Earthquake Report: Gulf of Alaska UPDATE #2

I thought it would be interesting to see the seismicity with time. Perhaps this could help us learn about the fault sources associated with this earthquake sequence.

I am not sure it worked as some issues cannot be dealt with simply with this visualization.

For example, the locations for these earthquakes may not be resolute enough [yet] to figure out the orientation of the faults at work here. The back projection data are perhaps the strongest evidence for an east-west fault. However, we still have the contradictory sense of motion along the fracture zones at the meso scale… (as revealed in the EMAG2 magnetic anomaly data).

As a reminder, if the M 7.9 earthquake fault is E-W oriented, it would be left-lateral. The offset magnetic anomalies show right-lateral offset across these fracture zones. This was perhaps the main reason why I thought that the main fault was not E-W, but N-S. After a day’s worth of aftershocks, the seismicity may reveal some north-south trends. But, as a drama student in 7th grade (1977), my drama teacher (Ms. Naichbor, rest in peace) asked our class to go stand up on stage. We all stood in a line and she mentioned that this is social behavior, that people tend to stand in lines (and to avoid doing this while on stage). Later, when in college, professors often commented about how people tend to seek linear trends in data (lines). I actually see 3-4 N-S trends and ~2 E-W trends in the seismicity data.

So, that being said, here is the animation I put together. I used the USGS query tool to get earthquakes from 1/22 until now, M ≥ 1.5. I include a couple inset maps presented in my interpretive posters. The music is copyright free. The animations run through twice.

Here is a screenshot of the 14 MB video embedded below. I encourage you to view it in full screen mode (or download it).


  • Here is the seismograph at Humboldt State University, Dept. of Geology. The seismometer is located in the basement of Founders Hall, across from the Geology Dept. office.

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Category(s): alaska, earthquake, education, geology, pacific, plate tectonics, strike-slip, subduction

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