Magnetotelluric imaging of the Kilauea Volcano, Hawaii

Abstract

A collaborative effort has been undertaken between Lawrence Berkeley National Laboratory, Sandia National Laboratories, the USGS Hawaiian Volcano Observatory, and Electromagnetic Instruments to study the Kilauea volcano in Hawaii using the magnetotelluric (MT) technique. We present results from the first phase of data acquisition, recorded in August 2002, where 33 MT sites over the southwest and east rift zones were acquired. Good to excellent quality data were obtained even in the harshest conditions, such as those encountered on the fresh lava flows of the eastern rift zone, where electrical contact resistances are extremely high. Electrical conductivity anomalies resulting from two dimensional inversion of sites, sorted into profiles, had a high degree of spatial correlation with previously published seismic velocity anomalies observed around the Kilauea caldera. In particular we were able to map the active magma in the East Rift Zone (ERZ) beneath currently active vents, as well as the upper portions of the magma conduit to the mantle. Active fault zones imaged by velocity tomography as low velocity zones tie to low resistivity zones on inverted MT lines. We have also undertaken a three dimensional (3D) MT model study of the volcano, island and ocean, to better access the role these features play in the observed MT measurements. Results from 3D model studies lend confidence to the data sensitivity of the magmatic structure beneath the volcano, and our ability to properly model island topography and coastal effects