Geophysical site assessment of an active urban development site, southeastern suburb of Cairo, Egypt

Medhat, Noha Ismail; Atya, Magdy; Ragab, El-Said A.; El-Kenawy, Abeer; Zaher, M. A.; Pringle, Jamie K.

doi:10.1144/qjegh2018-151

Cited by 3 publications

(1 citation statement)

References 29 publications

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“…Understanding the subsurface structure system at the Farafra Oasis is critical due to its geothermal and hydrological potential [1]. In addition, there is a continuous need to image subsurface structures to explore geothermal uid paths or even locate potential areas for groundwater accumulation over largescale regions [2]; on the other hand, conventional methods to image subsurface conditions using onground tools are rather expensive, time-consuming and labor intensive [3,4]. Earth observation radar satellites, with their multifrequency and multipolarization features, are an effective method for exploring large-scale and di cult-access areas.…”

Section: Introductionmentioning

confidence: 99%

Validation of ALOS/PALSAR subsurface penetration depth in arid regions based on field ground-penetrating radar measurements

Mansour

Zaher

Deep

et al. 2022

Preprint

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In the last few years, ALOS/PALSAR (L-band) (HH, HV, VH, and VV) images have been widely used due to their ability to penetrate the surface in certain conditions, such as low moisture or dry friable sandy soil. Images from the ALOS-1 sensor were used to delineate subsurface structures, and optical images such as Landsat-7 ETM + data were used to discriminate between scatterings from the Earth’s surface and subsurface materials. Thus, the Farafra Desert is an optimal geological environment for L-band microwave penetration, as its geology is characterized by friable sand sheets covering limestone (Tarawan Formation). Speckle noise is found in radar images for many reasons, such as when an object strongly reflected between itself and the spacecraft causes noise. Refined LEE filter (RLF) is applied for speckle noise reduction; moreover, full polarimetric ALOS/PALSAR images (PLR) are transformed into circular polarization by changing both angles into orientation angle ψ = 0° and elliptical angle χ = 45°. The validation of ALOS/PALSAR outputs was carried out using ground penetrating radar (GPR) measurements. Three GPR long profiles using a 200 MHz antenna were scanned along with areas that were annotated according to ALOS/PALSAR results (high backscattering coefficient). The GPR system operated by a low-frequency antenna with a frequency of 200 MHz was capable of detecting the annotated geological structures beneath the sand sheets. Furthermore, statistical comparison of L-band SAR and GPR data illustrated a correlation that can reveal identical regions to delineate subsurface structures. These results prove that the integration of synthetic aperture radar SAR (L-band) and on-site low-frequency radar systems can be vital to detect soil structures down to several meters, ultimately innovating Earth observation systems for geological and hydrogeological mapping in arid regions.

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Section: Introductionmentioning

confidence: 99%

Validation of ALOS/PALSAR subsurface penetration depth in arid regions based on field ground-penetrating radar measurements

Mansour

Zaher

Deep

et al. 2022

Preprint

View full text Add to dashboard Cite

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Validation of ALOS/PALSAR Subsurface Penetration Depth in Farafra Oasis as an Arid Region Based on Field Ground-Penetrating Radar Measurements

Mansour,

Zaher,

Al deep

et al. 2024

Sens Imaging

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Inclinometer and Improved SBAS Methods with a Random Forest for Monitoring Landslides and Anchor Degradation in Otoyo Town, Japan

2023

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Kochi Prefecture is located in an active zone of Japan that is frequently subjected to landslides due to heavy precipitation in typhoon seasons. Slow-moving landslides have been reported by both the local prefectural authorities and the National Government of Japan. We observed landslide movements in Otoyo Town by using ground- and satellite-based tools. Despite the high cost of establishing a borehole inclinometer survey to obtain accurate ground-based measurements, no previous InSAR study has been conducted in Otoyo Town, and the capacity for regional discrimination between active and inactive slow-moving landslides when using these tools remains unclear. We found that the horizontal velocity component was dominant at a rate of 21.4 mm/year across the whole of Otoyo Town. Satellite-based monitoring of ground-anchor efficiency may be possible in combination with ground-based inclinometer surveys. Three types of land cover are present in the study area—urban, field, and forests—and we selected a random forest (RF) model to extract low-coherence pixels by using optical and radar satellite sensors to identify important features and precisely remove pixels causing decorrelation. Long-term monitoring results from ground-based surveys, including inclinometer (boreholes) and anchor tension distribution data, were compared with the results of synthetic radar by using coherence-based small baseline subset (CB-SBAS) measurements. Generally, landslide occurrence was investigated across the whole of Otoyo Town, and we specifically evaluated the reliability of InSAR measurements in the Kawai landslide as a study site scale. The activity of the Kawai landslide channel was evaluated with borehole inclinometer displacement measurements (15.46 mm) and an anchor pressure survey (736 kN) from 2016 to 2019, as well as the steady state of the area (1.7 mm for the borehole inclinometer and 175 kN for the anchor pressure measurements), although a high cumulative precipitation of 3520 mm was reached during 2020 due to the ground anchor efficiency, which showed a consistent tendency with respect to the InSAR displacement measurements (14 mm during 2018 and 2019 and 0.7 mm during 2020). This comparison showed a consistent time-series displacement correlation, which was strengthened after introducing the RF mask into the analysis procedure, as the RF model correction reduced the standard deviation from the line-of-sight (LoS) average velocity estimation by 1.9 mm/year. Our research will help mitigate landslide impacts in Otoyo Town and its surroundings.

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Geophysical site assessment of an active urban development site, southeastern suburb of Cairo, Egypt

Cited by 3 publications

References 29 publications

Validation of ALOS/PALSAR subsurface penetration depth in arid regions based on field ground-penetrating radar measurements

Validation of ALOS/PALSAR subsurface penetration depth in arid regions based on field ground-penetrating radar measurements

Validation of ALOS/PALSAR Subsurface Penetration Depth in Farafra Oasis as an Arid Region Based on Field Ground-Penetrating Radar Measurements

Inclinometer and Improved SBAS Methods with a Random Forest for Monitoring Landslides and Anchor Degradation in Otoyo Town, Japan

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