Geobulletin alpha

Quake swarm resumes in northwest Arizona 

Two earthquakes in northwest Arizona demonstrate the swarm activity is not over yet.   A magnitude 1.7 earthquake occurred just before midnight, followed by a magnitude 2.0 event at 10:21 a.m. local time this morning.   It's been a few days with no reported activity.   [Right, red dot marks the epicenter of the magnitude 2.0 event, the orange dot shows the smaller quake. The red lines are

More small quakes on the Intermountain Seismic Belt 

There was yet another small quake in northwest Arizona, along the southern end of the Intermountain Seismic Belt [right, red lines are active faults]. This magnitude 1.8 event [blue dot in image] occurred at 4:04 p.m. on Friday, following two others [yellow dots in image] just before noon in the region.   Another tiny quake at magnitude 0.9, [orange dot in image] occurred this morning, at

More aftershocks to Duncan and Oak Creek Canyon earthquakes 

We had aftershocks on Wednesday from both of last year's more prominent earthquakes in Arizona. A magnitude 2.5 quake (orange dot  on AZ-NM border) is likely an aftershock to last June's M=5.3 Duncan earthquake.  It occurred at 3:50 p.m. local time on January 28.  The yellow dot is another aftershock, M=3.4 that occurred earlier in the week. Another magnitude 2.5 quake hit south of

Two small quakes on Arizona - Utah border 

There were two small quakes in northern Arizona in the past few days.  A magnitude 2.4 event hit 8 miles south of Colorado City on Dec. 22 at about 4:27 p.m. local time [yellow dot marks epicenter.   Credit, USGS] A magnitude 1.3 quake occurred on Dec. 23, at 11:57 a.m. local time, about 6 miles ESE of Colorado City [epicenter marked by orange

M3.5 aftershock to Duncan earthquake 

There was an additional >M3 aftershock on Sunday morning that was not in my previous posts (see orange dot at right).  The main M5.3 event was at about 10 pm on Saturday. Note that we have upped the magnitude to 5.3 from the initial 5.2.    I'll provide details on that later. AZGS has recorded a larger number of small aftershocks on our statewide seismic network that we are