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Radar Interferometry Measurement of Land Subsidence in Phoenix, Arizona

Results - Glendale / Peoria / Sun City subsidence

In this radar image subset over the cities of Glendale, Peoria and Sun City, Luke AFB is located to the southwest with the radiometrically-dark aircraft runways trending northeast-southwest.  The bright radar response to the west corresponds to agricultural fields and an area of historical subsidence.  The northern extent of the image is generally undeveloped with the Hedgpeth Hills, Pyramid Peak and Deem Hills mountains to the northeast.  Urban areas are identifiable from the speckled radar response from buildings and fine dark lines corresponding to major streets.  The urban areas in the image include Sun City immediately east of the agricultural area, Peoria to the northeast and Glendale to the south.


Glendale geocoded radar image

Several subsidence features appear in the three-year differential interferogram.  First, there is a 15-km diameter subsidence bowl spanning Glendale, Peoria and Sun City.  Also, there is a 3-km diameter subsidence bowl in Glendale.  Finally, there is an apparent subsidence bowl over the agriculture fields which abruptly ends just southeast of Luke AFB.


Glendale geocoded differential interferogram

The east-west trending line corresponds to Olive Avenue and crosses through the intense subsidence feature in Glendale.  Profiles were extracted along this line from the 3-year interferogram as well as two other interferograms.

Glendale interferogram profiles

The table summarizes the interferometry measurements at the intersection of 71st Avenue and Olive Avenue, near the center of the Glendale subsidence bowl.  Signs of subsidence at this intersection include several cracks up to 3/8-inch in adjacent cement residential privacy walls.  The differences between subsidence rates at this intersection illustrate the variability of subsidence over time.  For example, considering the vertical displacement and dates spanned by the 688-day and 1039-day interferograms, it is noted that for the 351-day period from Aug 27, 1995 to Aug 12, 1996, the 71st/Olive subsidence rate was 3.0 cm/year.
 

Interferogram
(dates and time separation)
Vertical Displacement
(cm)
SubsidenceRate
(cm/year)
931008-950827, 688-day -11.9 6.3
931008-960812, 1039-day -14.8 5.2
950514-980223, 1016-day -21.9 7.9
Interferometry measurements at 71st and Olive Avenues
 


Damage associated with subsidence at 71st and Olive Avenues (courtesy David Meer)

Additional subsidence is observed in north Scottsdale and east Mesa and is discussed in:  Buckley, Sean, Radar Interferometry Measurement of Land Subsidence, PhD dissertation, The University of Texas at Austin, 2000.