Susceptibility evaluation and mapping of China’s landslides based on multi-source data

Landslides are occurring more frequently in China under the conditions of extreme rainfall and changing climate, according to News reports. Landslide hazard assessment remains an international focus on disaster prevention and mitigation, and it is an important step for compiling and quantitatively characterizing landslide damages. This paper collected and analyzed the historical landslide events data of the past 60 years in China. Validated by the frequencies and distributions of landslides, nine key factors (lithology, convexity, slope gradient, slope aspect, elevation, soil property, vegetation coverage, flow, and fracture) are selected to construct landslide susceptibility (LS) empirical models by back-propagation artificial neural network method. By integrating landslide empirical models with surface multi-source geospatial and remote sensing data, this paper further performs a large-scale LS assessment throughout China. The resulting landslide hazard assessment map of China clearly illustrates the hot spots of the high landslide potential areas, mostly concentrated in the southwest. The study implements a complete framework of multi-source data collecting, processing, modeling, and synthesizing that fulfills the assessment of LS and provides a theoretical basis and practical guide for predicting and mitigating landslide disasters potentially throughout China.

     

How to avoid false interpretations of Sentinel-1A TOPSAR interferometric data in landslide mapping? A case study: recent landslides in Transdanubia,Hungary

Natural Hazards - It is a crucial issue to better understand the usability of Sentinel-1 satellites in geomorphologic applications, since Sentinel-1 and the Copernicus Program are considered to be...     

Estimating coastal flood hazard of Tossa de Mar,Spain: a combined model – data interviews approach

Natural Hazards - Human settlements in coastal areas are highly vulnerable to extreme events, especially in the Mediterranean area, which houses a large number of tourists during the summer and...     

Microfabric and anisotropy of elastic waves in sandstone – An observation using high-resolution X-ray microtomography

Petrophysical experiments, using acoustic velocities to characterise anisotropies of mechanical behaviour of rocks are of essential relevance to understand the geomechanical behaviour of sandstone reservoirs under changing stress fields. Here, we present high-resolution X-ray microtomography (μ-CT) as a supplementary research tool to interpret anisotropic ultrasound velocities in sandstones with variation of isotopic stress.Specimens of two Lower Cretaceous sandstones (localities Bentheim and Obernkirchen, both Germany) have been used in petrophysical laboratory experiments under dry conditions to study ultrasonic sound velocities (frequency of signal input 1 MHz). Subsequently, oriented micro-plugs drilled from the sandstone samples were investigated using high-resolution X-ray microtomography. By means of image processing of the reconstructed scan images, geometric attributes such as mean structural thickness, orientation and tortuosity were evaluated from the μ-CT data for both pore space and grain skeleton. Our observations clearly indicate the different roles of pore space and grain skeleton in regard to the propagation of ultrasonic waves: because the pores do not transmit the waves, it was sufficient to investigate the average thickness of this fabric element. In contrast, as the ultrasonic waves traverse the rock via the adjacent grains, it was necessary to survey the actual travel lengths of seismic waves in the sandstone grain skeleton.     

Glacitectonics – a key approach to examining ice dynamics,substrate rheology and ice-bed coupling

The role of ice masses within the Earth's climate system and in landscape change is increasingly being recognised within regions that are either currently glaciated or were glaciated during the geological past. There are many different remote and field-based approaches to studying the products of glaciation. One approach – that of glacitectonics, focuses on the styles of deformation and tectonic imprint (folds, fractures, fabrics, foliations and lineations) produced as ice overrides or pushes into pre-existing rocks or sediment. This approach, when used in combination with other types of evidence, can be used to infer ice-dynamics, substrate rheology and ice-bed coupling. Of equal significance is the influence of glacitectonic structure upon the applied properties of glaciated terranes such as ground stability, hydrogeology and fluid migration (e.g. water, gas hydrates and hydrocarbons). This paper provides an introduction to this Special Issue on Glacitectonics, outlining the significance and historical development of this field of glacial geology, before introducing and summarising the contributions that make up the volume.     

A chromate-contaminated site in southern Switzerland – Part 1: Site characterization and the use of Cr isotopes to delineate fate and transport

The risk of groundwater contamination by chromate at a former chromite ore processing industrial site in Rivera (Switzerland) was assessed by determining subsoil Cr(VI) concentrations and tracking naturally occurring Cr(VI) reduction with Cr isotopes. Using a hot alkaline extraction procedure, a total Cr(VI) contamination of several 1000 kg was estimated. Jarosite, KFe₃((SO₄)_x(CrO₄)_1−x)₂(OH)₆, and chromatite (CaCrO₄) were identified as Cr(VI) bearing mineral phases using XRD, both limiting groundwater Cr(VI) concentrations. To track assumed Cr(VI) reduction at field scale δ⁵³Cr values of contaminated subsoil samples in addition to groundwater δ⁵³Cr data are used for the first time. The measurements showed a fractionation of groundwater δ⁵³Cr values towards positive values and subsoil δ⁵³Cr towards negative values confirming reduction of soluble Cr(VI) to insoluble Cr(III). Using a Rayleigh fractionation model, a current Cr(VI) reduction efficiency of approximately 31% along a 120 m long flow path was estimated at an average linear groundwater velocity of 3.3 m/d. Groundwater and subsoil δ⁵³Cr values were compared with a site specific Rayleigh fractionation model proposing that subsoil δ⁵³Cr values can possibly be used to track previous higher Cr(VI) reduction efficiency during the period of industrial activity. The findings strongly favor monitored natural attenuation to be part of the required site remediation measures.     

High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.     

Groundwater mining of bedrock aquifers in the Denver Basin – past,present, and future

The Denver Basin bedrock aquifer system is an important source of water for municipal and agricultural uses in the Denver and Colorado Springs metropolitan areas. The Denver area is one of the fastest growing areas in the United States with a population of 1.2 million in 1960 that has increased to over 2.4 million by 2000. This rapid population growth has produced a corresponding increase in demand for potable water. Historically, the Denver area has relied on surface water, however, in the past 10 years new housing and recreation developments have begun to rely on groundwater from the bedrock aquifers as the surface water is fully appropriated and in short supply.The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills Aquifers. The number of bedrock wells has increased from 12,000 in 1985 to 33,700 in 2001 and the withdrawal of groundwater has caused water level declines of 76 m. Water level declines for the past 10 years have ranged from 3 to 12 m per year. The groundwater supplies were once thought to last 100 years but there is concern that the groundwater supplies may be essentially depleted in 10 to 15 years in areas on the west side of the basin.Extensive development of the aquifer system has occurred in the last 25 years especially near the center of the basin in Douglas and El Paso Counties where rapid urban growth continues and surface water is lacking. Groundwater is being mined from the aquifer system because the discharge by wells exceeds the rate of recharge. Concern is mounting that increased groundwater withdrawal will cause water level declines, increased costs to withdraw groundwater, reduced well yield, and reduced groundwater storage. As the long-term sustainability of the groundwater resource is in doubt, water managers believe that the life of the Denver Basin aquifers can be extended with artificial recharge, water reuse, restrictions on lawn watering, well permit restrictions and conservation measures.     

How much uncertainty does the choice of data transforming method brings to heat risk mapping? Evidence from China

Natural Hazards - Increasing extreme heat events have threatened human health seriously in the context of global climate change. As an important policy tool to resist heat-related risks, growing...     

A scalable cyberinfrastructure solution to support big data management and multivariate visualization of time-series sensor observation data

This paper reports our research in developing a cyberinfrastructure platform to support multivariate visualization of data collected from distributed sensor network. Three new techniques were introduced in this platform: (1) a hybrid data caching strategy that takes advantages of a scalable and distributed time series database, OpenTSDB, to realize efficient data retrieval; (2) a hyper-dimensional data cube is established to map and translate multivariate and heterogeneous sensor data into a common data structure to support location-aware visual analysis; and (3) a data-driven visualization module is implemented to support interactive and dynamic visualization on a simulated virtual globe. A series of experiments were conducted to demonstrate the good runtime performance of the proposed system. We expect this work to make a major contribution to both the visualization building block development in cyberinfrastructure research and the advancement of visual presentation and analysis of sensor data in domain sciences.     

Submicron scale imaging of soil organic matter dynamics using NanoSIMS – From single particles to intact aggregates

The specific features of the nano-scale secondary ion mass spectrometry (NanoSIMS) technology with the simultaneous analysis of up to seven ion species with high mass and lateral resolution enables us to perform multi-element and stable isotope measurements at the submicron scale. To elucidate the power of this technique, we performed an incubation experiment with soil particles of the fine silt and clay fractions (from an Albic Luvisol), with occluded particulate organic material and intact soil aggregates (from a Haplic Chernozem), using a ¹³C and ¹⁵N labelled amino acid mixture as tracer. Before and during 6-day incubation after the addition of the label, samples were consecutively prepared for NanoSIMS analysis. For this purpose, two different sample preparation techniques were developed: (i) wet deposition and (ii) the sectioning of epoxy resin embedded samples. Single soil particles (fine silt/clay fraction) showed an enrichment of ¹³C and ¹⁵N after label addition that decreased over time. On aggregates of particulate organic matter, re-aggregated during the 6-day incubation experiment, we could show a spatially heterogeneous enrichment of ¹³C and ¹⁵N on the particle surface. The enrichment in ¹⁵N demonstrated the diffusion of dissolved organic matter into intact soil aggregate interiors. The prospects of NanoSIMS for three dimensional studies of stable C and N isotopes in organo-mineral associations is demonstrated by the recorded depth profiles of the organic matter distribution on mineral particles.     

Bibliometric analysis of the scientific production on coastal communities’ social vulnerability to climate change and to the impact of extreme events

Natural Hazards - Bibliometric analysis is a quantitative evaluation method for scientific research aiming at measuring knowledge expressed as scientific publications in a given field. This paper...     

Effect of a broad shallow sill on tidal circulation and salt transport in the entrance to a coastal plain estuary (Mira—Vila Nova de Milfontes, Portugal)

We describe the tidal circulation and salinity regime of a coastal plain estuary that connects to the ocean through a flood tide delta. The delta acts as a sill, and we examine the mechanisms through which the sill affects exchange of estuarine water with the ocean. Given enough buoyancy, the dynamics of tidal intrusion fronts across the sill and selective withdrawal (aspiration) in the deeper channel landward appear to control the exchange of seawater with estuarine water. Comparison of currents on the sill and stratification in the channel reveals aspiration depths smaller than channel depth during neap tide. During neap tide and strong vertical stratification, seawater plunges beneath the less dense estuarine water somewhere on the sill. Turbulence in the intruding bottom layer on the sill promotes entrainment of fluid from the surface layer, and the seawater along the sill bottom is diluted with estuarine water. During ebb flow, salt is effectively trapped landward of the sill in a stagnant zone between the aspiration depth and the bottom where it can be advected farther upstream by flood currents. During spring tide, the plunge point moves landward and off the sill, stratification is weakened in the deep channel, and aspiration during ebb extends to the bottom. This prevents the formation of stagnant water near the bottom, and the estuary is flooded with high salinity water far inland. The neapspring cycle of tidal intrusion fronts on flood coupled with aspiration during ebb interacts with the sill to play an important role in the transport and retention of salt within the estuary.     

Application of stress mapping in cross‐section to understanding ore geometry,predicting ore zones and development of drilling strategies

Stress mapping is a numerical modelling technique used to determine the distribution and relative magnitude of stress during deformation in a mineralised terrane. It is based on the general principle that fluid flow in the Earth's crust is primarily related to pressure gradients. It is best applied to epigenetic hydrothermal mineral deposits, where fluid flow and fluid flux are enhanced in dilational sections of structures and in sites of enhanced rock permeability due to high fracture density. These are defined by sites of low minimum principal stress (σ₃). Most stress mapping is carried out in two dimensions in plan view using geological maps. This is suitable for terranes with steeply dipping lithostratigraphy and structures in which the distribution of mineral deposits is largely controlled by fault structures portrayed on the maps. However, for terranes with gently dipping sequences and structures, and for situations where deposits are sited in and near the hinges of complex fold structures, stress mapping in cross‐section is preferable. The effectiveness of stress mapping is maximised if mineralisation was late in the evolutionary history of the host terrane, and hence the structural geometry of the terrane and contained deposits were essentially that expressed today. The orientation of syn‐mineralisation far‐field stresses must also be inferred. Two examples of orogenic gold deposits, which meet the above criteria, are used to illustrate the potential of stress mapping in cross‐section. Sunrise Dam, located in the Archaean Yilgarn Craton, is a lode‐gold deposit sited in a thrust‐fold belt. Stress mapping illustrates the heterogeneity of stress distribution in the complex structural geometry of the deposit, and predicts the preferential siting of ore zones around the intersections of more steeply dipping, linking thrusts and banded iron‐formation units, and below the controlling more gently dipping basal thrust, the Sunrise Shear. The Howley Anticline in the Pine Creek block hosts several Palaeoproterozoic gold deposits, sited in complex anticlinal structures in greywacke sequences. Stress mapping indicates that gold ores should develop in the hinge zones of symmetrical anticlines, in the hinge zones and more steeply dipping to overturned limbs of asymmetric anticlines, and in and around thrusts in both anticlines and parasitic synclines. The strong correlation between the predictions of the stress mapping, based on the distribution of low σ₃, and the location of gold ores emphasises the potential of stress mapping in cross‐section, not only as an exploration tool for the discovery of additional resources or deposits, but also as a test of geological models. Knowledge of the potential siting of gold ores and their probable orientations also provides a guide to drilling strategies in both mine‐ and regional‐scale exploration.     

The response of the Gulf of Mexico to wind and heat flux forcing: What has been learned in recent years?

The Loop Current and its shed eddies dominate the circulation and dynamics of the Gulf of Mexico (GoM) basin. Those eddies are strongly energetic and are the cause of intense currents that may penetrate several hundred meters deep. However, there are regions in the GoM and periods of time in which the local atmospheric forcing plays an important role in its dynamics and thermodynamics. The circulation on the shelves, and particularly on the inner shelf, is mainly wind-driven with seasonality, changing direction during the year with periods of favorable upwelling/downwelling conditions. The wind-driven circulation is associated with the transport of waters with different temperature and salinity characteristics from one region to another. The interannual variability of the circulation on the shelves is linked to the atmospheric variability. Intraseasonal variability of the wind patterns considerably affects the likelihood and magnitude of upwelling and downwelling. The geometry of the GoM is such that large-scale winds may drive opposing upcoast/downcoast currents along different parts of the curving coast, resulting in convergence or divergence zones. The width of the shelves in the GoM is variable;while the West Florida Shelf, the Texas-Louisiana shelf and the Campeche Bank are more than 200 km wide, they are narrower near Veracruz and Tabasco. Another consequence of the GoM physiography and the wind forcing is the development of cross-shelf transports in the southern Bay of Campeche, the southern Texas shelf and southeast of the Mississippi river, which in turn vary during the year. During autumn-winter (from September to April), the GoM is affected by cold fronts coming from the northwest United States, which are associated with strong, dry, and cold winds that mix its waters and generate large sensible and latent heat fluxes from the ocean to the atmosphere. These frontal passages also cool the GoM surface waters due to mixing with lower temperature subsurface waters. During summer, tropical cyclones crossing the GoM can dramatically affect circulation and coastal upwelling.     

Satellite monitoring of spatio-temporal dynamics of China’s coastal zone eco-environments: preliminary analysis on the relationship between the environment,climate change and human behavior

In this paper, temporal dynamics of eco-environmental changes in coastal areas of China during 1981–2000 are investigated based on four key surface parameters including normalized difference vegetation index (NDVI), thermal index, moisture index and surface broadband albedo derived from quantitative remote sensing techniques and meteorological data. Firstly, land surface temperature (LST) and land surface broadband albedo are retrieved by the split-window algorithms and high-order polynomial regression method, respectively, using NOAA/AVHRR series images. Then, moisture index and thermal index, indicators of climate and moisture conditions in the study area, are computed from meteorological data and LST using principal component analysis (PCA). Finally, long-term dynamics of these eco-environmental factors and the reasons responsible for these changes are analyzed further. The results show that during the years from 1981 to 2000, the study area experienced a gradual increase in annual NDVI and climate factors and a decrease in surface annual broadband albedo, which indicates that the coastal thermal and moisture conditions and the subsistence conditions of natural vegetation have changed to a considerable extent. According to the results, a warming and wetting tendency over the last two decades is obvious in the China’s coastal zone that are mainly due to land use changes as of growing urbanization, exhaust emissions from industries and transportations and, partly global climate change. Uncontrolled rapid development of the study area may be blamed for these negative changes as a major driving force. The positive feedback mechanisms between albedo, NDVI and climate factors also partly explain these changes. This study suggests that the method integrating biophysical parameters retrieved from remote sensed images and meteorologic data provides a novel and feasible way to monitor large scale eco-environmental changes.

Geology and tectonics of Japanese islands: A review – The key to understanding the geology of Asia

The age of the major geological units in Japan ranges from Cambrian to Quaternary. Precambrian basement is, however, expected, as the provenance of by detrital clasts of conglomerate, detrital zircons of metamorphic and sedimentary rocks, and as metamorphic rocks intruded by 500 Ma granites. Although rocks of Paleozoic age are not widely distributed, rocks and formations of late Mesozoic to Cenozoic can be found easily throughout Japan. Rocks of Jurassic age occur mainly in the Jurassic accretionary complexes, which comprise the backbone of the Japanese archipelago. The western part of Japan is composed mainly of Cretaceous to Paleogene felsic volcanic and plutonic rocks and accretionary complexes. The eastern part of the country is covered extensively by Neogene sedimentary and volcanic rocks. During the Quaternary, volcanoes erupted in various parts of Japan, and alluvial plains were formed along the coastlines of the Japanese Islands. These geological units are divided by age and origin: i.e. Paleozoic continental margin; Paleozoic island arc; Paleozoic accretionary complexes; Mesozoic to Paleogene accretionary complexes and Cenozoic island arcs. These are further subdivided into the following tectonic units, e.g. Hida; Oki; Unazuki; Hida Gaien; Higo; Hitachi; Kurosegawa; South Kitakami; Nagato-Renge; Nedamo; Akiyoshi; Ultra-Tamba; Suo; Maizuru; Mino-Tamba; Chichibu; Chizu; Ryoke; Sanbagawa and Shimanto belts.The geological history of Japan commenced with the breakup of the Rodinia super continent, at about 750 Ma. At about 500 Ma, the Paleo-Pacific oceanic plate began to be subducted beneath the continental margin of the South China Block. Since then, Proto-Japan has been located on the convergent margin of East Asia for about 500 Ma. In this tectonic setting, the most significant tectonic events recorded in the geology of Japan are subduction–accretion, paired metamorphism, arc volcanism, back-arc spreading and arc–arc collision. The major accretionary complexes in the Japanese Islands are of Permian, Jurassic and Cretaceous–Paleogene age. These accretionary complexes became altered locally to low-temperature and high-pressure metamorphic, or high-temperature and low-pressure metamorphic rocks. Medium-pressure metamorphic rocks are limited to the Unazuki and Higo belts. Major plutonism occurred in Paleozoic, Mesozoic and Cenozoic time. Early Paleozoic Cambrian igneous activity is recorded as granites in the South Kitakami Belt. Late Paleozoic igneous activity is recognized in the Hida Belt. During Cretaceous to Paleogene time, extensive igneous activity occurred in Japan. The youngest granite in Japan is the Takidani Granite intruded at about 1–2 Ma. During Cenozoic time, the most important geologic events are back-arc opening and arc–arc collision. The major back-arc basins are the Sea of Japan and the Shikoku and Chishima basins. Arc–arc collision occurred between the Honshu and Izu-Bonin arcs, and the Honshu and Chishima arcs.     

From rebel governance to state consolidation – Dynamics of loyalty and the securitisation of the state in Eritrea

This paper discusses Eritrea as a contemporary case of state-making grounded in war, a fact that has resulted in the emergence of one of the ‘hardest’ states in sub-Saharan Africa. The state-making process in Eritrea is looked at with a focus on the legacies of liberation movement governance in the changing dynamics of state consolidation from 1993 to this day. Those dynamics are analysed by reverting to Hirsch-man’s categories of ‘loyalty’, ‘exit’ and ‘voice’. Hirschman’s framework is chosen because the category of loyalty and resulting dynamics illuminate particularly well the transitions within the Eritrean state making process.It is shown that the parameters of war that have resulted in the creation of the Eritrean state have led to a particular kind of state characterised by a high degree of loyalty, visible in the propensity of large segments of the population to associate with state activities. Over time and partly based on military defeat in renewed warfare, the exit option has gained prominence particular among the young generation. This has resulted in a drive towards state securitisation combined with measures to make exit a pillar of power consolidation. Those dynamics have not considerably altered the loyalty of Eritrea’s transnational citizenry to the wider project of state consolidation. The paper concludes that state consolidation in Eritrea can thus far be analysed as a successful shift from fostering voice via politics of mobilisation to controlling exit and voice in ways that keep citizens tied to the state project.     

Digital image processing of multispectral ASTER imagery for delineation of alteration and related clay minerals in Sakoli belt: Maharashtra – A case study

The extraction of spectral signature through remote sensing data in geological studies is very limited in Indian terrain. The present research is an attempt to delineate alteration and associated minerals using high resolution multispectral advanced space borne thermal emission and reflection (ASTER) data in Sakoli volcano-sedimentary sequence. The alteration zones are generally associated with certain types of mineral and mineral aggregates and are localized in the ground that can be mapped remotely using spectral mapping techniques. The band ratio and selective PCT were applied on calibrated ASTER image to extract spectral signature of index mineral. The results showed that high abundance of these minerals within pixels is corresponding to the alteration zones. The field observation, petrography and XRD analysis of the alteration zones confirmed the presence of dominant mineral phases that were identified remotely.