Determinación 3D de la superficie de acoplamiento sísmico entre la placa de Nazca y Sudamericana en la región de Valparaíso
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2022
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es
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Universidad Andrés Bello
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El borde occidental de Sudamérica es considerado, a nivel mundial, como el de mayor potencial sísmico y Chile forma parte de esta región, por ello a través de su historia ha sido afectado de manera reiterativa con la ocurrencia de eventos sísmicos de gran magnitud. El mayor número de estos eventos han tenido su origen en el proceso de convergencia entre las placas de Nazca y Sudamericana, el mismo que se desarrolla, en promedio en dirección N75ºE a una velocidad de 7-8 cm/año.
Los sismos que se producen sobre la superficie de fricción de placas han presentado sus focos a diversas profundidades. Por esto es necesario utilizar mayor cantidad de datos homogéneos y métodos para lograr mayor precisión en el conocimiento de esta fuente sismogénica. En este estudio se hace uso del catálogo sísmico del Neic, ISC-EHB y CMT Harvard (Global Centroit Moment Tensor) para determinar la geometría de la Superficie de Acoplamiento sísmico (SAS) analizando la distribución espacial de sismos en profundidad y de los principales ejes de deformación (P y T).
En el presente estudio se propone un modelo 3D para la geometría de la SAS asociada a la placa de Nazca que subduce por debajo del borde occidental de la Región de Valparaíso. Los resultados muestran que la SAS, desde la fosa, sigue una pendiente de 30° por debajo de la placa continental hasta una profundidad de 120 km, a partir de la cual, la subducción es de dos tipos, a partir de los 33°S al norte la placa de Nazca continua su proceso de subducción de manera sub horizontal hasta alcanzar distancias del orden de 350 km. Y a partir de los 33°S al sur la pendiente sigue siendo de 30° al oriente, lo que concibe una subducción de tipo normal.
La distribución de los esfuerzos P y T son coherentes con la deformación regional que permite que la placa de Nazca dentro del proceso de subducción se desplace de manera constante en dirección NE.
The western edge of South America is considered, worldwide, as the one with the greatest seismic potential and Chile is part of this region, which is why throughout its history it has been repeatedly affected by the occurrence of large-scale seismic events. The greatest number of these events have originated from the convergence process between the Nazca and South American plates, which develops, on average, in the N75ºE direction at a speed of 7-8 cm/year. The earthquakes that occur on the plate friction surface have had their foci at various depths. For this reason, it is necessary to use a greater amount of homogeneous data and methods to achieve greater precision in the knowledge of this seismogenic source. In this study, the seismic catalog of the Neic, ISC-EHB and CMT Harvard (Global Centroit Moment Tensor) is used to determine the geometry of the Seismic Coupling Surface (SAS) analyzing the spatial distribution of earthquakes in depth and of the main axes. deformation (P and T). In the present study, a 3D model is proposed for the geometry of the SAS associated with the Nazca plate that subducts below the western edge of the Valparaíso Region. The results show that the SAS, from the trench, follows a slope of 30° below the continental plate up to a depth of 120 km, from which subduction is of two types, starting at 33°S To the north, the Nazca plate continues its subduction process in a sub-horizontal manner until it reaches distances of the order of 350 km. And from 33°S to the south, the slope continues to be 30° to the east, which conceives a normal type of subduction. The distribution of the P and T stresses are consistent with the regional deformation that allows the Nazca plate to move constantly in a NE direction during the subduction process.
The western edge of South America is considered, worldwide, as the one with the greatest seismic potential and Chile is part of this region, which is why throughout its history it has been repeatedly affected by the occurrence of large-scale seismic events. The greatest number of these events have originated from the convergence process between the Nazca and South American plates, which develops, on average, in the N75ºE direction at a speed of 7-8 cm/year. The earthquakes that occur on the plate friction surface have had their foci at various depths. For this reason, it is necessary to use a greater amount of homogeneous data and methods to achieve greater precision in the knowledge of this seismogenic source. In this study, the seismic catalog of the Neic, ISC-EHB and CMT Harvard (Global Centroit Moment Tensor) is used to determine the geometry of the Seismic Coupling Surface (SAS) analyzing the spatial distribution of earthquakes in depth and of the main axes. deformation (P and T). In the present study, a 3D model is proposed for the geometry of the SAS associated with the Nazca plate that subducts below the western edge of the Valparaíso Region. The results show that the SAS, from the trench, follows a slope of 30° below the continental plate up to a depth of 120 km, from which subduction is of two types, starting at 33°S To the north, the Nazca plate continues its subduction process in a sub-horizontal manner until it reaches distances of the order of 350 km. And from 33°S to the south, the slope continues to be 30° to the east, which conceives a normal type of subduction. The distribution of the P and T stresses are consistent with the regional deformation that allows the Nazca plate to move constantly in a NE direction during the subduction process.
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Tesis (Geóloga)
Palabras clave
Sismología, Modelos Matemáticos, Zonas de Subducción, Chile, Valparaíso