Estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar: the 1997 eruption of okmok volcano, alaska

Abstract

Interferometric synthetic aperture radar (InSAR) techniques are used to calculate the volume of extrusion at Okmok volcano, Alaska by constructing precise digital elevation models (DEMs) that represent volcano topography before and after the 1997 eruption. The posteruption DEM is generated using airborne topographic synthetic aperture radar (TOPSAR) data where a three-dimensional affine transformation is used to account for the misalignments between different DEM patches. The preeruption DEM is produced using repeat-pass European Remote Sensing satellite data; multiple interferograms are combined to reduce errors due to atmospheric variations, and deformation rates are estimated independently and removed from the interferograms used for DEM generation. The extrusive flow volume associated with the 1997 eruption of Okmok volcano is 0.154 0.025 km 3 . The thickest portion is approximately 50 m, although field measurements of the flow margin's height do not exceed 20 m. The in situ measurements at lava edges are not representative of the total thickness, and precise DEM data are absolutely essential to calculate eruption volume based on lava thickness estimations. This study is an example that demonstrates how InSAR will play a significant role in studying volcanoes in remote areas.

Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 1. Intereruption deformation, 1997–2008

“…Very little volcano-wide deformation occurred during that period, so the stacked interferograms delineate the extent of the subsiding 1997 lava flow. The result is very similar to that derived from the thickness map of Lu et al [2003b].…”

“…[17] Our objective here was to model the source responsible for volcano-wide deformation at Okmok, so we masked the 1997 lava flow from InSAR images before modeling them to avoid any bias from flow-related deformation. A map showing the extent of the 1997 flow can be generated from the 1997 lava thickness map produced by Lu et al [2003b]. Alternatively, we determined the area covered by 1997 lava by stacking interferograms that span 2005-2007.…”

“…The 1997 lava flows traveled about 6 km, partly overriding the 1958 flows, and are generally similar to the a′a′ flows from the 1945 and 1958 eruptions. By differencing preand posteruption digital elevation models (DEMs) that were generated from interferometric synthetic aperture radar (InSAR) imagery, Lu et al [2003b] mapped the threedimensional distribution of the 1997 lava flow. The estimated average and maximum thicknesses of the 1997 flows are 17 and 50 m, respectively.…”

“…The estimated average and maximum thicknesses of the 1997 flows are 17 and 50 m, respectively. The 1997 flows cover about 8.9 km 2 , with an estimated bulk volume of 0.154 ± 0.025 km 3 [Lu et al, 2003b].…”

High‐resolution digital elevation model from tri‐stereo Pleiades‐1 satellite imagery for lava flow volume estimates at Fogo Volcano

“…Precise, quantitative analyses of topographic changes associated with volcanic eruptions provide the means to infer key parameters for the assessment of hazards associated with the volcanic activity (e.g., magma discharge rate in effusive events) [Pinel et al, 2014]. The topographic approach, which constrains the changes in topography by differentiating preeruptive, coeruptive, and posteruptive digital elevation models (DEMs) [Stevens et al, 1999], can nowadays be considered the most suitable method to accurately quantify the volume of new volcanic deposits, especially when data are acquired by spaceborne Earth Observation (EO) platforms [e.g., Lu et al, 2003;Rowland et al, 2003;Bignami et al, 2013;Poland, 2014;Albino et al, 2015;Kubanek et al, 2015;Martino et al, 2015]. These data sets provide densely spaced measurements of heights at relatively high temporal frequency (hours to days, if combined) and meter level vertical accuracy, without the need for direct field measurements.…”