Brawley Earthquake Swarm–26 August 2012


According to a report in “MyDesert.com”, today’s earthquake swarm m5 brawley swarm

at the south end of the Salton Sea is the first of its kind in 30 years.  Since the early morning hours more than 200 tremors have rippled through southeastern California.  The largest event was a magnitude 5.5 event at 1:57 p.m (PDT).  Two other M5 or 5+ events occurred, as well as a number of M4+ events. 

Lucy Jones (USGS seismologist) is quoted in “MyDesert.com” as saying that its likely there will be M4 and M5 events before the swarm ends.  (Image on the right is a USGS “Did you feel it?” map

showing the precise location of today’s M5.5 tremor.

SCA map

Index map of recent earthquakes in California and Nevada.  Brawley is situated in southcentral most California.  The large blue square represents today’s M5.5 event.

Michael Conway (26 August 2012)

M2.7 Earthquake north of Paulden, AZ

On25 June 2012, at 3:07 pm MST, a small, 2.7 magnitude earthquake struck 9 miles NNW of Paulden, Arizonaevent location2.  There were no reports of damage and USGS’s “Did you feel it” online reporting site only received fewer than 10 responses.  AZGS geoscientist Jeri Young used the Arizona Broadband Seismic Network to locate the event precisely (see Google Earth figure to right). 

She captured some waveforms from nearby seismometers, too (see below).  The area north of Prescott, Arizona is home to the Quaternary Big Chino and Little Chino fault systems, both of which are capable of generating a M6.0+ earthquake. 

For some recent videos on the Big and Little Chino fault systems, visit our YouTube channel .


Seismic-Hazard Maps for the Conterminous United States, 2008

The US Geological Survey recently released new seismic-hazard mapsus Seismic hazard map

for the conterminous U.S.  The six map sheets portray “peak horizontal acceleration and horizontal spectral response acceleration for 0.2- and 1.0-second periods with probabilities of exceedance of 10 percent in 50 years and 2 percent in 50 years. All of the maps were prepared by combining the hazard derived from spatially smoothed historic seismicity with the hazard from fault-specific sources.”

Citation: Petersen et al, 2011,  Seismic-Hazard Maps for the Conterminous United States, 2008, USGS Scientific Investigation Map 3195.

Mike Conway (2 January 2011)

Science Nation–Exploring fault zones

parkfield fault zoneScience Nation, the National Science Foundation’s online magazine, presents an excellent, short video on drilling into an active fault zone.  Researchers from Penn State University examined rock recovered from the Parkfield, California, segment of the San Andreas Fault.  What they discovered was incompetent clay-rich material, which explains the aseismic nature of deformation there.

Other fault segments host more competent rock that seize up until increasing stress causes the rock to fail brittlely. Earthquake!

Mike Conway (26 December 2011)

WESTCARB–Sacramento-San Joaquin Basin

cg_drill_12_19-20The West Coast Regional Carbon Sequestration Partnership (WESTCARB) is drilling a deep well in the Sacramento-San Joaquin Basin, California, to characterize two potential CO2 storage areas.  The first is a depleted natural gas reservoir and the second an underlying saline formation. 

Drilling began on 1 December and 0n 21 December the drillers were 7000 feet deep in a mixed sandstone-shale unit. 

For daily drilling reports and graphic, visit their Drilling Progress page. 

Mike Conway (24 December 2011)

QuakeSmart – Mitigation Works for Business

The Federal Emergency Management Agency’s (FEMA) newest publication, FEMA P-811, contains a mitigation toolkit for businesses. image

From their introductory page, “Actionable and scalable guidance and tools to the private sector, its owners, managers, and employees about the importance of earthquake mitigation and the simple things they can do to reduce the potential of earthquake damages, injuries, and financial losses.”

The QuakeSmart website includes documents, videos, and artwork.  Some prominent chapter headings:

  • How Earthquakes Affect Businesses
  • How QuakeSmart Can Help
  • Step 1: Identify Your Risk
  • Step 2: Make a Plan
  • Step 3: Take Action

There are three videos including, Mitigation Works for Business.

Mike Conway (24 December 2011)

Colorado City Earthquakes

A small swarm of earthquakes occurred south of Colorado City between December 12th and 13th. The largest event in the swarm was magnitude 3.1, the smallest was 1.7.

Year Month Day Lat Long Depth Hour Min Sec Mag (local) Location Catalog
2011 12 13 36.765 -113.018 13.9 0 43 0 2.8 Colorado City, AZ UU
2011 12 13 36.764 -113.017 8.2 23 36 22 3.1 Colorado City, AZ UU
2011 12 12 36.782 -113.001 2.8 9 44 37 1.7 Colorado City, AZ UU
2011 12 12 36.757 -113.02 7.9 8 3 0 2.2 Colorado City, AZ UU

This small swarm occurred between the terminus of the Southern Intermontain Seismic Belt (ISB) and the start of the Northern Arizona Seismic Belt. This region regularly experiences small to moderate sized earthquakes.  Earlier this summer there were several quakes of similar magnitude in the same area between the Hurricane and Sevier/Toroweap faults.

The National Earthquake Information Center Reports of the southern ISB:
The ISB in southern Utah coincides with a transition between east-west-directed stretching in the Basin and Range to the west and more stable crust of the Colorado Plateau to the east. Tectonic movement on generally north-trending, east- and west-dipping range- and plateau-bounding normal faults, which results in horizontal extension, characterizes this part of Utah. The Sevier Valley is an area of variable and complex deformation involving significant components of folding and both normal and strike-slip faulting. The most prominent geologically young faults in southwestern Utah are the Hurricane and Sevier faults. The Hurricane fault forms the west-facing Hurricane Cliffs, which define the eastern edge of the Basin and Range within the ISB. Faults in the ISB in southern Utah locally show evidence of displacement younger than 10,000 years, but average recurrence intervals are generally longer than those on faults in the ISB in northern Utah. Recurrence intervals for surface faulting on the most active segments of ISB faults in southern Utah are generally many thousand to tens of thousands of years.


The largest event in the swarm (3.1) as seen on the Arizona Broadband Seismic Network



Lisa LinvilleDecember 17, 2011

Lake Mary Fault – Potential Earthquake Threat to Flagstaff, Arizona

The Lake Mary Fault, situated immediately south of Flagstaff, Arizona, Dave brumbaughrepresents the greatest earthquake hazard to the more than 70,000 people of Flagstaff and environs. In a new video, Dr. David Brumbaugh, Arizona Earthquake Information Center (AEIC) at Northern Arizona University, narrates the, “Lake Mary Fault – Potential Earthquake Threat to Flagstaff, Arizona”. Since the mid-1980’s, Dr. Brumbaugh has studied faults and monitored earthquakes of northern Arizona using the AEIC seismic network.

As Dave Brumbaugh notes in the video, the maximum probable earthquake of the ~ 25 mile long, Lake Mary fault is estimated at magnitude (M) M6.9 to M7.0. An event of that magnitude wouldlake Mary swarm-video have dire consequences for older structures and for unreinforced masonry buildings in the Flagstaff area. And Flagstaff is no stranger to moderate-sized earthquakes. From 1906 to 1912, three magnitude 6.0 to 6.2 earthquakes occurred within 24 miles of the town.

Video LinkLake Mary Fault – Potential Earthquake Threat to Flagstaff, AZ

Mike Conway (9 December 2011)

Geospatial Platform – Cartographic Tool for the Masses

There is a new and powerful cartographic tool available to all.  The Geospatial Platform is the joint product of geospatial platformthe federal government and its geospatial partners.  You can build your own maps – at your own scale, from local to regional to nationwide -  using base maps and thematic data.  The Platform provides 12 base maps, ranging from aerial-satellite imagery to topo base to road maps.  Forty-nine thematic layers are now available with more to come later.

Examples of available themes: 

NOAA Nautical Charts, Housing Affordability Index, US-FWS Critical Habitat, World Topographic Map, PLSS, Landsat 7 Orthoimagery, Surface management, and dozens more.

You can add your own data, too.

In the space of a minute, I build a critical habitat map for the Coronado National Forest.

In the hands of teachers, the Geospatial Platform could be a powerful tool to combat the growing problem of map illiteracy in the U.S.

For more information see yesterday’s Dept. of the Interior press release .

Mike Conway (10 November 2011).

Arizona Vigilant Guard – AZ Emergency Preparedness Exercise

(Note: The following describes a statewide emergency preparedness exercise. The disaster events outlined below did not occur.) glendale emergency

How do you prepare for a civil emergency that results in thousands of people killed and wholesale destruction of a large metropolitan area? To answer that question, Arizona state, county, and municipal authorities, in close coordination with the Arizona National Guard, ran a week-long simulation – Arizona Vigilant Guard – that ends on Sunday, 6 November.

Arizona Vigilant Guard involves 8,000 people from more than 200 federal, state, county and municipal agencies, and with National Guard assets from Arizona and surrounding states – California, Nevada, Colorado and Utah. It is the largest exercise of its kind in the U.S. The Arizona Division of Emergency Management (ADEM) is the lead Arizona agency. decon team

The exercise began with a simulated breach of the Waddell Dam north of Phoenix. Flood waters spilling into west Phoenix caused widespread flooding, civil disruption, and some evacuations. This first disaster was followed within days by the detonation of an improvised explosive nuclear device (IND) in downtown Phoenix. For this exercise, the IND was a 10 kiloton device that destroyed everything within a 2 mile radius of the blast, killing tens of thousands of individuals.

AZGS participated on Friday, the day following the detonation of the IND. In our role, we visited emergency operations centers at ADEM headquarters, Phoenix, and the Glendale Regional Public Safety Training Center (top photo). We observed hospital personnel at the Maricopa Integrated Health System treating victims – some real people and some blowup dolls (middle photo) -, some of whom arrived via Air National Guard Blackhawk helicopters. All victims were immediately taken to decontamination (decon) stations to have their clothing removed and to be thoroughly rinsed of any residual radiologic products. We observed, too, a simulated rescue from a carefully engineered rubble pile (immediately right).extradition team

The exercise ends today, 6 November, with a recovery tabletop exercise. After-action reports and analysis will go on for months.

See the East Valley Tribune for some additional information.

Mike Conway (6 November 2011)

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