A Principal Component Analysis of Hawaiian Volcanoes Deformation

We use Principal Component Analysis (PCA) with mode rotation (Kawamura and Yamaoka, 2006) to analyze ground deformation at Kilauea and Mauna Loa volcanoes, Hawaii. A changing pattern of deformation at the summit and flanks of Mauna Loa, revealed by 13 years (1996-2008) of campaign GPS measurements, was analyzed. Two modes of deformation can explain ~98% of the data at Mauna Loa. The first mode records summit inflation which can be modeled by an inflating dike and a Mogi source ~6 km beneath the summit caldera. Summit deformation as revealed by the temporal mode does not begin until 2002, and has recently slowed. The second mode records flank deformation which can be modeled by slip on the basal décollement between Mauna Loa and Kilauea. Flank deformation occurs between 1996 and 2002 after which deformation of the flank ceases. The lack of flank deformation after 2002 suggests volcanic spreading at Mauna Loa is not steady and may be decoupled from summit activity. Eleven years (1998-2009) of continuous GPS data at Kilauea were analyzed. We find modes of deformation at Kilauea which represent episodic east rift zone intrusions, movement of magma beneath the summit and rift zones, and motion of the south flank associated with slow-slip events. The spatial density of stations is insufficient to distinguish individual events (such as the 1999 and 2007 intrusions) spatially, but these events are recorded in the temporal modes. Principal component analysis with mode rotation is a useful tool which can illuminate deformation due to multiple sources and improve detection of subtle transient events.