Understanding the rhyolitic magma system beneath Laguna del Maule, Chile: A Seismic Investigation

Monday, 8 January 2018: 17:25
Salon Quinamavida (Hotel Quinamavida)
Ninfa L Bennington1, Clifford H Thurber2, Crystal Wespestad1, Carlos Cardona Sr.3, Bethany Vanderhoof1, Xiangfang Zeng1, Federica Lanza1, Glyn Williams-Jones4, Craig Miller4, Katie M Keranen5 and Bradley S Singer6, (1)University of Wisconsin Madison, Geoscience, Madison, WI, United States, (2)University of Wisconsin-Madison, Geoscience, Madison, WI, United States, (3)University of Concepcion, Concepcion, Chile, (4)Simon Fraser University, Burnaby, BC, Canada, (5)Cornell University, Earth and Atmospheric Sciences, Ithaca, NY, United States, (6)University of Wisconsin Madison, Madison, WI, United States
Abstract:
Laguna del Maule is a large, rhyolitic volcanic system straddling the Chile-Argentina border at 36° S. A decade long period of rapid uplift likely reflects intrusion of new magma into a broad shallow reservoir of silicic mush. As part of a large interdisciplinary project supported primarily by the U.S. National Science Foundation Integrated Earth Systems program and the Observatorio Volcanológico de Los Andes del Sur (OVDAS) of SERNAGEOMIN, a temporary array of 48 broadband seismometers has been deployed across the 400 km2 central rhyolite field.

A variety of seismic studies are being carried out using the seismic array data, including body-wave tomography, surface-wave tomography (from ambient noise and earthquake data), attenuation tomography, teleseismic tomography, receiver function analysis, seismic interferometry, and focal mechanism and moment tensor determination. The main focus of these studies is to identify the magma reservoir beneath Laguna del Maule and characterize its dimensions and properties.

Progress on these seismic studies is ongoing and we discuss preliminary results from body-wave and ambient noise tomography, and compare those results to results obtained from other geophysical techniques. Initial body-wave (Vp and Vs) and ambient noise (Vs) images suggest the presence of magma storage beneath the SW edge of the lake. Specifically, results from surface wave inversion reveal a low Vs body inferred to represent the upper crustal magma reservoir. This low velocity body is closely aligned with the geodetically-defined center of rapid inflation and a Bouguer gravity low. The Bouguer gravity low is similarly interpreted to reflect crystal-rich magma storage. Given the similarity in Bouguer gravity and seismic velocity model anomaly features and locations, we are also carrying out the joint inversion of these complementary geophysical datasets. Since seismic and gravity data are sensitive to different properties of the subsurface, joint inversion of these two geophysical datasets should yield enhanced images of magma storage relative to separate inversion.

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