DEFORMATION OF KILAUEA VOLCANO: INSIGHTS FROM INSAR

Volcano-tectonic deformation of Kilauea volcano has been a subject of intensive study for almost 100 years. Until recently, the predominant methods used for measuring surface displacements were repeated surveys (e.g., tilt, triangulation, EDM, leveling, and GPS) of known ground points. Over the past decade, continuous deformation measurements, primarily from GPS and tilt, have provided greater temporal resolution of surface displacements. However, the aerial extent of a deforming region cannot be completely defined from the limited spatial resolution provided by point measurements, and smaller deforming zones may go undetected.

Radar interferometry (InSAR), in contrast, offers excellent spatial resolution of deformation on timescales spanning from one month to several years. Application of InSAR to Kilauea volcano in combination with tilt, GPS, and leveling measurements, has resulted in a more complete characterization of the temporal and spatial patterns of surface motion than was previously available. During 2003-2006, summit deformation at Kilauea was dominated by time-varying inflation. In 2003-2004, uplift was focused within the caldera near Halema`uma`u Crater. The following year, in 2004-2005, the center of uplift had shifted about 1 km south to near Keanakako`i crater. The 2005-2006 period was characterized by rapid uplift concentrated in the south part of the caldera and Southwest Rift Zone. InSAR provides exceptional coverage of these changes, and source models incorporating these results suggest three distinct areas of magma accumulation that were driving the observed deformation.

Application of InSAR to Hawai`i has also resulted in the discovery of several previously unknown areas of deformation. For example, subsidence amounting to 2-4 cm/yr is occurring at several locations on the volcano, including within the north part of Kilauea caldera and at the sites of two former pit craters that were filled by lava during the 1969-1974 Mauna Ulu eruption. The actively erupting Pu`u `O`o vent is subsiding as well, as is the coastal plain above the lava-ocean interface. The mechanisms for these small-scale displacements are not clear and warrant additional study.