Modelagem geométrica e análise de risco geológico em taludes rochosos aplicadas aos sistemas de falhas transversais (N120º e N090º) da Cidade do Salvador, Bahia, Brasil

Abstract

The city of Salvador has a large portion of the population residing in geological risk areas. Thus, a broad geological study is necessary to help to preserve the lives and properties of the people in these regions. Geologically, Salvador has two main fault systems, originating from the tectonic events they generated, the rift-type Recôncavo basin, at W, and the opening of the South Atlantic, at E, of the city, during the Cretaceous. A longitudinal system, oriented N030°-040º, and another transversal system, oriented N90°- 120° (STF). These systems control numerous valleys, highs, and local slopes. In this study, the main lineaments of the city of Salvador were delimited, and the Barra (SFB) and Brotas (SFBR) fault systems were modeled, in addition to the main N90°-120° orientation faults. From there, we generated predictive stereographic net models of mass movements based on data from fault plans in the Recôncavo basin, associated structures found in the city of Salvador. It was found through the study of these lineaments that : (i) transverse structures with direction N120º are the third largest in frequency (9.56%) and in length (10.86%), and, through kinematic modeling, ii) the wedge slip failure mechanism occurs more easily, followed by flexural tipping and planar sliding. The comparative analysis between the friction angles indicates that only the flexural toppling and wedge sliding mechanisms have their possibility of occurring increased. Besides that, 16 unstable slopes were also identified, 3 related to the SFB and 13 related to the SFBR, where the three failure mechanisms can occur, with predominantly mass movement directions to the South and Southwest, in heavily populated regions of the city of Salvador.