MASS TRANSPORT PROCESSES IN WORLDWIDE CONTINENTAL MARGINS AND THEIR SIGNIFICANCE FOR TSUNAMIGENIC HAZARDS

The magnitude of the waves generated by a submarine slide will depend primarily upon the volume of material that is moved, the depth of submergence in which the failure occurs, and the speed of the landslide. These parameters can be calculated using direct input from the 3D seismic volumes. Using 3D data offers a range of visualization and attribute analysis not afforded researchers working with 2D seismic or sea-floor imaging sonar. Several Cretaceous and Tertiary-age mass transport deposits have been mapped on margins of eastern Trinidad, western Morocco and eastern Mexico using 3D seismic data. Based upon our calculations, these submarine mass movements appear of sufficient scale to produce large tsunamigenic waves.

Several Tertiary age mass transport complexes, which range in area from 11.3 km2 to 2017 km2, have been identified in the continental margin of offshore Trinidad. These complexes were classified into three types based on the relationship between slope mass failures and the sourcing regions; 1) slope-attached systems 2) shelf-attached systems and 3) locally detached systems.

Maximum tsunami wave heights were estimated for these three types. Two key parameters were used as input; 1) the water depth in which the slides failed, and 2) the observed thicknesses of the slides. The results indicated that slope-attached systems can generate maximum tsunami wave heights in offshore Trinidad that can reach 8 to 11 m high above the slide failure. Due to changes in water depth, and variations on the geometry of the coast line, slope-attached systems could generate tsunamis with 16 to 21 m high run-up heights near the coast. In contrast, calculations show that shelf-attached systems could generate tsunamis with 11 to 14 m high run-up heights and locally detached systems could generate tsunamis with 8 to 11 m high run-up heights.

Similar mapping and analysis of mass transport failures in the margins of Morocco show potential for 5 meter high waves at the failure sites, likely reaching 10 m high at the coast. Failures along the Mexico margin have average thicknesses of 40 m with potential to generate 6 meter high waves at the failure site. These waves could reach up to 12 meters high in coastal zones.