FLAGSTAFF, Ariz. (AP) - An Arizona earthquake expert is trying to piece together what caused a 4.7 magnitude quake that rattled plates and shook pictures in the Flagstaff area last November.
The quake is puzzling because it ran in a northeasterly direction, while most other quakes in the area have been triggered by faults that trend almost northwesterly, said Dave Brumbaugh, director of the Arizona Earthquake Information Center at Northern Arizona University, where Brumbaugh is also a geophysics professor.
Brumbaugh said it’s also interesting that the earthquake’s foreshock and half of its approximately 20 aftershocks occurred on fault planes perpendicular to the main quake.
The Arizona Daily Sun (https://goo.gl/uFd0GJ) reported that the November quake was the strongest felt in Flagstaff since a 5.3 magnitude quake in 1993.
Brumbaugh said one possibility is that there is a previously unrecognized fault in the area. If that’s the case, it would need to be considered in the earthquake hazard calculations for the area, Brumbaugh said.
He said another possibility is that the November quake was connected to the already known Oak Creek fault. However, that would be curious because that fault runs north-south, which doesn’t align with the northeast trend of the 2014 earthquake, Brumbaugh said.
Brunbaugh said he hopes to spend this summer doing further research to map the fault surface slippage that caused the November earthquake.
But right now, there’s “nothing we can point to on a map and say, ’This must be it,’” he said.
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