Deflation-inflation events | John Seach


Deflation-inflation events at Kilauea volcano in Hawaii are caused by changes in a secondary magma chamber east of Halemaumau Crater at about 750 m below ground level. This secondary magma chamber produces episodic deformation events.

Deflation-inflation events typically have the following features:

1) In the first phase, tiltmeters surrounding Kilauea caldera record slow deflation centered at the Halemaumau magma chamber that persists for about 24 hours.

2) The second phase begins as the slow deflation abruptly gives way to rapid inflation, which is centred at Halemaumau magma chamber. The inflation phase is short-lived, lasting about 20 minutes.

3) In the final phase, tiltmeters record exponentially decaying deflation, lasting from 8 to 20 hours, which returns the final tilt close to pre-event levels. The seismicity during deflation-inflation events is dominated by bursts of volcanic tremor at the onset of the inflationary phase.

The events are caused by an interruption in magma supply. At the onset of the interruption, deflation begins at the summit as magma continues to exit the system through flank vents at Pu`u `O`o. When the interruption ends, rapid inflation occurs as the accumulated and over-pressurized magma below the locus of interruption surges up into the shallow magma system.

From the duration of the initial deflation and from its size, it is estimate the magma supply rate at Kilauea volcano into the shallow system to be (~ 5-10 x 105 m3 per day).

From the instantaneous volumetric inflation rate and the lag time between inflation at the summit and inflation at Pu`u `O`o cone, it is estimated the approximate radius of the connecting magma conduit to be 2 m.