Imaging Yellowstone's shallow Magma Reservoir

In this experiment, we will deploy ~600 nodal seismometers throughout Yellowstone National Park for a little over a month. For the passive portion of the array, we will deploy geophones more or less evenly along all accessible roads (~3 km spacing) within Yellowstone National Park to supplement the existing permanent network. About a month of passive data will be collected, and ambient noise tomography will be applied to determine both Rayleigh and Love wave phase velocity and Rayleigh wave H/V ratio maps. With the dense station coverage, we expect we will be able to obtain a Vs model with lateral resolution ~5 km compatible to the Vp model constructed using earthquakes. In addition to ambient noise, we will also utilize both local and teleseismic earthquakes to provide additional constraints. For the active array, we will deploy a dense linear array with ~1 km station spacing to investigate the possibility of imaging the detailed lateral variation of the magma body using receiver functions. The linear array will be deployed along roads cutting through the Yellowstone caldera as well as the upper crustal magma chamber identified by the previous studies. Based on our recent nodal study near Yellowstone, a conversion phase associated with the upper boundary of the magma chamber can be clearly identified in the teleseismic receiver functions. Although the number of good teleseismic events for receiver function analysis during the one-month experiment duration is likely going to be around 5, we will focus on the small-scale receiver function variation (~1 km resolution) across the array for each individual event. The main target of the study is to define the location and sharpness of the lateral edge of the magma chamber as well as investigate the small-scale topography variation of the top boundary of the magma body. Combined with the 3D model constructed using ambient noise tomography, the new constraints on the upper crustal magma chamber will be used to better determine the Yellowstone volcanic activity.