Impact of a 1755-like tsunami in Huelva, Spain

Coastal areas are highly exposed to natural hazards associated with the sea. In all cases where there is historical evidence for devastating tsunamis, as is the case of the southern coasts of the Iberian Peninsula, there is a need for quantitative hazard tsunami assessment to support spatial planning. Also, local authorities must be able to act towards the population protection in a preemptive way, to inform 'what to do' and 'where to go' and in an alarm, to make people aware of the incoming danger. With this in mind, we investigated the inundation extent, run-up and water depths, of a 1755-like event on the region of Huelva, located on the Spanish southwestern coast, one of the regions that was affected in the past by several high energy events, as proved by historical documents and sedimentological data. Modelling was made with a slightly modified version of the COMCOT (Cornell Multi-grid Coupled Tsunami Model) code. Sensitivity tests were performed for a single source in order to understand the relevance and influence of the source parameters in the inundation extent and the fundamental impact parameters. We show that a 1755-like event will have a dramatic impact in a large area close to Huelva inundating an area between 82 and 92 km(2) and reaching maximum run-up around 5 m. In this sense our results show that small variations on the characteristics of the tsunami source are not too significant for the impact assessment. We show that the maximum flow depth and the maximum run-up increase with the average slip on the source, while the strike of the fault is not a critical factor as Huelva is significantly far away from the potential sources identified up to now. We also show that the maximum flow depth within the inundated area is very dependent on the tidal level, while maximum run-up is less affected, as a consequence of the complex morphology of the area.

Estudo da resposta de um dosímetro eletrónico individual

Introdução – A monitorização da exposição ocupacional a doses de radiação ionizante pode ser complementada por dosímetros eletrónicos individuais que permitem uma leitura direta da dose de radiação recebida. Dada a dependência energética e de débito de dose já reportada para estes dosímetros, este trabalho pretende determinar a linearidade da resposta de um dosímetro eletrónico individual e estudar o comportamento da sua resposta em função da energia de radiação e do débito de dose. Metodologia – Para estudar a dependência da energia da radiação do dosímetro eletrónico pessoal Vertec Bleeper Sv procedeu‑se à sua irradiação com um equivalente de dose individual, Hp(10), de 500 μSv de radiação gama do Cobalto – 60 (60C) e Césio – 137 (137Cs) e das qualidades de radiação X da série Narrow (N): N‑30, N‑40, N‑60, N‑80, N‑100 e N‑120. Para investigar a dependência da resposta em função do débito de dose aplicaram‑se à ampola de raios X as intensidades de corrente elétrica de 1 mA, 5 mA, 10 mA, 15 mA e 20 mA. Resultados – Não existe uma relação entre a resposta do detetor e a energia de radiação a que este é exposto. Ocorre uma subestimação superior a 50% na grandeza medida para energias inferiores a 33 keV, mas ostenta uma medida relativamente linear da grandeza Hp(10) para doses inferiores a 100 μSv. Também se constata que, à medida que o débito de dose aumenta, existe uma diminuição na resposta do dosímetro. O menor decréscimo na resposta deste dosímetro eletrónico individual dá‑se para as qualidades de radiação N‑30 (1,1%), N‑40 (4,1%) e N‑120 (20,0%). Conclusão – Verifica‑se que a resposta do dosímetro individual Vertec Bleeper Sv depende fortemente da energia da radiação e do débito de dose. ABSTRACT: Introduction – The measurement of occupational exposure to radiation doses can be completed with an electronic personal dosemeter that allows a direct reading and alarm function of the received radiation dose. Due to the energy and dose rate dependence already reported for this type of dosemeter, it is intended, with this work, to determine the response linearity of an Electronic Personal Dosemeter and to study its response behavior to the dose rate and radiation energy. Methodology – The electronic personal dosemeter Vertec Bleeper Sv energy dependency was evaluated by its irradiation with 500 μSv from the radionuclides Cobalt – 60 (60C) and Cesium – 137 (137Cs) as well as by the radiation qualities of the Narrow (N) series: N‑30, N‑40, N‑60, N‑80, N‑100 e N‑120. To investigate the dose rate dependency, the intensities of electric current of 1 mA, 5 mA, 10 mA, 15 mA and 20 mA were applied to the X‑ray tube. Results – There is no relationship between the response of the detector and the radiation energy. For energies below 33 keV there is an underestimation over 50% of the radiation dose measured but the detector presents a linear response for energies under 100 μSv. A dependency on the dose rate is perceived since as the dose rate increases, the response of the individual monitor decreases. There is a smaller decrease for the radiation qualities of N‑30 (1.1%), N‑40 (4.1%) and N‑120 (20.0%). Conclusion – It is concluded that there is a strong dependence of radiation energy and dose rate on the response of an electronic personal dosemeter.