Monday, December 1, 2014

November 30, 2014 M4.7 earthquake between Sedona and Flagstaff

Last night, a M4.7 earthquake occurred between Flagstaff and Sedona (just west of Munds Park). I hope it was not too scary for my friends and colleagues. It sounds like it got their attention! I agree with Professor Brumbaugh from NAU who said: "It was a large enough earthquake to be felt, but not quite large enough to really get too concerned about" (link).

Arizona Geological Survey colleagues (some ASU alumns!) are responding. Here is a blog entry from Arizona Geology on the event. Here is a nice map from them with better locations:

The USGS shakemap indicates that light shaking is reported from north Phoenix to north of Flagstaff. If you know someone who felt it; tell them to go to that site and record their perceptions.

Here is the seismogram from Tucson:

and if you go to the IRIS page on the eventyou can hear it!

The earthquake occurred in an area where there are some active faults, most notably the Lake Mary fault system south of Flagstaff. Here is the epicenter on a map of USGS Quaternary Active Faults:

Here it is with historic seismicity (from Jeff Lockridge). There was an M3.5 within a few km of this event on November 25, 2014.
Here is the epicenter on the Geologic Map of Arizona:
The epicenter is right on top of the Oak Creek Fault. So it could be associated with that fault, but it would need to be located further east given the eastward dip of the Oak Creek fault. I see that the focal mechanism is available now from the USGS and it is a NE-trending mostly normal faulting event. The Earthly Musings blog has a nice entry on the Oak Creek Fault. Here is the earthquake on a compilation of active faults and earthquakes that I put together:
Here is the PDF. There have been some earthquakes in that area over the years.

Additional links:

I will continue to update as I learn more.