68 results found
Scoular J, Ghail R, Mason P, et al., 2022, Are measured InSAR displacements a function of the chosen processing method?, Quarterly Journal of Engineering Geology and Hydrogeology, Pages: qjegh2022-049, ISSN: 1470-9236
The benefits of InSAR to the civil engineering industry have been demonstrated on many occasions, however there is still a limited uptake by end-users, due to perceived differences between data providers and uncertainty around how to interpret results. This paper critically compares three datasets for London: Radarsat-2 (RS2) from 2011 to 2015, TerraSAR-X (TSX) from 2011 to 2017, and Sentinel-1 (STL1) from 2015 to 2017. Two of the datasets (TSX & RS2) were processed by commercial data providers, while the STL1 data were processed using ENVI® SARscape® by the authors. The results show an inverse relationship between the Pearson Correlation Coefficient and absolute total displacement of Persistent Scatterers (PS). There is a strong correlation between datasets for total displacement greater than 5 mm, but a weak or no correlation in the 0–3 mm range. Consequently, standard commercial InSAR datasets, processed with no a priori knowledge of the area of interest, have error margins below 3–5 mm but correctly detect all deformation phenomena exceeding this threshold. RS2-TSX both capture the spatial extent of the investigated area of dewatering induced subsidence, however STL1 measures a much broader, less pronounced zone of heave than TSX.
Wang Z, Lawrence J, Ghail R, et al., 2022, Characterizing micro-displacements on active faults in the Gobi Desert with time-series InSAR, Applied Sciences-Basel, Vol: 12, Pages: 1-24, ISSN: 2076-3417
This research investigates small-scale tectonic activity in the Jiujing region in Beishan, northwest China through the application of persistent scatterer (PS) Interferometric synthetic aperture radar (InSAR). PS InSAR is an effective monitoring tool in this unpopulated, arid, and unvegetated rural area, whose surface geology is dominated by a single large granitic intrusion, and which represents a candidate site for a geological disposal facility (GDF) for high-level radioactive waste (HLW) in China. This research demonstrates that faults F16-2, F17, F18, and F20-2 are still active, producing dip-slip motions along the fault planes. The lithological variations in weathering and erosion can be discounted as the cause for these small-scale displacement variations. The work has also identified 11 previously unknown faults, characterising them from vertical (DU) and eastward horizontal (DE) displacements along and across the faults. These newly discovered structures demonstrate how PS InSAR can be used to monitor and measure micro-scale movements on regional-scale faults, which, in many cases, were previously considered to be inactive. Thus, this also improves our understanding of local stress regimes in this area. The Jiujing region is part of a convergent fault zone dominated by NE-SW compression, leading to NE-SW crustal shortening and NW-SE elongation. Through determination of the sense of ground movement measured at irregularly distributed PS points, some faults are reverse and trending NW-SE, while others are normal and trending NE-SW, highlighting how InSAR can be used to resolve fault type and relative movements to monitor tectonic fault blocks at a regional scale.
Edgar J, Ghail R, Lawrence J, et al., 2022, The impact of facies variability within the Harwich Formation on ground engineering in the London area, UK, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 55, ISSN: 1470-9236
The Eocene Harwich Formation, underlying the Greater London (UK) area, presents many construction problems for design and location of tunnels, pipelines, and other engineering infrastructure projects. Variable deposits make up the sequence of the Harwich Formation. These include cemented fault zones, hard grounds, loose gravel and sand that, when unexpectedly encountered, can cause construction delays and increase costs. Here, we interpret borehole cores and logs, in-situ observations coupled with borehole derived samples, and calculate particle-size distributions to develop a general facies model that accounts for the lithological distribution within the Harwich Formation. This provides an improved geological framework for proposed subsurface construction that can reduce inherent engineering uncertainties, not only in the London region, but potentially in other similar geological environments.
Mider G, O'Connor W, Lawrence J, et al., 2021, An investigation into ground movement on the Ventnor landslide complex, UK using Persistent Scatterer Interferometry, Remote Sensing, Vol: 13, Pages: 1-20, ISSN: 2072-4292
Analysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data, historical ground investigation records and monitoring surveys carried out at Ventnor to relate observations to geology, geomorphology and rainfall. Decomposition of InSAR viewing geometries to vertical and horizontal aligned well with previous ground-based studies. Subsidence of −9.8 mm a−1 at the Lowtherville Graben and heave of +8.5 mm a−1 along the coastline south of Ventnor Park were observed. Decomposition to east-west geometry results showed an eastward displacement of approximately 12.4 mm a−1 along the coastline south of Ventnor Park, and a westward displacement of −3.7 mm a−1 throughout built up sections of Ventnor town, indicating the landslide was displacing more in an eastern direction than vertically. The cause of this movement was investigated by using publicly available intrusive boreholes paired with Persistent Scatterer Interferometry, and a new ground model spanning east-west parallel to the coastline was presented. No evidence of significant ground movement was observed along heavily protected sections of the coastline, suggesting coastal defences comprised of concrete aprons and rip rap appear to be an effective coastal management/landslide stabilisation tool when compared to rip rap alone. The mechanism of this increased stability is likely due to the combination of toe weighting and reduced toe erosion. A lag of approximately 13–20 days was observed between high rainfall events and subsequent peaks in ground displacement, which was shorter than a 29 day lag observed in a previous study. Similar observations of prolonged rainfall resulting in prolonged displacements were also observed. The study demonstrate
Kumar Joshi S, Gupta S, Sinha R, et al., 2021, Strongly heterogeneous patterns of groundwater depletion in Northwestern India, Journal of Hydrology, Vol: 598, Pages: 1-17, ISSN: 0022-1694
Northwestern India has been identified as a significant hotspot of groundwater depletion, with major implications for groundwater sustainability caused by excessive abstraction. We know relatively little about the detailed spatial and temporal changes in groundwater storage in this region, nor do we understand the interplay of factors controlling these changes. Groundwater managers and policymakers in India require such information to monitor groundwater development and make strategic decisions for the sustainable management of groundwater. Here, we characterise high-resolution spatio-temporal variability in groundwater levels and storage change across northwestern India through analysis of in situ measurements of historical groundwater level data. We note a slow gain in groundwater storage of + 0.58 ± 0.35 km3 for the pre-monsoon and + 0.40 ± 0.35 km3 for the post-monsoon period between 1974 and 2001. However, from 2002 to 2010, groundwater storage was rapidly depleted by −32.30 ± 0.34 km3 in the pre-monsoon and −24.42 ± 0.34 km3 in the post-monsoon period. Importantly, we observe marked spatial heterogeneity in groundwater levels and storage change and distinct hotspots of groundwater depletion with lateral length scales of tens of kilometers. Spatial variability in groundwater abstraction partially explains the depletion pattern, but we also find that the sedimentological heterogeneity of the aquifer system correlates broadly with long-term patterns of groundwater-level change. This correlation, along with the spatial agreement between groundwater level change and water quality, provides a framework for anticipating future depletion patterns and guiding groundwater monitoring and domain-specific management strategies.
Mider G, Lawrence J, Mason P, et al., 2020, Monitoring Littoral Platform Downwearing using Differential SAR Interferometry, Remote Sensing, Vol: 12, ISSN: 2072-4292
A methodology for the remotely sensed monitoring, measurement and quantification of littoral zone platform downwearing has been developed and is demonstrated, using Persistent Scatterer Interferometric Synthetic Aperture Radar data and analysis. The research area is a 30 km section of coast in East Sussex, UK. This area combines a range of coastal environments and is characterised by the exposure of chalk along the cliffs and coastal platform. Persistent Scatterer Interferometry (PSI) has been employed, using 3.5 years of Sentinel-1 SAR data. The results demonstrate an average ground level change of −0.36 mm a−1 across the research area, caused by platform downwearing. Protected sections of coast are downwearing at an average of −0.33 mm a−1 compared to unprotected sections, which are downwearing more rapidly at an average rate of −1.10 mm a−1. The material properties of the chalk formations in the platform were considered, and in unprotected areas the weakest chalk types eroded at higher rates (−0.66 mm a−1) than the more resistant formations (−0.53 mm a−1). At a local scale, results were achieved in three studies to demonstrate variations between urban and rural environments. Individual persistent scatterer point values provided a near-continuous sequence of measurements, which allowed the effects of processes to be evaluated. The results of this investigation show an effective way of retrospective and ongoing monitoring of platform downwearing, erosion and other littoral zone processes, at regional, local and point-specific scales.
Scoular J, Ghail R, Lawrence J, et al., 2020, Retrospective InSAR analysis of East London during the construction of the Lee Tunnel, Remote Sensing, Vol: 12, Pages: 1-19, ISSN: 2072-4292
The Lee Tunnel was constructed as the first part of the Thames Tideway Improvement scheme, between 2010 and 2016. With tunnelling for the East section of the main Thames Tideway Tunnel, which joins the Lee Tunnel at Abbey Mills Pumping Station, beginning in early 2020, this paper investigates patterns of deformation in East London during construction of the Lee Tunnel. An unexpected geological feature, later identified as a drift filled hollow, was discovered during tunnelling. This study demonstrates that had eight years of ERS Persistent Scatterer Interferometry (PSI) data been analysed prior to tunnelling, the unusual pattern of displacement may have been recognised and further targeted borehole investigations taken place before the launch of the tunnel boring machine. Results also show how areas of different land use, including cemeteries and historic landfill, exhibit differences in settlement behaviour, compared with surrounding terraced housing. This research highlights the challenges in interpreting PSI results in an urban area with ongoing construction and the value of a long archive of data, which now spans almost three decades in London, that can be used to establish a baseline prior to construction.
Brooke SAS, DArcy M, Mason PJ, et al., 2020, Rapid multispectral data sampling using Google Earth Engine, Computers & Geosciences, Vol: 135, Pages: 104366-104366, ISSN: 0098-3004
The advent of cloud-based GIS tools has enabled the rapid exploration and processing of geospatial datasets. The Google Earth Engine (GEE) platform provides a library of algorithms and a powerful application programming interface (API) to produce flexible cloud-based applications that leverage Google’s computing infrastructure for geospatial analysis. We introduce ”Spectral Point”, a new GUI tool developed in GEE that allows users to explore, process and extract multispectral data rapidly within a single browser window. The ability to access and measure spectral signals from surface deposits using the entire available Landsat and Sentinel 2 archive is of tremendous benefit to geomorphic research, removing the need to download and process terabytes worth of imagery. Spectral values from composite imagery collected in GEE that relate to changes in surface mineral composition agree with corresponding point values using conventional desktop Landsat processing. The ”Spectral Point” tool makes it fast and simple to extract quantitative, contrast-corrected brightness data from multispectral imagery compared conventional desktop-based approaches. At the same time, the user needs no experience developing code, proprietary third-party software or dedicated high-performance computing and only a modern web browser. The ”Spectral Point” tool has many potential applications in the remote study of Earth’s surface; for example, we explore a case study from the western United States that demonstrates how the tool can be used for mapping, geochronology, and estimating weathering rates for Quaternary landforms. With increasing numbers of satellites, we are now faced with a growing deluge of geospatial data. Cloud-based solutions to mapping, field reconnaissance and image processing will be increasingly necessary to handle this valuable but untapped satellite image resource. ”Spectral Point” is an example of a new generation o
Bischoff CA, Ghail RC, Mason PJ, et al., 2020, Revealing millimetre-scale ground movements in London using SqueeSAR™, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 3-11, ISSN: 1470-9236
A series of illustrated examples is presented here to demonstrate the capabilities of ground-level monitoring using InSAR (interferometric synthetic aperture radar). Greater London is an ideal area to demonstrate and validate measurements derived using InSAR; its continuous urban fabric and the regular acquisition of SAR images from high-resolution sensors, such as TerraSAR-X, allows detection and monitoring of over 1.7 million measurement points with millimetre-scale accuracy. The results, some of which are shown here, reveal fascinating spatial and temporal patterns of ground motion across London and demonstrate the benefit of using high-resolution InSAR technologies in engineering applications. Interpreting the motion patterns can be challenging, however, owing to their complex and sometimes mysterious causes; we therefore welcome any assistance in doing so and we hope this photographic feature serves to trigger interest.
Scoular JM, Croft J, Ghail RC, et al., 2019, Limitations of persistent scatterer interferometry to measure small seasonal ground movements in an urban environment, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 39-48, ISSN: 1470-9236
London Clay, which underlies the majority of Greater London, has a high shrink–swell potential that can result in damage to foundations and surface infrastructure due to seasonal expansion and contraction of the clay. Currently, surface movement as a result of shrink–swell is not monitored in London, meaning that the magnitude and cyclicity of these movements is poorly understood. Persistent Scatterer Interferometric (PSI) Synthetic Aperture Radar data provide high-precision line-of-sight displacement measurements at a high point density across urban areas, offering the possibility of routine shrink–swell monitoring across whole cities. To test this, PSI data derived from TerraSAR-X (TSX) observations for the period from May 2011 to April 2017 were analysed for shrink–swell patterns across three areas of London in Hammersmith, Muswell Hill and Islington. A consistent cyclicity and amplitude was detected at all sites and the number of cycles is comparable with those identified in rainfall data. The amplitude of these cycles is smaller than anticipated, most probably because of the resisting effect of roads and pavements. The Cranfield University Leakage Assessment from Corrosivity and Shrinkage (LEACS) database was used to subdivide the PSI data and the average velocity and amplitude of each class statistically tested for significant differences between classes. The results show that it is not possible to statistically isolate possible soil shrink–swell movement in TSX PSI data in London.
Bischoff CA, Mason PJ, Ghail RC, et al., 2019, Monitoring excavation-related ground deformation in london, uk using squeesar™, Pages: 5360-5367
InSAR technologies are becoming increasingly important in all phases of civil engineering projects. The high-resolution TerraSAR-X (TSX) data presented here demonstrate the unique advantages of using SqueeSARTM to monitor excavation-related ground deformation. The data reveal settlement troughs caused by Crossrail tunnels along their entire length. The settlement patterns are shown to be heterogeneous, both in extent and time. Ground-based monitoring data allow us to validate the remotely sensed measurements at Bond Street Station and the Limmo Peninsula. We also detect active dewatering, which has caused ground deformation over an area of several km². The TSX data show both ground settlement and the subsequent ground rebound caused by the different stages of dewatering. SqueeSARTM is used for historical ground deformation analysis and for ongoing monitoring. In general, InSAR is complementary to conventional ground-based measurement systems, and is the only way to create regional ground surface deformation maps with millimetre-scale accuracy.
D'Arcy M, Mason PJ, Roda-Boluda DC, et al., 2018, Alluvial fan surface ages recorded by Landsat-8 imagery in Owens Valley, California, Remote Sensing of Environment, Vol: 216, Pages: 401-414, ISSN: 0034-4257
Alluvial fans are important depositional landforms that offer valuable records of terrestrial sedimentation history if their surfaces can be mapped and dated accurately. Unfortunately, as this often depends on detailed field mapping and intensive absolute dating techniques, it can be a challenging, expensive and time-consuming exercise. In this study, we demonstrate that quantitative information about the ages of alluvial fan surfaces in Owens Valley, California, is recorded by Landsat-8 multispectral satellite imagery. We show that systematic changes in the wavelength-dependent brightness of fan surfaces occur gradually over a timescale of ~100 kyr in this semi-arid setting, and are highly correlated with known deposit ages. Using spectro-radiometry and X-ray diffraction analysis of sediment samples collected in the field, we interpret that surface reflectance evolves primarily in response to the in-situ production of secondary illite and iron oxide by weathering in this landscape. Furthermore, we demonstrate that first-order predictions of absolute fan surface age can be derived from multispectral imagery when an initial age calibration is available. These findings suggest that multispectral imagery, such as Landsat data, can be used (i) for preliminary mapping of alluvial fans prior to detailed field work and before choosing sampling sites for conventional dating techniques, and (ii) to extend age models to un-dated neighbouring surfaces with equivalent physical properties, once an age-brightness calibration has been established.
Agar S, Lawrence J, Ghail R, et al., 2018, PSInSAR remote sensing observations of deformation behaviour at Salisbury Plain, UK, Chalk 2018, Publisher: ICE Publishing, Pages: 269-274
PSInSAR is a radar remote sensing approach that offers measurements of ground deformation over large areas at sub-mm precision. The technique has significant potential for granting insight into ongoing geological processes. Data recovery in rural areas is challenging due to the highly inconsistent radar scattering behaviour exhibited by vegetated ground, and thus a rural area of the UK – Salisbury Plain - was used as a case study to examine the challenges and potential for PSInSAR techniques in rural areas. Results showed regional uplift of clay formations relative to the Chalk, which was attributed to clay shrink-swell correlated with seasonal increases in groundwater levels.
Mason P, 2018, The Earth as a planet
Liu J, Mason PJ, Bryant EC, 2018, Regional assessment of geohazard recovery eight years after the Mw7.9 Wenchuan earthquake: a remote-sensing investigation of the Beichuan region, International Journal of Remote Sensing, Vol: 39, Pages: 1671-1695, ISSN: 0143-1161
The earthquake of 12 May 2008 in Wenchuan County, Sichuan Province, China, devastated the entire Beichuan region. Sitting at the intersection of the Yingxiu-Beichuan and Pengguan faults, the region experienced seismic intensities of VIII–XI on the Liedu scale. High seismic intensity combined with inherent geomorphological and climatic susceptibility to slope failure resulted in widespread co-seismic geohazards (slope failures of various types), which decimated the region. The seismic characteristics of the Wenchuan earthquake and the co-seismic geohazard distribution in relation to various conditioning factors have previously been examined in depth. However, there has been a lack of regional assessment of temporal and spatial recovery from co-seismic geohazards. Triggered by the authors’ field observation of rapid recovery, this study presents a temporal series of geohazard maps, produced by manual interpretation of satellite imagery, to present an initial assessment of changes in geohazard occurrence in the Beichuan region since the Wenchuan earthquake. In particular, landscape recovery at the co-seismic geohazard sites, as indicated by re-vegetation, is analysed based on temporal/spatial characteristics of geohazard distribution, in relation to co-seismic deformation, distance from the rupture zone and slope angle. Eight years after the Wenchuan earthquake, the overall recovery stands at 65.48%, with approximately uniform annual rates of recovery at 13.45% a year between 2009 and 2011 and 10.56% a year between 2012 and 2016. Whilst co-seismic geohazards are concentrated on the hanging wall of the seismic fault, landscape recovery is more significant in the very highly deformed zone than in other areas. Recovery has been the greatest on slopes of <50° and peaks on 40°–50° slopes, where the area occupied by co-seismic geohazards was the largest. The block-slides and rock topples, which characterize high angle slopes, show much slower
Gupta S, Singh A, Thomsen KJ, et al., 2017, Counter-intuitive influence of Himalayan river morphodynamics on Indus Civilisation urban settlements, Nature Communications, Vol: 8, Pages: 1-14, ISSN: 2041-1723
Urbanism in the Bronze-age Indus Civilisation (~4.6–3.9 thousand years before the present, ka) has been linked to water resources provided by large Himalayan river systems, although the largest concentrations of urban-scale Indus settlements are located far from extant Himalayan rivers. Here we analyse the sedimentary architecture, chronology and provenance of a major palaeochannel associated with many of these settlements. We show that the palaeochannel is a former course of the Sutlej River, the third largest of the present-day Himalayan rivers. Using optically stimulated luminescence dating of sand grains, we demonstrate that flow of the Sutlej in this course terminated considerably earlier than Indus occupation, with diversion to its present course complete shortly after ~8 ka. Indus urban settlements thus developed along an abandoned river valley rather than an active Himalayan river. Confinement of the Sutlej to its present incised course after ~8 ka likely reduced its propensity to re-route frequently thus enabling long-term stability for Indus settlements sited along the relict palaeochannel.
Neal LC, Wilkinson JJ, Mason PJ, et al., 2017, Spectral characteristics of propylitic alteration minerals as a vectoring tool for porphyry copper deposits, Journal of Geochemical Exploration, Vol: 184, Pages: 179-198, ISSN: 0375-6742
Short-wave infrared (SWIR) reflectance spectroscopy is a quick and effective method of detecting and characterising hydrothermal alteration associated with ore deposits, and can identify not only mineral species but also changes in the major element composition of minerals. Porphyry deposits represent large accumulations of valuable metal in the Earth's crust and have extensive alteration signatures making them an attractive target for exploration, particularly by remote sensing which can cover large areas quickly. Reflectance spectroscopy has been widely applied in sericitic (phyllic), argillic and advanced argillic alteration domains because it is particularly effective in discriminating bright clay minerals. However, the propylitic domain has remained relatively unexplored because propylitic rocks are typically dark and produce relatively poorly-defined spectra.This study utilised an ASD TerraSpec 4 handheld spectrometer to collect SWIR spectra from rocks surrounding the Batu Hijau Cu-Au porphyry deposit in Indonesia, where previous work has identified systematic spatial variations in the chemistry of chlorite, a common propylitic alteration mineral. Spectra were collected from 90 samples and processed using The Spectral Geologist (TSG) software as well as the Halo mineral identifier to characterise mineralogy and extract the positions and depths of spectral absorption features, which were then correlated with major element geochemistry. Two diagnostic chlorite absorption features located at around 2250 nm and 2340 nm correlate with the Mg# (Mg/[Mg + Fe]) of chlorite, both in terms of wavelength position and depth. As the Mg# increases, the wavelengths of both features increase from 2249 nm to 2254 nm and from 2332 nm to 2343 nm respectively, and absorption depths also increase significantly. In the spatial dimension, these feature variations act as reasonably strong vectors to the orebody, showing systematic increases over a transect away from the porphyry centr
Ghail RC, Hall D, Mason PJ, et al., 2017, VenSAR on EnVision: taking Earth Observation radar to Venus, International Journal of Applied Earth Observations and Geoinformation, Vol: 64, Pages: 365-376, ISSN: 0303-2434
Venus should be the most Earth-like of all our planetary neighbours: its size, bulk composition and distance from the Sun are very similar to those of Earth. How and why did it all go wrong for Venus? What lessons can be learned about the life story of terrestrial planets in general, in this era of discovery of Earth-like exoplanets? Were the radically different evolutionary paths of Earth and Venus driven solely by distance from the Sun, or do internal dynamics, geological activity, volcanic outgassing and weathering also play an important part? EnVision is a proposed ESA Medium class mission designed to take Earth Observation technology to Venus to measure its current rate of geological activity, determine its geological history, and the origin and maintenance of its hostile atmosphere, to understand how Venus and Earth could have evolved so differently. EnVision will carry three instruments: the Venus Emission Mapper (VEM); the Subsurface Radar Sounder (SRS); and VenSAR, a world-leading European phased array synthetic aperture radar that is the subject of this article. VenSAR will obtain images at a range of spatial resolutions from 30 m regional coverage to 1 m images of selected areas; an improvement of two orders of magnitude on Magellan images; measure topography at 15 m resolution vertical and 60 m spatially from stereo and InSAR data; detect cm-scale change through differential InSAR, to characterise volcanic and tectonic activity, and estimate rates of weathering and surface alteration; and characterise of surface mechanical properties and weathering through multi-polar radar data. These data will be directly comparable with Earth Observation radar data, giving geoscientists unique access to an Earth-sized planet that has evolved on a radically different path to our own, offering new insights on the Earth-sized exoplanets across the galaxy.
Toms E, Mason PJ, Ghail RC, 2016, Drift-filled hollows in Battersea: investigation of the structure and geology along the route of the Northern Line Extension, London, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 49, Pages: 147-153, ISSN: 1470-9236
Drift filled hollows (DFHs) are a major subsurface hazard for engineering in London. They are characterised by a steeply inclined cone-shaped hollow into (sometimes through) the London Clay Formation, filled with unconsolidated fine to coarse-grained drift and often covered by terrace gravels, making them difficult to identify at the surface. Their origin remains uncertain but most likely formed towards the end of glacial epochs by meltwater scouring, perhaps of collapsed pingos. Usually associated with tributaries to the Thames, DFHs are particularly prevalent in the Battersea area, through which the Northern Line Extension (NLE) is to be built. This study uses 283 public borehole records and site reports to build a 3D geological ground model of two known DFHs in the Battersea area to develop a more complete understanding of their origin. We show that DFHs are likely older than previously assumed, dating from the end Anglian [MIS 12], ~300 ka ago, before the deposition of the River Terrace Deposits. The two DFHs modelled fall into distinct types: a small shallow DFH that is probably a purely scour feature in origin, and a larger, deeper DFH which probably formed by the scouring of a perhaps fault controlled pingo. It is unclear whether the faults controlled pingo formation passively by acting as a conduit for water, or in a more active sense by driving ground movements. Both DFHs represent a significant hazard for the NLE and require more detailed investigations to properly constrain their extent.
Liu JG, Mason PJ, 2016, Image Processing and GIS for Remote Sensing, Publisher: John Wiley & Sons, Ltd, ISBN: 9781118724200
Van Dijk W, Densmore A, Singh A, et al., 2016, Linking the morphology of fluvial fan systems to aquifer stratigraphy in the Sutlej-Yamuna plain of northwest India, Journal of Geophysical Research, Vol: 121, Pages: 201-222, ISSN: 0148-0227
The Indo-Gangetic foreland basin has some of the highest rates of groundwater extractionin the world, focused in the states of Punjab and Haryana in northwest India. Any assessment of theeffects of extraction on groundwater variation requires understanding of the geometry and sedimentaryarchitecture of the alluvial aquifers, which in turn are set by their geomorphic and depositional setting. Toassess the overall architecture of the aquifer system, we used satellite imagery and digital elevation modelsto map the geomorphology of the Sutlej and Yamuna fan systems, while aquifer geometry was assessedusing 243 wells that extend to ∼200 m depth. Aquifers formed by sandy channel bodies in the subsurfaceof the Sutlej and Yamuna fans have a median thickness of 7 and 6 m, respectively, and follow heavy-tailedthickness distributions. These distributions, along with evidence of persistence in aquifer fractions asdetermined from compensation analysis, indicate persistent reoccupation of channel positions and suggestthat the major aquifers consist of stacked, multistoried channel bodies. The percentage of aquifer material inindividual boreholes decreases down fan, although the exponent on the aquifer body thickness distributionremains similar, indicating that the total number of aquifer bodies decreases down fan but that individualbodies do not thin appreciably, particularly on the Yamuna fan. The interfan area and the fan marginal zonehave thinner aquifers and a lower proportion of aquifer material, even in proximal locations. We concludethat geomorphic setting provides a first-order control on the thickness, geometry, and stacking pattern ofaquifer bodies across this critical region.
Ghail RC, Mason PJ, Skipper JA, 2015, The geological context and evidence for incipient inversion of the London Basin, XVI ECSMGE 2015, Pages: 3523-3528
A reappraisal of ground investigation data across London reveal that a range of unexpected ground conditions, encountered in engineering works since Victorian times, may result from the effects of ongoing inversion of the London Basin. Site investigation borehole data and the distribution of river terrace deposits of the Thames and its tributaries reveal a complex pattern of block movements, tilting and dextral transcurrent displacement. Significant displacements (~10 m) observed in Thames terrace gravels in borehole TQ38SE1565 at the Lower Lea Crossing, showing that movement has occurred within the last ~100 ka. Restraining bends on reactivated transcurrent faults may ex-plain the occurrence of drift filled hollows, previously identified as fluvially scoured pingos, by faulting and upward migration of water on a flower structure under periglacial conditions. Mapping the location of these features constrains the location of active transcurrent faults and so helps predict the likelihood of encountering hazardous ground conditions during tunnelling and ground engineering.
Mason PJ, Ghail RC, Bischoff C, et al., 2015, Detecting and monitoring small-scale discrete ground movements across London, using Persistent Scatterer InSAR (PSI), XVI ECSMGE, Publisher: ICE Publishing
The geology of London is surprisingly poorly understood and, until recently, has been accepted as that of an unfaulted subsidingintraplate basin. The detection of deformation in such quiescent intraplate regions is, however, rather difficult since the movementrates are at least an order of magnitude less than those at plate margins. Growing evidence from across the capital indicates that London'sground conditions are considerably more complex than expected and that faulting is almost always involved.PSInSAR is a developing technique widely used to detect and monitor ground subsidence, especially in urban settings, the movements ofwhich may be up to tens of millimetres. This work focuses on the detection of smaller scale ground movements (of a few millimetres),which we believe are caused by fault-controlled intraplate adjustments, using PSInSAR.The London PSInSAR dataset derives from an imaging SAR archive spanning 18 years (1992 - 2000 and 2001 to 2010). Our preliminaryfindings have revealed systematic patterns of both vertical and horizontal ground displacement. These displacements appear to be faultconstrained and fit the predicted framework of Caledonian, Variscan/Alpine structures known to exist across southern Britain. More detailedanalysis has revealed some surprising patterns, which hint at discrete movements rather than continuous 'creep' over the 18 year period;we believe these are driven by basement faults beneath an inverting London basin.
Turconi L, Tropeano D, Savio G, et al., 2015, Landscape analysis for multi-hazard prevention in Orco and Soana valleys, North-Western Italy, Natural Hazards and Earth System Sciences Discussions, Vol: 3, Pages: 2221-2246, ISSN: 2195-9269
A Civil Protection Plan has been drafted for a 600 km2 mountainous region in NWItaly Consisting of Orco and Soana Valleys. It is a part of the oldest natural park inItaly and attracts several thousand tourists every year. The work is concerned with the analysis of relevant physiographic characteristics of this Alpine landscapehavingextremely variable geomorphology and possess a long history of instability. Thousandsof records as well as digital maps (involving overlay and comparison of up to 90 GISlayers) have been analyzed and cross-correlated to find out the details of the events.The study area experienced different types of natural hazards, typical of the whole Alpine environment. Thus, the present area has been selected for such multi-hazardresearch in which several natural processes have been investigated, concerning theirdamaging effects over the land. Due to 36 different severe hazardous events at least250 deaths have been recorded in the area since 18th Century, in the occasion of.
Singh A, Gupta S, Sinha R, et al., 2015, Large–scale avulsion of the late Quaternary Sutlej river in the NW Indo–Gangetic foreland basin, European Geosciences Union General Assembly 2015
River avulsions are important processes in the spatial evolution of river systems in tectonically active sedimentary basins as they govern large–scale patterns of sediment routing. However, the pattern and timing of avulsions in large river systems are poorly documented and not well understood. Here we document late Quaternary paleo– river channel changes in the Indo–Gangetic basin of northwest India. Using a combination of satellite remote sensing and detailed sediment coring, we analyse the large–scale planform geometry, and detailed sedimentary andstratigraphic nature of a major fluvial sedimentary deposit in the shallow subsurface. This sediment body records aggradation of multiple fluvial channel fills. Satellite remote sensing analysis indicates the trace of the buried channel complex and demonstrates that it exists in region of the Himalayan foreland where no major rivers are currently present. Thus it records the former drainage pathway of a major river, which has since been diverted. We use optically stimulated luminescence dating techniques to develop an age model for the stratigraphic succession and hence constrain the timing of river channel existence and diversion. Provenance analysis based on U–Pb dating of detrital zircons and detrital mica Ar–Ar ages indicate sediment sources in the Higher Himalayan Crystalline andLesser Himalayan Crystalline Series indicating that this paleo–river channel system formed a major perennial river derived from the main body of the Himalaya. Specifically we are able to fingerprint bedrock sources in thecatchment of the present–day Sutlej river indicating that the paleo–fluvial system represents the former course of the Sutlej river prior to a major nodal avulsion to its present day course. Our results indicate that on geologically relatively short time–scales, we observe dramatic along strike shifts in the location of major Himalayan rivers. Our sediment records
Turconi L, Tropeano D, Savio G, et al., 2015, Landscape analysis for multi-hazard prevention in Orco and Soana valleys, Northwest Italy, NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, Vol: 15, Pages: 1963-1972, ISSN: 1561-8633
Ghail RC, Skipper J, Mason PJ, 2014, Identification of Ground Engineering Hazards in London Through the Use of Predictive 4D Geomodelling Tools, Switzerland, Engineering Geology for Society and Territory, Publisher: Springer International Publishing, Pages: 907-911
Unexpected ground conditions are responsible for a number of engineering problems and hazards across London. A major reason for the unexpected nature of these events is the historical proprietary approach to site investigation, which has restricted knowledge transfer and inhibited the development of a London-wide geological context. Recent changes mean that much of these data are now accessible in the public domain for site investigation and useful in predicting the engineering hazards resulting from complex and variable geology. We advocate applying predictive 4D modelling to better constrain geological structures, facies, fissures and groundwater flow, and adopting an iterative approach that both informs local site models and updates the regional context. Reverse normal faulting, indicative of basin inversion, pull-apart structures and periglacial scour/pingo features are identified in a pilot study regional model. Applying this model to a small site investigation predicted otherwise unexpected faulting, generating horizontal fissuring that causes water to flow along the length of the fault system. Widely adopting this approach in London and other urban areas may substantially reduce the risk of unexpected ground hazards.
Wu M-C, Liu J, Cosgrove J, et al., 2014, Modelling of Yingxiu-Seichuan fault zone based on refined DInSAR data of 2008 Wenchuan earthquake, TECTONOPHYSICS, Vol: 630, Pages: 193-207, ISSN: 0040-1951
Barrott JJ, Dudeney AWL, Mason PJ, 2014, Spatial and temporal relationships between Eocene sand horizons and iron contamination in stream water in the Thames Basin west of London, UK, Geochemistry-Exploration Environment Analysis, Vol: 14, Pages: 33-44, ISSN: 1467-7873
Analyses of stream water samples associated with Tertiary (Eocene) sands of the Bracklesham Formation 30–60 km west of London showed numerous occurrences of groundwater containing elevated iron(II) concentrations (1–15 mg/l Fe), which oxidise to red-brown ferrihydrite in localised wetlands and streams and join onward flows towards the River Thames. GIS mapping of iron concentrations in relation to topographical and geological data within a 20×30 km project area indicated some 168 km of iron-contaminated water.The results are consistent with downward permeation of groundwater through contained Camberley, Windlesham and Bagshot sand horizons and predominant W-E groundwater flow of up to 35 km in the Bagshot horizon, which rests on impermeable London Clay. Glauconite, comprising up to 70% of the sand near the base of the Windlesham horizon, apparently provides the main source of soluble iron in the near-anoxic, near-neutral, conditions normally prevailing. Pyrite is also a possible source, especially where quarrying or other excavation releases water from previously isolated volumes, simultaneously causing elevated sulphate and acidity levels via relatively rapid sulphide oxidation. Mechanisms proposed are underpinned through comparison with reports on analogous systems in the UK and abroad.Streams and lakes in the vicinity of seepages are highly visible and of decreased biodiversity. However, because of their natural origin, they are not subject to the same public concern and environmental control as compositionally similar near-neutral water from many former coal mines elsewhere - where iron derives primarily from pyrite. Also, while comparatively persistent, they appear destined for rapid depletion in geological terms: the unusual isolation of the sands until the Quaternary indicates a short leaching period and suggests a reason why iron-rich water from natural ferruginous sands is seldom of sufficient significanc
Wu M-C, Liu JG, Mason PJ, 2013, Adaptive local kriging to retrieve slant-range surface motion maps of the Wenchuan earthquake, INTERNATIONAL JOURNAL OF REMOTE SENSING, Vol: 34, Pages: 7589-7606, ISSN: 0143-1161
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