Verification of landslide susceptibility mapping: a case study

A methodology is proposed for mapping susceptibility to landsliding and validating the results. Heavy rains in late 1996 and early 1997 led to a large number of landslids in the Rute sector (Córdoba, Southern Spain), where landslide susceptibility mapping had previously been carried out using a ‘matrix’ method developed with a Geographical Information System (GIS). Analysis of the distribution of the new landslides (or reactivated earlier ones) enabled the methodology to be validated by calculating association coefficients and determining the closeness of the match between subsequent field evidence and the previously defined susceptibility levels. From the data obtained, it can be concluded that the susceptibility mapping effectively explained the spatial distribution of landslides, thus providing valuable information on stability conditions over a widespread area. Copyright © 1999 John Wiley & Sons, Ltd.     

Evaluation of a seismic damage parameter

Several parameters have been proposed in the literature for the evaluation of seismic damage. However, in most cases the correlation between results obtained using these parameters and observed damage in structures has not been satisfactory. A parameter for measuring seismic damage previously proposed by the first author is used in this study to analyse a set of 15 accelerograms recorded in 11 earthquakes experienced in different countries. Results using this parameter are compared to global building damage observed during these earthquakes. The use of the parameter proposed here yields results which are consistent with building damage observed in the earthquakes studied. Copyright © 1999 John Wiley & Sons, Ltd.     

Shallow lake trophic status linked to late Holocene climate and human impacts

Lake Mattamuskeet, North Carolina, USA is a large (162 km²) and shallow (mean depth = 1 m) coastal lake, which was significantly modified to support agricultural activities following European settlement in 1850. Paleolimnological proxies measured on a 400-cm sediment core collected from Lake Mattamuskeet reveal shifts in organic matter input and primary producer community structure in response to climatic and human impacts on the lake during the late Holocene. Stratigraphic changes in organic matter content, nutrients, metals, lignin phenols and photosynthetic pigments were used to divide the sediment core into three intervals. Interval I includes sediment deposited between A.D. 360–1584 and indicates a clear-water, sand-bottom state with low algal abundance. In addition, the lake catchment area experienced two significant fires during this interval that were recorded as charcoal layers in the core around A.D. 360 and A.D. 1435 (calibrated ¹⁴C AMS dates). Trophic structure changed with the onset of Interval II (A.D. 1584–1860) when total algal abundance increased, and the primary producer community was comprised primarily of diatoms, chrysophytes, cryptophytes and cyanobacteria. During this interval there was also an increase in terrestrial organic material input into the lake as well as a shift in plant type from woody gymnosperms to non-woody angiosperms as determined from lignin data. Sediment deposited in Lake Mattamuskeet following European settlement (Interval III, A.D. 1860-present) suggests a dramatic increase in organic-matter deposition, metals, primary-producer abundance and the onset of cyanobacterial dominance. Sedimentary evidence indicates that shallow-water primary producers can respond rapidly to climate change and human development.     

Seismic response and damage analysis of buildings supported on flexible soils

The investigation reported in this paper studies the effects of soil–structure interaction (SSI) on the seismic response and damage of building–foundation systems. A simple structural model is used for conducting a parametric study using a typical record obtained in the soft soil area of Mexico City during the 1985 earthquake. Peak response parameters chosen for this study were the roof displacement relative to the base and the hysteretic energy dissipated by the simple structural model. A damage parameter is also evaluated for investigating the SSI effects on the seismic damage of buildings. The results indicate that in most cases of inelastic response, SSI effects can be evaluated considering the rigid‐base case and the SSI period. Copyright © 2000 John Wiley & Sons, Ltd.     

Accurate automated assessment of gully cross‐section geometry using the photogrammetric interface FreeXSapp

During recent years, 3‐D techniques such as LiDAR and Structure‐from‐Motion (SfM) photogrammetry have been increasingly used for gully erosion assessment. However, innovative image‐based approaches based on these advances may also be used to provide accurate cross‐sectional measurements which are less expensive and time‐demanding. In this work, we present the FreeXSapp methodology, a new piece of freely‐available software based on existing SfM tools (MicMac and PMVS2) and augmented‐reality targets (ArUco markers) which performs the automated 3‐D reconstruction, scaling, orientation and analysis of gully cross‐sections (XSs) from images taken from the gully margin using a smartphone camera. As a field application, the volume of a 60‐m‐long medium‐size gully was evaluated, where a total of 10 XSs were measured and analyzed in approximately 30 min. The relative accuracy in estimating width and depth dimensions was in the order of 0.5%, with a precision ratio (relative to the camera–XS distance) of ~1500. Overall, using this methodology showed excellent performance in terms of time and cost requirements when compared with typical 3‐D and conventional 2‐D techniques. The FreeXSapp interface is downloadable for free for Windows operating systems at http://www.uco.es/users/ccastillo/freexsapp. Copyright © 2018 John Wiley & Sons, Ltd.     

A texture‐based region growing algorithm for volume extraction in seismic data

We present a novel approach to automated volume extraction in seismic data and apply it to the detection of allochthonous salt bodies. Using a genetic algorithm, we determine the optimal size of volume elements that statistically, according to the U‐test, best characterize the contrast between the textures inside and outside of the salt bodies through a principal component analysis approach. This information was used to implement a seeded region growing algorithm to directly extract the bodies from the cube of seismic amplitudes. We present the resulting three‐dimensional bodies and compare our final results to those of an interpreter, showing encouraging results.     

Compositional variability on the surface of 1 Ceres revealed through GRaND measurements of high‐energy gamma rays

High‐energy gamma rays (HEGRs) from Ceres’s surface were measured using Dawn's Gamma Ray and Neutron Detector (GRaND). Models of cosmic‐ray‐initiated gamma ray production predict that the HEGR flux will inversely vary with single‐layer hydrogen concentrations for Ceres‐like compositions. The measured data confirm this prediction. The hydrogen‐induced variations in HEGR rates were decoupled from the measurements by detrending the HEGR data with Ceres single‐layer hydrogen concentrations determined by GRaND neutron measurements. Models indicate that hydrogen‐detrended HEGR counting rates correlate with water‐free average atomic mass, which is denoted as <A>*. HEGR variations across Ceres’s surface are consistent with <A>* variations of ±0.5 atomic mass units. Chemical variations in the CM and CI chondrites, our closest analogs to Ceres’s surface, suggest that <A>* variations on Ceres are primarily driven by variations in the concentration of Fe, although other elements such as Mg and S could contribute. Dawn observations have shown that Ceres’s interior structure and surface composition have been modified by some combination of physical (i.e., ice‐rock fractionation) and/or chemical (i.e., alteration) processes that has led to variations in bulk surface chemistry. Locations of the highest inferred <A>* values, and thus possibly the highest Fe and least altered materials, tend to be younger, less cratered surfaces that are broadly associated with the impact ejecta of Ceres’s largest craters.     

The autonomous <Emphasis Type="Italic">Simpatico</Emphasis> system for real-time continuous water-quality and current velocity monitoring: examples of application in three Portuguese estuaries

This technical paper describes an autonomous recording system with remote data access for the continuous, long-term in situ monitoring of water quality and discharge, as well as current velocity. The Simpatico system has been recently deployed in three estuaries in Portugal (Mondego and Tagus in July 2007; Guadiana in March 2008), highly suitable to illustrate its multifaceted potential applications: surveillance of the effects of mitigation measures to combat eutrophication (lower Mondego Estuary); real-time implementation of boundary conditions for a water modelling system (upper Tagus Estuary); study of dam-induced impacts in terms of water quality, water discharge and sediment budgets (mouth of the Guadiana Estuary). An extract of recorded data serves as an example to discuss data reliability, as well as field maintenance of the system, with implications for labour and operational costs. The use of a new generation of copper-based anti-biofouling kits significantly reduced the need for field maintenance operations. Other examples of possible application of the system include the assessment of gas accumulation in coastal waters.     

Time-series measurements of Th in water column and sediment trap samples from the northwestern Mediterranean Sea

Disequilibrium between ²³⁴Th and ²³⁸U in water column profiles has been used to estimate the settling flux of Th (and, by proxy, of particulate organic carbon); yet potentially major non-steady-state influences on ²³⁴Th profiles are often not able to be considered in estimations of flux. We have compared temporal series of ²³⁴Th distributions in the upper water column at both coastal and deep-water sites in the northwestern Mediterranean Sea to coeval sediment trap records at the same sites. We have used sediment trap records of ²³⁴Th fluxes to predict temporal changes in water column ²³⁴Th deficits and have compared the predicted deficits to those measured to determine whether the time-evolution of the two coincide. At the coastal site (327 m water depth), trends in the two estimates of water column ²³⁴Th deficits are in fairly close agreement over the 1-month deployment during the spring bloom in 1999. In contrast, the pattern of water column ²³⁴Th deficits is poorly predicted by sediment trap records at the deep-water site (DYFAMED, 2300 m water depth) in both 2003 and 2005. In particular, the transition from a mesotrophic to an oligotrophic system, clearly seen in trap fluxes, is not evident in water column ²³⁴Th profiles, which show high-frequency variability. Allowing trapping efficiencies to vary from 100% does not reconcile the differences between trap and water column deficit observations; we conclude that substantial lateral and vertical advective influences must be invoked to account for the differences.Advective influences are potentially greater on ²³⁴Th fluxes derived from water column deficits relative to those obtained from traps because the calculation of deficits in open-ocean settings is dominated by the magnitude of the “dissolved” ²³⁴Th fraction. For observed current velocities of 5–20 cm s⁻¹, in one radioactive mean-life of ²³⁴Th, the water column at the DYFAMED site can reflect ²³⁴Th scavenging produced tens to hundreds of kilometers away. In contrast, most of the ²³⁴Th flux collected in shallow sediment traps at the DFYFAMED site was in the fraction settling >200 m d⁻¹; in effect the sediment trap can integrate the ²³⁴Th flux over distances 40-fold less than water column ²³⁴Th distributions. In some sense, sediment trap and water column sampling for ²³⁴Th provide complementary pictures of ²³⁴Th export. However, because the two methods can be dominated by different processes and are subject to different biases, their comparison must be treated with caution.