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Evidence for the timing and pace of past grounding line retreat of the Thwaites Glacier system in the Amundsen Sea embayment (ASE) of Antarctica provides constraints for models that are used to predict the future trajectory of the West Antarctic Ice Sheet (WAIS). Existing cosmogenic nuclide surface exposure ages suggest that Pope Glacier, a former tributary of Thwaites Glacier, experienced rapid thinning in the early to mid-Holocene. There are relatively few exposure ages from the lower ice-free sections of Mt. Murphy (<300 m a.s.l.; metres above sea level) that are uncomplicated by either nuclide inheritance or scatter due to localised topographic complexities; this makes the trajectory for the latter stages of deglaciation uncertain. This paper presents 12 new 10Be exposure ages from erratic cobbles collected from the western flank of Mt. Murphy, within 160 m of the modern ice surface and 1 km from the present grounding line. The ages comprise two tightly clustered populations with mean deglaciation ages of 7.1 ± 0.1 and 6.4 ± 0.1 ka (1 SE). Linear regression analysis applied to the age–elevation array of all available exposure ages from Mt. Murphy indicates that the median rate of thinning of Pope Glacier was 0.27 m yr−1 between 8.1–6.3 ka, occurring 1.5 times faster than previously thought. Furthermore, this analysis better constrains the uncertainty (95 % confidence interval) in the timing of deglaciation at the base of the Mt. Murphy vertical profile (∼ 80 m above the modern ice surface), shifting it to earlier in the Holocene (from 5.2 ± 0.7 to 6.3 ± 0.4 ka). Taken together, the results presented here suggest that early- to mid-Holocene thinning of Pope Glacier occurred over a shorter interval than previously assumed and permit a longer duration over which subsequent late Holocene re-thickening could have occurred.

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 demonstrates the capabilities of the PSI methodology in identifying the same ground movements that conventional methods provide. By providing detailed analysis of ground deformation of the Ventnor landslide, we demonstrate small ground movements, validated with existing ground movement surveys. Similar methodology can be applied to coastal landslides in urban environments worldwide, providing a relatively cheap and rapid resource for coastal landslide monitoring.

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. Thematic collection: This article is part of the ‘Measurement and monitoring’ collection available at: https://www.lyellcollection.org/cc/measurement-and-monitoring

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.

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, and 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 also in other similar geological environments.

If Venus were a newly discovered exoplanet, it would be one of the most Earth-like yet identified. Its similarity in size, bulk density and cloud top temperatures give no clue to the hellish temperatures at its surface. Venus hosts an array of geological features as complex as Earth, but without its organisation, and sustains a chemically reactive atmosphere, but without life. Proposed in response to ESA’s M5 call, with enabling support from NASA, EnVision is currently in Phase A study for the next medium-class mission opportunity proceeding towards a final mission selection in summer 2021 for a launch in 2032. Here we discuss the science questions motivating the mission in more detail. Building on discoveries from Magellan, Venus Express and Akatsuki, EnVision will focus on three overarching questions: Is Venus geodynamically active? How did Venus arrive at its current state? How does the Venus climate work and how do the interior, surface and atmosphere interact? 1 – Is Venus geodynamically active? Venus should be geologically active today and its globally young surface implies extensive volcanic resurfacing, but whether this happened in episodic global events or in a continuous process of small-scale resurfacing is uncertain. Constraining the rate of volcanic and tectonic activity can reveal whether Venus occupies one of these end members, or lies somewhere on the spectrum between. Magellan radar image mosaic of a 550 km wide region of Lada Terra (47°S, 25°E) showing a system of radar-bright and dark lava flows breaching a ridge belt and ponding in a large radar-bright deposit covering 100,000 km². Ammavaru, the source caldera, lies 300 km to the west (JPL/Caltech). Understanding the tectonic regime driving resurfacing and heat loss is as important as knowing the rate of activity. The surface appears partitioned into areas of low strain bounded by narrow high strain margins. The abundance of steep slopes and landslides implies active uplift in these high strain areas, but existing data provide no constraint on the frequency of landslides or rates of tectonic movement. Are the low strain regions actively created and destroyed, like Earth’s oceanic plates, or simply mobilised locally? What is the significance of the global network of elevated rift systems and linear lowland wrinkle-ridged plains? Unique to Venus are coronae, quasi-circular volcano-tectonic features, typically 100–500 km across. Are they the surface expression of plumes, or magmatic intrusions, or subduction zones? The processes of weathering, mass wasting and aeolian transport are critical for understanding both the geological history and climatic evolution of Venus. Venus Express found anomalously high IR emissivities near suspected active volcanoes, interpreted as fresh, unweathered lava flows, but both their mineralogy and the weathering processes involved are unknown. Magellan detected several, probably impact-related, dune fields at the limit of its resolution, and found indirect evidence for globally distributed smale-scale ripples. 2 – How Did Venus Arrive at its Current State? The cratering record reveals that the Venus surface is, on average, under 1 Ga old. While some areas are likely active today, other regions, e.g. the tessera highlands, may be considerably older. Magellan data imply a variety of age relationships and long-term activity, with a non-random association between geological features and elevation, e.g. the uplands are consistently more deformed than the lowlands. Impact craters themselves show alteration to dark floors, perhaps from airfall deposits or magmatic resurfacing. Densely fractured plains (right) abutting tessera (bottom); both are embayed by younger plains (dark areas). A steep-sided volcanic dome (upper left) may be the source of the plains or unrelated to them, and older or younger than the tesserae. Magellan image at 46°N, 360°E, after Basilevsky and McGill (2007). Constraining the history is critical to understanding not only when and how resurfaced, but whether that activity has changed systematically through time. Were the plains formed in a short period by massive outpourings or by many thousands of small flows over their entire history? Or did many different mechanisms – including sedimentary processes – operate at different times and places? Globally, Venus exhibits perhaps even more tectonic deformation than Earth: what is its role in resurfacing the planet and have the regimes of tectonic deformation changed over time? How did tesserae, especially, accumulate their extraordinary degree of deformation? The interior of Venus is probably Earth-like, but not the same; its core size is poorly constrained by Magellan gravity data. These data are consistent with an organised pattern of mantle convection but lack the resolution necessary to connect it with geological-scale features. 3 - How does the Venus climate work and how do the Interior, Surface and Atmosphere Interact? How and why the atmospheres of two Earth-like planets evolved so differently is one of the many compelling reasons to study Venus, directly addressing the question of how our own world became habitable. Understanding its evolution depends on knowing the exchanges between its interior, surface and space. The lower/middle clouds of Venus as imaged by Akatsuki IR2 camera. Dark areas represent thicker clouds, which may represent volcanic plumes of ash or sulphate particulates. (JAXA/ISAS/DART/Damia Bouic) Models suggest that the clouds are maintained by a constant input of H2O and SO2, both of which vary considerably, perhaps because of volcanic emissions. Elevated D/H ratios indicate the loss of early oceans, but the ‘starting’ mantle D/H ratio is unknown. Identification of granites in the ancient highlands would support this inference, but the direct detection and characterisation of volcanic volatiles is key to inferring past climate evolution. Beyond the specific investigations outlined above, however, the most important unknown factor in determining the present day state of Venus and its atmosphere, and how it arrived at that state, is the interaction between the interior, surface and atmosphere: the whole being more than the sum of the parts. References Basilevsky and McGill (2007), Surface evolution of Venus, in Exploring Venus as a Terrestrial Planet, Geophysical Monograph Series 176, edited by L. W. Esposito, E. R. Stofan and T. E. Cravens, pp. 23-43, American Geophysical Union, Washington, DC

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.

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.

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 of web-based remote sensing tools available for Earth scientists, leveraging the revolution in cloud-based processing power and access to entire satellite image archives.

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.

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 centre, peaking at distances of around 1.6 km, which matches the spatial trend displayed by Mg#, as well as various trace element indicators in chlorite. The hull slope in spectra between 1400 nm and 1900 nm is also shown to increase with Mg#, and the position of an absorption feature at 1400 nm increases with the Al:Si ratio, a parameter that also tends to increase with proximity to porphyry deposits. Feature depth variations in particular appear to represent a new finding in chlorite reflectance spectroscopy; however, the causes are not entirely clear and require further investigation. Nonetheless, the systematic behaviour provides a potentially useful new tool for exploration in propylitic alteration zones.

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

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.

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.

The study area (600 km2), consisting of Orco and Soana valleys in the Western Italian Alps, experienced different types of natural hazards, typical of the whole Alpine environment. Some of the authors have been requested to draw a civil protection plan for such mountainous regions. This offered the special opportunity (1) to draw a lot of unpublished historical data, dating back several centuries mostly concerning natural hazard processes and related damages, (2) to develop original detailed geo-morphological studies in a region still poorly known, (3) to prepare detailed thematic maps illustrating landscape components related to natural conditions and hazards, (4) to thoroughly check present-day situations in the area compared to the effects of past events and (5) to find adequate natural hazard scenarios for all sites exposed to risk. The method of work has been essentially to compare archival findings with field evidence in order to assess natural hazard processes, their occurrence and magnitude, and to arrange all such elements in a database for GIS-supported thematic maps. Several types of natural hazards, such as landslides, rockfalls, debris flows, stream floods and snow avalanches cause huge damage to lives and properties (housings, roads, tourist sites). We aim to obtain newly acquired knowledge in this large, still poorly understood area as well as develop easy-to-interpret products such as natural risk maps.

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.

Differential interferometric synthetic aperture radar (DInSAR) provides an essential constraint for forward modelling of seismic faulting. However, the crucial evidence of deformation along the very near vicinity of a seismic fault is often missing because chaotic ruptures destroy the InSAR signal coherence; such is the case of the Yingxiu–Beichuan fault zone of the 2008 Wenchuan earthquake. We developed an Adaptive Local Kriging (ALK) interpolation method to produce a refined DInSAR dataset which continues without the interruption of decoherence gaps. Thus the 3D configuration of the seismic faulting can be better constrained for forward modelling using the Poly3D software. Through parameter fine tuning in a sequence of trial and error simulation, the best fitting between the simulated interferogram and the ALK refined DInSAR interferograms is achieved using a structural model of the Yingxiu–Beichuan fault zone which comprises a total of 14 segments with dip angles varying from 20° to 60°, in the south-west, to 40° to 70°, in the north-east; some major fault segments are composed of multiple planes with varying dip angles. The model reveals that in the much disputed Beichuan–Pengguan area, the Yingxiu–Beichuan fault links with the Pengguan fault (which dips to the NW at ~ 30°) at a depth of ~ 13 km. These two structures are interpreted as representing the foreland propagation of the Yingxiu–Beichuan fault by footwall collapse, a process that, in the vicinity of the Pengguan fault, involves the transfer of displacement from the older, Yingxiu–Beichuan fault to the younger Pengguan fault.

Kriging is a widely used technique for raster data interpolation from point samples, such as in the generation of digital elevation models and geochemical maps. The quality of the result depends on both spatial distribution of the sampled values and nature of the semivariogram model, which fits an empirical global function to the sample data set to predict values at the unknown locations. However, such a semivariogram model may not be suitable for data sets with complex local trends in spatial distribution, such as those observed in differential interferometric synthetic aperture radar DInSAR data of the Wenchuan earthquake. Here we propose a modified kriging method, adaptive local kriging ALK, for the retrieval of data lost through decoherence in Advanced Land Observing Satellite ALOS phased array L-band synthetic aperture radar PALSAR DInSAR data, within the intensely deformed fault zone of the 2008 Wenchuan earthquake. In ALK, a series of dynamic linear local semivariogram models is used rather than a global semivariogram for the whole data set. The localized adaptive approach ensures accurate interpolation in the areas of good DInSAR data with small decoherence gaps and avoids drastic errors in the extensive decoherence gaps; the overall value prediction is thus significantly improved, as confirmed by comparison with the original DInSAR data and fidelity verification experiments.

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 significance to be reported.

EnVision is an ambitious but low-risk response to ESA's call for a medium-size mission opportunity for a launch in 2022. Venus is the planet most similar to Earth in mass, bulk properties and orbital distance, but has evolved to become extremely hostile to life. EnVision's 5-year mission objectives are to determine the nature of and rate of change caused by geological and atmospheric processes, to distinguish between competing theories about its evolution and to help predict the habitability of extrasolar planets. Three instrument suites will address specific surface, atmosphere and ionosphere science goals. The Surface Science Suite consists of a 2.2 m 2 radar antenna with Interferometer, Radiometer and Altimeter operating modes, supported by a complementary IR surface emissivity mapper and an advanced accelerometer for orbit control and gravity mapping. This suite will determine topographic changes caused by volcanic, tectonic and atmospheric processes at rates as low as 1 mm a -1. The Atmosphere Science Suite consists of a Doppler LIDAR for cloud top altitude, wind speed and mesospheric structure mapping, complemented by IR and UV spectrometers and a spectrophotopolarimeter, all designed to map the dynamic features and compositions of the clouds and middle atmosphere to identify the effects of volcanic and solar processes. The Ionosphere Science Suite uses a double Langmiur probe and vector magnetometer to understand the behaviour and long-term evolution of the ionosphere and induced magnetosphere. The suite also includes an interplanetary particle analyser to determine the delivery rate of water and other components to the atmosphere. © 2011 Springer Science+Business Media B.V.

The devastating earthquake that occurred in Wenchuan County, Sichuan Province, China, on the 12th May 2008, caused widespread damage and devastation to rural communities and economy. The terrain of the entire region has been weakened and is now highly susceptible to long-term slope instability that will trouble this region for many years to come. Before the earthquake, the maximum seismic intensity expected in the region was VI–VIII in the 12-degree Liedu scale (the intensity measure adopted in China). However, the actual intensity caused by the earthquake ranged between VIII and XI. The seismic intensity map is practical for regional guidance but lacks the detail to provide an adequate representation of the true damage level, in terms of current status and future potential in such a seismically active and populated region, especially when the hazards and risks are likely to be multiple and cascading in high relief areas. This paper presents a GIS based novel approach to earthquake damage zone modelling using satellite remote sensing and DEM data. The novelty is to take into account the co-seismic ground deformation (measured using differential SAR interferometry) as an important modulating factor in modelling the susceptibility of earthquake related geohazards, together with conventional multi-criteria factors which draw on geological and topographical variables such as rock competence, slope, proximity to drainage, and fracture density. The modulating effect of the earthquake greatly enhances the susceptibility in the areas where the majority of the ensuing landslides and debris-flows actually took place. When this susceptibility model is further modulated by the mapped surface disruption caused by the earthquake (which encompasses all forms of mass movement and urban destruction), it is directly linked to seismic intensity and we call it “earthquake damage”. The output earthquake damage map represents both the current damage status as well as the future damage (hazard) potential. The resulting earthquake damage map for the Beichuan region clearly defines a series of zones of increasing seismic intensity, approximately corresponding to Liedu values VIII–XI but with great details.

The launch of the first spaceborne hyperspectral instrument, Hyperion, in 2000 has provoked further research into its capabilities with regard to mineral exploration. Our study in the remote, mountainous region of Pulang, China employed a two-step progressive approach, first to locate target areas characterized by hydrothermal mineral alteration, using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and secondly, to attempt detailed mineral mapping using Hyperion. The preliminary target detection involved principal components and broad-band spectral analysis and led to the detection of two target areas characterized by argillic alteration, iron-oxide-and sulphate-bearing minerals. A focused hyperspectral study followed using Spectral Angle Mapper (SAM) and Mixture Tuned Matched Filtering (MTMF) techniques, which allowed mineral species to be discriminated and mapped in more detail. This combined broad-band and hyperspectral approach is feasible and advantageous for mineral exploration in remote areas where primary information is limited or unavailable.

Observations of neutral flow around an isolated island are presented. the island has a fairly smooth shape with slopes of about 30° and a horizontal section which is roughly elliptical with axis ratio 1.5. the flow field 4 m above the surface shows a speed-up around the sides and over the summit, with reverse flow on the lee slope. Measurements with an instrumented aircraft, of the mean flow in the wake of the island reveal a single very powerful trailing vortex, with axis close to the upstream wind direction. There are indications that the single vortex was a consequence of the asymmetry caused by the island's elliptical shape. Measurements of fluctuating quantities with a tethered balloon system show marked changes in the components of the turbulence energy in the flow around the side of the hill.

Observations of flow in a nearly two-dimensional valley located within a succession of similar ridges and valleys are presented. Measurements of the mean flow have been made at all times of the day and are found to be well characterized by a suitably defined Froude number. the unstable and neutral daytime flow shows a flow separation whilst when the Froude number has a value of about two (usually around evening and dawn transitions) the flow is attached and the valley well ventilated. For smaller values of Froude number the flow speed in the valley reduces and a characteristic ‘drainage’ flow occurs. In addition to mean flow measurements and soundings of temperature structure, measurements were also made of turbulence energy and stress. This allows an estimate of the effective value of the surface roughness, zo, and an indication of the stability dependence of the momentum transfer to be made.

This paper is focussed on the hazard impact of landslides in the Three Gorges, and represents the progression of our ongoing study on regional land instability assessment in the Three Gorges area using imagery data from the Advanced Spaceborne Thermal Emission Radiometer (ASTER). The key development here is the establishment of a model that integrates land instability with several factors that can relate hazard to human life, such as slope failures occurring in proximity to built-up areas and roads, and areas of high landslide risk along the bank of Yangtze and its major tributaries. The method correctly identifies some of the known destructive landslides in the region, like Qianjiangping and Huangtupo, as belonging to areas of potentially high landslide impact. Our results suggest that several population centres, including the towns of Wushan and Badong, are rated at high landslide hazard levels. This study highlights the importance of differentiating between landslide types within susceptibility assessment, and identifies those locations in the Three Gorges where the probability of landslide occurrence with negative impact to life and property is greatest.

An imageodesy study has been carried out, using pre‐ and post‐event Landsat‐7 Enhanced Thematic Mapper Plus (ETM+) images, to reveal regional co‐seismic displacement caused by the Ms 8.1 Kunlun earthquake in November 2001. The two Landsat scenes, Kusai Lake and Buka Daban, cover an area of some 57 600 km2 (320 km W–E and about 180 km N–S), which includes most of the fault rupture zone. The co‐seismic displacement measured in the Kusai Lake scene shows that the average left‐lateral shift along the Kunlun fault is 4.8 m (ranging from 1.5 to 8.1 m) and the maximum shift appears west of the Kusai Lake. The splayed nature of the fault to the west of Buka Daban, where the fault splits into three branches, causes the displacement pattern to become complicated. Here the average left‐lateral shift, between the south side of the southern branch and the north side of the northern branch, is 4.6 m (ranging from 1.0 to 8.2 m). Our results also illustrate that the south side of the fault is the ‘active’ block, moving s...

This paper presents an integrated remote sensing—GIS approach for identifying areas vulnerable to rapid erosion in Almeria Province, Southeast Spain. Earth Resources Satellite (ERS) Synthetic Aperture Radar (SAR) multi-temporal interferometric coherence imagery has been used to detect rapid erosion that causes random changes in the micro-topography of a land surface. These small scale changes result in reduced coherence of the radar signals between the initial and eroded states. However, the detection solely based on coherence imagery is not exclusive because other factors may cause losing coherence as well. A Geographic Information System (GIS) is then used to derive criteria for a set of environmental conditions favourable to rapid erosion from multi-datasets including Landsat Enhanced Thematic Mapper (ETM� ) imagery and geological maps. The areas predicted to be most vulnerable to rapid erosion across the imagery are then identified where hard evidence of low coherence coincides with favourable conditions.

This paper reports a regional assessment of landslide hazard in the Three Gorges area, China, based on Terra-1 satellite Advanced Spaceborne Thermal Emission Radiometer (ASTER) imagery data, including a stereo image-derived Digital Elevation Model (DEM) and multi-spectral reflective and thermal imagery, in combination with limited field investigation. The Three Gorges dam and reservoir project has gained international attention, not only for its great potential for hydro-electrical power generation and flood control, but also for its potentially harmful effects on the environment and socio-economy. The most significant and widespread natural hazard in the region is slope instability. A simple, multi-variable elimination and characterisation model, employing geometric mean and Boolean decision rules, has been applied to a multi-criterion image dataset to categorise the area into a series of potential landslide hazard levels, which are presented in map form. The results presented here show high levels of hazard in and around all the main inhabited areas along the river. Limited fieldwork has been conducted to provide reliable ground control and the results of this paper show good correlation with this field evidence.

Geohazard mapping has been developed using multi-form, digital image data, permitting a regional assessment of risk concerning slope instability. Landsat Thematic Mapper and multi-temporal SPOT-Panchromatic image data have been processed to identify land use patterns and soil mineralogy information, supported by field measurements using spectroscopy and X-Ray Diffraction (XRD). These have been used to identify slope instabilities generated by the storm that struck Piemonte in November 1994. This event caused many fatalities and produced widespread mass movement, flooding and consequential damage to property. Slope angle and slope aspect data were derived from a Digital Elevation Model (DEM), produced from stereo air-photographs. The geohazard map was then compiled by merging digital slope data with geotechnical characteristics,utilizing map algebra within a Geographical Information Systems (GIS).

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.

Large eddy simulations sometimes use monotone advection schemes. Such schemes are dissipative, and the effective subgrid model then becomes the combined effect of the intended model and of the numerical dissipation. The impacts on simulation reliability are examined for the cases of dry convective and neutral planetary boundary layers. In general it is found that the results in the well-resolved flow interior are insensitive to the details of the advection scheme. However, unsatisfactory results may be obtained if numerical dissipation dominates where the flow becomes less well resolved as the surface is approached.

Large eddy simulations use a subgrid model, which is characterized by a length scale that is often related to the scale of the computational mesh by a numerical constant, Cs. Mason and Callen argued that this subgrid model and its length scale define and impose the filter operation of the simulation. They saw Cs as a measure of numerical accuracy. Others have sought to link the filter operation to the computational mesh and have viewed Cs as needing determination for correct implementation. Here tests with a high resolution of 224 × 224 × 200 grid points are found to confirm Mason and Callen’s view. These simulations are also used together with lower-resolution simulations to illustrate the degree of convergence achieved. Some erroneous features of the simulations are identified through this test. For the case of buoyant convection, the buoyancy dependence of the subgrid model is further examined. Most available subgrid models allow for buoyancy fluxes changing the level of the subgrid energy but...

Textural enhancements using co-registered, multi-temporal, digital remotely sensed imagery have been used to study slope instability at three landslide localities. The remotely sensed imagery consists of Landsat TM, SPOT Pan and Daedalus 1268 Airborne Thematic Mapper (ATM); stereo, black and white aerial photographs have also been used. Image processing provides spatial and textural information concerning landform change, landslide location and morphology. The enhanced imagery can be integrated with digital elevation models (DEMs), as can other map and geotechnical data, into a GIS to analyse quantitatively the effect of slope geometries on the observed landsliding. The suitability of available imagery depends upon the type and scale of the study and the landslide dimensions. The case histories have shown that spatial resolution is the most important parameter for successful landslide identification. The optimum imagery is provided by a combination of textural and spectral enhancements using different types of imagery.