October 2012 earthquake swarm near Morenci, Greenlee County, Arizona
Contacts:
Mike Conway: 520-209-4146, michael.conway@azgs.az.gov
Jeri Young: jeri.young@azgs.az.gov
Tucson. Six earthquakes, ranging from 2.5- to 4.1-magnitude (ML and MD), occurred about 25 miles north-northeast of Morenci in Greenlee County, east-central Arizona in October 2012 (Fig 1.). Numerous smaller events with magnitudes < 2.2 M occurred, but because of a lack of resources for AZGS’ seismic network, were not located. Steven Rutherford, Greenlee County Emergency Management, said his office had not received any reports of felt earthquakes from residents of Clifton or Morenci.
The Alma Mesa fault system is the only identified fault in the area, and it is located well east of the recent earthquakes. There is, however, a strong west-east lineament near the ML 4.1 location suggestive of a fault trace. The Clifton-Morenci area is one of the most seismically active areas in southeastern Arizona (Wallace, 1989) and multiple earthquake swarms have been recorded in this area. In May of 2010, 12 earthquakes ranging from Md 2.0 to 3.5, and 5 events below Md 2.0 occurred near here.
According to US Geological Survey probability models, the likelihood of a substantial M5.0+ earthquake within about 30 miles of the Clifton-Morenci area over the next 25 years is ~20%.
Table 1. Location of October 2012 earthquakes near Clifton-Morenci, Greenlee County, Arizona. |
||||||
|
Date |
Magnitude |
Mag. Type |
Depth (km) |
Source Catalog |
Latitude |
Longitude |
| 10/31/2012 | 2.45 | MD | 1 | AZGS | 33.37 | -109.09 |
| 10/29/2012 | 2.51 | MD | 2 | AZGS | 33.35 | -109.17 |
| 10/29/2012 | 3.4 | ML | 4 | USGS | 33.39 | -109.24 |
| 10/15/2012 | 1.5 | M | 5 | New Mexico* | 33.84 | -109.54 |
| 10/14/2012 | 1.8 | M | 5 | New Mexico* | 33.59 | -109.45 |
| 10/14/2012 | 2.5 | ML | 4 | USGS | 33.39 | -109.21 |
| 10/10/2012 | 1.7 | M | 5 | New Mexico* | 33.73 | -109.46 |
| 10/9/2012 | 3.12 | MD | 6.2 | AZGS | 33.40 | -109.17 |
| 10/8/2012 | 2.6 | M | 5 | New Mexico* | 33.34 | -109.16 |
| 10/8/2012 | 3.6 | ML | 5 | USGS | 33.39 | -109.30 |
| 10/8/2012 | 4.1 | ML | 5 | AZGS/USGS | 33.43 | -109.28 |
| References: Wallace, T.C., 1989, Summary of Earthquake Activity in Arizona: Southern Arizona. Arizona Geology, Vol. 20, #1, p. 7.*New Mexico Tech Seismic Network | ||||||
Figure 1. Google Earth map showing the distribution and magnitudes of October 2012 earthquakes near Morenci, Arizona.