Aftershock regions of Aleutian-Alaska earthquakes, 1938–2021

Carl Tape and Anthony Lomax

Journal of Geophysical Research: Solid Earth, 2022

A relocated catalog of 324 aftershocks from 12 earthquakes (1938–2021) along the Aleutian-Alaska megathrust is presented.
The catalog establishes revised aftershock regions, with smaller events (Mw = 7.7–8.2) postdating five larger, earlier events (1938, 1946, 1957, 1964, and 1965).
The aftershock regions provide better resolution of the trench-normal extent of aftershocks, enabling a nuanced view of coseismic slip.

Download published paper here

Supplemental materials

The supplement to the submitted papers, accessible from a link at the bottom here, includes the digitized aftershock regions (as text files, such as for GMT) as well as a summary text file table of the 553 earthquakes analyzed in this study. These two files were also provided within a zenodo collection, listed next.
Aftershock regions of Aleutian–Alaska megathrust earthquakes: digital files [https://doi.org/10.5281/zenodo.6415340]. The aftershock regions are provided in three formats:
- text files (e.g., for GMT or Python) - zenodo
- ArcGIS shape files - zenodo
- kmz file for Google Earth - here (converted from shape files)
Documentation and digital files in support of "Aftershock regions of Aleutian–Alaska megathrust earthquakes, 1938-2021" by Carl Tape and Anthony Lomax: Part A [https://doi.org/10.5281/zenodo.6330285].
Documentation and digital files in support of "Aftershock regions of Aleutian–Alaska megathrust earthquakes, 1938–2021" by Carl Tape and Anthony Lomax: Parts B, C, and D [https://doi.org/10.5281/zenodo.6274313]. Part B includes aftershock regions (text files, shape files) that were georeferenced from three previous studies: Sykes (1971), McCann et al. (1979), and Sykes et al. (1981).

Previous studies of aftershock regions

AGU highlight written by JGR Editor Dr. Agnes Helmstetter

2022 EOS article led by USGS scientists

Aftershock regions for 11 mainshock earthquakes in this study. (image credit: Owen Larson, UAF/GINA)

1964-03-28 Mw 9.2

Mainshock and aftershocks of the 1964-03-28 Mw 9.2 earthquake in south-central Alaska. The large dots, colored by depth, are the relocated maximum likelihood epicenters; the small dots display the probability density function for each epicenter. Dashed lines depict the aftershock regions from Sykes et al. (1981); solid line depicts the aftershock regions from this study. Black lines depict active faults of Koehler et al. (2012). Magenta contours show the subduction interface for Slab 2.0 (Hayes et al., 2018), from 10 to 80 km in 10 km intervals. Thick red line is the trench (Krabbenhoeft et al., 2018).

1938-11-10 Mw 8.3

Mainshock and aftershocks of the 1938-11-10 Mw 8.3 earthquake near southwestern Alaska. The large dots, colored by depth, are the relocated maximum likelihood epicenters; the small dots display the probability density function for each epicenter. Dashed outlines depict the aftershock regions published in Sykes et al. (1981); solid black outlines depict the regions determined in this study, with the 1938 region emphasized. Thick red line depicts the trench plate boundary (Bird, 2003). Magenta contours show the subduction interface for Slab 2.0 (Hayes et al., 2018), from 10 to 80 km in 10 km intervals. Maximum likelihood epicenters for the mainshocks are plotted as stars. Geographic labels include Unga Island (U), Shumagin Islands (S), and Kodiak Island (K).