Attempts to study earthquake recurrence in space and time are limited by the short history of instrumental seismology compared to the long and variable recurrence time of large earthquakes. As a result, apparent concentrations and gaps in seismicity and hence seismic hazard within a seismic zone, especially where deformation rates are slow (<10 mm/yr), are likely to simply reflect the short earthquake record. Simple numerical simulations indicate that if seismicity were uniform within a tectonically similar seismic zone, such as the Atlantic coast of Canada, St. Lawrence valley, or the coast of North Africa, thousands of years of record would be needed before apparent concentrations and gaps of seismicity and hazard did not arise. Hence, treating sites of recent seismicity as more hazardous for future large earthquakes is likely to be inappropriate, and it would be preferable to regard the hazard as comparable throughout the seismic zone.

Evidence for environmental conditions in the Saint Lawrence Valley between 8,000 and 3,000 B.P. comes from three sources: (1) pollen stratigraphy, (2) macro and microfossils found at archaeological sites, and (3) association of the latter with geological features that can be used to reconstruct conditions of occupation. The Archaic Period is included in the Hypsithermal interval when assumed mean annual temperatures exceeded those of the present. Evidence available from pollen data suggests that the early inhabitants of the Saint Lawrence Valley were not influenced by this phenomenon as there is no agricultural activity before 3,000 B.P. Some changes in the cultural systems may be related to climatic fluctuations but the nomadic way of life prevailed throughout the whole period. The Archaic Period is divided into four subperiods: the Early Archaic, which is contemporaneous with the Late Paleoindian Period, extends from 10,000 to 8,000 B.P.; the Middle Archaic (8,000 to 6,000 B.P.); the Late Archaic (6,000 to 4,000 B.P.); and the Terminal Archaic (4,000 to 3,000 B.P.) By 8,000 B.P., freshwater species were available in the valley as well as in numerous lakes of the Canadian Shield where the Atlantic salmon ( Salmo salar) had become landlocked. Large mammals like deer, moose, and caribou were available in the forest from the Great Lakes to Gaspé, as well as beaver, porcupine, and hare. The present configuration of the Saint Lawrence River system was probably attained between 8,000 to 6,000 B.P. in the Montréal area. After 7,000 B.P., only minor fluctuations of the water level are recorded. However, these variations had great impact on the archaeological record. Many known archaeological sites are associated with beach ridges at low level along the shores of the Champlain and Goldthwait Seas or the ancestral Saint Lawrence River. The Archaic Period was characterized by a permanent occupation of the lowlands bordering the Saint Lawrence and by a growth in total population. The relations between physical environments and cultural systems are thus crucial if we want to discuss the evolution of adaptive strategies in the Saint Lawrence Valley where minor fluctuations of water level drastically change the landscape.