Building a 3D Seismic Velocity Model for the Gulf of Alaska
Description:
Offshore regions in tectonically active margins such as Alaska or southern California exhibit extreme structural complexity and produce a wide range of earthquake mechanisms and ground motions. A significant challenge in modeling ground motion at coastal cities is the lack of offshore stations near the offshore earthquakes, which poses challenges both for understanding the offshore earthquakes and for imaging the offshore structure. In south-central Alaska, the active collision and accretion of Yakutat microplate beneath North America plate creates an extremely complex regional structure, including low-velocity accretionary strata. The onshore region has been imaged using permanent stations installed during the STEEP project and augmented by stations from the EarthScope Transportable Array. Most of these tomographic models include inherent smoothing that cannot capture the sharp interfaces of the offshore setting. By comparison, the offshore region of the Gulf of Alaska has been studied only with a sparse array of high-resolution 2D velocity models derived from marine studies conducted between the 1980s and 2000s. Here we leverage these 2D models to create experimental 3D velocity models with known geological features, such as a low-velocity accretionary wedge and the Yakutat block. We then perform 3D seismic wavefield simulations of earthquakes and virtual sources derived from ambient noise cross-correlations on our experimental models and three tomographic models from the EarthScope IRIS EMC repository. These simulations provide insights into the complexity of the recorded seismic wavefield, as well as the limitations of our experimental velocity models. The results of this study should enable us to build a comprehensive 3D seismic velocity model for the Gulf of Alaska.
Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone [Poster Session]
Type: Poster
Date: 5/3/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Evans
Student Presenter: No
Invited Presentation:
Authors
Evans Onyango Presenting Author Corresponding Author eaonyango@alaska.edu University of Alaska Fairbanks |
Carl Tape ctape@alaska.edu University of Alaska Fairbanks |
Amanda McPherson ammcpherson@alaska.edu University of Alaska Fairbanks |
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Building a 3D Seismic Velocity Model for the Gulf of Alaska
Category
Structure and Behavior of the Alaska-Aleutian Subduction Zone