Seismotectonics and lithospheric-scale strain partitioning in relation to complex plate convergence settings
Complex plate convergence contexts are characterized by the interaction of various types of active faults (normal, reverse, and strike-slip) or, on a larger scale, by the convergence of different tectonic plates. These scenarios create regions of high seismic-tectonic complexity, some of which are l...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universidad de Huelva (UHU) |
| Repositorio: | Arias Montano. Repositorio Institucional de la Universidad de Huelva |
| Idioma: | inglés |
| OAI Identifier: | oai:ariasmontano.uhu.es:10272/27332 |
| Acceso en línea: | https://hdl.handle.net/10272/27332 |
| Access Level: | acceso abierto |
| Palabra clave: | Complex contexts Seismotectonics Slice method HVSR method 3D architecture Contextos complejos Sismotectónica Método de las lonchas Método HVSR Arquitectura 3D 2507.07 Tectónica 2507.06 Geofísica de la Masa Sólida Terrestre 2507.05 Sismología y Prospección Sísmica 2506.16 Teledetección (Geología) 2506.20 Geología Estructural |
| Sumario: | Complex plate convergence contexts are characterized by the interaction of various types of active faults (normal, reverse, and strike-slip) or, on a larger scale, by the convergence of different tectonic plates. These scenarios create regions of high seismic-tectonic complexity, some of which are located near densely populated areas or industrial zones. Thus, it is essential to study and develop more precise seismic hazard maps. One of the key advances of this research is the use of seismic big data for the development of a new analytical method known as the "slice method." This method allows for the delimitation of seismogenic levels ("slices"), from which density maps (kernel) are generated, facilitating the construction of three-dimensional models of seismically active structures. Taking advantage of the significance of the 2023 earthquakes in Turkey and Syria, this methodology was tested by applying it to two seismic datasets: one unprocessed and the other consisting of highly reliable relocated earthquakes. In both cases, the same procedure was applied, yielding consistent interpretations and demonstrating the method's effectiveness. The use of the kernel method acted as a filter, allowing for comparable results. Analysis of the East Anatolian Fault Zone identified five slices, generating a three-dimensional image of the fault. Previously inactive areas were reactivated after the 2023 seismic events, and a palm-like structure was observed along the main fault. Moreover, differences in seismic-tectonic behavior were identified along the fault, distinguishing transtensional regions to the south and west, a transpressive zone to the north, and a central strike-slip segment. The Nurdagi-Pazarcik fault, previously considered a splay fault, was reinterpreted not as a secondary branch but as part of the eastern arm of the main fault, converging at depth with the so-called main fault. A kinematic study and the development of rheological profiles were also conducted to explain the fault segmentation within the framework of plate tectonics and the seismic distribution at depth. This method was also applied to the Granada Basin, a region with a history of significant seismic activity and multiple recent seismic swarms, including three notable events between 2020 and 2022. Four slices with NW-SE and NE-SW seismicity patterns were identified. At depth, these patterns appear to converge in a basal detachment at 10-15 km depth, with a slight dip toward the WSW. This structure is associated with an extensional regime linked to the convergence between the Nubian and Eurasian plates. From the density cores, high- and low-angle faults converging at the detachment were identified, suggesting a predominant displacement toward the SSW. This detachment appears to be truncated in the east by a north-south oriented structure with a southward dip in the Sierra de Loja and in the west by an NW-SE fault at the eastern end of the basin. The estimated orientation of the density cores matches the extension of the boundary between the internal and external zones of the Betics. In the second part of the thesis, the effectiveness of the Horizontal-to-Vertical Spectral Ratio method was evaluated for studying the basement of the Guadalquivir Basin. Seismic noise measurements were taken in the western end of the basin, which enabled the development of a new empirical relationship for the region (ℎ=80.16·0-1.48). This relationship allowed for the estimation of the mechanical basement depth, reconstruction of the Tortonian paleotopography, and detection of fractures that influence the current terrain morphology. The results determined that the mechanical basement trends parallel to the basement-cover contact, with a 1-3º dip toward the southeast and slope breaks coincident with river courses. Minor discrepancies were found between mechanical boreholes and the estimates from this method, likely due to the presence of mechanically hard units, such as the Niebla calcarenites. The resulting model suggests a horst-and-graben configuration, where the structural highs correspond to elevated zones (such as the Cabezos de Huelva) and the depressions correspond to marshland areas. These advances open new research opportunities in other tectonic contexts, with potential applications in seismic risk studies, territorial planning, and the evaluation of tectonic evolution in active orogens. ------------------------------------------------------------------------------------------------- |
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