Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): an Operational Methodology for Ground Deformation Measurements

Recent methodological progress, Co-Registration of Optically Sensed Images and Correlation, outlined here, makes it possible to measure horizontal ground deformation from optical images on an operational basis, using the COSI-Corr software package. In particular, its sub-pixel capabilities allow for accurate mapping of surface ruptures and measurement of co-seismic offsets. We retrieved the fault rupture of the 2005 Mw 7.6 Kashmir earthquake from ASTER images, and we also present a dense mapping of the 1992 Mw 7.3 Landers earthquake of California, from the mosaicking of 30 pairs of aerial images

Quantifying near-field and off-fault deformation patterns of the 1992 M_w 7.3 Landers earthquake

Coseismic surface deformation in large earthquakes is typically measured using field mapping and with a range of geodetic methods (e.g., InSAR, lidar differencing, and GPS). Current methods, however, either fail to capture patterns of near-field coseismic surface deformation or lack preevent data. Consequently, the characteristics of off-fault deformation and the parameters that control it remain poorly understood. We develop a standardized method to fully measure the surface, near-field, coseismic deformation patterns at high resolution using the COSI-Corr program by correlating pairs of aerial photographs taken before and after the 1992 M_w 7.3 Landers earthquake. COSI-Corr offers the advantage of measuring displacement across the entire zone of surface deformation and over a wider aperture than that available to field geologists. For the Landers earthquake, our measured displacements are systematically larger than the field measurements, indicating the presence of off-fault deformation. We show that 46% of the total surface displacement occurred as off-fault deformation, over a mean deformation width of 154 m. The magnitude and width of off-fault deformation along the rupture is primarily controlled by the macroscopic structural complexity of the fault system, with a weak correlation with the type of near-surface materials through which the rupture propagated. Both the magnitude and width of distributed deformation are largest in stepovers, bends, and at the southern termination of the surface rupture. We find that slip along the surface rupture exhibits a consistent degree of variability at all observable length scales and that the slip distribution is self-affine fractal with dimension of 1.56

Quantifying co-seismic and post-seismic slip on fault scarps and their erosional modification using high-resolution Pleiades optical satellite data and repeat Terrestrial Laser Scanning: the 2016 Mw 6.6 Norcia earthquake (Central Italy)

Fault scarps are a topographical expression of sharp gradients in ground movements in an active tectonic region. However, inferences of slip history and causative earthquake sizes may be biased by co-seismic slip gradients, near-fault deformation, afterslip and erosional processes. To address these biases, I investigate co-seismic and continuing post-seismic deformation of near-fault areas and degradation of fault scarps, using high resolution Pleiades optical satellite images and repeat Terrestrial Laser Scans (TLS). The study area is Monte Vettore in the Apennines, Cental Italy, which has extensive surface ruptures associated with the Mw 6.6 30th October 2016 Norcia earthquake, part of the Central Italy Earthquake Sequence. I combine image correlation techniques with novel median-based filtering to effectively de-noise the Pleiades data, creating Digital Elevation Models (DEMs) from before and after the Norcia earthquake. Those DEMs are then differenced horizontally and vertically. The results identify detail of near-fault co-seismic surface deformation. I jointly invert those data with far-field InSAR (Interferometric Synthetic Aperture Radar) and GNSS (Global Navigation Satellite System) datasets to model co-seismic slip at depth. My model reveals detail of slip transfer from the Monte Vettore fault at shallow depth. This provides insights into the distribution of near-fault co-seismic slip in an area of complex faulting by slip being partitioned onto minor near-surface hanging wall structures, with slip vectors diverging from those at greater depth. The causes of post-seismic alteration or degradation of fault scarps are expected to be tectonic-related after-slip and/or erosion. Combining careful alignment of repeat TLS, use of an ICP (Iterative Closest Point) algorithm, filtering and detrending techniques, I characterise post-seismic deformation at 6 individual sites at ~centimetre scale. This provides insights into how individual factors (e.g. underlying geology, topography, and co-seismic slip gradients and distribution) influence which causes dominate and how degradation develops spatially and temporally. I show that fault scarps are highly variable records of a fault’s slip history. Any assessment of previous slip history using fault scarps as evidence needs to have regard to all those factors.

Resolving the Kinematics and Moment Release of Early Afterslip within the First Hours following the 2016 M_w 7.1 Kumamoto Earthquake: Implications for the Shallow Slip Deficit and Frictional Behavior of Aseismic Creep

As stresses following rupture are dissipated continuous measurements of postseismic surface deformation provide insight into variations of the frictional strength of faults and the rheology of the lower crust and upper mantle. Due to the difficulty of capturing the earliest phase of afterslip, most analyses have focused on understanding postseismic processes over timescales of weeks to years. Here we investigate the kinematics, moment release, and frictional properties of the earliest phase of afterslip within the first hours following the 2016 M_w 7.1 Kumamoto earthquake using a network of 5‐minute sampled continuous Global Positioning System (GPS) stations. Using independent component analysis to filter the GPS data, we find that (1) early afterslip contributes only ~1% of total moment release within the first hour and 8% after 24 hr. This suggests that the lack of a coseismic slip deficit, which we estimate using standard geodetic data sets (e.g., InSAR, GPS, and pixel offsets) and which span the first 4 days of the postseismic period, is largely reflective of the dynamic rupture process and we can rule out contamination of moment release by early afterslip. (2) Early afterslip shows no evidence of a delayed nucleation or acceleration phase, where instead fault patches transition to immediate deceleration following rupture that is consistent with frictional relaxation under steady state conditions with dependence only on the sliding velocity. (3) There is a close correlation between the near‐field aftershocks and afterslip within the first hours following rupture, suggesting afterslip may still be an important possible triggering mechanism during the earliest postseismic period

Wenchuan Earthquake Deformation 3D Modelling based on ALOS/PALSAR Data

A devastating earthquake of magnitude Mw 7.9 occurred in Wenchuan area of Sichuan Province, China on 12th May 2008 and caused great casualties and economic damage. This study is aiming to investigate the faulting geometry and motion of the major seismic faults in Longmenshan fault thrust belt that caused this earthquake, based on the surface rupture displacement data measured using differential interferometric synthetic aperture radar (DInSAR) and SAR amplitude pixel-offset techniques. The cross-event Japanese ALOS PALSAR data have been used for this study. First, the methodology for recovering the missing data in the decoherence zone of the DInSAR line-of-sight (LOS) surface motion maps was developed. In the area along the seismic fault zone, the coherence between pre- and post-event SAR images is completely lost because of the earthquake induced violent and chaotic destruction on the land surface and as the result, no surface displacement can be measured using the DInSAR technique. An Adaptive Local Kriging (ALK) technique has then been developed to retrieve the interferometric fringe patterns in the decoherence zone. The novel ALK operating in a multi-step approach enables to retrieve and interpolate the values with high fidelity to the original dataset. Thus a map of continuous radar LOS displacement was generated. Then, the horizontal displacement motion maps in ground range and azimuth direction were derived from cross-event SAR amplitude image pairs using advanced sub-pixel offset technique, Phase Correlation based Image Analysis System (PCIAS). Though the ground range pixel-offset is proportional to the LOS displacement, the azimuth pixel-offset data provide extra information of the coseismic motion. Thus the horizontal displacement vector field can be obtained in order to constrain the faulting motions in key areas. Finally, with the constraints of the ALK refined DInSAR data and the horizontal displacement data together with the published seismic focal mechanism solutions, seismic reflection profiles and field observations, forward modelling was proceeded using the Poly3D software to decide the most likely faulting geometry based on the optimal matching between the simulated and the measured surface displacement. In the much disputed Beichuan – Pengguan area, the best fit is achieved only when the Pengguan fault is set as the main fault that intercept the Yingxiu-Beichuan fault at a depth of about 13 kilometres. This geometric relationship between the two faults and the distribution of slip is compatible with them being two adjacent splay faults on a propagating thrust

Master of Science

thesisThe Malaspina Glacier of Southern Alaska /Yukon Canada provides the opportunity to investigate the interaction between glaciers and tectonics, in an active orogen that is forming from the collision and accretion of the Yakutat Microplate in the Gulf of Alaska. Several large alpine glaciers coalesce on the piedmont of the Saint Elias Mountains to form the Malaspina Glacier. We use feature tracking by cross correlation of Landsat satellite images to map the velocity and strain rate fields on the surface of the Malaspina Glacier to explore how the structural geology at the bed of the glacier affects the dynamics and structure of the moving ice on the surface. Rates of flow in alpine areas are fast and ice can move 90+ m/month in the summer and on the piedmont ice can move over 100-300 m a year. Strain rates calculated from the velocity fields are on the order of 10^-9 / s on the surface of the glaciers. Strain rate maps reveal the nature of the stress field in the ice where it moves over topographic features at the bed of the glacier. The results bear directly on the origin of ice falls that originate at thrust faults on the limbs of large folds, the origin of fast glacier flow along fault zones where rheology at the bed of the glacier is presumably impacted by rapid erosion and development of weak water saturated till, the pattern of ice flow around the termination of a large strike slip fault, and the presence and extent of subglacial lakes and distributary channels that feed outburst flooding at the terminus of glaciers. The morphology and dynamics of the Malaspina piedmont lobes also provide insight into the strike slip component of motion along the Esker Creek Fault that was activated during an M 8.1 earthquake in 1899, as well as some control on the basal topography, and perhaps structural geology, where the Fairweather Transform Fault and Aleutian Megathrust are currently linking together beneath the Malaspina Glacier

Investigations using data in Alabama from ERTS-A, volume 3

There are no author-identified significant results in this report