Inflation of Kilauea Along the Southwest Rift Zone in 2006

We report on InSAR and GPS results showing the first crustal inflation along the southwest rift zone at Kilauea volcano in over 30 years. Two independent interferograms (May 2 to August 2, 2006 and June 22 to Nov 7, 2006) from the ALOS PALSAR instrument reveal domal uplift located southwest of the main caldera. The uplift is bounded on the northeast by the caldera and follows the southwest rift zone for about 12 km. It is approximately 8 km wide. We use data derived from permanent GPS stations to calibrate the InSAR displacement data and estimate uplift of 8.3 cm during the first interferogram and 8.7 cm during the second with volumes of 2.8x106 m3 and 2.4x106 m3 respectively. The earthquake record for the periods before, during, and after inflation shows that a swarm of shallow earthquakes (z < 5 km) signaled the beginning of the uplift and that elevated levels of shallow seismicity along the rift zones occurred throughout the uplift period. GPS data indicate that the inflation occurred steadily over nine months between mid-January and mid-October, 2006 making injection of a sill unlikely.