Seafloor Classification and Marine Geohazards in the Coastal and Offshore Areas by Using Acoustic Techniques

Abstract

In tectonically active areas like the southern Red Sea, neotectonics plays a significant role in regulating the evolution of landforms. The Farasan Islands' fluvial systems have also been extensively impacted. In 2015, a high-resolution marine geophysical study was conducted in the southern Red Sea. It provided the first acoustic imaging of the sea floor across the Farasan Islands. The availability of such data enables the development of a 1-m digital terrain model for the area. The current study develops and proposes a method for reliably using digital terrain models generated using high-resolution marine acoustic methods to identify tectonic processes from geomorphology for the seafloor throughout the Farasan Islands. The drainage system and geomorphic conditions of the area have been severely impacted by tectonic activity. In light of structural geology, tectonics, and geomorphology, morphometric features of the seafloor across the Farasan Islands represented by digital terrain models will be retrieved, characterised, and interpreted. We describe a technique for calculating the index of relative active tectonics (IRAT), which is based on geomorphic indices obtained from digital terrain models of the seafloor beneath the Farasamn Islands and is useful for assessing topography and morphology. The five geomorphic indices that make up the basis of the current study are amplitude relief (Ar), the corresponding slope and aspect, the topographic wetness index (TWI), the terrain ruggedness index (TRI), the topographic position index (TPI), the slope-length gradient factor (LS-factor), and the stream power index (SPI). To identify relative tectonic activity within the plotted area, all indices were used. All the estimations were obtained using drainages and watershed basins extracted from the digital terrain models of the seafloor across the Farasan Islands in the Geographic Information System (GIS) environment. Based on the developed 1-m-resolution digital terrain models from the bathymetry of the seafloor across the Farasan Islands, drainage basins were extracted, and relative active tectonic geomorphic indices were estimated using the ArcGIS and SAGA-GIS software. The majority of the geomorphic indices were divided into five classes, and the relative ratios were arranged. For each class, the ratio of the number of drainage basins to the number of watershed basins for each geomorphic index was calculated and evaluated. The index of relative active tectonics (IRAT) was derived using the indexes' average class values. For each class of IRAT, the ratio between the number of drainage basins and watershed basins was calculated. The IRAT classifications were then used to define the probable risk level. Finally, the combined effect of the probable risk level and occurrence frequency of the morphotectonic feature was used to determine the active tectonic danger for each drainage basin. The findings demonstrated a strong correlation between IRAT classes and the ratio of morphotectonic valleys to drainage basins. On the sea bottom of the Farasan Islands, about 37% of the drainage basins with occured morphotectonic valleys are at a high-risk level, while 43% of the drainage basins without occured morphotectonic valleys are at a low-risk level. The remaining portion of the Farasan Islands' seafloor is regarded as having a medium risk rating. It has been found that after comparing with the past studies with the obtain results that provide higher accuracy which is greater than 87%. Therefore, it is a clear demonstration of the developed topography which had been bought though rapid electronic deformations it has higher chances of morphotectonic activity.