Whats New in InSAR Research?
NEW RESEARCH, RESULTS, and/or PROJECTS
New InSAR Study of Aleutian Arc VolcanoesZhong Lu and Dan Dzurisin processed nearly 12,000 SAR images to produce about 25,000 interferograms for volcanoes in the Aleutian arc, which they analyzed for evidence of surface deformation at each of the arc's 52 historically active volcanoes. They concluded that magmatic, hydrothermal, tectonic, and thermoelastic (cooling) processes all play a role in causing surface deformation at Aleutian volcanoes. Only 13 of the 44 volcanoes where the InSAR observations were adequate showed no evidence of surface deformation of any kind during 1992-2010. Three of those 13 (Cleveland, Shishaldin, and Pavlof) erupted repeatedly without deforming. Surface deformation attributed to magmatic intrusions occurred beneath 21 of the volcanoes with adequate observations, and also in the Strandline Lake area north of Mount Spurr. Lu and Dzurisin attributed shallow-seated subsidence seen at 7 of the 44 well-observed volcanoes to thermoelastic contraction of young volcanic flows or to fluid loss from hydrothermal systems. The most likely cause of deeper-seated deflation at the Fisher, Emmons Lake, and Aniakchak calderas is volatile loss from crustal magma reservoirs. During the ~20 year study period, eruptions occurred at 17 of the 52 historically active Aleutian volcanoes, and InSAR detected some form of deformation at more than 80 percent of the 44 well-observed volcanoes. A book-length manuscript that discusses these results and their implications for magmatic systems beneath Aleutian volcanoes is currently in USGS review.
UPDATE:Zhong Lu and Dan Dzurisin revised a draft of their book InSAR Imaging of Aleutian Volcanoes: Insights into the Behavior of Volcanic Arcs in response to reviewers' comments and submitted the manuscript for USGS approval. Following approval, the book (700+ manuscript pages, 300+ illustrations) will be submitted to Springer-Praxis for publication.
Temporary GPS Networks Deployed at YellowstoneTemporary GPS networks were deployed at the Yellowstone caldera (9 stations) and Three Sisters area (12 stations) to supplement InSAR observations of ground deformation. The networks operate during summer months only to avoid the need for telemetry and winter-hardened stations. They have been deployed each summer since 2008 at Yellowstone and since 2009 at Three Sisters.
InSAR Evidence for Spokane FaultIn 2001 a sequence of earthquakes struck the city of Spokane Washington. Wicks et al. have used InSAR to show that the earthquakes occurred on a shallow thrust fault beneath the city of Spokane. The previously unknown fault, which the authors named the "Spokane Fault", presents a seismic hazard to Spokane that will require further study to better assess the potential.
Wicks, C.; Weaver, C.; Bodin, P.; and Sherrod, B., 2013, InSAR Evidence for an active shallow thrust fault beneath the city of Spokane Washington, USA, J. Geophys. Res. Solid Earth, 118, doi:10.1002/jgrb.50118.
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