GF - Comunicações em actas de encontros científicos internacionais
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Browsing GF - Comunicações em actas de encontros científicos internacionais by Author "Carvalho, João P. F."
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- Assessing the degree of fracturing and weathered layer thickness using seismic and GPR dataPublication . Carvalho, João P. F.; Pinto, Carlos C.; Lisboa, Jose; Sardinha, Rui; Catrapona, Afonso; Borges, José Fernando; Tlemçani, M.
- Characterization of a concealed fault zone using P and S-wave seismic reflection dataPublication . Carvalho, João P. F.; Ghose, R.; Pinto, Carlos C.; Borges, José Fernando
- Improving the seismic hazard evaluation of the Lisbon and Lower Tagus Valley areaPublication . Carvalho, João P. F.; Pinto, Carlos C.; Costa, M.; Heleno, S.; Silva, M.; Rabeh, Taha; Cooksley, G.; Carrilho, F.The Lisbon and surrounding area of the Lower Tagus Valley has experienced in the past the effects of several moderate sized earthquakes that caused significant damage and destruction. They have been attributed to local sources, though in some cases the source remains to be located. The lack of outcrops in the flat lying Quaternary terrains, the low slip-rates of the area in connection with sedimentation and erosion rates that erase surface ruptures are among the causes of a poor association between faults and seismicty, which has opened way to geophysical studies. Seismic, potential-field and seismicity data have been recently used to improve the seismic hazard evaluation of the area. In this work we complement these studies with DTM and PSInSAR data with the purpose of obtaining an accurate evaluation of the seismic hazard of the study area. The correlation of improved epicentre locations with major fault zones located from the above mentioned data shows that we have progressed in the understanding of the earthquake sources in the region. Some structures show no apparent relationship with present-day seismicity but some are known to be active into the Quaternary. Further geophysical and geological studies are required to understand the causes.
- Looking for earthquake sources in the Lisbon areaPublication . Carvalho, João P. F.; Pinto, Carlos C.; Costa, M.; Rabeh, TahaThe Lisbon and surrounding areas have suffered the effect of historical earthquakes that caused important damages and loss of lives. Some of these earthquake sources are local but they are still poorly known. The knowledge of these sources is important for seismic hazard studies. The use of geophysical methods in the area is required due to the difficulty in finding geological outcrops, together with low-slip rates and erosion/sedimentation processes that erase surface ruptures. Furthermore, most of earthquake occurs at great depth, emphasizing the need for the application of the latter methods. In this paper we present a revised structural interpretation of the area using newly reprocessed and reinterpreted seismic reflection and potential-field data, relocated epicentres, geological outcrop and well data. This interpretation differs in some aspects from previous ones. Well known active faults zones like the Azambuja fault and the Pinhal Novo-Setúbal fault have new interpretations, while other previously unknown structures, like the Ota-V. F. de Xira-Lisbon-Sesimbra fault zone, for example, have been interpreted. These studies, together with shallow geophysical data, which has been and will be acquired over selected targets from this work, will constitute na improvement to the seismic hazard evaluation of the area.
- Seismogenic sources in the Lower Tagus Area using geophysical dataPublication . Pinto, Carlos C.; Carvalho, João P. F.; Costa, M.; Catrapona, Afonso; Rabeh, Taha; Terrinha, Pedro; Duarte, Henrique; Borges, José Fernando; Caldeira, Bento; Cabral, João
- A soil classification for seismic hazard assessment and mitigation of the AlgarvePublication . Carvalho, João P. F.; Dias, Ruben Pereira; Pinto, Carlos C.; Leote, Jaime; Victor, L. MendesThe Algarve province of Portugal is located near the E-W Eurasia-Africa plate boundary. It is characterized by a moderate seismicity, with some important historical earthquakes causing important damage and economical losses. Not only has it suffered the effects of large plate boundary events but also the impact of local onshore moderate-sized earthquake sources. The seismic hazard evaluation and mitigation of the area is therefore of great importance to the local populations and the large number of tourists that frequent the region. This paper focuses the evaluation of the most interesting and useful geotechnical near-surface parameters and a soil classification. The classification based upon the European Code 8 for civil engineering and SPT bedrock data, was carried out for land use planning and design of critical facilities. P-wave and S-wave seismic velocities were obtained through the acquisition, processing and interpretation refraction profiles. Hundreds of SPT parameters from available boreholes drilled for engineering and water supply were used and subsoil classification based on geophysical and geotechnical parameters is presented. Other parameters, such as Vp/Vs ratios and the Poisson coefficient were estimated and were computed to provide information for future site effect studies. The experimental procedure tested here is relatively fast, economical and easy to perform and can be useful to estimate soil microzoning and seismic hazard mapping in the absence of local earthquake records.