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InSAR observations of deformation associated with new episodes of volcanism at Kilauea volcano, Hawai`i, 2007

Michael Poland(1)

(1) US Geological Survey, PO Box 51, Hawaii National Park, HI 96718-0051, United States


Kilauea volcano, on the Island of Hawai`i, has been erupting almost continuously from vents on the east rift zone (ERZ) since 1983. The last major pause in the eruption followed a small dike intrusion in the upper ERZ in 1999, and since that time the effusion of lava has occurred without significant interruption. Starting in mid-2007, the long-lived eruption experienced a major change in the pattern of activity.

The events of mid-2007 can be traced back to late 2003, when Kilauea began to inflate due to an inferred increase in magma supply to the shallow magmatic system. By May 2007, the caldera had uplifted by about 30 cm and extended by about 55 cm relative to mid-2003. On May 24, two M4+ earthquakes occurred on the south caldera bounding faults, probably in response to the inflation. On June 17, the caldera abruptly subsided by over 12 cm as summit magma fed an intrusion in the upper/middle ERZ that eventually resulted in a small eruption on June 18/19. Magma stored beneath Pu`u `O`o, the dominant eruptive vent since January 1983, was also diverted to the intrusion, as suggested by collapse of the cone in the days after June 17. Following the intrusion, lava returned to Pu`u `O`o on July 1-2, but the collapse apparently caused a reorganization of the magma plumbing system there. In the early morning of July 21, eruptive fissures opened on the east flank of Pu`u `O`o and propagated 2 km downrift within a few hours. The easternmost fissure continues to erupt as of mid-September.

An abundance of look angles from ENVISAT’s ASAR instrument has allowed for the construction of several independent interferograms that span these events. Surface deformation associated with the May 24 earthquakes, June 17-19 intrusion/eruption, and July 21 fissure eruption is obvious in these interferograms. Results spanning the June 17-19 intrusion/eruption suggest that the dike that fed the eruption was deeper to the west and shallowed to the east, towards the eruption site. A lack of significant deformation around Pu`u `O`o in the interferograms indicate that magma storage beneath Pu`u `O`o is shallow, probably less than 1 km deep. The shallow depth of Pu`u `O`o’s magma plumbing system is further supported by deformation visible in interferograms spanning the July 21 fissure eruption, which show very localized deformation around the fissures, indicating magma transport close to the surface. Two magma storage areas in Kilauea’s summit region can be identified by InSAR as feeding intrusive and effusive activity in mid-2007. Deflation of a shallow storage area about 1 km beneath Halema`uma`u crater dominated the summit deformation field during the June 17-19 intrusion/eruption, while a deeper reservoir beneath the south caldera has deflated at a relatively constant rate during eruptive activity from the July 21 fissure system.


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry