Morphological and structural analysis in the Anaga offshore massif, Canary Islands:: fractures and debris avalanches relationships

As part of the 'National Hydrographic and Oceanographic Research Plan for the Spanish Exclusive Economic Zone', multibeam bathymetry and seismic reflection profiles were obtained in the Canary Islands aboard the R/V Hesperides. The submarine flanks of the Anaga offshore extension of Tenerife Island are here Studied to analyze its geomorphology. In the north sector of the Anaga submarine massif the extension of the Anaga Debris Avalanche has been mapped for the first time, and a Volume of 36 km(3) was calculated. The relationship between the Anaga and Orotava Debris Avalanches is also described. Faulting has been recognized as a key process for the occurrence of debris avalanches and the growth of volcanic lineaments. Moreover, faulting affects previous structures and the channelling of debris flows. Structural analysis shows the typical radial pattern of an oceanic island. In addition, a NE-SW dominant direction of faulting was obtained, consistent with the Tenerife Island Structural trend seen in the Anaga Massif and Cordillera Dorsal. NW-SE and E-W are two other main trends seen in the at-ea. Special interest is manifest in two long faults: 'Santa Cruz Fault' bounds the Southern edge of Anaga offshore Massif with a length of 50 kill and a direction that changes from NE-SW to almost E-W. The Guimar Debris Avalanche was probably channeled by this fault. The 'Guayota Fault' was recognized in several seismic profiles with a N-S direction that changes towards NW-SE at its southern end. This fault affects the more recent sediments with a vertical offset of 25-30 m, along 60 kill. It has been interpreted as a transpressive strike-slip fault.