Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations

Bulletin of Volcanology
By: , and 

Links

Abstract

Uplift of a broad area centered ~6 km west of the summit of South Sister volcano started in September 1997 (onset estimated from model discussed in this paper) and was continuing when surveyed in August 2006. Surface displacements were measured whenever possible since August 1992 with satellite radar interferometry (InSAR), annually since August 2001 with GPS and leveling surveys, and with continuous GPS since May 2001. The average maximum displacement rate from InSAR decreased from 3–5 cm/yr during 1998–2001 to ~1.4 cm/yr during 2004–2006. The other datasets show a similar pattern, i.e., surface uplift and extension rates decreased over time but deformation continued through August 2006. Our best-fit model to the deformation data is a vertical, prolate, spheroidal point-pressure source located 4.9–5.4 km below the surface. The source inflation rate decreased exponentially during 2001–2006 with a 1/e decay time of 5.3 ± 1.1 years. The net increase in source volume from September 1997 to August 2006 was 36.5–41.9 x 106 m3. A swarm of ~300 small (M max = 1.9) earthquakes occurred beneath the deforming area in March 2004; no other unusual seismicity has been noted. Similar deformation episodes in the past probably would have gone unnoticed if, as we suspect, most are small intrusions that do not culminate in eruptions.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations
Series title Bulletin of Volcanology
DOI 10.1007/s00445-009-0296-4
Volume 71
Year Published 2009
Language English
Publisher Springer
Contributing office(s) Cascades Volcano Observatory, Volcano Hazards Program
Description 20 p.
First page 1091
Last page 1110
Country United States
State Oregon
Other Geospatial Cascade Mountains