Monday, November 02, 2015

Black Canyon City Earthquake Sequence



The Arizona Geological Survey (AZGS) and Northern Arizona University operate several seismometers throughout the state.  Using 15 stations, 5 of which are not currently used by the National Earthquake Information Center run by the USGS, AZGS has refined the locations for the foreshock, mainshock and the large aftershock from the November 2nd [using UTC time - using local time, the events were on Nov. 1] Black Canyon City sequence of quakes (Table below).  The M3.2 foreshock was located at approximately 5km north of Black Canyon City at a very shallow depth, between 1-5km.  The mainshock was located approximately 18km NNE of Black Canyon City and occurred at approximately 11km depth.  The largest aftershock an Mw 4.0 occurred only 20 minutes following the mainshock at a depth of approximately 5km.  There have been multiple smaller aftershocks, but there are not enough seismometers close enough to the area of the sequence to accurately locate them.  The closest station is located near Payson at about 65km, with the Wickenburg station being 88km away.  
 

The closest known active fault is the Horseshoe Fault, located 35km SSE of the mainshock.  The Black Canyon City Sequence has not generated a quake large enough to break the surface.  Aftershocks will continue for several months or longer. 

The table below lists the revised locations, and the extent of possible errors in location, horizontally (ERH) and vertically (ERZ).



Mw
Time -UTC
Date
Lat
Long
Depth (km)
RMS
(Seconds)
ERH
(km)
ERZ
(km)
3.2
03:59.33
11-02-15
34.11016
-112.1460
<1 .0="" p="">
0.16
1.05
5.27
4.1
06:29.66
11-02-15
34.23350
-112.12366
11.2
0.07
1.01
3.18
4.0
06:49.32
11-02-15
34.17950
-112.08633
5.19
0.10
0.83
2.77

Post from Dr. Jeri Young, AZGS

4 comments:

  1. I felt nothing. I live in Cordes Lakes (Junction).

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  2. The relative energies of the main quake and the aftershock, judged by integrating the amplitude vs time for each event, as well as the huge "Did you feel it?" difference in responses for each on USGS's website, seem to suggest that the difference in MMI between the two was greater than 0.1. Am I wrong, that these two quakes had to have been more than 0.1 magnitude different?

    Here's my own plot from a vertical sensor in my Tempe garage, paired with U of A's BHZ sensor on the second trace: https://www.dropbox.com/s/ed0n7mkau99zln5/PhoenixQuakes110115.tiff?dl=0

    And here's my seismo (sub-hobby) website: http://general.fastq.com/~stefano/pages/seismic.html

    Feeling this quake gave me a new respect for the instability of the inverted pendulum formed by the concrete tiles on my roof. I saw first hand the danger of that kind of structure in L'Aquila, Italy after their 2009 quake.

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  3. Anonymous4:13 AM

    Hi. I live in Black Canyon City and of course felt two of the earthquakes in this cluster. I did not feel the lesser 3.2 earthquake but felt the other two. I also felt one a few years before this that was 2.8. I knew right away that it was an earthquake.. the second after shock that was 4.0 that I felt seemed to me that it had a higher wave than the later 4.0 earthquake. I am also curious if any studying has been done since this earthquake cluster. Any damage to the rock slides? It seems to me they look like they collapsed more. I need to go hiking up there, but I havent had the time. During coverage of this earthquake I got quite annoyed by all the attention it got from the Phoenix area, and yet here I lived much closer to the quakes.. The energy must have been focused on a hard rock or something to be transmitted so far away.. down into the Phoenix area. Anyways, It was a fun experience. After the second one i felt I wondered if a bigger one was coming or not.. took me quite a few hours ot fall asleep that night :)

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