{"id":7555,"date":"2018-08-12T15:11:37","date_gmt":"2018-08-12T23:11:37","guid":{"rendered":"http:\/\/earthjay.com\/?p=7555"},"modified":"2018-08-12T15:11:37","modified_gmt":"2018-08-12T23:11:37","slug":"earthquake-report-northern-alaska","status":"publish","type":"post","link":"https:\/\/earthjay.com\/?p=7555","title":{"rendered":"Earthquake Report: northern Alaska"},"content":{"rendered":"

Well, I awakened shortly after this M 6.4 earthquake hit the northern part of Alaska, along the north Slope, north of the Brooks Range.
\nMy inbox has had a lower frequency of USGS ENS notifications since Kilauea has settled down somewhat. However, today, the aftershocks just keep rolling in. Those who are on the north slope are getting rattled for sure. I have had to reproduce my seismicity maps several times as the epicenters keep getting updated (thanks USGS). The two largest earthquakes are now actually aligned with the west northwest strike of the earthquake.
\nThere are no active faults mapped in the region of today’s earthquakes. There is a series of thrust faults that form the mountains in this area (e.g. the Sadlerochit Mountains). To the north is a Quaternary active fold (the Marsh Creek anticline), however, this structure is too far away to be related to today’s activity.
\nThe interesting thing is that today’s series of earthquakes are strike-slip earthquakes. It is possible that one of these thrust faults has been reactivated as a strike-slip fault (but they are probably dipping too shallow to do this). So, i suspect that these earthquakes are either on an un-mapped active fault or are distributed throughout the region on a variety of different faults (seems more likely, but I would defer to those who are studying the tectonics on the North Slope to be more informed about this). These earthquakes remind me of the 2002 dextral (right-lateral) strike-slip Denali fault earthquake<\/a>. More on the Denali Earthquake can be found here too<\/a>.
\nI include a second poster below that has more details about the regional geology. On this map I include faults and folds from the Alaska Quaternary Active Faults and Folds database (Keohler et al., 2013).
\nBased upon the seismicity, I interpret these earthquakes (at least the ones with mechanisms) as east striking right-lateral strike-slip earthquakes. The historic earthquakes are not as easy to interpret, so I include both nodal plane solutions as being possible. However, if they are related in some way to today’s seismicity, they are probably also right-lateral strike-slip earthquakes.<\/p>\n

Below is my interpretive poster for this earthquake<\/font><\/h2>\n

I plot the seismicity from the past month, with color representing depth and diameter representing magnitude (see legend). I include earthquake epicenters from 1918-2018 with magnitudes M \u2265 3.0 in one version.
\nI plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.<\/p>\n