Are large submarine landslides temporally random or do uncertainties in available age constraints make it impossible to tell?

Abstract

Large (N~1 km 3 ) submarine landslides can potentially generate very destructive tsunamis and damage expensive 19 sea floor infrastructure. It is therefore important to understand their frequency and triggers, and whether their 20 frequency is likely to change significantly due to future climatic and sea level change. It is expensive to both 21 collect seafloor samples and to date landslides accurately; therefore we need to know how many landslides 22 we need to date, and with what precision, to answer whether sea level is a statistically significant control. Previ-23 ous non-statistical analyses have proposed that there is strong correlation between climate driven changes and 24 landslide frequency. In contrast, a recent statistical analysis by Urlaub et al. (2013) of a global compilation of 25 41 large (N1 km 3 ) submarine landslide ages in the last 30 ka concluded that these ages have a temporally random 26 distribution. This would suggest that landslide frequency is not strongly controlled by a single non-random global 27 factor, such as eustatic sea level. However, there are considerable uncertainties surrounding the age of almost all 28 large landslides, as noted by Urlaub et al. (2013). This contribution answers a key question that Urlaub et al. 29 (2013) posed, but could not address -are large submarine landslides in this global record indeed temporally ran-30 dom, or are the uncertainties in landslide ages simply too great to tell? We use simulated age distributions in 31 order to determine the significance of available age constraints from real submarine landslides. First, it is 32 shown that realistic average uncertainties in landslide ages of ±3 kyr may indeed result in a near-random distri-33 bution of ages, even where there are non-random triggers such as sea level. Second, we show how combination of 34 non-random landslide ages from just 3 different settings, can easily produce an apparently random distribution if 35 the landslides from different settings are out of phase. Third, if landslide frequency was directly proportional to 36 sea level, we show that at least 10 to 53 landslides would need to be dated perfectly globally -to show this cor-37 relation. We conclude that it is prudent to focus on well-dated landslides from one setting with similar triggers, 38 rather than having a poorly calibrated understanding of ages in multiple settings. (Hampton et al., 1996; Hühnerbach and Masson, 2004; 55 Talling et al., 2007). Perhaps the most remarkable aspect of large sub-56 marine landslides is that they typically can occur on very low gradients worldwide, which includes the last 120 ka (Fig. 1). This is the largest The analysis by Urlaub et al. (2013) included the often considerable un-136 certainties in landslide ages in this analysis (Fig. 1), unlike most previ- bin, and the number of bins with one, two or more landslide ages. 154It was found that there was no statistically significant difference be- 155tween the frequency of bins with 1, 2, 3 or more landslide ages, both 156 real and s...

Tsunamigenic potential of a Holocene submarine landslide along the North Anatolian Fault (northern Aegean Sea, off Thasos island): insights from numerical modelling

“…Although earthquake shaking related to the activity of the North Anatolian Fault may be considered the most likely trigger of submarine landslides, recent M w ∼ 7 events did not trigger significant landslides and tsunami, despite the unstable state of the North Aegean Trough slopes (Lykousis et al, 2002). This discrepancy between strong earthquakes and landslide frequencies has been highlighted in various tectono-sedimentary contexts (Völker et al, 2011;Strozyk et al, 2010;Pope et al, 2015Pope et al, , 2016. Various processes may explain this discrepancy, including the amount and the nature of sedimentary supply, local variations in physical properties of the sediments (Lafuerza et al, 2012) or the overcompaction of the sediments subsequent to the fluid release induced by the seismic wave shaking (Hampton et al, 1996;Strozyk et al, 2010).…”

Giant sublacustrine landslide in the Cretaceous Songliao Basin, NE China

“…Slopes, whether subaerial or subaqueous, are inherently unstable because the sediments deposited on them are subjected to gravitational forces along an inclined surface (Posamentier & Martinsen, ). Moreover, subaqueous landslides can be much larger than those on land (Cruden, ; Pope et al, ; Shanmugam, ). Several possible mechanisms have been proposed to account for the vast subaqueous landslides (Galloway et al, ; Lewis, ).…”

“…Slopes, whether subaerial or subaqueous, are inherently unstable because the sediments deposited on them are subjected to gravitational forces along an inclined surface (Posamentier & Martinsen, 2011). Moreover, subaqueous landslides can be much larger than those on land (Cruden, 1991;Pope et al, 2015;Shanmugam, 2015). Several possible mechanisms have been proposed to account for the vast subaqueous landslides (Galloway et al, 2000;Lewis, 1971 overpressure of underlying sediments, salt-shale withdrawal from underlying sediments, slippery basal surfaces, rapid sedimentation rates, fluctuations in sea level, deltaic progradation, increased rate of erosion at the shelf edge and others.…”

The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long‐term (>1 Ma) record offshore Montserrat, Lesser Antilles

“…Many landslides have large age uncertainties, and if age errors are too large (i.e., on the order of sea level cycles) then relationships between sea level, volcanism, and landslides cannot be determined [ Pope et al ., ]. Our age‐uncertainty criterion of <± 22.5 ka has been selected on this basis, because it provides a sufficiently large data set to observe potential patterns, with age errors that are a similar order of magnitude to the periodicity of sea level cycles (10 3 −10 4 years).…”