An Active-Source Seismic Investigation of Newberry Volcano: Large-Offset Reflections from a Shallow, Upper-Crustal, Magma Body

In the summer of 2008 we deployed a temporary seismic array across Newberry Volcano to record reflections off of the geophysically-identified magma body underlying the volcano. Newberry is a large, recently active volcano that is most likely underlain by a shallow magma chamber; characterizing the size, depth, and percentage of melt in a magma-rich volume is critical for assessing the hazard posed by a volcano. But imaging magma systems with seismic techniques is difficult because they are anisotropic, highly attenuating, and seismic waves tend to refract around them. Theoretical waveform modeling and seismological surveys, however, show that low-incidence-angle reflections from explosive sources produce energetic P- and S-wave signals from contacts with large impedance contrasts, such as the top of a magma-rich body. We propose to test this technique by taking advantage of previously planned explosions near Newberry Volcano in central Oregon. Newberry is an important target for study due to the high hazard it poses for Bend, Oregon and surrounding communities. The existence of a previously planned, National Science Foundation (NSF) funded, active-source seismic survey designed to study the structure of the adjacent High Lava Plains in eastern Oregon, affords us a unique opportunity to investigate this promising technique for minimal cost.