Co-seismic horizontal offsets and fault trace mapping using phase correlation of IRS satellite images: the 1999 Izmit (Turkey) earthquake

On August 17, 1999, a strong earthquake
(Mw ≈ 7.4) occurred along the western sector of the North
Anatolian Fault system in Turkey. The epicenter was located
near the city of Izmit, 50 km east of Istanbul. Previous works
determined the coseismic surface displacements by satellite
synthetic aperture radar (SAR) interferometry (InSAR) and
satellite optical-image correlation. In 1999, the highest spatial
resolution orbiting camera was the panchromatic sensor (PAN), a
5.8-m pixel sensor (SPOT 2 was a 10-m pixel sensor) onboard the
Indian Remote Sensing (IRS) satellite. We propose to apply a new
phase-correlation method to PAN images to study the coseismic
rupture due to the Izmit earthquake. The phase-correlation
method does not need phase unwrapping and was proved to be
robust under a wide variety of circumstances. Image correlometry
deals with the quantification of the subpixel offsets over the whole
image, allowing displacement measurement with an accuracy
that is proportional to the pixel size. We measured the near-field
deformations exploiting two geometrically corrected IRS images
with similar look angles. A quality check of the derived offset map
was performed by comparison with GPS benchmarks and SPOT
offsets. The results show that IRS PAN images can be correlated
to derive coseismic slip offsets due to a large earthquake (and to
map its fault trace).