Two maps of the study region displaying earthquake depth as colored dots.
Earthquakes in the region of the 28 March 1964 magnitude Mw=9.2 earthquake. Dot color represents earthquake depth. Dashed lines depict aftershock regions from Sykes et al. [1981]. Solid lines depict aftershock regions from this study for the 1938 and 1964 megathrust earthquakes, suggesting some overlap of the rupture areas. (a) All events with magnitude Mw ≥ 5.45 from the original GCMT catalog, 1976–2022, (b) relocated shallow thrust events that are within ±100 days of the 1964 mainshock. Credit: Tape and Lomax [2022], Figure 9
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Solid Earth

Between 1938 and 1965, five megathrust earthquakes ruptured the Aleutian-Alaska subduction plate boundary over a length of 3,548 kilometers. Tape and Lomax [2022] revisit these earthquakes, first studied in detail by Sykes [1971], through probabilistic relocation of Mw ≥ 7.7 megathrust earthquakes and their aftershocks. The relocated catalog of 324 events is then used to map the aftershock region of each megathrust earthquake, which reveals the extent of the coseismic rupture.

These aftershock zones differ from previous studies in subtle but significant ways. Several aftershock regions are larger than previously indicated, specifically 1938 and 1964. These results enable a better understanding of how slip occurs along the Aleutian-Alaska subduction zone, either coseismically during earthquake rupture or aseismically by slow slip. The conclusion that aftershock zones of megathrust earthquakes can overlap also has implications for seismic hazard analysis.

Citation: Tape, C., & Lomax, A. (2022). Aftershock regions of Aleutian-Alaska megathrust earthquakes, 1938–2021. Journal of Geophysical Research: Solid Earth, 127, e2022JB024336.

—Agnes Helmstetter, Associate Editor, Journal of Geophysical Research: Solid Earth

Text © 2022. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.