Publication: Interpretación sismotectónica de las series sísmicas de Lugo (1995 y 1997): un caso de triggering en una zona continental estable
Loading...
Files
Full text at PDC
Publication Date
2002
Advisors (or tutors)
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Sociedad Geológica de España
Citations
Exportar
Abstract
El noroeste de la Península Ibérica ha experimentado un aumento considerable de la actividad sísmica entre el año 1979 y el 2002, a pesar de ser considerada como una zona sísmicamente estable. Los mecanismos focales publicados hasta la fecha en trabajos previos para los eventos principales de las series de Lugo de 1995 (4,6) Y 1997 (5,1) difieren completamente en función. del método de cálculo utilizado. El presente trabajo se ha desarrollado con el objetivo de determinar los mecanismos de foco más coherentes con la geología local utilizando datos geológico-estructurales de campo y sismotectónicos. Asimismo, se ha realizado una modelización de las modificaciones de esfuerzos de Coulomb estáticos generadas por la primera serie con el fin de identificar posibles relaciones genéticas. Entre todos los modelos de esfuerzos el que mejor explica la distribución espacial de la serie de 1997 es el asociado a una falla oblicua inverso-direccional similar a la falla de Baralla, que por tanto se propone como posible fuente sísmica. La evolución de las series sísmicas apoya el funcionamiento de un proceso de triggering generado por la modificación de esfuerzos de Coulomb causada por el primer evento de magnitud 4,6 en 1995. La posición más profunda de la segunda serie parece indicar que las modificaciones del esfuerzo de fractura de Coulomb que ocasionó la primera serie desestabilizó un segmento más profundo de la misma falla que un año más tarde generó la serie de 1997.
Despite the northwestern area of the Iberian Peninsula was considered as a seismically stable area this region has suffered from 1979 to the present significant increase of the seismic activity rateo The focal mechanisms calculated in previous works for the mainshocks of the 1995 (Mb 4.6) and 1997 (Mb 5.1) Lugo sequences using first arrival polarities do not agree with the mechanisms calculated using the Centroid Moment Tensor method. In this work we propose the focal mechanisms solutions that have more coherence with the local structural and seismotectonic data. Moreover, we have performed a modelling of the coseismic Coulomb stress changes driven by the occurrence of the 1995 sequence, in order to find possible genetic relations with the 1997 sequence. The models using an oblique (reverse strike-slip) kinematics in a fault with the same geometry and orientation as the Baralla fault yield the best fitting with the spatial distribution of the 1997 sequence. The development of these two series and the modelling support the existence of a triggering process driven by coseismic Coulomb stress changes. The deeper position of the 1997 sequence suggests that the 1995 series destabilised a deeper segment of the same fault giving rise to the last one
Despite the northwestern area of the Iberian Peninsula was considered as a seismically stable area this region has suffered from 1979 to the present significant increase of the seismic activity rateo The focal mechanisms calculated in previous works for the mainshocks of the 1995 (Mb 4.6) and 1997 (Mb 5.1) Lugo sequences using first arrival polarities do not agree with the mechanisms calculated using the Centroid Moment Tensor method. In this work we propose the focal mechanisms solutions that have more coherence with the local structural and seismotectonic data. Moreover, we have performed a modelling of the coseismic Coulomb stress changes driven by the occurrence of the 1995 sequence, in order to find possible genetic relations with the 1997 sequence. The models using an oblique (reverse strike-slip) kinematics in a fault with the same geometry and orientation as the Baralla fault yield the best fitting with the spatial distribution of the 1997 sequence. The development of these two series and the modelling support the existence of a triggering process driven by coseismic Coulomb stress changes. The deeper position of the 1997 sequence suggests that the 1995 series destabilised a deeper segment of the same fault giving rise to the last one