|Region:||Canada and Western USA|
|Measurement method(s):||InSAR, GPS - continuous, GPS - campaign, Levelling, Tiltmeter, EDM|
|Duration of observation:||1932 - 1934, 1980 - 1984, 1991, 1996 - 2000, 2007 - present|
|Inferred cause of deformation:||Uncertain|
|Characteristics of deformation:|
Lassen Volcanic Center, which includes Lassen Peak, first underwent leveling surveys by the U.S Coast and Geodetic Survey in 1932 and 1934. These surveys were repeated by the U.S. Geological survey in 1991, who found no changes larger than the uncertainty in the measurements (Dzurisin, 1999). In 1980-1984 the U.S Geological Survey established and remeasured a trilateration network at Lassen Volcanic Center, measuring slope distances with EDM. Repeat measurements of this network were probably within measurement error (Chadwick et al. 1985).
An ERS-1/2 InSAR survey of the volcano in 1996-2000 indicated up to 10 mm/yr subsidence over a ~40 km diameter area centred 5 km southeast of Lassen Peak (Poland et al. 2004). During this time the EDM network was reoccupied with campaign GPS, which indicated shortening of up to 145 mm suggesting that subsidence is a longer lived process. The cause of this deformation is uncertain but the volume loss is modelled at a depth of 11.6 km and rate of 0.007 km³/yr.
Most recently in 2007-2008, 8 continuous GPS receivers were installed to make up the continuous monitoring network at Lassen Volcanic Center (CalVO website) (http://earthquake.usgs.gov/monitoring/gps/NCalifornia/).
|Reference:||Chadwick, W. W., Iwatsubo, E. Y., Swanson, D. A., and Ewert, J. W. (1985) Measurements of Slope Distances and Vertical Angles at Mount Baker and Mount Rainier, Washington, Mount Hood and Crater Lake, Oregon, and Mount Shasta and Lassen Peak, California, 1980-1984, US Department of the Interior, Geological Survey, Open File Report 85-205.|
|Reference:||Dzurisin, D. (1999) Results of repeated leveling surveys at Newberry Volcano, Oregon, and near Lassen Peak Volcano, California, Bulletin of Volcanology, , 61, pp. 83-91. doi:10.1007/s004450050264.|
|Reference:||Poland, M., Bawden, G., Lisowski, M., and Dzurisin, D. (2004) Newly discovered subsidence at Lassen Peak, southern Cascade Range, California, from InSAR and GPS, American Geophysical Union, Fall Meeting 2004, abstract #G51A-0068.|
|Reference:||USGS California Volcano Observatory (CalVO) website http://volcanoes.usgs.gov/volcanoes/lassen_volcanic_center/lassen_volcanic_center_monitoring_62.html|
View of Lassen Peak from the south. Source: U.S. Geological Survey CalVO website