Airborne electromagnetic and magnetic survey data, Iliamna Volcano, Alaska, June 2012

Airborne electromagnetic (AEM) and magnetic survey data were collected during June 2012 along 556 line-kilometers over Iliamna Volcano, Alaska. These data were collected in support of alteration and volcano flank instability mapping as part of the U.S. Geological Survey (USGS) Volcano Hazards Program. Data were acquired by SkyTEM Survey ApS SkyTEM304 system with the Soloy Helicopters Eurocopter Astar 350 B3 and Bell 407 dual-moment, time-domain helicopter-borne electromagnetic system together with a Geometrics G822A cesium vapor magnetometer with Kroum KMAG4 counter. The survey was flown at a nominal flight height of 30 meters (m) above terrain along block-style lines with a nominal spacing of 250 m. The survey was designed to cover the summit and flanks of Iliamna volcano and includes transit lines east of the volcano which provide additional information on nearby structures and glacial thickness and resistivity. There are data gaps near Iliamna’s summit due to poor flight visibility. Data acquisition, minimal processing, and initial inversions were conducted by SkyTEM Survey ApS and described in detail in the contractor’s report. The AEM depth of investigation varied with subsurface resistivity and averaged approximately 338 m. This data release includes minimally processed (raw) AEM, SkyTEM Survey ApS initial processed and inverted data, and unprocessed and processed magnetic data. Shapefile versions of the flight lines and flight area are provided. This release also includes unprocessed and processed magnetic data that have been drift corrected and draped to terrain. Digital data from production flights are provided and described in the data dictionary. Final electromagnetic inversions were carried out in Aarhus workbench and magnetic susceptibility modeling was done using a 3D voxel modeling program. Results of the electromagnetic inversion and magnetic model are both included in this data release.