CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Doig, R.
Date : 1991
Title : Effects of strong seismic shaking on lake sediments, and earthquake recurrence interval, Temiscaming, Quebec
Publication : Canadian Journal of Earth Sciences.
Issue : 28(9):
Page(s) : 1349-1352
Abstract
The magnitude 6.3 Timiskaming earthquake of 1935 resulted in discoloration in small lakes in the epicentral region. Sonar profiles for Lac Tee have shown that organic-rich gyttja has been removed from the sides and redeposited in the deep parts of the lake. Lake sediment cores from deep basins contain a 2-3 cm uppermost layer, which is interpreted as the normal accumulation of sediment since 1935. This is followed by a 20 cm chaotic zone of black gyttja mixed with partly tabular fragments of a previously formed silt layer, underlain by a dense 1-2 cm thick silt horizon. The latter is interpreted as having formed by rapid settling of the denser silicate portion of the resuspended sediment. This 20 cm zone is insufficient to account for the abnormal thickness of gyttja in the basins, so events of this kind would have had to have occurred repeatedly since deglaciation. The only major prehistoric event revealed by these approximately 100 cm cores is at a depth equivalent to about 1500 years ago, based on the amount of sediment deposited since 1935. A minor silting event occurred about 400 years ago. On this basis, the recurrence interval of magnitude 6 or greater earthquakes is longer at Temiscaming than at Charlevoix, Quebec (75 years historically), consistent with the present relative frequency of small earthquakes in these two regions.
Bibliography of Canadian Geomorphology