32 Geological Impacts of Extreme Events on Land and Sea (Storms, Floods, Climate Variability, Tsunamis)

Friday, 28 March 2003
1:40 PM - 5:00 PM

TSUNAMI DEPOSITS FROM THE 1929 GRAND BANKS EARTHQUAKE AND SUBMARINE LANDSLIDE, TAYLOR’S BAY, NEWFOUNDLAND

Paper number: 32-4
Program: THEME SESSIONS
Time: 2:40 PM – 3:00 PM

Authors

Abstract

On November 18th, 1929, Canada was struck by its worst earthquake-related disaster. The magnitude 7.2 Grand Banks earthquake released an offshore landslide, best known for the turbidity current that it evolved into as it progressed down the continental slope to the abyssal plain, cutting trans-Atlantic telegraph cables along the way. What is not as well known is that the landslide caused a tsunami that hit Newfoundland’s Burin Peninsula with heights exceeding 13 m, killing 28 people. When viewed in the light of recent studies that have made a link between offshore landslides triggered by earthquakes that dramatically increase the amplitude of the tsunami (e.g. 1998 Papua New Guinea M=7.0 with a 7-10 m runup), this event is of particular importance as it occurred on a passive margin, and it is very unlikely that tectonic displacement of the seafloor caused the tsunami.

We studied the sand deposited in the marsh at Taylor’s Bay on the Burin, where the tsunami deposited sediment some 300 m inland, and laterally over ~400 m to an elevation ~7 m above mean sea level. The thickness of the deposit ranges from a trace of sand to over 25 cm thick, with no systematic variations. We sampled the sediment over the area of the deposit in a 10 m grid with the aim of characterizing the deposit to determine the extent of inundation and the wave height/velocity. Preliminary results show the expected fining of the sediment landward, which is consistent with results from other tsunami-lain sands. Our long-term goal is to develop a model that uses grain size variation to estimate the maximum velocity/depth of the wave.