Submarine Slides North of Puerto Rico and Their Tsunami Potential

Abstract

New multibeam bathymetry of the entire Puerto Rico trench reveals numerous retrograde slope failures at various scales at the edge of the carbonate platform north of Puerto Rico and the Virgin Islands. The slumped material comprises carbonate blocks, which fail, at least in initial stages, as a coherent rock mass. This, combined with the fact that the edge of the carbonate platform is steeper than most continental slopes, indicates a higher potential for run-up than along many other U.S. coasts. The style of slope failure appears to be rock falls, slide blocks and debris avalanches. Secondary failure of the failed carbonate products and of the underlying forearc sediments and rocks may lead to debris flows and turbidity flows. Fissures, discovered in the ocean floor near the edge of the platform, indicate that the process is expected to continue in the future. One of the slope failures, the Arecibo amphitheater, previously thought to represent a single giant slide with a volume of 900-1500 cu. km, appears to comprise smaller failures. The expected maximum tsunami run-up on the northern coast of Puerto Rico from one of these slope failures is <20 m, much lower than previously estimated. A recurrence rate of 100s ky was calculated for the largest observed failures along the edge of the carbonate platform north of Puerto Rico using simple assumptions. Smaller landslides would presumably occur at a higher recurrence rate. Elsewhere around the island, a 20-km wide failure scarp was discovered in the Upper Mona rift and could be associated with the 1918 tsunami and earthquake that hit northwestern Puerto Rico. Large slope failures were also discovered for the first time on the northern side of the Puerto Rico trench. Because Puerto Rico trench slides occur at large water depths (~6000 m), have large horizontal and vertical dimensions, and the directivity from tsunamis emanating from these slides is toward Puerto Rico, they may be of particular concern and may necessitate further study.

Size distribution of submarine landslides and its implication to tsunami hazard in Puerto Rico

“…The landslides are located at the edge of a 1–2 km thick massive and layered limestone [e.g., van Gestel et al , 1999], where slopes exceed 20°. Observations from this area [ ten Brink et al , 2006] indicate that slope failures have occurred as rotational slumps, rock slides, and debris avalanches (as classified by Lee et al [1993]). Densmore et al [1998] proposed that the probability distribution of subaerial landslide volumes follows a power‐law distribution with an exponent that depends on the mechanical properties of the rock mass (cohesion and internal friction angle).…”

“…[3] The north shore of Puerto Rico and its offshore region are covered by thick layers of carbonate rocks that now dip northward at an angle of 4° (Figure 1). These layers were deposited horizontally near sea level, and were titled about 3.3 Ma, such that their northernmost extent is at a depth of 4000 m and their southern extent on land in Puerto Rico is at a reconstructed elevation (before erosion) of +1300 m [ten Brink, 2005]. The tilt episode may have been very short, 40 kyr [ten Brink, 2005].…”

“…These layers were deposited horizontally near sea level, and were titled about 3.3 Ma, such that their northernmost extent is at a depth of 4000 m and their southern extent on land in Puerto Rico is at a reconstructed elevation (before erosion) of +1300 m [ten Brink, 2005]. The tilt episode may have been very short, 40 kyr [ten Brink, 2005]. The tilting has likely increased the probability of seismically induced landslides.…”

The Malta-Sicily Escarpment: Mass Movement Dynamics in a Sediment-Undersupplied Margin

“…Due to the composition of the failed material, the chaotic seismic signature of the deposits, and their linear to arcuate steep headwalls, we infer that the style of failure was either a translational slide or debris avalanche (e.g. ten Brink et al 2006). The amphitheatre-shaped depressions are likely canyon heads that result from coalescing, arcuate scars (Mulder et al 2012).…”

Semi‐automated bathymetric spectral decomposition delineates the impact of mass wasting on the morphological evolution of the continental slope, offshore Israel

“…Some of these studies highlight specific, usually exceptionally large, submarine slide scars (Gee, Gawthorpe, & Friedmann, ). While others take a regional perspective, by inspecting submarine slides over substantial expanses of continental margins (Chaytor, ten Brink, Solow, & Andrews, ; Harders, Ranero, Weinrebe, & Behrmann, ; Katz, Reuven, & Aharonov, ; McAdoo, Pratson, & Orange, ; ten Brink, Geist, Lynett, & Andrews, ; ten Brink, Lee, Geist, & Twichell, ). These studies usually consider the large‐scale slope morphology primarily as a pre‐conditioning factor for sliding, while studies on the morphological evolution of the margin usually take a generalized view of submarine mass transport features.…”