Collaborative Research: Understanding the Structure of the Cascadia Volcanic Arc using Passive Imaging Techniques

Volcanic eruptions represent a threat to society. Thus, it is important to understand where magma is stored and how it moves below the surface prior to eruption. The Cascades Arc in the Pacific Northwest of the United States consists of eleven "high" or “very high threat” volcanoes as classified by the United States Geological Survey. However, little is known about the systems that control many of these volcanoes. This project will examine the structure beneath nine of the eleven volcanoes allowing for an evaluation of differences between them and their relationship with regional geologic factors. The results of this study will improve understanding of how the Cascades volcanoes vary, providing useful information about these volcanoes and the threats that they pose to the Pacific Northwest. Controls on structural, geochemical, and eruptive variability at volcanic arcs remain poorly understood largely due to sampling and imaging differences at active volcanic centers. Such variability may be closely related to individual magma system structure (i.e., magma pathways and reservoir locations), which depends on many parameters, including the geologic properties of the crust, magma composition, and magma flux at both the local and regional scales. While understanding magma system structure is complex, new seismic methodologies that allow for the recovery of complementary structures are critical for comparative study. This project will consist of a systematic, multiscale seismic imaging analysis to understand how the structure of the Cascades magmatic arc varies below volcanic centers at both the local and regional scale. The researchers will apply adaptive common conversion point stacking, the joint inversion of receiver function and surface wave data, and the newly developed Ps-P tomography technique, which are all sensitive to the 3D shear-wave velocity structure of the Earth. Detailed, local models will be created at nine individual volcanoes along the arc and will be put in the context of regional-scale arc imaging. These methodologies will image the structure of the trans-crustal magmatic system below individual Cascade volcanic centers, as well as variations in the regional lithospheric architecture, and will be interpreted in the context of tectonic, petrologic and geochemical characteristics. This project will train three graduate students and one undergraduate student in geophysical analysis and research skills, while generating publicly available K-12 educational content. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.