Sensitivity analysis of the backprojection imaging method for seismic event location
Resumen
La precisión de los métodos de localización de señales sísmicas depende de la calidad de los datos de entrada. En la práctica, existen múltiples fuentes de incertidumbre que afectan la solución, incluyendo modelos de velocidad incorrectos, baja relación señalruido y cobertura azimutal deficiente. Además, existen señales sísmicas sin fases distinguibles que impiden su localización por métodos convencionales y requieren otro enfoque. En este trabajo, se realiza un análisis de sensibilidad de los métodos Back-Projection Imaging (BPI), aplicables para localizar sismos convencionales, microsismicidad inducida, señales tipo tremor y otros. Consecuentemente, se lleva a cabo un estudio controlado en el cual los datos sintéticos se modelan con fuentes explosivas de espectro fijo, donde cada parámetro puede perturbarse independientemente asegurando que sus efectos se manifiesten por separado en el resultado. Los resultados muestran la necesidad de pre-acondicionar los datos para reducir el ruido, el número de artefactos y mejorar la resolución de la imagen. Procesar las bajas frecuencias mejora la estabilidad del método, mientras que las altas frecuencias mejoran su exactitud. Adicionalmente, una buena cobertura azimutal reduce el error en la ubicación de un evento, en donde la profundidad resultó ser la coordenada espacial más sensible a los cambios de velocidad y geometría.
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