Zambrano, Oscar Marcos; Gulisano, Adriana Maria; Poma, Stella Maris; Ruocco, María Inés
2 022
Revista de la Asociación Geológica Argentina Volumen 79 (3) 03-2022
Se realizó una tomografía sísmica de inversión conjunta basada en los residuales de tiempo de viaje de las ondas P y S, con el objeto de estudiar la estructura sísmica del manto superior infrayacente a la dorsal Sur del Scotia y extremo norte de la Península Antártica. La misma se basó en registros sismográficos adquiridos en forma continua en estaciones sismológicas situadas en bases antárticas argentinas, procedentes del Proyecto Argentino Italiano para la gestión y mantenimiento de la red ASAIN: Antarctic Seismograph Argentinian ItalianNetwork. Las señales analizadas corresponden a eventos sismotectónicos locales de moderada a elevada mag-nitud ocurridos entre los años 2009 y 2019. Para la inversión discreta de los datos se implementó el método de regularización. Los resultados fueron evaluados mediante pruebas de resolución sintéticas. Se caracterizaron e interpretaron las estructuras sísmicas resueltas en las tomografías. El estudio se complementó mediante la estimación del módulo de Poisson y de la anomalía de velocidad acústica Vφ, lo cual permitió incorporar condiciones de restricción y por tanto de valoración a la interpretación de las tomografías. Se destaca la presencia de una anomalía negativa de velocidad de onda S en el sector de la cuenca Bransfield, en correspondencia con lo reportado por otros autores. Se interpreta como una región de la corteza y manto sometida a modificaciones del estado reológico (disminución de la rigidez, incremento de la incompresibilidad y aumento de la anelasticidad) causadas por un flujo térmico anómalo proveniente de una fuente localizada a mayor profundidad en el manto.
Characterization of upper mantle structures in the northern region of the Antarctic Peninsula, through an analysis of seismic velocity anomalies.
In order to study the seismic structure of the upper mantle underlying the South ridge of Scotia and the northern end of the Antarctic Peninsula, a joint inversion seismic tomography, based on the travel time residuals of the P and S waves, was carried out. It was based on seismographic records acquired continuously at seismological stations located in Argentine Antarctic bases, from the Argentine-Ita-lian Project for the management and maintenance of ASAIN: Antarctic Seismograph Argentinian Italian Network. The signals used correspond to local seismotectonic events of moderate to large magnitude that occurred between 2009 and 2019. The regularization method was implemented for the data discrete inversion. The results were evaluated by synthetic resolution tests. The seismic structures resolved with the tomographies were characterized and interpreted. The study was complemented by estimating the Poisson's modulus and the bulk sound velocity anomaly, which allowed the incorporation of restriction conditions and, therefore, assessment conditions in the interpretation of the tomographies. The presence of a negative S-wave velocity anomaly in the Bransfield basin sector is highlighted, in correspondence with that reported by other authors. It is interpreted as a region of the crust and mantle subjected to modifications of the rheological condition (decrease in rigidity, increase in incompressibility and increase in anelasticity) caused by an anomalous thermal flux from a source located deeper in the mantle.
In order to study the seismic structure of the upper mantle underlying the South ridge of Scotia and the northern end of the Antarctic Peninsula, a joint inversion seismic tomography, based on the travel time residuals of the P and S waves, was carried out. It was based on seismographic records acquired continuously at seismological stations located in Argentine Antarctic bases, from the Argentine-Ita-lian Project for the management and maintenance of ASAIN: Antarctic Seismograph Argentinian Italian Network. The signals used correspond to local seismotectonic events of moderate to large magnitude that occurred between 2009 and 2019. The regularization method was implemented for the data discrete inversion. The results were evaluated by synthetic resolution tests. The seismic structures resolved with the tomographies were characterized and interpreted. The study was complemented by estimating the Poisson's modulus and the bulk sound velocity anomaly, which allowed the incorporation of restriction conditions and, therefore, assessment conditions in the interpretation of the tomographies. The presence of a negative S-wave velocity anomaly in the Bransfield basin sector is highlighted, in correspondence with that reported by other authors. It is interpreted as a region of the crust and mantle subjected to modifications of the rheological condition (decrease in rigidity, increase in incompressibility and increase in anelasticity) caused by an anomalous thermal flux from a source located deeper in the mantle.
