A magnitude 6.5 earthquake devastated the small city of Bam in southeast
Iran on December 26, 2003 at 5:26 AM local time.
While there have been several recent earthquakes on faults in the region,
the city of Bam had not been affected by earthquakes for at least 500
years. Initial field studies found some minor evidence of fault motion,
but the main fault rupture that caused the earthquake was discovered by
analysis of data from the recently launched Envisat synthetic aperture
radar system. Scientists from NASA's JPL and the Centre for Observation
and Modelling of Earthquakes and Tectonics (University of Oxford, UK and
the University of Cambridge, UK) used interferometry analysis of the
Envisat radar data and seismology to study the fault rupture, that passed
directly beneath the center of the city of Bam. The interferometry
analysis was performed with software developed at JPL. A less used type
of radar interferometry analysis called the interferometric correlation
(shown in this figure) was used to locate the surface trace of the fault
rupture. Scientists from the Geological Survey of Iran mapped the surface
ruptures in the field at the locations discovered on these correlation
images.
The two images show similar measures of the radar interferometric
correlation in grayscale on the left and in false colors on the right.
The city of Bam is at the top edge of the images, which are each 5 km (3
miles) wide. In the left image, the irregular black line between the two
red arrows shows the fault rupture, where the interferometric correlation
is very low. The "S" shaped dark line running across the image from top
left to lower right is a railroad, and some other straight lines are
roads that also have low correlation. The right image shows the
correlation in colors with the darkest red-orange color indicating low
correlation on the fault ruptures and other features.
For more information, see the following paper, published recently in
Geophysical Research Letters:
Talebian, M., Fielding, E.J., Funning, G.J., et al. (2004), The 2003 Bam
(Iran) earthquake: Rupture of a blind strike-slip fault, L11611,
doi:10.1029/2004GL020058.
The full paper is available (subscription required) can be found at
http://www.agu.org/pubs/crossref/2004/2004GL020058.shtml
and for United States Government research a reprint is available at
http://trs-new.jpl.nasa.gov/dspace/handle/2014/6130.
Radar data used in this research were acquired by the Envisat satellite
operated by the European Space Agency, which kindly made this data
available for research. Part of this research was performed at the Jet
Propulsion Laboratory, California Institute of Technology under contract
with NASA. Part of this research was performed at the Centre for the
Observation and Modelling of Earthquakes and Tectonics supported by the
U.K. Natural Environment Research Council. Research was also performed by
the Geological Survey of Iran.
Size: Images are 5 km (3 miles) wide
Location: 29.1 degrees North latitude, 58.3 degrees East longitude
Orientation: North is up (UTM projection)
Image Data: Envisat ASAR interferometric correlation
Image resolution: 20 meters (60 feet)
Dates Acquired: December 3, 2003 and January 7, 2004