I’m most interested in surface deformation monitoring which is why I chose this case study. My interest is interferometric synthetic aperture radar, but GPS stations are the primary method of tracking surface movement at volcanoes currently. Compared to InSAR, GPS measurements are accurate and highly reliable. However, these are expensive to maintain and only provide point data. There are only three deformation monitoring stations on Okmok (they are shown on following hazard map). The advantage of InSAR is that it provides regional information. The downside of course is that this technology is relatively new and the processing algorithms needed to extract this data are still maturing.
Beget, J.E., Larsen, J.F., Neal, C.A., Nye, C.J., and Schaefer, J.R. Preliminary volcano-hazard assessment for Okmok Volcano, Umnak Island, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 2004-3, 32 p., 1 sheet, scale 1:150,000. 2005.
The following image shows the progressive InSAR deformation time series retrieved from two different TerraSAR-X tracks after the 2008 eruption (Qu et al., 2015). Each image subsequent image is cumulative, where reds correspond to uplift and blue to subsidence. The gray relief map shows through in many areas because the pixels decorrlated between the image aquisitions, so these areas can’t be reliably tracked. Nonetheless, there are some pixels in the caldera that are coherent and show significant deformation. Considering this is following the 2008 eruption, the pattern of uplift at the eastern part of the caldera is as expected. The magma recharge started very soon after the eruption. I will be interested to see how this trend continues until the next eruption and at which maximum deformation relative to 2008 that this happens.
Qu, F.; Lu, Z.; Poland, M.; Freymueller, J.; Zhang, Q.; Jung, H.-S. Post-Eruptive Inflation of Okmok Volcano, Alaska, from InSAR, 2008–2014. Remote Sens. 2015, 7, 16778-16794.