G015-08
When water meets fire: The Effects of Hydrologically-Related Processes in Long Valley Caldera at Multiple Temporal and Spatial Scales

Monday, 14 December 2020: 16:28
Virtual
Francesca Silverii1, Fabio Sebastiano Pulvirenti2, Emily K. Montgomery-Brown3, Adrian A Borsa4, Andrew J Barbour5 and Wesley Neely4, (1)German Research Institute for Geoscience (GFZ), Potsdam, Germany, (2)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (3)USGS, Volcano Science Center, Menlo Park, CA, United States, (4)Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, United States, (5)U.S. Geological Survey, Menlo Park, CA, United States
Recorded Presentation
Abstract:
Located at the eastern edge of the Sierra Nevada range (SNR),Long Valley Caldera (LVC), California, is a volcanic area experiencing frequent episodes of unrest identified by increased deformation and earthquake swarms. In addition to steady tectonic deformation, seismicity, and caldera inflation, LVC is affected by hydrological deformation at different temporal and spatial scales, controlled/forced by the large amounts of precipitation falling on the adjacent SNR. Instruments measuring deformation in this area, such as Global Navigation Satellite System (GNSS), may therefore record the superimposed effects of tectonic and non-tectonic processes.

We analyze the non-tectonic deformation affecting the LVC region and the adjacent SNR by combining data from permanent GNSS sites and hydrological records. The vertical and horizontal components of GNSS displacement show a clear correlation with hydrological trends at both multiyear and seasonal time scales.

At the seasonal timescale, deformation is largely controlled by the response to hydrological surface loading. However, several GNSS sites, mainly clustered in the south/south-western rim of LVC, show anomalous horizontal deformation not explainable as an elastic response to surface load. This is also the area where most of the recharging of the LVC hydrothermal system occurs and where runoff-induced seismicity has been identified. Based on the shape and timing of the seasonal deformation, and its temporal correlation with runoff and shallow seismicity rates, we hypothesise that the signals at these GNSS sites reflects poroelastic deformation in response to surface water recharge into SNR slopes.

In late 2011, the latest episode of inflation began, while the Western US was affected by highly variable climatic conditions with alternations between high precipitation in 2010–2011 and 2017–2018 and a severe drought between 2012 and 2016. We show the effect of this multiyear hydrological trend on the GNSS records in LVC. We apply a decomposition method to isolate inflation-related signals from the effect of this hydrological forcing. Finally, we invert inflation signals using a 3D numerical model to study the evolution of the recent inflation episode and assess the influence of topography and realistic heterogeneous material properties.

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