Characterization of ground motions using recurrence plots

The current analysis of earthquakes is typically based on linear mathematical models that may fail to describe and forecast particular behaviors, because in many cases the data complexity may induce a highly non linear behavior. In this paper the implementation of an alternative method for seismic time series analysis is presented. The RPs (Recurrence Plots) enables recognition and treatment of measured accelerations. An RP obtained from seismic data allows a more efficient interpretation of the ground motions and this explanation contributes to characterize materials and responses. The nonlinear attributes from RPs analysis can be used as filters to reveal patterns or be combined to predict a seismic property. Automated seismic data characterization, based on nonlinear seismic attributes, could rewrite the rules of earthquake phenomena interpretation. The objective of this work is to establish a new methodology for practical application of nonlinear dynamics in seismic pattern/attributes recognition, an evolving and challenging engineering field.     

Tectonic framework and extensional pattern of the Malaguide Complex from Sierra Espuña (Internal Betic Zone) during Jurassic–Cretaceous: implications for the Westernmost Tethys geodynamic evolution

Mapping, lithostratigraphic, biostratigraphic and structural detailed analyses in Sierra Espuña area (Internal Betic Zone, SE Spain) have allowed us to reconstruct the Jurassic–Cretaceous evolution of the Westernmost Mesomediterranean Microplate palaeomargin and, by correlation with other sectors (Northern Rift, central and western Internal Betic Zone), to propose a geodynamic evolution for the Westernmost Tethys. Extension began from Late Toarcian, when listric normal faults activated; these faults are arranged in three categories: large-scale faults, separating hectometric cortical blocks; main faults, dividing the former blocks into some kilometre-length blocks; and secondary faults, affecting the kilometric blocks. This fault ensemble, actually outcropping, in the Sierra Espuña area, broke the palaeomargin allowing the westerly Tethyan Oceanic aperture with an extension at about 17.2%. Extension was not homogeneous in time, being the Late Toarcian to the Dogger–Malm boundary the period when blocks underwent the greatest movement (rifting phase), leading to the drowning of the area (8.2% extension). During the Malm (drifting phase) extension followed (5.7%), while during the Cretaceous a change to pelagic facies is recorded with an extension of about 3.3% (post-drift stage). This evolution in the Westernmost Tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low-angle fault of the rifting.     

Geochemical characterization of the salinity of irrigated soils in arid regions (Biskra,SE Algeria)

Acta Geochimica - The agriculture in Biskra, southeastern Algeria, is based on traditional practices and characterized by small irrigated fields. In the last decades, the increasing demand in water...     

The Class 0 source Barnard 1c

We present our most recent results from an ongoing study of the Class 0 source Barnard 1c in Perseus. This source is of particular interest because it exhibits evidence of strong alignment of grains all the way to the core’s centre, which is contrary to all other low-mass protostellar cores observed to date. Our goal is to clarify the source of poor alignment in other sources by identifying the source of strong alignment in B1c. A central cavity has been identified in N₂H⁺ emission; its anticorrelation with C¹⁸O emission suggests that heating in the centre has released CO from grain mantles, in turn destroying N₂H⁺. We present sensitivity-limited, high spatial resolution polarimetry data from the SubMillimeter Array and discuss the potential implications of these data.     

Progressive extensional shear structures in a detachment contact in the Western Sierra Nevada (Betic Cordilleras,Spain)

Abstract

The present contact caused by the superposition of the Alpujarride complex over that of the Nevado-Filabride in the western area of Sierra Nevada and Sierra de Filábres corresponds to a detachment. The deformation in the footwall associated with this contact, produced mylonitic fabrics with a significant stretching-lineation, over which brittle structures are superimposed. The deformation in the hanging wall associated with this contact is, on the other hand, essentially brittle. These deformations are subsequent to a series of syn-to post-metamorphic structures related to thrust phases.

The micro- and meso-structures indicate that the hanging wall has moved towards the west-south-west.

Other brittle structures, which began during the same extensional regime, are superimposed on the detachment and have continued to develop up to the present time. These structures were produced in an extensional regime with a non-coaxial deformation component and suggest the possibility of a tectonic evolution similar to that described for core complexes in the USA.     

Dynamics of sedimentary environments in the accelerated siltation of a reservoir: the case of Alhama de Granada,southern Spain

An analysis has been made of sedimentary systems involved in the rapid silting of a reservoir constructed in 1974 in Alhama de Granada (S. Spain); in only 30 years the storage capacity of the reservoir has shrunk by 80% and its perimeter has decreased by 64%. A study of sediment lithofacies identified in a series of shallow trenches and of georadar facies identified in a series of almost 900 m lines of ground penetrating radar (GPR) images, together with a survey of surface geology, has identified 3 alluvial systems (2 transversal systems and a longitudinal system) whose deltas have filled in the reservoir. Thus, there are three phases in the evolution of the reservoir siltation: (1) an initial stage (1974–1977) typified by northward progradation of the longitudinal river delta of about 100 m year⁻¹ and an eastward progradation of the transversal system delta of about 20 m year⁻¹; (2) an intermediate stage (1977–1984) in which the longitudinal river delta progradation slowed to 25 m year⁻¹ and the axial drainage became obstructed due to the considerable eastward progradation of the transversal delta; and (3) a final phase (1984–present) in which there have been few changes in the areal distribution of the deltas apart from a southeastward expansion of the transversal delta. Generally, aggradational growth patterns (vertical accretion) have dominated in this final phase. The lithology of the source area, the slope and precipitation distribution has a significant effect not only on the sediment supply, but also indirectly on the creation of accommodation space and on the evolution of stratal growth patterns.