Fractal approaches in investigating the time dynamics of self-potential hourly variability

Fractal tools have been used to investigate the time dynamics of hourly self-potential data, recorded during the year 2001 by five geoelectrical stations located in one of the most seismic areas of southern Italy. Scaling behaviour has been revealed by means of different statistics: the Lomb Periodogram method, the Detrended Fluctuation Analysis, the Higuchi analysis and the mean distance spanned within the time L. The values of the scaling exponents estimated by means of these methods indicate that the temporal fluctuations of the geoelectrical signals are not typical of purely random stochastic processes (i.e. white noise), but evidence the presence of long-range correlations. Furthermore, it is found that these correlations are linear.     

Applications of maximum entropy and optimal number of class interval concepts: Two examples

Two data sets, one from surface sediment samples obtained from a subtidal sand wave and another consisting of three wave-height records representing different oceanographic conditions, are employed to test the application of maximum entropy (ME) and optimal number of class interval (K) concepts. Each data set was modified further to obtain a frequency distribution determined by eight unequal-size class intervals. Both original and modified sets were treated by a reliable statistical method. Comparison of relative entropies and results from statistical treatments show the advantage of the transformation of any original data set by means of ME and K methods before analyzing it further.Contribution 127, Instituto Argentino de Oceanografia.     

Determination of optimal numbers of class intervals using maximum entropy

Based on the maximum entropy concept, optimal numbers of class intervals(K) for a closed array of samples has been determined. From the analysis, two values ofK (8 and 19) are selected as the most appropriate. ForK=8, the probability of occurrence on each unequal-size interval isp _i=0.125, whereasK=19 results inp _i=0.0526. An objective method for determining interval limits, modified from a previous method by Full et al. (1984), is also included.Contribution 114, Instituto Argentino de Oceanografia.     

HYDRAULIC ANALYSES FOR A NEW BRIDGE OVER THE PARANA RIVER, ARGENTINA

1 INTRODUCTION The Parana River in South America ranks as the sixth largest in the world in terms of average discharge (22 x 103 m3/s according to Schumm and Winkley, 1994), and its Argentinean reach stretches from Puerto Iguazu on the north to the Rio de la Plata estuary in the south (Fig. 1). Its estimated average suspended load, bed load, and total load are 23 x 106, 2.2 x 106, and 25.2 x 106 metric tons per year, respectively (Paoli and Schreider, 2001.) The economic developmen…     

Reduced-dynamic and kinematic baseline determination for the Swarm mission

GPS Solutions - The Swarm mission of the European Space Agency was launched in November 2013 with the objective of performing measurements of the earth’s magnetic field with unprecedented...     

Spatio-temporal variations of seismicity in the southern Peru and northern Chile seismic gaps

The spatio-temporal variation of seismicity in the southern Peru and northern Chile seismic gaps is analyzed with teleseismic data (m _b 5.5) between 1965 and 1991, to investigate whether these gaps present the precursory combination of compressional outer-rise and tensional downdip events observed in other subduction zones. In the outer-rise and the inner-trench (0 to 100 km distance from the trench) region, lower magnitude (5.0m _b <5.5) events were also studied. The results obtained show that the gaps in southern Peru and northern Chile do not present compressional outer-rise events. However, both gaps show a continuous, tensional downdip seismicity. For both regions, the change from compressional to tensional regime along the slab occurs at a distance of about 160 km from the trench, apparently associated with the coupled-uncoupled transition of the interplate contact zone. In southern Peru, an increase of compressional seismicity near the interplate zone and of tensional events (5.0m _b 6.3) in the outer-rise and inner-trench regions is observed between 1987 and 1991. A similar distribution of seismicity in the outer-rise and inner-trench regions is observed with earthquakes (m _b <5.5). In northern Chile there is a relative absence of compressional activity (m _b 5.5) near the interplate contact since the sequence of December 21, 1967. After that, only a cluster of low-magnitude compressional events has been located in the area 50 to 100 km from the trench. The compressional activity occurring near the interplate zone in both seismic gaps represents that a seismic preslip is occurring in and near the plate contact. Therefore, if this seismic preslip is associated with the maturity of the gap, the fact that it is larger in southern Peru than in northern Chile may reflect that the former gap is more mature than the latter. However, the more intense downdip tensional activity and the absence of compressional seismicity near the contact zone observed in northern Chile, may also be interpreted as evidence that northern Chile is seismically more mature than southern Peru. Therefore, the observed differences in the distribution of stresses and seismicity analyzed under simple models of stress accumulation and transfer in coupled subduction zones are not sufficient to assess the degree of maturity of a seismic gap.     

Calibration and validation of rockfall modelling at regional scale: application along a roadway in Mallorca (Spain) and organization of its management

The Tramuntana range, in the northwestern sector of the island of Mallorca (Balearic Islands, Spain), is frequently affected by rockfalls which have caused significant damage, mainly along the road network. In this work, we present the procedure we have applied to calibrate and validate rockfall modelling in this region, using 103 cases of the available detailed rockfall inventory (630 rockfall events collected since the eighteenth century). We have exploited STONE (Guzzetti et al. 2002), a GIS-based rockfall simulation software which computes 2D and 3D rockfall trajectories starting from a DTM and maps of the dynamic rolling friction coefficient and of the normal and tangential energy restitution coefficients. The appropriate identification of these parameters determines the accuracy of the simulation. To calibrate them, we have selected 40 rockfalls along the range which include a wide variety of outcropping lithologies. Coefficients values have been changed in numerous attempts in order to select those where the extent and shape of the simulation matched the field mapping. Best results were summarized with the average statistical values for each parameter and for each geotechnical unit, determining that mode values represent more precisely the data. Initially, for the validation stage, 10 well-known rockfalls exploited in the calibration phase have been selected. Confidence tests have been applied to their modelling results taking into account not only the success but also the mistakes. The best accuracy is obtained when the rockfall has a preferential trajectory and worse results when the rockfall follows two or more trajectories. Additionally, the greater the rockfall runout length, the less precise the simulation is. We have further validated the calibrated parameters along the Ma-road (111 km), the main transportation corridor in the range, using 63 rockfall events that occurred during the past 18 years along the road. Of the rockfalls where source areas were properly identified, 81.5 % are well represented by STONE modelling, as the travel paths and the depositional areas are successfully ascertained. Results of the analysis have been used by the Road Maintenance Service of Mallorca to assess hazard and risk posed by rockfall at regional scale to design the road management plan.     

Self-organization maps (SOM) in the definition of a “transfer function” for a diatoms-based climate proxy

Climate Dynamics - This study utilizes self-organizing maps (SOM) —a particular type of artificial neural network (ANN) — as a nonlinear analysis tool for identifying species that can...