Seismic reflections from the top of the magma reservoir beneath Yellowstone Caldera

Seismic reflection data showing the top of the magma reservoir beneath Yellowstone Caldera along a cross section that runs from Canyon Village in the northwest (X) to near Lake Butte in the southeast (X`).  The top panel shows seismic P-wave (compressional wave) reflectivity, with evidence for the sharp reservoir top labeled. The middle panel shows seismic reflections where P-waves convert to S-waves (shear waves) as they reflect off the top of the reservoir. Combined information from the two reflection types helps constrain the total fluid fraction and relative amounts of bubbles and magma at the very top of the reservoir. The bottom panel shows a schematic cartoon interpretation in which a large reservoir that is several kilometers thick mostly contains a small amount of magma in the pore space between crystals, and a thin layer at the very top transiently accumulates bubbles that rise through the magma and temporarily reside in pore space between crystals and some melt.