The May 12, 2008, (Mw 7.9) Sichuan Earthquake (China): Multi-frame ALOS – PALSAR DInSAR Analysis of Coseismic Deformation

A destructive (Mw 7.9) earthquake affected the
Sichuan province (China) on May 12, 2008. The seismic event
ruptured approximately 270 km of the Yingxiu–Beichuan fault
and about 70 km of the Guanxian–Anxian fault. Surface effects
were suffered over a wide epicentral area (about 300 km E–W
and 250 km N–S). We apply the differential synthetic aperture
radar interferometry (DInSAR) technique to detect and measure
the surface displacement field, using a set of ALOS-PALSAR
L-band SAR images.We combine an unprecedented high number
of data (25 frames from six adjacent tracks) to encompass the
entire area which has coseismically displaced. The resulting mosaic
of differential interferograms covers an overall area of about
340 km E–W and 240 km N–S. We investigate the source of the
Sichuan earthquake by modeling the DInSAR data. The geometry
and position of the fault parameters are inferred by a nonlinear
inversion, followed by a linear inversion to retrieve the relative slip
distribution. Our results show two different source mechanisms
for the 145-long Yingxiu–Beichuan fault and for the 105-long
Beichuan–Qingchuan fault. Both faults are characterized by slip
concentrations of up to 8 m.