Abstract
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.
Highlights
On 18 November 1929, an Mw 7.2 earthquake occurred beneath the upper Laurentian Fan, south of Newfoundland (Johnstone 1930; Hasegawa & Kanamori 1987; Bent 1995)
The earthquake caused the largest observed historical landslide on Earth, displacing at least 100 km3 of sediment volume. This rapidly evolved into a turbidity current, as revealed by a series of successive breaks in telecommunication cables (Heezen & Ewing 1952; Heezen et al 1954)
The first modern reanalysis of seismic signals suggested that the earthquake resulted from a major slump initiated just south of the Laurentian Channel, which rapidly spread laterally (Hasegawa & Kanamori 1987)
Summary
On 18 November 1929, an Mw 7.2 earthquake occurred beneath the upper Laurentian Fan, south of Newfoundland (Johnstone 1930; Hasegawa & Kanamori 1987; Bent 1995). The simulations with a longer duration of slump motion (tf = 120 s) resulted in roughly halved wave amplitudes (compared with tf = 60 s) and waves that were smaller than the field observations.
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