F. Ayoub - Academia.edu (original) (raw)

Papers by F. Ayoub

Research paper thumbnail of Coseismic thrusting and folding in the 1999 M w 7.6 Chi-Chi earthquake: A high-resolution approach by aerial photos taken from Tsaotun, central Taiwan

Journal of Geophysical Research: Solid Earth, 2014

We used aerial photos taken before and after the 21 September 1999, M w 7.6, Chi-Chi earthquake i... more We used aerial photos taken before and after the 21 September 1999, M w 7.6, Chi-Chi earthquake in central Taiwan to measure the near-field ground deformation.

Research paper thumbnail of Two Tales of Martian Sands and Dust

Research paper thumbnail of Studies of Aeolian Bedforms and Wind Activity in Gale Crater from Surface to Orbital Scales

Research paper thumbnail of Measurement of High Martian Sand Fluxes: Implications for Landscape Modification

Research paper thumbnail of Image cross-correlation using COSI-Corr: A versatile technique to monitor and quantity surface deformation in space and time

Research paper thumbnail of Measuring Mars sand flux seasonality from a time series of images

Research paper thumbnail of 3D high resolution tracking of ice flow using mutli-temporal stereo satellite imagery, Franz Josef Glacier, New Zealand

Research paper thumbnail of Deformation during the 1975-84 Krafla rifting crisis, NE Iceland, measured by optical image correlation

ABSTRACT In this study we combine results from optical image correlation of SPOT, KH-9 spy satell... more ABSTRACT In this study we combine results from optical image correlation of SPOT, KH-9 spy satellite and aerial photos, EDM data and high resolution topographic data to better constrain the 3D deformation associated with the 1975-84 Krafla rifting crisis, NE Iceland. Inversion of the various geodetic datasets yields new volumes for the amount of material injected into the crust during this rifting crisis. Correlation of aerial photos from 1957 and 1990 for the middle section of the 2 km-wide Krafla fissure swarm, along with DEM differencing of their respective 1957 and 1990 DEM's (extracted using photogrammetric techniques), provides constraints on the full 3D displacement field spanning the entire rifting period. Elastic dislocation modeling of this displacement data is then used to determine the geometry of faulting and diking in the crust. In contrast to leveling data from the northern end of the fissure swarm (Rubin, et al., 1988), we find that dikes do not extend into the upper 1-2 km, where extension is accommodated primarily by faulting in the fissure swarm. Dislocation modeling of a 4 m-wide dike injected between 2 km and 6 km in the crust produces a maximum surface strain which reaches the elastic yield limit for rock (derived from laboratory experiments of deformed granite) at two points spanning a 2 km-wide zone above the dike, and which corresponds with the location of the major rift-bounding faults of the Krafla fissure swarm. If dikes extend nearer to the surface, the predicted fissure zone width would be correspondingly smaller (consistent with the southern-end of the fissure swarm), while deeper diking produces a wider fissure swarm (consistent with the northern-end of the fissure swarm). The apparent northward increase in depth of diking is consistent with the flexural effects of rift-margin topography (Behn, et al., 2006); increased flexure in the south, where the Krafla caldera is located, results in the promotion of shallow diking, where as subdued topography in the north promotes deeper diking. Correlation of aerial photos between 1957 and 1976 (during the early stages of the rifting crisis) indicate 2 m extension, which is localized on faults along the northern end of the fissure swarm. No fault slip occurs in the central section of the fissure swarm during the same period, suggesting extension in the north during the early stages of rifting may result from dike injections sourced from the north (possibly offshore), rather than the Krafla caldera to the south. A similar variation in magmatic source region was also observed during the 2005-2009 Afar rifting crisis in East Africa.

Research paper thumbnail of Analysis of the shallow slip deficit using sub-pixel image correlation: implications for fault slip rates, and seismic hazards

Research paper thumbnail of Analysis of the shallow slip deficit using sub-pixel image correlation: examples from various large continental strike-slip earthquakes

Research paper thumbnail of Measuring sand flux on Mars using HiRISE Images

ABSTRACT As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeo... more ABSTRACT As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeolian processes is therefore essential to assess recent geological evolution and current climate. We adapted the Co-registration of Optically Sensed Image and Correlation (COSI-Corr) toolbox to the MRO HiRISE imager specifications to produce a dense map of the ripples migration on the surface of the Martian dunes on the Nili Patera area. The ripple migration rate, along with an estimate of the ripple height, were used to derive the sand flux, a key quantity that controls the style and rate of landscape evolution. Using the dunes shape, size, and height, which were extracted from a DEM of the dune field, we show that the dunes are near steady state, and we observe that dune migration rate varies inversely with size and position within the dune field. The time scale associated with the formation and evolution of the Nili Patera dune field, estimated from comparing the sand volume with the sand flux and the dunes migration rates with the length scale of the dune field, is on the order of 10s to 100s of thousands Earth years. However, sand fluxes at the dune crests are 0.7 - 4.8 m3 m-1 per Earth year, which is comparable to that of dunes in Victoria Valley, Antarctica. This implies that rates of landscape modification from aeolian abrasion on Mars may be comparable to that on Earth.

Research paper thumbnail of High Sand Fluxes and Abrasion Rates on Mars Determined from HiRISE Images

ABSTRACT We derive the reptation and saltation sand fluxes in Nili Patea, Mars. The dunes have un... more ABSTRACT We derive the reptation and saltation sand fluxes in Nili Patea, Mars. The dunes have unexpectedly high fluxes that are like those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.

Research paper thumbnail of Measuring mars sand flux seasonality from a time series of HiRISE images

Research paper thumbnail of Tracking Topographic Changes from Multitemporal Stereo Images, Application to the Nili Patera Dune Field

Research paper thumbnail of Measuring Mars sand flux seasonality from a time series of HiRISE images and calibrating the threshold for sand mobility

Research paper thumbnail of Bedform Migration on Mars: Current Results, Implications, and Future Plans

Research paper thumbnail of Dune and ripple migration along Curiosity's traverse in Gale Crater on Mars

Research paper thumbnail of Windy Mars: A Record of Bedform Migration and Sand Activity

Research paper thumbnail of Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux

Nature Communications, 2014

Coupling between surface winds and saltation is a fundamental factor governing geological activit... more Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τ(s)=0.01±0.0015 N m(-2).

Research paper thumbnail of Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): An operational methodology for ground deformation measurements

International Geoscience and Remote Sensing Symposium (IGARSS), 2007

Recent methodological progress, Co-Registration of Optically Sensed Images and Correlation, outli... more 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.

Research paper thumbnail of Coseismic thrusting and folding in the 1999 M w 7.6 Chi-Chi earthquake: A high-resolution approach by aerial photos taken from Tsaotun, central Taiwan

Journal of Geophysical Research: Solid Earth, 2014

We used aerial photos taken before and after the 21 September 1999, M w 7.6, Chi-Chi earthquake i... more We used aerial photos taken before and after the 21 September 1999, M w 7.6, Chi-Chi earthquake in central Taiwan to measure the near-field ground deformation.

Research paper thumbnail of Two Tales of Martian Sands and Dust

Research paper thumbnail of Studies of Aeolian Bedforms and Wind Activity in Gale Crater from Surface to Orbital Scales

Research paper thumbnail of Measurement of High Martian Sand Fluxes: Implications for Landscape Modification

Research paper thumbnail of Image cross-correlation using COSI-Corr: A versatile technique to monitor and quantity surface deformation in space and time

Research paper thumbnail of Measuring Mars sand flux seasonality from a time series of images

Research paper thumbnail of 3D high resolution tracking of ice flow using mutli-temporal stereo satellite imagery, Franz Josef Glacier, New Zealand

Research paper thumbnail of Deformation during the 1975-84 Krafla rifting crisis, NE Iceland, measured by optical image correlation

ABSTRACT In this study we combine results from optical image correlation of SPOT, KH-9 spy satell... more ABSTRACT In this study we combine results from optical image correlation of SPOT, KH-9 spy satellite and aerial photos, EDM data and high resolution topographic data to better constrain the 3D deformation associated with the 1975-84 Krafla rifting crisis, NE Iceland. Inversion of the various geodetic datasets yields new volumes for the amount of material injected into the crust during this rifting crisis. Correlation of aerial photos from 1957 and 1990 for the middle section of the 2 km-wide Krafla fissure swarm, along with DEM differencing of their respective 1957 and 1990 DEM's (extracted using photogrammetric techniques), provides constraints on the full 3D displacement field spanning the entire rifting period. Elastic dislocation modeling of this displacement data is then used to determine the geometry of faulting and diking in the crust. In contrast to leveling data from the northern end of the fissure swarm (Rubin, et al., 1988), we find that dikes do not extend into the upper 1-2 km, where extension is accommodated primarily by faulting in the fissure swarm. Dislocation modeling of a 4 m-wide dike injected between 2 km and 6 km in the crust produces a maximum surface strain which reaches the elastic yield limit for rock (derived from laboratory experiments of deformed granite) at two points spanning a 2 km-wide zone above the dike, and which corresponds with the location of the major rift-bounding faults of the Krafla fissure swarm. If dikes extend nearer to the surface, the predicted fissure zone width would be correspondingly smaller (consistent with the southern-end of the fissure swarm), while deeper diking produces a wider fissure swarm (consistent with the northern-end of the fissure swarm). The apparent northward increase in depth of diking is consistent with the flexural effects of rift-margin topography (Behn, et al., 2006); increased flexure in the south, where the Krafla caldera is located, results in the promotion of shallow diking, where as subdued topography in the north promotes deeper diking. Correlation of aerial photos between 1957 and 1976 (during the early stages of the rifting crisis) indicate 2 m extension, which is localized on faults along the northern end of the fissure swarm. No fault slip occurs in the central section of the fissure swarm during the same period, suggesting extension in the north during the early stages of rifting may result from dike injections sourced from the north (possibly offshore), rather than the Krafla caldera to the south. A similar variation in magmatic source region was also observed during the 2005-2009 Afar rifting crisis in East Africa.

Research paper thumbnail of Analysis of the shallow slip deficit using sub-pixel image correlation: implications for fault slip rates, and seismic hazards

Research paper thumbnail of Analysis of the shallow slip deficit using sub-pixel image correlation: examples from various large continental strike-slip earthquakes

Research paper thumbnail of Measuring sand flux on Mars using HiRISE Images

ABSTRACT As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeo... more ABSTRACT As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeolian processes is therefore essential to assess recent geological evolution and current climate. We adapted the Co-registration of Optically Sensed Image and Correlation (COSI-Corr) toolbox to the MRO HiRISE imager specifications to produce a dense map of the ripples migration on the surface of the Martian dunes on the Nili Patera area. The ripple migration rate, along with an estimate of the ripple height, were used to derive the sand flux, a key quantity that controls the style and rate of landscape evolution. Using the dunes shape, size, and height, which were extracted from a DEM of the dune field, we show that the dunes are near steady state, and we observe that dune migration rate varies inversely with size and position within the dune field. The time scale associated with the formation and evolution of the Nili Patera dune field, estimated from comparing the sand volume with the sand flux and the dunes migration rates with the length scale of the dune field, is on the order of 10s to 100s of thousands Earth years. However, sand fluxes at the dune crests are 0.7 - 4.8 m3 m-1 per Earth year, which is comparable to that of dunes in Victoria Valley, Antarctica. This implies that rates of landscape modification from aeolian abrasion on Mars may be comparable to that on Earth.

Research paper thumbnail of High Sand Fluxes and Abrasion Rates on Mars Determined from HiRISE Images

ABSTRACT We derive the reptation and saltation sand fluxes in Nili Patea, Mars. The dunes have un... more ABSTRACT We derive the reptation and saltation sand fluxes in Nili Patea, Mars. The dunes have unexpectedly high fluxes that are like those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.

Research paper thumbnail of Measuring mars sand flux seasonality from a time series of HiRISE images

Research paper thumbnail of Tracking Topographic Changes from Multitemporal Stereo Images, Application to the Nili Patera Dune Field

Research paper thumbnail of Measuring Mars sand flux seasonality from a time series of HiRISE images and calibrating the threshold for sand mobility

Research paper thumbnail of Bedform Migration on Mars: Current Results, Implications, and Future Plans

Research paper thumbnail of Dune and ripple migration along Curiosity's traverse in Gale Crater on Mars

Research paper thumbnail of Windy Mars: A Record of Bedform Migration and Sand Activity

Research paper thumbnail of Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux

Nature Communications, 2014

Coupling between surface winds and saltation is a fundamental factor governing geological activit... more Coupling between surface winds and saltation is a fundamental factor governing geological activity and climate on Mars. Saltation of sand is crucial for both erosion of the surface and dust lifting into the atmosphere. Wind tunnel experiments along with measurements from surface meteorology stations and modelling of wind speeds suggest that winds should only rarely move sand on Mars. However, evidence for currently active dune migration has recently accumulated. Crucially, the frequency of sand-moving events and the implied threshold wind stresses for saltation have remained unknown. Here we present detailed measurements of Nili Patera dune field based on High Resolution Imaging Science Experiment images, demonstrating that sand motion occurs daily throughout much of the year and that the resulting sand flux is strongly seasonal. Analysis of the seasonal sand flux variation suggests an effective threshold for sand motion for application to large-scale model wind fields (1-100 km scale) of τ(s)=0.01±0.0015 N m(-2).

Research paper thumbnail of Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): An operational methodology for ground deformation measurements

International Geoscience and Remote Sensing Symposium (IGARSS), 2007

Recent methodological progress, Co-Registration of Optically Sensed Images and Correlation, outli... more 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.