Location of the 29 June Arizona/New Mexico earthquake, northwest of Lordsburg, New Mexico. Image credit: USGS
Sunday’s magnitude 5.2 (M5.2) earthquake on the border between New Mexico and Arizona is, at present, something of an enigma.
With no information available from the USGS as to its cause, this quake north-west of Lordsburg New Mexico is worth looking at possible culprits for this, one of the largest earthquakes to occur in either of the two states.
The Usual Quake Suspects: Tectonics
Most earthquakes are caused by movement along existing faults. States such as California, Oregon and Nevada are affected by the uplift of the Rocky Mountains and by the relative movements of the Pacific and North American plates.
Even in the eastern and central states, natural or human-induced stresses can reactivate ancient faults, with small to medium earthquakes not uncommon. Clear examples of this are found in New Madrid and in the Appalachians.
There are many mapped faults in both Arizona and New Mexico, including a broad zone stretching along the eastern margin of the Rockies from near the town of Hatch, NM, through the Socorro fault zone right the way north to Denver in Colorado.
This is the location of the state’s largest earthquakes to date (the earliest and probably the largest, in 1906, has no assigned magnitude). Arizona’s largest historic earthquake, an M5.6 in 1959, is also probably associated with faulting along the margin of the Rockies.
The 29 June New Mexico/Arizona earthquake, however, seems not to fit this bill. The area is distant from plate boundaries and although there are mapped fault zones, the epicentre of the most recent tremor was not located directly on any of these. The closest faults mapped by the USGS on the real time earthquake map are the two short lengths of the Pearson Mesa faults, around 20km to the west. Nor are there any clues from the maps of past seismicity or seismic hazard.
Volcanoes can cause earthquakes – but not in this case. Image credit: National Parks Service
Whodunnit: Nature or Humans?
Volcanoes also cause earthquakes – and there’s plenty of evidence of volcanicity in both New Mexico and Arizona. But again there’s a problem in pointing the finger. Arizona’s active volcanic fields are far distant to the west and the rest of the state’s volcanoes, along with those in New Mexico, are either long extinct or haven’t erupted for thousands of years.
This doesn’t mean that they can’t – or won’t – erupt, of course. But there’s no evidence to link the most recent earthquake with volcanic activity. In addition, it would certainly be worthy of note if even a currently-active volcano had triggered an earthquake of so large a magnitude.
So was it humans? Human-induced seismicity has been linked to earthquakes in Oklahoma and elsewhere. But the area surrounding the epicentre is not actively or extensively exploited for fracking. Or mining? Again, there’s no obvious candidate – and in both cases, the size of the earthquake is again problematic, with the largest mining-related earthquakes registering around M5 and the largest fracking-related ones possibly slightly smaller (although this area is subject to ongoing research).
New Mexico/Arizona Earthquake Verdict: Not Proven
At the time of writing there’s not enough available information to point the finger conclusively at one cause or another, although the emergence of further data may well shed more light upon the event.
Reviewing the location (at the edge of the Peloncillo Mountains) and depth (5km) of the tremor in the light of geology and economic activity leads to the conclusion that the probable cause of the tremor was slippage along a previously unmapped fault.
As in all the best whodunits – it looks as if it was the obvious suspect all along.
My own personal opinion… I think that the Morenci and Safford mine may be somewhat in blame, I do know that there are some volcanos throught this region that has not been active for many, many years. The mining may be disrupting the volcanos.
Sorry but I find it hilarious that people are trying to blame the mine and storage of acid and explosives….. As a person that works in morenci and actually works all my overtime with the blasting crew there I can say its not cause by the mine. I’ve seen one person say it was caused by the mine using dynamite for blasting at the mine which once again made laugh til I was in tears. First off the mine hasnt used dynamite in years…and yes morenci is a very large mine, it is however, only the second largest open pit mine. North americas largest open pit mine is actually outside of salt lake city in Utah. As for this report Jennifer I think it was very well written and being that both my parents are geologists they actually do believe it was caused by settling of an unmapped fault as well.
What makes you so sure Haarp is shut down? All indications show that they are talking about doing it.
My apologise, but…
The Pearson Mesa Faults are actually 10.7 km to the EAST, not 20 km to West. The nearest one to the west is the Safford Fault Zone and is a distance of 40 km.
Jennifer: Nice article on Saturday night’s 5.2M earthquake. There have been at least 5 measurable aftershocks and one foreshock. There is little drilling and no fracing going on in that part of eastern Arizona. In 1938-39, there were M5+ and M4+ events very near this same locale. US Geological Survey probability models showed a 20% chance of a M5 in the area in a 25-year period.
In short, this sort of seismic behavior is consistent with the Basin and Range Province of eastern Arizona. FYI, we just released online an excellent publication detailing the 1887 N7.5 earthquake that in Sonora, Mexico, about 40 km south of Douglas, Arizona.
http://1.usa.gov/1pEph2q
Mike Conway
Arizona Geological Survey
Tucson, AZ
It was caused by mining in the area. No evidence of a unmapped fault, because there would have been more seismic events over the years.
I enjoyed your article, Jennifer. I have been wondering myself about this enigma of an earthquake.
I grew up in Lordsburg, and I can tell you that, where the earthquake happened, I don’t believe there is any human development at all. And I am surprised that the USGS did record the origin as 31 miles NW of Lordsburg when Duncan, AZ, is much closer to the epicenter. So, I can understand Sheree’s frustration about the origin of the earthquake.
I agree. Thank you. Franklin/Duncan area is within 15 miles from there. But Noone seems to question the inhabitants of my hometown. I’m guessing people can look at a map, but not read the names of the places closest to the events.
OK, i found some more info so I’ll post a followup myself :-)
“Our mechanism for this event was what we call normal faulting,” said Bruce Presgrave, a geophysicist with the U.S. Geological Survey’s National Earthquake Information Center in Golden, Colorado. “It’s kind of typical faulting of the basin and range province mostly associated with the state of Nevada, but Southern Arizona is considered to be part of the basin and range region.”
Quakes of similar magnitude have been felt in the area before, Presgrave said.
“Typically it’s what we call an extensional or spreading section within the North American plate. Most of the faults are nearly vertical faults that are extensional, that are spreading apart a little bit,” he said. “That’s why you get the basin and range region… as the earth gradually spreads in the plate, the valley floors slowly drop down and that’s what we call basin and range,” Presgrave said.
Thanks for a good initial analysis of the quake Jennifer. As you know, they are very rare here, so all us locals are wondering what caused it. I can’t imagine it’s related to the open pit mines in the area as they’ve been here for so long without any other quakes. And there are no military test sites in the area (secret or otherwise), so nuclear testing is out. :) If you get any more info (unmapped fault, volcanic event, etc.) I hope you’ll post a followup.
What about all the quakes in California recently? What about British Columbia, Idaho, Texas. Virginia?
This isn’t a science form – it’s a freak show. And for all of you debunkers and operatives out there – better get familiar with the Nuremberg War Crime Trials. You WILL be tracked down and prosecuted for what you’ve done these past five years. THAT’s what I’m talking about!
Ma’am, can you please enlighten the scientific community (&media) as to map reading & local time zones. Arizona was the location of the epicenter, so legal recording should reflect this- (just east of the town of Safford on hwy 70). Also, Arizona also DOES NOT participate in daylight savings time. So, therefore the actual date & time were Saturday night (28 June, 2014), at approx. 2159 hours (9:59 pm) local time.
As an Arizona native, it’s quite offensive that the reporting is showing “NW of Deming or Lordsburg, New Mexico” (why not declare “SW of New York?”)- Not to mention the day & date are COMPLETELY WRONG! As a follower of good science, I feel this needs rectifying- though I thoroughly enjoyed the rest of your well written article.
p.s. As to the cause…Fracking into the Permian Basin & other sites has been increasing exponentially of late, whereas copper mining in the region has existed for a long time (& doesn’t inject gases underground).
Thanks Sheree – point taken! I shall be more more careful in future.
In my defence, it was the USGS who initially described as NW of Lordsburg, and they also give the time in UTC on their earthquake report; but yes, I’ll be a bit more specific in future. (And thanks for the compliment, by the way.)
Sheree, did you seriously just mention fracking as a possible cause? And specifically fracking in the Permian Basin?? You are sooo concerned with the reported location but are you aware of just how far the Permian Basin is from the location of the epicenter? It would be wise of you to look into the geology of Arizona and New Mexico before you start hopping on the “fracking-is-bad-and-causes-earthquakes” bandwagon.
May I suggest that local Arizona time be used for a local Arizona event? The earthquake was felt in Bisbee, Arizona at 10pm June 28th, not after midnight June 29th.
The USGS is a scientific sight, therefore, reports from them use scientific conventions…such as listing time in UTC. Let the local papers use local times in their reports.
I think there is a lot more going on under the plates than we fully understand. Perhaps all that water down there is trying to work its’ way up. With the right activity, ancient volcanos can revive, new oceans appear, and plates shift to reform new land masses. We know that all of this has happened over eons in gelogic time, yet catastrophic events occur with extreem rapicidy. You did not discuss the possibility of underground nuclear testing.
HAARP you jackasses
HAARP shut down in May 2013.
Was kinda awesome! It does raise some concern due to the mines it the area and acid storage along with exposives and numerous other chemicals. Looking forward to more info on this. Can we expect stronger earthquakes and how often should the come ?
Thanks, that’s helpful. It would still be surprising if it were directly caused by mining given the size of the tremor. But information is very thin on the ground so I can only go on the available evidence.
There is a underground gold mine near Duncan, AZ. Haven’t heard of any reports from there thought.
The epicenter is within a very small radius of two copper mines, one being Morenci, AZ. The largest open pit copper mine in North America [Possibly world].
Posted my reply in the wrong place – see above!
You should be bloody ashamed of yourself! What about the Mexico coastal quake previous day? What about the Utah quake(s)? What rubbish woman!
What are you talking about? This article is about the AZ quake and ONLY that quake. It is discussing the possible causes of THAT quake. What you’re asking for should be covered in a broader article on recent seismicity in that part of the country, and not in a site-specific, incident-specific article.