Imaging 3D seismic velocity along the seismogenic zone of Algarve region (southern Portugal)

The present seismic tomographic study is focused around Algarve region, in South of Portugal. To locate the seismic events and find the local velocity structure of epicentral area, the P and S arrival times at 38 stations are used. The data used in this study were obtained during the Algarve campaign which worked from January/2006 to July/2007. The preliminary estimate of origin times and hypocentral coordinates are determined by the Hy- poinverse program. Linearized inversion procedure was applied to comprise the following two steps: 1) finding the minimum 1D velocity model using Velest and 2) simultaneous relocation of hypocenters and determination of local velocity structure. The velocity model we have reached is a 10 layer model which gave the lowest RMS, after several runnings of eight different velocity models that we used “a priori”. The model parameterization assumes a continuous velocity field between 4.5 km/s and 7.0 km/s until 30 km depth. The earth structure is represented in 3D by velocity at discrete points, and velocity at any intervening point is determined by linear interpolation among the surrounding eight grid points. A preliminary analysis of the resolution capabilities of the dataset, based on the Derivative Weight Sum (DWS) distribution, shows that the velocity structure is better resolved in the West part of the region between the surface to15 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity in the first 12 kms in the studied region. We also identified the occurrence of local seismic events of reduced magnitude not catalogued, in the neighbourhood of Almodôvar (low Alentejo). The spatial distribution of epicentres defines a NE-SW direction that coincides with the strike of the mapped geological faults of the region and issued from photo-interpretation. Is still expectable to refine the seismicity of the region of Almodôvar and establish more rigorously its role in the seismotectonic picture of the region. This work is expected to produce a more detailed knowledge of the structure of the crust over the region of Algarve, being able to identify seismogenic zones, potentially generators of significant seismic events and also the identification of zones of active faults

Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements

Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods

TRANSIENT KNICKPOINTS” NO LEITO DOS RIOS, SIGNIFICADO NA EVOLUÇÃO DA PAISAGEM

Neste trabalho apresenta-se uma síntese sobre a relevância dos knickpoints na estruturação do perfil longitudinal dos rios e indirectamente, na evolução da paisagem. Aborda-se o significado dos knickpoints relativamente aos conceitos de equilíbrio e desequilíbrio do perfil longitudinal, difundidos na literatura. Leis que regem a incisão fluvial, testadas em modelos físico-matemáticos, estabelecidos nas duas últimas décadas, são também referidas. Salientam-se as potencialidades que decorrem deste tipo de análise quantitativa dos perfis longitudinais dos rios, nomeadamente: a identificação de troços relíquia e troços ajustados a novas condições de equilíbrio; a reconstituição de antigos leitos (erodidos) a jusante de knickpoints transitórios e a correlação com outras unidades geomorfológicas, como sejam os terraços fluviais. A relação entre o comportamento das vagas de erosão com a morfologia dos knickpoints e com certos modelos de evolução da paisagem é salientada neste trabalho

Ground Motion Simulations of the SW Iberia Margin: Rupture Directivity and Earth Structure Effects.

Abstract In this study, we focus on the region between Gorringe Bank and the Horseshoe Fault located in the SW Iberia margin, which is believed to be the site of the great 1755 earthquake. We model ground motions using an extended source located near the Horseshoe scarp to generate synthetic waveforms using a wave propagation code, based on the finite-difference method. We compare the simulated waveforms, for the Algarve Basin and the Lower Tagus Valley Basin (Portugal), using a 3-D velocity model down to the Moho discontinuity with a simple 1-D layered model. The radiated wave field is very sensitive to the velocity model and a small number of source parameters, in particular, the rupture directivity. The rupture directivity, the strike direction and the fault dimensions are critical to the azimuthal distribution of the maximum amplitude oscillations. We show that the use of a stratified 1-D model is inappropriate in SW Iberia, where sources are located in the oceanic domain and receivers in the continental domain. The crustal structure varies dramatically along the ray paths, with large-scale heterogeneities of low or high velocities. Moreover, combined with the geometric limitations inherent to the region, a strong trade-off between several parameters is often observed; this is particularly critical when studying moderate magnitude earthquakes (M < 6), which constitute the bulk of the seismic catalogue in SW Iberia

Risk management in landfills. A public health perspective

Currently, sanitary landfill is an appropriate option for disposal of waste, mainly because it is a technology with little aggressive environmental impact and associated to low costs and simple operation. However, the deficit in best practices in solid waste management is recognized in scientific literature as the cause of adverse effects on the environment and public health. Since landfill has a relevant social, economic and environmental impact as a sanitary urban infrastructure, new control approach based on public health and environmental integrity should be developed in order to prevent diseases propagation and negative environmental impacts. This research work presents a novel concept of landfill safety plan, using similar approach as the well established water safety plan methodology, structured on risk assessment and risk management throughout the waste collection and disposal system.CAPES scholarship and Science Without Borders program Bex Process 12993-13-

A male-produced sex pheromone from the neotropical redbanded stink bug, Piezodorus guildinii (W.).

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Improving the Knowledge on Seismogenic Sources in the Lower Tagus Valley for Seismic Hazard Purposes

The Lower Tagus Valley, that includes the metropolitan area of Lisbon, has been struck by several earthquakes which produced significant material damage and loss of lives. Their exact location remains unknown. Our goal is to shed some light into the seismogenic sources in the area using seismic reflection and geological data. In areas with no seismic coverage, potential-field data interpretation was carried out. Seismicity was overlaid to the potential seismogenic structures and high-resolution data was acquired in order to confirm which structures have been active into the Quaternary. Three major fault-zones affecting the Neogene were identified: V. F. Xira, Samora-Alcochete and Pinhal Novo. For the first fault, strong evidences suggest it is active. The other two fault-zones and other structures previously unknown can be correlated with several epicentres. Empirical relationships between maximum moment magnitude and fault area indicate that MW > 6.5 earthquakes can be expected for the larger structures