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Alaska megathrust 1: Seismicity 43 years after the great 1964 Alaska megathrust earthquake

Li, Jiyao et al.

Journal of geophysical research. Solid earth. Volume 118:Issue 9 (2013); pp 4861-4871 -- John Wiley & Sons Inc

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  • Title:
    Alaska megathrust 1: Seismicity 43 years after the great 1964 Alaska megathrust earthquake
  • Author: Li, Jiyao;
    Abers, Geoffrey A.;
    Kim, YoungHee;
    Christensen, Douglas
  • Found In: Journal of geophysical research. Solid earth. Volume 118:Issue 9 (2013); pp 4861-4871
  • Journal Title: Journal of geophysical research. Solid earth
  • Subjects: Earth sciences--Periodicals; Geochemistry--Periodicals; Geomagnetism--Periodicals; Geophysics--Periodicals; Megathrust location--1964 Alaska Mw 9.2 Earthquake--Interseimic period--Yakutat terrane--Microseismicity relocation; Dewey: 551.1
  • Rights: legaldeposit
  • Publication Details: John Wiley & Sons Inc
  • Abstract: Abstract:

    [1] The largest moment release during the 1964 Mw 9.2 Alaska earthquake was on the portion of the megathrust under the eastern Kenai Peninsula and the Prince William Sound. The area is currently locked geodetically and corresponds to where the Yakutat terrane is subducting. In 2006–2009, a seismic array consisting of 34 broadband seismometers was deployed in the region. An automatic algorithm was used to detect 12, 563 local earthquakes using 13 months of data from the experiment. Of these, 9427 good quality earthquakes could be relocated in a joint inversion for hypocenters and velocity structure. They were then relocated by double difference to generate a final catalog of 8308 hypocenters. These microearthquakes delineate a deeper steeply dipping Wadati‐Benioff zone contiguous with an 11 km wide seismic zone dipping at 3° between 20 km and 40 km depth along the 1964 earthquake's rupture zone. Focal mechanisms do not show interplate thrust faulting events, but mostly normal faulting events with T axes generally parallel the slab dip direction, indicating them to be intraslab seismicity. The shallow narrow band of seismicity lies within the subducting Yakutat terrane and right below the thrust zone. Possibly, thrust faulting has not yet resumed yet in this early phase of the earthquake cycle. Thick subducted sediments overlying the Yakutat terrane could also form a large strong contact zone on a relatively smooth plate boundary, which does not favor seismic sliding on small patches but ruptures homogenously in great earthquakes.

    Key Points:

    Relocate 8, 308 microearthquakes with high precision.

    Focal mechanisms do not show interplate thrust faulting events.

    The locked zone of the megathrust fault in this region is completely aseismic.


  • Identifier: System Number: LDEAvdc_100044311130.0x000001; Journal ISSN: 2169-9313; 10.1002/jgrb.50358
  • Publication Date: 2013
  • Physical Description: Electronic
  • Shelfmark(s): ELD Digital store

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