Earthquake Report: Nikolski!

As I was writing my page on the 1964 Great Alaska Earthquake (here), there was a M 5.7 earthquake along the Aleutian Trench east of the Amlia fracture zone. Here is the USGS web page for this earthquake. The region around the AFZ is quite active, with the most recent series of earthquakes this month. Here is my earthquake report on those earthquakes.
I put together a quick earthquake report poster posted below. I include the USGS moment tensor. More on the tectonics of Alaska can be found in this USGS Open-File Report (Benz et al., 2010).
There is a legend that shows how moment tensors can be interpreted. Moment tensors are graphical solutions of seismic data that show two possible fault plane solutions. One must use local tectonics, along with other data, to be able to interpret which of the two possible solutions is correct. The legend shows how these two solutions are oriented for each example (Normal/Extensional, Thrust/Compressional, and Strike-Slip/Shear). There is more about moment tensors and focal mechanisms at the USGS.

    I include some inset figures.

  • In the upper left corner, I place a map created by Peter Haeussler, USGS, which shows the historic earthquakes along the Alaska and Aleutian subduction zones.
  • To the right of Hauessler’s map, I show a cross section of a subduction zone through the two main parts of the earthquake cycle. The interseismic part (in-between earthquakes) and the coseismic part (during earthquakes). This was developed by George Plafker and published in his 1972 paper on the Good Friday Earthquake.
  • To the right of that is from Saltus and Barnett (2000) shows an oblique cross section of the Aleutian subduction zone that is a part of the “Eastern Aleutian Volcanic Arc Digital Model.’
  • Below the Plafker and Saltus and Bernett figures is a figure from Atwater et al. (2005) that shows the earthquake cycle and how a tsunami can be generated at a subduction zone.
  • In the lower right corner, I include the USGS intensity map.

More Alaska-Aleutian related earthquakes can be found in my earthquake reports posted here.

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