Em resposta à forte corrente de desenvolvimento e criação de institutos dedicados à observação e ... more Em resposta à forte corrente de desenvolvimento e criação de institutos dedicados à observação e estudo dos fenómenos atmosféricos e geomagnéticos, que atravessava boa parte dos países europeus desde o final da primeira metade do séc. XIX, foi criado, em 1864, o Observatório Meteorológico e Magnético da Universidade de Coimbra (OMMUC). À frente de tão marcante empreendimento esteve Jacinto de Sousa (1818-1880), à época, lente e director do Gabinete de Física da Faculdade de Filosofia. Após missão, em 1860, a vários estabelecimentos científicos da Europa, viu aprovado pelo Conselho da Faculdade um voto de confiança para levar a cabo a construção do observatório, “que há muito devera funcionar em Coimbra”. Este viria a ser construído segundo o modelo do conceituado Observatório de Kew, pois foi aqui que Jacinto de Sousa e o projecto que o animava encontraram o entusiasmo de geofísicos ilustres como Balfour Stewart (1828-1887) e Edward Sabine (1788-1883). As observações meteorológicas e geomagnéticas foram iniciadas pela própria mão de Jacinto de Sousa, que justamente tinha sido conduzido a primeiro director do OMMUC; lugar que ocupou desde Fevereiro de 1864 até à sua morte em Agosto de 1880. O presente estudo visa assim subsidiar o conhecimento da obra de Jacinto de Sousa e do contexto institucional e científico que conduziram à fundação do OMMUC, que viria a marcar o desenvolvimento das ciências geofísicas na Universidade de Coimbra.
Bulletin of the Seismological Society of America, 2014
The West Iberia Lithosphere and Asthenosphere Structure (WILAS) project densely covered Portugal ... more The West Iberia Lithosphere and Asthenosphere Structure (WILAS) project densely covered Portugal with broadband seismic stations for 2 yrs. Here we provide an overview of the deployment, and we characterize the network ambient noise and its sources. After explaining quality control, which includes the assessment of sensor orientation, we characterize the background noise in the short-period (SP), microseismic, and long-period (LP) bands. We observe daily variations of SP noise associated with anthropogenic activity. Temporary and permanent stations present very similar noise levels at all periods, except at horizontal LPs, where temporary stations record higher noise levels. We find that median noise levels are extremely homogeneous across the network in the microseismic band (3-20 s) but vary widely outside this range. The amplitudes of microseismic noise display a strong seasonal variation. The seasonality is dominated by very-long-period double-frequency microseisms (8 s), probably associated with winter storms. Stacks of ambient noise amplitudes show that some microseismic noise peaks are visible across the whole ground-motion spectrum, from 0.3 to 100 s. Periods of increased microseismic amplitudes generally correlate with ocean conditions offshore of Portugal. Some seismic records display an interesting 12 hr cycle of LP (100-s) noise, which might be related to atmospheric tides. Finally, we use plots of power spectral density versus time to monitor changes in LP instrumental response. The method allows the identification of the exact times at which LP response changes occur, which is required to improve the understanding of this instrumental artifact and to eventually correct data.
Portugal and the SW Iberian region have experienced moderate to strong earthquakes in the past ( ... more Portugal and the SW Iberian region have experienced moderate to strong earthquakes in the past ( e.g. 1344, 1531, 1858, and 1909 events). These earthquakes are generally linked with the Lower Tagus Valley Fault Zone (LTV) and its associated splays. However, despite major contention with respect to its activity, the LTV region is one of two regions identified in Portugal with the highest seismic hazard. Thus, to address the very important issues relating to the fault activity of the LTV, several studies were undertaken to identify and characterize the deformation related to this structure, specifically its location and geometry. To ascertain and establish the location of the LTV, topographic maps, aerial photos, and river systems were analyzed together with other remotely-sensed data coupled with numerous field mapping activities. Results from these efforts indicate recent faulting along the LTV with the trace located within the valley that transects major rivers, tributaries and you...
The seismic station COI, located in Coimbra, Portugal, is the
oldest seismic station in Portugal ... more The seismic station COI, located in Coimbra, Portugal, is the oldest seismic station in Portugal and among the oldest in the world. Experimental seismic recording began in 1891 with an Angot seismograph. Continuous recording of ground motion began in 1903 with a Milne seismograph, and is still on-going at the same site, now with a broadband Streckeisen STS-2 seismometer. Coimbra’s observatory owns an over 100-year long, well-preserved collection of seismograms, seismograph and bulletins. Station COI is taken into account in early seismological works, for example, in the 1901 compila- tion of stations equipped with seismographs recommended by the British Association for the Advancement of Science, in the earthquake catalog of the International Association of Seismology for the year of 1904, in the San Francisco earthquake report or in the classical book “Seismicity of the Earth”. However, throughout time station COI lost its early importance and was progressively forgotten. Station COI is missed even by recent compilations of his- torical seismic data.
RESUMO: O Instituto Geofísico da Universidade de Coimbra (IGUC) foi fundado em 1864 como observat... more RESUMO: O Instituto Geofísico da Universidade de Coimbra (IGUC) foi fundado em 1864 como observatório meteorológico. As observações sísmicas só terão sido iniciadas de forma regular 43 anos mais tarde, em 1907. Os registos sísmicos que o IGUC possui actualmente representam uma das maiores e melhor conservadas séries de registos sísmicos a nível mundial. Neste trabalho apresentaremos os registos e os instrumentos utilizados no estudo da sismologia no IGUC, bem como o seu actual estado de preservação, e a importância dos antigos registos sísmicos nos estudos científicos modernos.
The Geophysical Institute of the University of Coimbra (IGUC) was founded in 1864 as the meteorol... more The Geophysical Institute of the University of Coimbra (IGUC) was founded in 1864 as the meteorological observatory. The seismic observations only started regularly 43 years later, in 1907. The seismic records that the IGUC have currently represent one of the largest and best preserved series of seismic record worldwide. Ins this work we present the records and the instruments used in the study of the seismology in the IGUC, as well as your current state of preservation, and the importance of the old seismic records in the modern scientific studies.
Em resposta à forte corrente de desenvolvimento e criação de institutos dedicados à observação e ... more Em resposta à forte corrente de desenvolvimento e criação de institutos dedicados à observação e estudo dos fenómenos atmosféricos e geomagnéticos, que atravessava boa parte dos países europeus desde o final da primeira metade do séc. XIX, foi criado, em 1864, o Observatório Meteorológico e Magnético da Universidade de Coimbra (OMMUC). À frente de tão marcante empreendimento esteve Jacinto de Sousa (1818-1880), à época, lente e director do Gabinete de Física da Faculdade de Filosofia. Após missão, em 1860, a vários estabelecimentos científicos da Europa, viu aprovado pelo Conselho da Faculdade um voto de confiança para levar a cabo a construção do observatório, “que há muito devera funcionar em Coimbra”. Este viria a ser construído segundo o modelo do conceituado Observatório de Kew, pois foi aqui que Jacinto de Sousa e o projecto que o animava encontraram o entusiasmo de geofísicos ilustres como Balfour Stewart (1828-1887) e Edward Sabine (1788-1883). As observações meteorológicas e geomagnéticas foram iniciadas pela própria mão de Jacinto de Sousa, que justamente tinha sido conduzido a primeiro director do OMMUC; lugar que ocupou desde Fevereiro de 1864 até à sua morte em Agosto de 1880. O presente estudo visa assim subsidiar o conhecimento da obra de Jacinto de Sousa e do contexto institucional e científico que conduziram à fundação do OMMUC, que viria a marcar o desenvolvimento das ciências geofísicas na Universidade de Coimbra.
Bulletin of the Seismological Society of America, 2014
The West Iberia Lithosphere and Asthenosphere Structure (WILAS) project densely covered Portugal ... more The West Iberia Lithosphere and Asthenosphere Structure (WILAS) project densely covered Portugal with broadband seismic stations for 2 yrs. Here we provide an overview of the deployment, and we characterize the network ambient noise and its sources. After explaining quality control, which includes the assessment of sensor orientation, we characterize the background noise in the short-period (SP), microseismic, and long-period (LP) bands. We observe daily variations of SP noise associated with anthropogenic activity. Temporary and permanent stations present very similar noise levels at all periods, except at horizontal LPs, where temporary stations record higher noise levels. We find that median noise levels are extremely homogeneous across the network in the microseismic band (3-20 s) but vary widely outside this range. The amplitudes of microseismic noise display a strong seasonal variation. The seasonality is dominated by very-long-period double-frequency microseisms (8 s), probably associated with winter storms. Stacks of ambient noise amplitudes show that some microseismic noise peaks are visible across the whole ground-motion spectrum, from 0.3 to 100 s. Periods of increased microseismic amplitudes generally correlate with ocean conditions offshore of Portugal. Some seismic records display an interesting 12 hr cycle of LP (100-s) noise, which might be related to atmospheric tides. Finally, we use plots of power spectral density versus time to monitor changes in LP instrumental response. The method allows the identification of the exact times at which LP response changes occur, which is required to improve the understanding of this instrumental artifact and to eventually correct data.
Portugal and the SW Iberian region have experienced moderate to strong earthquakes in the past ( ... more Portugal and the SW Iberian region have experienced moderate to strong earthquakes in the past ( e.g. 1344, 1531, 1858, and 1909 events). These earthquakes are generally linked with the Lower Tagus Valley Fault Zone (LTV) and its associated splays. However, despite major contention with respect to its activity, the LTV region is one of two regions identified in Portugal with the highest seismic hazard. Thus, to address the very important issues relating to the fault activity of the LTV, several studies were undertaken to identify and characterize the deformation related to this structure, specifically its location and geometry. To ascertain and establish the location of the LTV, topographic maps, aerial photos, and river systems were analyzed together with other remotely-sensed data coupled with numerous field mapping activities. Results from these efforts indicate recent faulting along the LTV with the trace located within the valley that transects major rivers, tributaries and you...
The seismic station COI, located in Coimbra, Portugal, is the
oldest seismic station in Portugal ... more The seismic station COI, located in Coimbra, Portugal, is the oldest seismic station in Portugal and among the oldest in the world. Experimental seismic recording began in 1891 with an Angot seismograph. Continuous recording of ground motion began in 1903 with a Milne seismograph, and is still on-going at the same site, now with a broadband Streckeisen STS-2 seismometer. Coimbra’s observatory owns an over 100-year long, well-preserved collection of seismograms, seismograph and bulletins. Station COI is taken into account in early seismological works, for example, in the 1901 compila- tion of stations equipped with seismographs recommended by the British Association for the Advancement of Science, in the earthquake catalog of the International Association of Seismology for the year of 1904, in the San Francisco earthquake report or in the classical book “Seismicity of the Earth”. However, throughout time station COI lost its early importance and was progressively forgotten. Station COI is missed even by recent compilations of his- torical seismic data.
RESUMO: O Instituto Geofísico da Universidade de Coimbra (IGUC) foi fundado em 1864 como observat... more RESUMO: O Instituto Geofísico da Universidade de Coimbra (IGUC) foi fundado em 1864 como observatório meteorológico. As observações sísmicas só terão sido iniciadas de forma regular 43 anos mais tarde, em 1907. Os registos sísmicos que o IGUC possui actualmente representam uma das maiores e melhor conservadas séries de registos sísmicos a nível mundial. Neste trabalho apresentaremos os registos e os instrumentos utilizados no estudo da sismologia no IGUC, bem como o seu actual estado de preservação, e a importância dos antigos registos sísmicos nos estudos científicos modernos.
The Geophysical Institute of the University of Coimbra (IGUC) was founded in 1864 as the meteorol... more The Geophysical Institute of the University of Coimbra (IGUC) was founded in 1864 as the meteorological observatory. The seismic observations only started regularly 43 years later, in 1907. The seismic records that the IGUC have currently represent one of the largest and best preserved series of seismic record worldwide. Ins this work we present the records and the instruments used in the study of the seismology in the IGUC, as well as your current state of preservation, and the importance of the old seismic records in the modern scientific studies.
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oldest seismic station in Portugal and among the oldest in the
world. Experimental seismic recording began in 1891 with an
Angot seismograph. Continuous recording of ground
motion began in 1903 with a Milne seismograph, and is still
on-going at the same site, now with a broadband Streckeisen
STS-2 seismometer. Coimbra’s observatory owns an over
100-year long, well-preserved collection of seismograms, seismograph and bulletins. Station COI is taken into account
in early seismological works, for example, in the 1901 compila-
tion of stations equipped with seismographs recommended by
the British Association for the Advancement of Science, in the earthquake catalog of the International Association of Seismology for the year of 1904, in the San Francisco earthquake report or in the classical book “Seismicity of the Earth”. However, throughout time station COI lost its early importance and was progressively forgotten. Station COI is missed even by recent compilations of his- torical seismic data.
seismic record worldwide. Ins this work we present the records and the instruments used in the study of the seismology in the IGUC, as well as your current state of preservation, and the importance of the old seismic records in the modern scientific studies.
oldest seismic station in Portugal and among the oldest in the
world. Experimental seismic recording began in 1891 with an
Angot seismograph. Continuous recording of ground
motion began in 1903 with a Milne seismograph, and is still
on-going at the same site, now with a broadband Streckeisen
STS-2 seismometer. Coimbra’s observatory owns an over
100-year long, well-preserved collection of seismograms, seismograph and bulletins. Station COI is taken into account
in early seismological works, for example, in the 1901 compila-
tion of stations equipped with seismographs recommended by
the British Association for the Advancement of Science, in the earthquake catalog of the International Association of Seismology for the year of 1904, in the San Francisco earthquake report or in the classical book “Seismicity of the Earth”. However, throughout time station COI lost its early importance and was progressively forgotten. Station COI is missed even by recent compilations of his- torical seismic data.
seismic record worldwide. Ins this work we present the records and the instruments used in the study of the seismology in the IGUC, as well as your current state of preservation, and the importance of the old seismic records in the modern scientific studies.