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Inversion models, Iliamna Volcano, Alaska June 2012

Metadata Updated: October 28, 2023

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 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 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.
Deterministic laterally and spatially constrained inversions of the processed airborne electromagnetic data were developed using the AarhusINV code (Auken et al. 2014, implemented in Aarhus Workbench software. Spatially constrained inversion was used over the main survey grid area and laterally constrained inversions were used for transit lines east of the main grid. Inversion parameters were selected by running a series of test models with varying starting model resistivity values, layer discretization, horizontal/lateral constraints, and other inversion parameters. A smooth 40-layer fixed-depth inversion model was developed with layer thickness increasing with depth (see model data for exact thicknesses). Moderate vertical and lateral constraints on resistivity were used with values of 2.0 and 1.5, respectively. An automatically determined starting model was used. Sensor altitude was treated as a free parameter after the 5th iteration. The final model parameters described above were selected because they best represented the physical understanding of the system and minimized data misfit. The data provided include spatially constrained and laterally constrained inverted resistivity models and plotted depth sections along all flight lines. Digital data are described in the data dictionary; additional details regarding data inversion are described in the metadata processing steps.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date June 1, 2023
Metadata Updated Date October 28, 2023

Metadata Source

Harvested from DOI EDI

Additional Metadata

Resource Type Dataset
Metadata Created Date June 1, 2023
Metadata Updated Date October 28, 2023
Publisher U.S. Geological Survey
Identifier USGS:5d485fd5e4b01d82ce8ddc12
Data Last Modified 20200827
Category geospatial
Public Access Level public
Bureau Code 010:12
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Harvest Object Id a6185ccd-2e13-4ee0-a71d-bbc7aaf11d0a
Harvest Source Id 52bfcc16-6e15-478f-809a-b1bc76f1aeda
Harvest Source Title DOI EDI
Metadata Type geospatial
Old Spatial -153.1698,59.9766,-152.6403,60.1053
Publisher Hierarchy White House > U.S. Department of the Interior > U.S. Geological Survey
Source Datajson Identifier True
Source Hash 43f6bf56009b6e358b8c78b53d7edd5387f5eb0b55537213f9ca8edcbbd0127b
Source Schema Version 1.1
Spatial {"type": "Polygon", "coordinates": -153.1698, 59.9766, -153.1698, 60.1053, -152.6403, 60.1053, -152.6403, 59.9766, -153.1698, 59.9766}

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