Figure 1. Location map showing Quaternary fault systems and epicenters of earthquakes in Arizona from 1 September to 30 November 2009. Source: AEIC.

arizona seismicity summer 2009
an aisn update

Fall-2009 has been a busy one for the Arizona Integrated Seismic Network (AISN) partners. We recorded four episodes of seismic activity, with an additional 100 micro-earthquakes occuring 10-16 miles below the San Franciso volcanic field near Flagstaff, Arizona.  Our partner universities have turned out some eye-opening, earthquake-visualization products.  We continue to work on a comprehensive seismic network implementation plan to address both short- and long-term needs. In addition, AZGS received funding to conduct an earthquake awareness campaign (AZ SHAKE).

Seismic Activity

Between 1 September and 30 November 2009, AISN seismometers recorded four episodes of seismic activity from earthquakes originating in Arizona.   Yuma experienced ground shaking as a result of an earthquake near Guadalupe, Mexico (Table 1). Our research partners at the Arizona Earthquake Information Center (AEIC), located at Northern Arizona University (NAU), catalogued the earthquake data (Fig. 1).  (For AEIC online seismic catalog, click here)

Table 1. Earthquakes that occurred in, or impacted, Arizona from 1 September to 30 November 2009. Source: Arizona Earthquake Information Center (AEIC).
Date (2009)




Time (local)


3 Sep



M 3.0

11:00 p.m.

Smaller foreshock occurred at 1:59 a.m. the previous night

4 Sep

Wild Bend

25 mi S of Colorado City

M 3.5

4:48 a.m.

Toroweap fault zone

4 Sep

Wild Bend

23 mi S of Colorado City

M 2.8

4:53 a.m.


19 Sep


43 mi SW of Yuma

M 5.1

3:55 p.m.

Epicenter in Mexico

9 Oct

Hoover Dam

10 mi E of AZ/NV border

M 3.9

3:13 p.m.

Felt reports in Bullhead City

31 Oct

Halloween Swarm

15 mi NE of Flagstaff, near Sunset Crater

< M 2.5

12:15  – 6:30 a.m.

>100 micro-earthquakes at depths of 17-27km

Network Implementation Plan

One of the main challenges facing AISN is to develop a financial solution for maintaining and operating a fully functional seismic network. We have an agreement in place with the Incorporated Research Institutions for Seismology (IRIS) to maintain the seismometers and manage the data through 2011. Our goal is to make operations, maintenance, and data management an in-house function and thereby reduce operating costs.

Arizona is one of the few western states that does not receive State funding to run a seismic network, despite having a statutory obligation to monitor known geologic hazards (ARS 27-152).



Mimi Diaz
Research Geologist
Chief-Phoenix Branch

Arizona Geological Survey
Phoenix, AZ

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