Thickness distribution of a cooling pyroclastic flow deposit on Augustine Volcano, Alaska: Optimization using InSAR, FEMs, and an adaptive mesh algorithm

Pyroclastic Flow Deposits and InSAR: Analysis of Long-Term Subsidence at Augustine Volcano, Alaska

“…A summary of the available values is presented in Table 2. Our estimates of thickness and volume for 1986 compare well to the 1986 topographic map and observations reported by Swanson and Kienle [64], but differ more significantly from the results modeled by Masterlark et al, [20]. Given the observations of dome growth by Swanson and Kienle [64] and Waitt and Begét [28], however, it seems fair to attribute differences in maximum thickness, particularly in the area proximal to the summit, to andesitic dome growth rather than PFDs alone.…”

“…Given the observations of dome growth by Swanson and Kienle [64] and Waitt and Begét [28], however, it seems fair to attribute differences in maximum thickness, particularly in the area proximal to the summit, to andesitic dome growth rather than PFDs alone. Differences in volume are likely due to uncertainties of the finite element model used by Masterlark, et al, [20]. While these uncertainties are not numerically specified, model runs with different initial parameter settings resulted in PFD volume estimates ranging from 9.9 × 10 6 m 3 to 5.7 × 10 7 m 3 encompassing our result.…”

“…They also report that a post-eruption topographic map, prepared from aerial photographs taken on 9 September 1986, indicated that dome elevation had increased by~26 m between 1976 and the close of the 1986 eruption (consistent with Waitt and Begét's observation, between 1992 and 2003, of a 1986 andesite dome forming a prominent part of the summit area [28]). More recently, a finite element model developed by Masterlark et al, [20], predicted PFDs with a mean thickness of 9.3 m, a maximum of 126 m, and a volume of 2.1 × 10 7 m 3 (0.021 km 3 ); Masterlark et al, similarly report a total PFD volume of 9.9 × 10 6 m 3 (~0.01 km 3 ) estimated by differences in DEMs. A summary of the available values is presented in Table 2.…”

“…We are able to pretermit the effects of compaction as a cause of persistent subsidence, because such effects last as little as hours or days after emplacement [19,54], while thermoelastic contraction persists for years [20]. Our consideration of poroelastic compaction is therefore limited to the period immediately after emplacement (Equation (8)).…”

“…Obtaining data from direct observation of pyroclastic emplacement may be hampered by continuing volcanic activity, remote locations, arduous terrain, and other obstacles. Numerical modeling has proven highly effective in estimating deformation, particularly when geometric data, such as deposit thickness from repeated DEMs, are unavailable [20]. Modeling, however, may require significantly simplifying assumptions, and be valid only for individual field situations [66].…”