USGS - VHP InSAR Research Group

PROJECT ABSTRACT

Interferogram showing uplift about 3 miles west of South Sister; Interferogram by C. Wicks

InSAR

This site provides mostly nontechnical information about InSAR, an exciting new remote-sensing technique used to study, among other things, volcanoes and earthquakes. InSAR stands for Interferometric Synthetic Aperture Radar. Satellites record images of the Earth's surface, and these images can be combined to show subtle movements of the ground surface, called deformation.

InSAR is a proven technique for mapping ground deformation using radar images from Earth-orbiting satellites. InSAR greatly extends the ability of scientists to monitor volcanoes because, unlike other techniques that rely on measurements at a few points, InSAR produces a spatially complete map of ground deformation with centimeter-scale accuracy without subjecting field crews to hazardous conditions on the ground. This project combines InSAR results with those from other geodetic techniques including the Global Positioning System (GPS), borehole sensors such as dilatometers and tiltmeters, and precise leveling to characterize ground deformation at volcanoes in space and time. The resulting data help to constrain models of the causes of volcanic unrest, which in turn aids in the assessment of short-term volcano hazards. More detail can be found by checking out the InSAR Fact Sheet: Monitoring Ground Deformation from Space by Rosalind L. Helz.

The Research Group

The InSAR Research Group is composed of many scientists in various locations for the purpose of studying ground deformation. Find out who they are at the Group Members page. Learn more about what they do from information posted on the InSAR Research Results page.

Learn more about InSAR.

Other methods for monitoring ground deformation:
EDM | Tiltmeters | GPS

What's new?

Research:

New InSAR Study of Aleutian Arc Volcanoes
Zhong 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.

InSAR Evidence for Spokane Fault
In 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.
Paper

Also:

Find out a little more about each InSAR Group Member here.
InSAR Fact Sheet: Monitoring Ground Deformation from Space by Rosalind L. Helz and Figures from the Fact Sheet
Current update of Mt. St. Helens activity.
Mt. St. Helens is at Alert Level NORMAL; Aviation Color Code GREEN. (Click here for info on these levels.)
Extended research information can be found at the InSAR Research Results page.

Website:

Check out the new personal pages for each InSAR Group Member.
Email the Webmaster with any comments you want to share about the website.