Autocorrelation of the Seismic Wavefield at Newberry Volcano: Reflections From the Magmatic and Geothermal Systems

We show that seismic autocorrelations provide new depth constraints on upper crustal magmatic systems. Autocorrelations of both ambient noise recorded on seismometers and geophones and teleseismic earthquake coda recorded on seismometers elucidate the structure of Newberry Volcano. These autocorrelations result in the two‐way, body wave Green's function beneath a station. Within the caldera, a reproducible, coherent P wave reflection is inferred to come from the top of a magma body at ~2.5 km depth and maps with the lateral extent of an anomalously low‐velocity body imaged tomographically. On the west flank of the volcano, a reflection that deepens with distance from the caldera is inferred to result from a temperature‐dependent change in metamorphic facies and may map the thermal structure of the edifice. Our results show that the autocorrelation of diffuse seismic energy reconstructs reflections from seismically sharp boundaries associated with the upper crustal magmatic structure. Plain Language Summary By studying records of seismic noise recorded on seismometers, seismic energy reflecting off an inferred magma body at Newberry Volcano was recovered. We use the time it takes for energy to go from the surface, down to the magma body, and back up to the surface to measure the depth to the top of the body. This study suggests there is a partly melted body at ~2.5 km depth beneath the caldera at Newberry Volcano. These results compare well with previous magma body models for Newberry. Key Points Autocorrelation of seismic noise and teleseismic coda provides two‐way reflections beneath a dense seismic line crossing Newberry Volcano A reflection attributed to the top of a magma body yields new depth constraints on the magmatic system Reflections on the west flank are likely due to changes in metamorphic facies and may map the thermal structure of the volcano