Modelling the 1929 Grand Banks slump and landslide tsunami

Abstract

On 18 November 1929, an M w 7.2 earthquake occurred south of Newfoundland, displacing >100 km 3 of sediment volume that evolved into a turbidity current. The resulting tsunami was recorded across the Atlantic and caused fatalities in Newfoundland. This tsunami is attributed to sediment mass failure because no seafloor displacement due to the earthquake has been observed. No major headscarp, single evacuation area nor large mass transport deposit has been observed and it is still unclear how the tsunami was generated. There have been few previous attempts to model the tsunami and none of these match the observations. Recently acquired seismic reflection data suggest that rotational slumping of a thick sediment mass may have occurred, causing seafloor displacements up to 100 m in height. We used this new information to construct a tsunamigenic slump source and also carried out simulations assuming a translational landslide. The slump source produced sufficiently large waves to explain the high tsunami run-ups observed in Newfoundland and the translational landslide was needed to explain the long waves observed in the far field. However, more analysis is needed to derive a coherent model that more closely combines geological and geophysical observations with landslide and tsunami modelling.

A Massive Slump on the St. Pierre Slope, A New Perspective on the 1929 Grand Banks Submarine Landslide

“…A recent tsunami simulation by Løvholt et al () supports the hypothesis of this study that the tsunami was generated by a massive slump. They numerically simulated a tsunami that matches the observations from the 1929 event, concluding that the 1929 landslide likely was a combination of a major slump on the St. Pierre Slope, as proposed in this study (Figure ), and more distributive surficial sediment failures that occurred in shallower water near the shelf edge of St. Pierre Slope and along the Laurentian Channel, as proposed by Piper et al ().…”

“…It is argued that the slump is a much more probable mechanism to account for generation of the observed tsunami than the surficial sediment failures. Simulations by Løvholt et al (), however, show that both mechanisms were required. The main slump generated the principal component of the tsunami that impacted the south coast of Newfoundland, while the more distributive surficial sediment failures account for the more widely distributed tsunami wave that was recorded in Halifax and even at the Azores in the central North Atlantic (Løvholt et al, ).…”

Tsunamigenic Potential of the Baiyun Slide Complex in the South China Sea

“…Maximum sliding velocities of these scenarios reach 20–30 m/s (Figure ), which are comparable to the simulated slide speeds (30–35 m/s) of the Storegga Slide (Løvholt et al, ) and the estimated moving speeds (15–30 m/s) of a turbidity current during the 1929 Grand Bank landslide (Løvholt et al, ). Such extreme velocities are sufficiently destructive to break submarine cable lines, as evidenced by multiple cable breaks caused by turbidity currents during the 2006 Pingtung Earthquake off SW Taiwan (Hsu et al, ).…”

Landslide Material Control on Tsunami Genesis—The Storegga Slide and Tsunami (8,100 Years BP)

“…The Storegga Slide also generated a large tsunami, whose deposits have been identified along the coastlines of the North Sea, Norway (Bondevik et al, , ; Romundset & Bondevik, ), Scotland and England (Smith et al, ), Denmark (Fruergaard et al, ), and possibly Greenland (Wagner et al, ). With regard to tsunami genesis, the Storegga Slide differs from the majority of smaller tsunami‐generating slides, which are of a more impulsive nature, such as the 1998 Papua New Guinea slump (Lynett et al, ; Okal & Synolakis, ; Synolakis et al, ; Tappin et al, ) and the slump part of the Grand Banks event Løvholt et al (). It appears to share many features with other voluminous long‐runout deepwater events such as the neighboring Trænadjupet Slide (Laberg & Vorren, ; Løvholt et al, ) as well as several large landslides off the U.S. East Coast (Chaytor et al, ; Hill et al, ; Lee, ).…”

“…Despite their large complexity, submarine landslide tsunamis are traditionally treated with simplified source models (Fine et al, ; Grilli & Watts, ; Hill et al, ; Løvholt et al, ). The most common example is the block modeling approach, which has been successful in describing certain key historical tsunamis, such as the 1998 Papua New Guinea event (Lynett et al, ; Synolakis et al, ; Tappin et al, ) and the first phase of the 1929 Grand Banks event (Løvholt et al, ), both of which were caused by slumps. Such simplified approaches will, however, fall short in describing voluminous submarine landslides where more complex displacement processes such as remolding that alter material behavior and mass during the flow (Elverhøi et al, ; Talling, ) are important.…”