Geodetic Evidence of Magma Beneath the Puna Geothermal Ventures Power Plant, LERZ Kilauea, Hawaii

Precise level surveys of the Puna Geothermal Ventures power plant site have been conducted at 2 to 3 year intervals over the past 16 years following an initial pre-production base-line survey in 1992.

Pre-1992 USGS studies near the plant showed slow general subsidence and this pattern has continued since then. The average rate of subsidence for the first 11 years of the present survey series was 0.71 cm per year (1992- 2003).

It was against this background of subsidence that small but significant upward movements were detected in 2005 in an area approximately 500 m wide directly under the power plant. This positive anomaly had an amplitude of only 0.5 cm but was clearly discernable because of the part-per-million resolution possible with traditional precise leveling. The 13-year (at that time) data set made it possible to interpret this event with confidence.

The cause of the deformation was reported in 2005 to be shallow and localized in comparison to factors contributing to the subsidence of the surrounding area. Subsequent drilling activity penetrated magma beneath the anomaly, providing strong physical evidence that fluid pressure was the probable cause of the anomaly.

https://ui.adsabs.harvard.edu/abs/2008AGUFM.V23A2131A/abstract

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