Caracterización de patrones morfológicos asociados a los procesos de subducción en el centro-norte de Chile.
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Date
2026
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Publisher
Universidad de Concepción
Abstract
El segmento de Atacama del norte-central de Chile (24◦–31◦S) es una brecha sísmica madura que no ha experimentado un gran terremoto (Mw ∼ 8,5) desde 1922, a pesar de la compleja deformación asociada a la subducción de topografía oceánica rugosa. Investigamos cómo las características batimétricas subducidas modulan el campo de esfuerzos y el estilo de deformación utilizando un nuevo conjunto de datos sísmicos de alta resolución. Analizamos ∼125,000 sismos registrados entre 2020 y 2025, relocalizados dentro de un modelo de velocidad 3D, y derivamos 90 mecanismos focales de alta calidad de un subconjunto de 602 eventos utilizando polaridades de onda P seleccionadas manualmente y el algoritmo SKHASH. La integración de los mecanismos focales con la estructura de VP /VS nos permite resolver variaciones espaciales en el esfuerzo y su relación con la distribución de fluidos y la geometría de la placa. Nuestros resultados muestran un régimen compresional dominante a lo largo de la interfaz del megathrust, con una pronunciada variabilidad a lo largo del rumbo que define una segmentación cinemática. La dorsal de Taltal está asociada con un campo de esfuerzos coherente, mientras que la dorsal de Copiapó exhibe orientaciones de esfuerzos heterogéneas y perturbadas. A profundidades intermedias (>60 km), el fallamiento generalizado de rumbo y normal indica una compleja deformación intraslab impulsada por procesos de flexión, fragmentación y deshidratación de la placa. Proponemos que las dorsales subducidas actúan como asperezas de primer orden que reorganizan localmente el campo de esfuerzos y promueven una deformación heterogénea. Estos hallazgos resaltan el papel de la rugosidad estructural y los fluidos en el control del comportamiento del deslizamiento dentro de una brecha sísmica madura, con implicaciones para el peligro sísmico en el norte-central de Chile.
The Atacama segment of north-central Chile (24◦–31◦S) is a mature seismic gap that has not experienced a great (Mw ∼ 8,5) earthquake since 1922, despite complex deformation associated with the subduction of rough oceanic topography. We investigate how subducted bathymetric features modulate the stress field and deformation style using a new high-resolution seismic dataset.We analyze ∼125,000 earthquakes recorded between 2020 and 2025, relocated within a 3D velocity model, and derive 90 high-quality focal mechanisms from a subset of 602 events using manually picked P-wave polarities and the SKHASH algorithm. Integrating focal mechanisms with VP /VS structure allows us to resolve spatial variations in stress and their relationship with fluid distribution and slab geometry. Our results show a dominant compressional regime along the megathrust interface, with pronounced along-strike variability that defines a clear kinematic segmentation. The Taltal Ridge is associated with a coherent stress field, whereas the Copiapó Ridge exhibits highly heterogeneous and perturbed stress orientations. At intermediate depths (>60 km), widespread strike-slip and normal faulting indicate complex intraslab deformation driven by slab bending, fragmentation, and dehydration processes. We propose that subducted ridges act as first-order asperities that locally reorganize the stress field and promote heterogeneous deformation. These findings highlight the role of structural roughness and fluids in controlling slip behavior within a mature seismic gap, with implications for seismic hazard in north-central Chile.
The Atacama segment of north-central Chile (24◦–31◦S) is a mature seismic gap that has not experienced a great (Mw ∼ 8,5) earthquake since 1922, despite complex deformation associated with the subduction of rough oceanic topography. We investigate how subducted bathymetric features modulate the stress field and deformation style using a new high-resolution seismic dataset.We analyze ∼125,000 earthquakes recorded between 2020 and 2025, relocated within a 3D velocity model, and derive 90 high-quality focal mechanisms from a subset of 602 events using manually picked P-wave polarities and the SKHASH algorithm. Integrating focal mechanisms with VP /VS structure allows us to resolve spatial variations in stress and their relationship with fluid distribution and slab geometry. Our results show a dominant compressional regime along the megathrust interface, with pronounced along-strike variability that defines a clear kinematic segmentation. The Taltal Ridge is associated with a coherent stress field, whereas the Copiapó Ridge exhibits highly heterogeneous and perturbed stress orientations. At intermediate depths (>60 km), widespread strike-slip and normal faulting indicate complex intraslab deformation driven by slab bending, fragmentation, and dehydration processes. We propose that subducted ridges act as first-order asperities that locally reorganize the stress field and promote heterogeneous deformation. These findings highlight the role of structural roughness and fluids in controlling slip behavior within a mature seismic gap, with implications for seismic hazard in north-central Chile.
Description
Tesis presentada para optar al grado de Magíster en Geofísica.
Keywords
Zonas de subducción, Batimetría, Terremotos, Tectónica de placas