Revisiting Submarine Mass Movements Along The U.S. Atlantic Continental Margin: Implications For Tsunami Hazards

Abstract

Interest in the generation of tsunamis by submarine mass movements has warranted a reassessment of their distribution and the nature of submarine landslides offshore of the eastern U.S. The recent acquisition and analysis of multibeam bathymetric data over most of this continental slope and rise provides clearer view into the extent and style of mass movements on this margin. Debris flows appear to be the dominant type of mass movement, although some translational slides have also been identified. Areas affected by mass movements range in size from less than 9 km 2 to greater than 15,200 km 2 and reach measured thicknesses of up to 70 m. Failures are seen to originate on either the openslope or in submarine canyons. Slope-sourced failures are larger than canyon-sourced failures, suggesting they have a higher potential for tsunami generation although the volume of material displaced during individual failure events still needs to be refined. The slope-sourced failures are most common offshore of the northern, glaciated part of the coast, but others are found downslope of shelf-edge deltas and near salt diapirs, suggesting that several geological conditions control their distribution.

Morphology of late Quaternary submarine landslides along the U.S. Atlantic continental margin

“…Weaver et al, 2000;Piper and McCall, 2003;Huhnerbach et al, 2004;and Masson et al, 2006), and studies specific to the U.S. Atlantic margin have been summarized by Embley and Jacobi (1986), Booth et al (1993), and Chaytor et al (2007). Prior to the widespread introduction of acoustic mapping methods, techniques for identifying and mapping landslides were based on widely spaced seismic profiles and piston cores (Embley and Jacobi, 1986;and Pratson and Laine, 1989 and references in these reviews).…”

“…GLORIA sidescan sonar imagery provided the first continuous coverage image of this margin, and allowed a more detailed mapping of their spatial extent (EEZ-SCAN 87, 1991;Booth and O'Leary, 1991;Schlee and Robb, 1991;Popenoe and Dillon, 1996). The availability of high-quality multibeam bathymetric data allows detailed mapping of several geomorphic traits of the landslides that were not possible in previous data sets (McAdoo et al, 2000;Chaytor et al, 2007). For example, the location and relief of headwall scarps, the slope of landslide source areas, their height and length measures, and whether they are multistaged or single events are readily identified in these new data.…”

“…While McAdoo et al (2000) tabulated many of these traits in localized areas; the recent acquisition of multibeam bathymetry along much of the U.S. Atlantic margin (Gardner et al, 2006) allows analysis of the entire margin. Chaytor et al (2007) used these data to map the distribution of landslides along this margin. Here we further characterize the geomorphic traits of the landslides that occurred Marine Geology 264 (2009) [4][5][6][7][8][9][10][11][12][13][14][15] during the late Quaternary and are still expressed on the sea floor.…”

Assessment of tsunami hazard to the U.S. Atlantic margin

“…Past compilations of landslides along the U.S. Atlantic margin utilized a variety of geophysical imaging techniques, beginning with single-channel airgun and sparker seismic reflection profiles (Embley and Jacobi, 1977), to GLORIA sidescan backscatter and early lowresolution swath bathymetry (Booth et al, 1993), and higherresolution but incomplete swath bathymetry coverage of the margin (Chaytor et al, 2007;Twichell et al, 2009). Based on the recent compilation of high-resolution mapping data (Andrews et al, 2013 and references/sources within), landslides and related features along the margin fall into 3 types: Type 1: a landslide 'complex' with a clearly-coupled source/evacuation and deposit areas, Type 2: a landslide 'zone', where a deposition zone either does not exist next to the source/ evacuation zone, or if one is present, it cannot be related to a specific source, and Type 3: mass transport deposits (MTD) with no associated source/evacuation zone.…”

Mass Transport Events and Their Tsunami Hazard

“…Off the US margin 48 landslides have been mapped (Chaytor et al 2007), the largest of which, the Cape Fear Slide, has a volume of 200 km 3 (Lee in press). Landslides on the slope are generally larger than on the rise, thus having a higher potential to generate damaging tsunamis.…”