Utility of aeromagnetic studies for mapping of potentially active faults in two forearc basins: Puget Sound, Washington, and Cook Inlet, Alaska

Abstract

High-resolution aeromagnetic surveys over forearc basins can detect faults and folds in weakly magnetized sediments, thus providing geologic constraints on tectonic evolution and improved understanding of seismic hazards in convergent-margin settings. Puget Sound, Washington, and Cook Inlet, Alaska, provide two case histories. In each lowland region, shallow-source magnetic anomalies are related to active folds and/or faults. Mapping these structures is critical for understanding seismic hazards that face the urban regions of Seattle, Washington, and Anchorage, Alaska. Similarities in aeromagnetic anomaly patterns and magnetic stratigraphy between the two regions suggest that we can expect the aeromagnetic method to yield useful structural information that may contribute to earth-hazard and energy resource investigations in other forearc basins.

Interpretation of gravity and magnetic data and development of two-dimensional cross-sectional models for the Border Ranges fault system, south-central Alaska

“…Magnetization values used in the 2DGAM models were based on measured magnetic susceptibilities for the Cook Inlet (Altstatt et al, 2002;Saltus et al, 2005;Saltus et al, 2007) and Talkeetna Mountains regions (Sanger and Glen, 2003), and geophysical magnetic surveys covering the Kenai Peninsula (Table 1) (e.g., Burns, 1982;Saltus et al, 2001). Altstatt et al (2002) classifi ed magnetic source rocks into three groups based on susceptibility measurements, including low (<0.01 SI), moderate (0.01-0.10 SI), and high (>0.10 SI) magnetic sources.…”

“…Note: Data source abbreviations: NP-calculated from the Nettleton-Parasnis inversion method (Mankhemthong et al, 2012); FV-converted from seismic tomography data (Fisher and von Huene, 1984); Y-converted from seismic tomography data (Ye et al, 1997); EP-converted from seismic tomography data (Eberhart-Phillips et al, 2006); HS-measured from rock hand samples; DL-determined from density logs; SH-based on Saltus and Haeussler (2004); SG-based on Sanger and Glen (2003); A-based on Altstatt et al (2002); Sa-based on Saltus et al (2005); CM-based on Carlson and Miller (2003); Sb-based on Saltus et al (2007).…”

Previously unrecognized regional structure of the Coastal Belt of the Franciscan Complex, northern California, revealed by magnetic data

“…Aeromagnetic data have been used to map large, regional crustal structures, such as crystalline basement, in subduction zones (Grantz et al, 1963;Finn, 1990); only in the past decade or two have advances in measurement and navigation technology, data processing, and interpretational methods made it possible to investigate structures such as faults and folds within the overlying sedimentary sequence in settings such as the forearc (Saltus et al, 2005). Our study is the fi rst that we know of that maps and analyzes shallow struc-ture within an accretionary prism using detailed aeromagnetic data.…”

Structure and evolution of Cenozoic arc magmatism on the Antarctic Peninsula: a high resolution aeromagnetic perspective

“…Here we use recently acquired high resolution aeromagnetic data over Adelaide Island, on the western margin of the AP (Figs 1 and 2), to investigate the processes occurring along the arc/forearc boundary. High resolution aeromagnetic data has elsewhere been used to reveal tectonic structures in forearc regions (Ponce et al 2003;Saltus et al 2005), the geometry of arc magmatic intrusions (De Ritis et al 2010), and tectonic and magmatic patterns in rift systems formed along the reactivated margins of older magmatic arc terranes (Ferraccioli et al 2005). We apply digital enhancement, 2-D modelling and 3-D inversion to the new magnetic data in order to reveal the structure of the AP arc/forearc boundary.…”