Collaborative Research: High resolution passive seismic imaging beneath Valles caldera

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The Valles caldera is one of three supervolcanoes in North America and has a long history of volcanism with documented magma flows as recent as ~70,000 years. Seismic imaging allows visualization of volcanic subterranean structures by using seismic waves in a similar way ultrasound sonography in medical imaging. Seismic imaging of the Valles Caldera was lacking until recently, which in turn has hindered estimate of melt volumes, melt extent, and understanding of the plumbing system. A joint University of Texas at El Paso (UTEP)/University of New Mexico (UNM) deployment in 2019 resulted in a 97-seismometer line crossing the entire caldera for 1 month. A primary objective of this initiative is to resolve the spatial extent and concentration of melt under the caldera, with other standing questions including the depth of any magma body underlying the dome, the thickness of intra-caldera fill and fractured basement blocks, and the nature of the crust/mantle boundary. Using cutting edge techniques, researchers probe and unveil the subterranean magmatic system of the volcano and foster a collaboration between UTEP and UNM, two minority serving institutions. The outcomes of this project improve earthquake and volcanic hazard assessment in the region, and support the training of graduate and undergraduate students from underrepresented minorities in science. The Valles caldera, a Quaternary-active supervolcanoes, is the textbook example of a resurgent caldera. It has largely escaped seismic scrutiny in the past two decades. Here the researchers probe the magmatic system beneath Valles caldera. They quantify the spatial extent of melt structures, the depth and emplacement of scattering boundaries, and assess the assumed aseismic nature of the caldera system. Ambient noise seismic interferometry is leveraged to estimate dispersion curves for long period Rayleigh and Love waves; these will be jointly inverted in a transdimensional Bayesian scheme with receiver functions, H/V ratios, and noise autocorrelations. The goal is to accurately estimate velocity structures under the Valles caldera. Targets include bounding the spatial extent and concentration of melt through shear-wave velocity and Vp/Vs estimates, depth to magmatic structures and caldera fill under the resurgent dome through scattered wave analysis, and detection and location of any local seismicity that may reveal magma and fluid movements. This project complements sparser long-term seismic monitoring efforts by Los Alamos National laboratory. It serves as an educational primer and complement to frequent geophysics field camps using the caldera as a natural laboratory. Its outcomes improve the assessment of the volcano life-cycle stage and allow better comparison with other Quaternary supervolcanoes.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.