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- Volume 36, Issue 8, 2018
First Break - Volume 36, Issue 8, 2018
Volume 36, Issue 8, 2018
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Fault activity studies in the Lower Tagus valley and Lisbon region using geophysical data
Authors João Carvalho, Ranajit Ghose, José Borges, Daniela Alves, Elsa Ramalho and Jaime LeoteAbstractThe Metropolitan Area of Lisbon and the Lower Tagus Valley (LTV) region are located in central Portugal and inhabited by nearly 4 million people. The region has suffered throughout its history the effect of destructive earthquakes caused by hidden faults, possibly related to the plate boundary, which is sited approximately 400 km south of the region (Figure 1). In spite of low slip-rates and big recurrence times that have been estimated for these local, regional faults, they can produce moderate-to-large earthquakes that cause large damage and loss of life, as in 1344, 1531, or 1909 (e.g. Justo and Salwa, 1998; Cabral et al., 2003; 2013). The shorter occurrence time of the earthquakes might be owing to the existence of multiple active faults and/or time clustering owing to stress drop caused by proximal faults (e.g. Carvalho et al., 2006). Therefore, the seismic hazard and risk evaluation of the region has long been a reason of concern.
Figure 1 Seismotectonic of the Azores-Iberia region (after Custódio et al., 2016 and references therein), where the study area is included (dashed square). Earthquakes recorded instrumentally since 1996 are shown by small brown dots. Historical earthquakes reported by the SHARE European Earthquake Catalogue – SHEEC – with magnitudes larger than 5.5 are shown by circles with a radius corresponding to the earthquake magnitude (Stucchi et al., 2013). The earthquakes with magnitudes equal to or larger than 7.0 are labelled with year of occurrence and magnitude. The plate boundaries of the global plate tectonics NNR-MORVEL56 model are shown by dark-blue lines (DeMets et al., 2010; Argus et al., 2011). The surface projection of potentially active faults compiled on the SHARE database are shown by red rectangles, the surface trace of the faults is marked by a thick red line (Basili et al., 2013; Vilanova et al., 2014). The SHARE faults in western Iberia are underlain by the original fault traces proposed by Cabral (2012) (green) and Duarte et al. (2013) (blue). The topography in the background is taken from the global SRTM30+ model, obtained from satellite altimetry and ship depth soundings (Smith and Sandwell, 1997; Becker et al., 2009).
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An airborne survey in Cabo Delgado, Mozambique, to enhance knowledge of geology and tectonics
Authors Danta Marizane Rosse, Manuel Senos Matias and Elsa Cristina RamalhoAbstractAirborne geophysical surveys are very useful in Africa, since large areas can be covered in a short period of time, enhancing interpretation and models that otherwise could not be possible to achieve and triggering the plan of more specific forward studies. This study uses airborne spectrometric and magnetic data to investigate the geology and tectonics of Block 5 in Cabo Delgado Province, North of Mozambique (Figure 1). The area under investigation extends from 11°S to 13°S and from 38°E to 40°E, and covers an area of about 5000 km2.
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TDEM and VES soundings applied to a hydrogeological study in the central region of the Taubaté Basin, Brazil
AbstractThe use of TDEM data for hydrogeological studies has increased substantially in the last few years owing to its versatility and sensitivity, which helps to determine conductor layers in the subsurface.
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Evaluation methodology for obtaining geotechnical parameters using electrical resistivity
AbstractFor any type of construction it is necessary to accurately determine the parameters of characterization, permeability and resistance-deformation of the soil. That analysis is carried out with laboratory tests on samples extracted during the geotechnical field investigation. The advantage of this method is the direct measurement of more important properties controlling the environment and contour conditions. Although the process of extracting the samples tries not to modify the initial conditions of the soil, the intervention of the test generates changes in the initial structure, thus the results cannot fully represent the real conditions in the field. (Liu, 2008)
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Improvement of sonic tests methodology for the characterization of stone masonry
Authors Rachel Martini, Jorge Carvalho, António Arêde and Humberto VarumAbstractThe maintenance and rehabilitation of historical buildings is vital and it is not recommended to use destructive investigative techniques on them.
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GPR profiles over plastic drums buried at the IAG/USP geophysical test site-I, São Paulo, Brazil: a controlled experiment applied to environmental studies
More LessAbstractNowadays, population growth in the large urban centres and uncontrolled use of natural resources has provoked environmental impacts that limit the quality of life. Thus, there is an increase in research related to environmental contamination, geotechnical, urban planning studies, among others, aiming at a better knowledge of the subsurface in support of the management of soil use in a sustainable way, without impacting the future generations.
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Geophysical methods to characterize a mass movement event in tropical soils in Campos do Jordão City, Brazil
AbstractEvery year landslides happen in Brazil, causing injuries and deaths. Generally, the events are fast and destructive, and it is the natural disaster that kills the most people in Brazil (UFSC-CEPED, 2012). However, there are landslide types which occur more slowly and progressively, and keep going for several years. They are called rotational landslides.
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Recovering TURAM geophysical data towards 3D modelling of the Caveira-Lousal mining area, southern Portugal
Authors Fernando Almeida, Alexandre Guerra, Elsa C. Ramalho and João Xavier MatosAbstractThe Iberian Pyrite Belt (IPB), partially located in the Alentejo region, southern Portugal, is known worldwide for the existence of several exploitable massive sulphide ores (e.g., the Neves Corvo copper and zinc ore) that have been supporting the activity of major mining companies for several decades. In 1944, the former Serviço de Fomento Mineiro (SFM) (currently the Laboratório Nacional de Energia e Geologia, LNEG) introduced the use of geophysical methods applied to mining prospecting with the TURAM electromagnetic method through the ABEM Company (Gomes and Silva, 1955).
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Drone-borne ground-penetrating radar suitability for specific surveys: a comparative study of feature sizes versus antenna frequency and elevation over the ground
Authors Reinaldo Alvarez Cabrera and Goran BekicAbstractThe applications of airborne ground-penetrating radar (GPR) antennas or systems are not as widespread and well-developed as their counterparts, the conventional ground coupled antennas and While GPR airborne systems are not a novelty at systems. This has led to a situation in which airborne systems are normally used in a niche industry with very strict guidelines and expectations, such as the road surveying industry (Saarenketo and Scullion, 2000). Airborne antennas are, regrettably, often operated in very inefficient ways, sometimes disregarding basic physical laws or plain, fundamental principles of GPR technology. When the antenna is lifted from the ground a whole new set of problems and complexities arise and, if not taken into consideration, they can lead to very unreliable data and wrong interpretation of the obtained results.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)