seismic Attenuation Tomography in Central Myanmar and Its Implications on Continental Subduction and Arc Magmatism

Myanmar is located on the eastern margin of the India-Eurasia collision zone, where the Indian sub-continent is subducting beneath the Burma microplate. Magmatic processes during subduction and collision in orogenic belts are significant and well-studied for oceanic subduction; however, the magmatism associated with continental subduction remains poorly understood. Seismic attenuation is highly sensitive to changes in lithospheric thermodynamics and fluid content. Understanding arc volcanism is vital for comprehending a key manifestation of subduction-related processes. However, there is still no high-resolution 3D attenuation model for this region. Here, we use the coda-normalized method to image the lithospheric-scale 3D attenuation structure in the Indo-Burma subduction zone. Our results reveal high attenuation in major sedimentary basins. The prominent high-attenuation anomalies in the mid-to-lower crust of the Indo-Burma Ranges (IBR) may represent thick, fluid-rich sediments scraped off from the subducting Indian Plate and accumulated beneath the IBR. Low-attenuation anomalies at depths of 30–50 km beneath the Monywa volcano are a clear signature of a cooled mantle wedge, which currently overlies strong attenuation anomalies deeper than 50 km, likely associated with the upwelling of hot asthenospheric material. Compared to oceanic subduction systems, the insufficient water content of the continental subduction plate, coupled with the compressional regime induced by oblique subduction, leads to weak attenuation within the mantle wedge.