Resumen Este trabajo tiene como objetivo estudiar las perturbaciones en el campo geomagnético (GMF), nivel del agua (WL) y presión atmosférica a nivel del mar (AP) asociadas a eventos sísmicos Mw≥ 6.6 en el arco de Scotia, en el Atlántico Sur. Registros GMF de los observatorios de la Red Internacional de Observatorios Magnéticos (INTERMAGNET), registros WL de las estaciones de mareas de la Comisión Oceanográfica Intergubernamental y registros AP por hora de las bases de datos de la Oficina Global de Modelado y Asimilación de la Administración Nacional de Aeronáutica y el Espacio han sido analizadas en el área de estudio. Para el análisis de perturbaciones geomagnéticas se consideró la componente horizontal GMF, la cual es más susceptible a variaciones. Para el análisis WL, se calculó la discrepancia (residuo) entre la serie temporal WL de las estaciones de mareas y el nivel pronosticado de las mareas astronómicas, durante un período de 10 días antes y después de la ocurrencia de cada terremoto. Para el análisis AP se calculó la variación de los datos grillados entre 1 y 2 horas antes y después del sismo. El análisis de los datos geomagnéticos previos al evento sísmico, utilizando un filtro de paso alto y el método wavelet, mostró: a) altos rangos de energía en todas las frecuencias, incluso en las muy altas; y b) oscilaciones en el filtro con picos de amplitud de ± 0.2 nT, y con una anticipación y duración consistente con el método wavelet. En cuanto a los residuos WL calculados, hubo oscilaciones en las mayores amplitudes en los sensores ubicados más cerca del sismo, por lo que esas grandes amplitudes correspondieron a tiempos de llegada más cortos. El estudio AP mostró un máximo seguido de un mínimo local dentro de un rango de ± 0,3 hPa alrededor de la ubicación del terremoto. Mientras que el análisis GMF anticipó eventos sísmicos dentro de un rango de 6-2 horas, las técnicas utilizadas para WL y AP pudieron detectar terremotos Mw>7, asociándolos con la superficie ascendente/descendente del mar. Estas tres técnicas pueden ser utilizadas en conjunto para implementar un sistema de prevención o alerta temprana de eventos sísmicos o peligros relacionados tales como tsunamis y/o seiches en la región de estudio.

Abstract This paper is aimed at studying disturbances in the geomagnetic field (GMF), water level (WL) and sea-level atmospheric pressure (AP) associated with Mw≥ 6.6 seismic events in the Scotia arch, in the South Atlantic. GMF records from observatories of the International Magnetic Observatory Network (INTERMAGNET), WL records from tide stations of the Intergovernmental Oceanographic Commission, and hourly AP records from databases of the Global Modeling and Assimilation Office of the National Aeronautics and Space Administration have been analyzed in the area under study. For the analysis of geomagnetic disturbances, the GMF horizontal component (H), which is more susceptible to variations, was considered. For the WL analysis, the discrepancy (residue) between the WL time series from tide stations and the predicted level of astronomical tides, for a 10-day period before and after the occurrence of each earthquake, was calculated. For the AP analysis, the variation of data gridded between 1 and 2 hours before and after the earthquake was calculated. The analysis of the geomagnetic data prior to the seismic event, using a high-pass filter and the wavelet method, showed: a) high energy ranges in all frequencies, even in very high ones; and b) oscillations in the filter with amplitude peaks of ± 0.2 nT, and with an anticipation and duration consistent with the wavelet method. As regards the WL residues calculated, there were oscillations in the largest amplitudes in the sensors located closest to the earthquake, thus, those large amplitudes corresponded to shorter times of arrival. The AP study showed a maximum followed by a local minimum within a range of ± 0.3 hPa around the location of the earthquake. While the GMF analysis anticipated seismic events within a range of 6-2 hours, the techniques used for WL and AP could detect Mw>7 earthquakes, associating them with the rising/falling surface of the sea. These three techniques can be used jointly to implement a prevention or early warning system for seismic events or related hazards such as tsunamis and/or seiches in the study region.

Foram estudados 26 pacientes com epilepsia do lobo temporal clinicamente documentada por vários EEGs com atividade epileptiforme intercrítica e TC de crânio normal. SPECT com99mTC HMPAO e ressonância magnética (RM) foram realizados em todos os casos. 61.5% (n=16) das RM e 65.4% (n=17) dos SPECTs revelaram algum tipo de anormalidade. Atrofia hipocampal, nas imagens enfatizadas em Tl e presença de hipersinal nas imagens enfatizadas em T2, sugerindo esclerose mesial temporal, foram o principal achado (n=12; 75% das RM anormais). RM correlacionou-se ao EEG em 50% (n=13). Concordância entre RM e SPECT ocorreu em 30.7% (n=8) e entre SPECTe EEG em 57.7% (n=15). RM, SPECT e EEG foram congruentes em 26.9% (n=7). Estes resultados refletem o valor do SPECT intercrítico e RM na detecção e lateralização de anormalidades em epilepsia do lobo temporal. Por outro lado, em dois casos, o SPECT correlacionou-se mal com o EEG. Este método funcional não deve ser utilizado isoladamente na detecção de focos temporais. RM é mais útil do que a TC como recurso de neuroimagem na epilepsia do lobo temporal. Ela pode detectar pequenas lesões estruturais e esclerose mesial temporal, não facilmente identificáveis pela TC.

26 patients with temporal lobe epilepsy clinically documented by several abnormal interictal surface EEGs with typical unitemporal epileptiform activity and a normal CT scan were studied. Interictal99mTC HMPAO brain SPECT and MRI were performed in all subjects. Abnormalities were shown in 61.5% of MRI (n=16) and 65.4% of SPECT (n=17). Hippocampal atrophy associated to a high signal on T2-weighted MRI slices suggesting mesial temporal sclerosis was the main finding (n=12; 75% of abnormal MRI). MRI correlated well to surface EEG in 50% (n=13). There was also a good correlation between MRI and SPECT in 30.7% (n=8). SPECT and EEG were in agreement in 57.7% (n=l5). MRI, SPECT and EEG were congruent in 26.9% (n=7). These results support the usefulness of interictal brain SPECT and MRI in detecting lateralized abnormalities in temporal lobe epilepsy. On the other hand, in two cases, interictal SPECT correlated poorly with surface EEG. This functional method should not be used isolately in the detection of temporal lobe foci. MRI is more useful than CT as a neuroimaging technique in temporal lobe epilepsy. It may detect small structural lesions and mesial temporal lobe sclerosis which are not easily seen with traditional CT scanning.