Geophysical Investigations of Southcentral Alaska

Felix Ziwu Dziedzorm, University of Texas at El Paso

Abstract

The Castle Mountain Fault (CMF) is the closest (<50 >km) active fault to Anchorage, Alaska and is known to be capable of producing earthquakes of magnitude 7.0 – 7.1. While several mapping and trenching studies have been conducted along the CMF, geophysical investigations along the fault zone have been limited. We use over 700 recently collected, closely spaced gravity observations, in addition to existing regional gravity, aeromagnetic, seismic reflection, well log data, and geologic information, to develop new 2D models of the deeper structure of the CMF system. We developed four 2D integrated forward models across the Castle Mountain Fault. These models indicate differences between the western and eastern segments of the Castle Mountain Fault. The models show a thick sequence of Tertiary to Mesozoic sediments overlying the Peninsular terrane basement at varying depths within the area. We identified two main intrusive granitic rocks based on the varying susceptibilities. These granitic rocks share a possible fault contact with the Mesozoic sedimentary rocks. The model also shows that the CMF cuts through the Mesozoic sediments at depth. These rocks can create strong coupling along the fault and with the decreasing eastward angle of subduction, it is highly for fluid migration to the eastern edge of the subducting Yakutat microplate. Seismic events plotted along the profiles supports the Holocene motion along the western CMF (WCMF) and indicates a deeper extent of the CMF into the crust. The eastern CMF shows high rate of deformation based on the structures associated with the Mesozoic rocks.

Subject Area

Geophysics

Recommended Citation

Dziedzorm, Felix Ziwu, "Geophysical Investigations of Southcentral Alaska" (2018). ETD Collection for University of Texas, El Paso. AAI13422300.
https://digitalcommons.utep.edu/dissertations/AAI13422300

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