Surface displacements in the 1980 Mw6.9 Irpinia earthquake (Italy) ; new constraints from optical image correlation

On 23rd November 1980, the Mw 6.9 Irpinia earthquake devastated the Campania region of southern Italy, killing 2.5k people, injuring 8k, and leaving 250k homeless. The earthquake represents one of the worst natural disasters to have affected Italy in modern history. In this project, the student will take advantage of new image processing methods to build a high resolution mosaic of aerial photos acquired before and after the earthquake, from which ground displacements close to the surface rupture will be retrieved using image correlation. The processing will involve using Structure-from-Motion techniques to assemble the large number of aerial photos into coherent networks, followed by bundle adjustment to optimize the various camera parameters. Stereo-matching and triangulation of the resulting disparity maps (using the high quality cameras) will allow pre- and post-earthquake digital elevation models to be generated. The DEMs will then be used to orthorectify the aerial photos, thus removing topographic distortions from the images. Iterative Closest Point registration techniques will be used to co-register the pre- and post-event DEMs and orthomosaics. Subsequent correlation of the orthorectified imagery, coupled with DEM differencing (with horizontal back-slip resampling), will then allow the 3D displacement field to be characterized in the near-fault region (spanning the surface rupture). From this, the student will investigate (1) the spatial location and magnitude of slip, (2) the fault zone width and off-fault deformation, (3) near-field strain (shear and dilatation), and (4) along-strike slip variability associated with this earthquake. Results will then be integrated with field measurements made at the time (under challenging winter conditions), as well as geological and topographic information, to determine which parameters may control the expression and localization of slip at the surface. Additional processing of pre- and post-event satellite imagery (KH9 8m and SPOT 10m, respectively) will provide a broader-scale view of the ground deformation, providing information on the medium- and far-field ground displacement, which may potentially be used to invert for the fault slip distribution. Finally, the student will accompany ISTerre researchers James Hollingsworth and Anne Socquet on a field trip to the Irpinia region in spring 2021, to ground-truth optical correlation results with field and structural observations, and verify any new ruptures found.

Start Date : 1st February
Duration : 5 months

Advisors :
James Hollingsworth (ISterre)
Anne Socquet (ISTerre)

Contact :
james.hollingsworth univ-grenoble-alpes.fr