Hodge, B. and Crider, J., 2007, Characterizing magmatic activity at Mount Baker, Washington with inversion of slope distance data: Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract V11C-743

Characterizing magmatic activity at Mount Baker, Washington with inversion of slope distance data

Surface deformation studies at active volcanoes are used to detect changes to magmatic source regions beneath the volcano. At Mount Baker, Washington, continued elevated gas (CO2 and H2S) and heat flux from fumaroles in Sherman Crater indicate the presence of a degassing magma reservoir. We assess if surface deformation has occurred on Mount Baker during the last quarter century by collecting a modern geodetic data set to compare with previous slope distance measurements acquired in 1981 and 1983 with EDM. Campaign GPS surveys in 2006 and 2007 provide slope distance measurements of all 19 trilateration lines on Mount Baker. These surveys determined that slope distances have predominantly shortened around the edifice at rates of less than 2 mm/yr. The greatest slope length change detected (HDLY-RSVT) is -17 4 ppm on the northern flank of the volcano. We fit a strain model to the weighted slope change data using a nonlinear least-squares regression to characterize a two dimensional surface strain tensor. These results indicate contractional strain centered near the crater with and aerial dilation rate of less than 0.5 microstrain/yr. We also use these data to invert source parameters for a spherical magma source at depth to provide estimates of net volume and mass change of the magma reservoir. The inversion results are analyzed in conjunction with microgravity and gas flux data to better understand the current magmatic quiescence at Mount Baker.