An integrated approach for evaluating the effectiveness of landslide risk reduction in unplanned communities in the Caribbean

Despite the recognition of the need for mitigation approaches to landslide risk in developing countries, the delivery of ‘on-the-ground’ measures is rarely undertaken. With respect to other ‘natural’ hazards, it is widely reported that mitigation can pay. However, the lack of such an evidence base in relation to landslides in developing countries hinders advocacy amongst decision makers for expenditure on ex-ante measures. This research addresses these limitations directly by developing and applying an integrated risk assessment and cost–benefit analysis of physical landslide mitigation measures implemented in an unplanned community in the Eastern Caribbean. In order to quantify the level of landslide risk reduction achieved, landslide hazard and vulnerability were modelled (before and after the intervention), and project costs, direct and indirect benefits were monetised. It is shown that the probability of landslide occurrence has been substantially reduced by implementing surface-water drainage measures and that the benefits of the project outweigh the costs by a ratio of 2.7–1. This paper adds to the evidence base that ‘mitigation pays’ with respect to landslide risk in the most vulnerable communities—thus strengthening the argument for ex-ante measures. This integrated project evaluation methodology should be suitable for adoption as part of the community-based landslide mitigation project cycle, and it is hoped that this resource, and the results of this study, will stimulate further such programmes.     

SVME: an ensemble of support vector machines for detecting oil spills from full resolution MODIS images

This paper addresses oil spill detection from remotely sensed optical images. In particular, it focuses on the automatic classification of regions of interest (ROIs) in two classes, namely oil spills or look-alikes. Candidate regions and the corresponding boundaries have been manually identified from full resolution Moderate Resolution Imaging Spectroradiometer images, related to the Mediterranean Sea over the years 2008 and 2009. Then, a set of features has been extracted from each ROI, allowing to formulate the oil spill detection problem as a two-class classification task on the provided regions (i.e. using a supervised learning strategy). Since ROI classification is challenging, some desired characteristics for the classification algorithm are first identified, such as accuracy, robustness, etc. Then, a solution (called SVME) is provided: it is based on an ensemble of incremental/decremental cost-oriented Support Vector Machines, aggregated with the Receiving Operating Characteristic (ROC) convex hull method in the ROC space. Such a solution addresses all the desired characteristics. Finally, the results obtained on the collected dataset are shown. The importance of this study is the devising of a powerful classification technique that may have an impact on optical oil spill detection from space, especially if fused with satellite synthetic aperture radar data. Moreover, it is shown how the proposed system can be used as a decision support tool, to help a junior operator in making more reliable detections.     

A new method for the determination of the specific kinetic energy (SKE) released to pyroclastic particles at magmatic fragmentation: theory and first experimental results

Brittle magmatic fragmentation plays a crucial role in explosive eruptions. It represents the starting point of hazardous explosive events that can affect large areas surrounding erupting volcanoes. Knowing the initial energy released during this fragmentation process is fundamental for the understanding of the subsequent dynamics of the eruptive gas-particle mixture and consequently for the forecasting of the erupting column’s behavior. The specific kinetic energy (SKE) of the particles quantifies the initial velocity shortly after the fragmentation and is therefore a necessary variable to model the gas-particle conduit flow and eruptive column regime. In this paper, we present a new method for its determination based on fragmentation experiments and identification of the timings of energy release. The results obtained on compositions representative for basaltic and phonolitic melts show a direct dependence on magma material properties: poorly vesiculated basaltic melts from Stromboli show the highest SKE values ranging from 7.3 to 11.8 kJ/kg, while experiments with highly vesiculated samples from Stromboli and Vesuvius result in lower SKE values (3.1 to 3.8 kJ/kg). The described methodology presents a useful tool for quantitative estimation of the kinetic energy release of magmatic fragmentation processes, which can contribute to the improvement of hazard assessment.     

Interaction of geometry and mechanical property of trapezoidal sedimentary basins with incident <Emphasis Type="Italic">SH</Emphasis> waves

This paper investigated the effects of basin geometry and material property on the response of 2D trapezoidal sediment-filled basin to incident plane SH waves. Ten basin configurations with different geometries were developed, and then their seismic responses to both Ricker wavelets and seismic records were simulated by using an explicit finite difference scheme. The definition of deep/shallow basin, the precondition for the observation of prominent surface waves and the influential area of edge effects of the shallow basin were discussed quantitatively in this study. The followings were concluded: in the common velocity contrast range (v _s1/v _s2 < 10), the fundamental frequency a basin with W/H > 3.0 can be estimated approximately by 1D theory. The complexity of peak ground acceleration distribution pattern, the width of the most affected section as well as the amplitude of ground motion in the Edge Region increase with incident frequency. Prominent surface waves can only be observed when the incident wavelength is shorter than the critical wavelength λ _c . The interaction between incident wave and basin dynamic property plays a dominant role on the peak ground acceleration amplitude while the interaction between incident wave and geometry plays a more significant role on the peak ground acceleration distribution. For very shallow basin, different areas along the basin width are affected to different extents. Only a limited area close to the basin edge is influenced significantly. It is more feasible to propose spectral aggravation factor for different surface zones respectively than a uniform constant as a tool to calibrate the 1D-based design spectrum so as to take the basin effects into account.     

Newmark design spectra considering earthquake magnitudes and site categories

Newmark design spectra have been implemented in many building codes, especially in building codes for critical structures. Previous studies show that Newmark design spectra exhibit lower amplitudes at high frequencies and larger amplitudes at low frequencies in comparison with spectra developed by statistical methods. To resolve this problem, this study considers three suites of ground motions recorded at three types of sites. Using these ground motions, influences of the shear-wave velocity, earthquake magnitudes, source-to-site distances on the ratios of ground motion parameters are studied, and spectrum amplification factors are statistically calculated. Spectral bounds for combinations of three site categories and two cases of earthquake magnitudes are estimated. Site design spectrum coefficients for the three site categories considering earthquake magnitudes are established. The problems of Newmark design spectra could be resolved by using the site design spectrum coefficients to modify the spectral values of Newmark design spectra in the acceleration sensitive, velocity sensitive, and displacement sensitive regions.     

Developing a small lake: The case of Palakpakin Lake,San Pablo City,Philippines

This study assesses the development issues of Palakpakin Lake. Premised on the scarcity of development studies on lakes (as the field is dominated by limnology and aquaculture studies) and small-lake studies (as the field is heavily concentrated on big-lake studies), the article argues that the lake has long been wanting of development initiatives from its administrative agencies. It further contends that the Laguna Lake Development Authority and the City Government of San Pablo must now act to promote development of the lake; specifically, by modifying their model-template approach, by formulating a zoning-development plan, and by fostering ecotourism. These basic actions are necessary in managing, developing and conserving the natural resource, as well as in preparing, informing and precipitating other actions on the lake.     

Multi-resolution graph-based clustering analysis for lithofacies identification from well log data: Case study of intraplatform bank gas fields,Amu Darya Basin

In this study, we used the multi-resolution graph-based clustering (MRGC) method for determining the electrofacies (EF) and lithofacies (LF) from well log data obtained from the intraplatform bank gas fields located in the Amu Darya Basin. The MRGC could automatically determine the optimal number of clusters without prior knowledge about the structure or cluster numbers of the analyzed data set and allowed the users to control the level of detail actually needed to define the EF. Based on the LF identification and successful EF calibration using core data, an MRGC EF partition model including five clusters and a quantitative LF interpretation chart were constructed. The EF clusters 1 to 5 were interpreted as lagoon, anhydrite flat, interbank, low-energy bank, and high-energy bank, and the coincidence rate in the cored interval could reach 85%. We concluded that the MRGC could be accurately applied to predict the LF in non-cored but logged wells. Therefore, continuous EF clusters were partitioned and corresponding LF were interpreted, and the distribution and petrophysical characteristics of different LF were analyzed in the framework of sequence stratigraphy.     

Digitized Database of Old Seismograms Recorder in Romania

The aim of this paper is to describe a managing system for a unique Romanian database of historical seismograms and complementary documentation (metadata) and its dissemination and analysis procedure. For this study, 5188 historical seismograms recorded between 1903 and 1957 by the Romanian seismological observatories (Bucharest-Filaret, Foc?ani, Bac?u, Vrincioaia, Câmpulung-Muscel, Ia?i) were used. In order to reconsider the historical instrumental data, the analog seismograms are converted to digital images and digital waveforms (digitization/ vectorialisation). First, we applied a careful scanning procedure of the seismograms and related material (seismic bulletins, station books, etc.). In a next step, the high resolution scanned seismograms will be processed to obtain the digital/numeric waveforms. We used a Colortrac Smartlf Cx40 scanner which provides images in TIFF or JPG format. For digitization the algorithm Teseo2 developed by the National Institute of Geophysics and Volcanology in Rome (Italy), within the framework of the SISMOS Project, will be used.