On the Potential Duration of the Aftershock Sequence of the 2018 Anchorage Earthquake

Open-File Report 2018-1195



Currently, an aftershock sequence is ongoing in Alaska after the magnitude 7.0 Anchorage earthquake of November 30, 2018. Using two scenarios, determined with observations as of December 14, 2018, this report estimates that it will take between 2.5 years and 3 decades before the rate of aftershocks decays to the rate of earthquakes that were occurring in this area before the magnitude 7.0 mainshock. All of the time estimates have significant uncertainty owing to different scenarios of how the sequence may decrease over time and could also change if a large aftershock occurs. The report also estimates the amount of time after the mainshock until the annual probability of magnitude 5 or greater and 6 or greater aftershocks—which could cause additional damage—decreases to 50, 25, 10, and 5 percent. For instance, the probability of one or more magnitude 6 or greater aftershocks in the following year decreases to 10 percent between 7 and 250 days after the mainshock. The same probability for magnitude 5 or greater earthquakes is reached between 500 and 7,000 days after the mainshock.

Suggested Citation

Michael, A.J., 2018, On the potential duration of the aftershock sequence of the 2018 Anchorage earthquake: U.S. Geological Survey Open-File Report 2018–1195, 6 p., https://doi.org/10.3133/ofr20181195.

ISSN: 2331-1258 (online)

Table of Contents

  • Abstract
  • Introduction
  • 2018 Anchorage Earthquake Aftershock Sequence and Earlier Earthquakes
  • Modeling The Aftershock Sequence
  • Conclusions
  • Acknowledgments
  • References
  • Appendix 1
Publication type Report
Publication Subtype USGS Numbered Series
Title On the potential duration of the aftershock sequence of the 2018 Anchorage earthquake
Series title Open-File Report
Series number 2018-1195
DOI 10.3133/ofr20181195
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description Report: ii, 6 p.
Country United States
State Alaska
City Anchorage
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details