2017 Volume 123 Issue 12 Pages 999-1014
In this paper, we review the general characteristics of submarine slides and their short- and long-term trigger mechanisms. Submarine slides have been reported from various sedimentary environments, including: 1) fjords; 2) active river deltas on continental margins; 3) submarine canyon-fan systems; 4) open continental slopes; 5) oceanic volcanic islands and ridges; 6) glacially influenced continental margins; and 7) continental slopes with active faults. From their geometry, submarine slides can generally be subdivided into three morphological domains: a headwall domain, a translational domain and a toe domain. Even in the initial stages of deformation, these domains can be clearly distinguished, as the headwall domain includes fissures, the translational domain includes asymmetric deformation structures due to shear deformation, and the toe domain is dominated by pressure ridges. Most of the slip surfaces correspond to clay-rich layers, although slip surfaces may also be sand layers in poorly drained environments, as reported in the Nankai Trough. The geological record over the past 20,000 years suggests there have been no large submarine slides in the last 5000 years, although data are scarce. In the Nankai Trough, there have been six large submarine slides in the last ~1 million years. The occurrence of these six slides does not correspond to sea-floor displacement resulting from large earthquakes. The trigger mechanism more likely relates to smaller earthquakes, resulting in an abrupt increase in ground acceleration and increased pore fluid pressure. The precondition for submarine slides includes many factors, such as a gradual increase in pore pressure by the decomposition of methane hydrate due to climate change, an increase in pore pressure as a result of high sedimentation rates, ground deformation due to the subduction/collision of seamounts, and/or slope steepening due to volcanic activity.
