An Overview of Some Significant Eastern Canadian Earthquakes and Their Impacts on the Geological Environment,Buildings and the Public

Numerous moderate to large earthquakes have occurred in eastern Canada. Some ofthese events had significant geological effects such as surface faulting, liquefaction,submarine slumping, rock avalanches, rock falls, landslides, railroad embankmentslides, and one tsunami. Some of these earthquakes caused considerable damage tobuildings with unreinforced masonry elements that were located on thick clay deposits. These events also had strong psychological and social impacts, mainly due to the unpreparedness of the population. To minimize these impacts, programs should be designed to map the land and offshore areas most susceptible to mass movements (Earth Sciences), to define buildings most at risk (Engineering) and to educate the public about mitigation actions (Education, science popularization).     

The Applicability of Modern Methods of Earthquake Location

We compare traditional methods of seismic event location, based on phase pick data and analysis of events one-at-a-time, with a modern method based on cross-correlation measurements and joint analysis of numerous events. In application to four different regions representing different types of seismicity and monitored with networks of different station density, we present preliminary results indicating what fraction of seismic events may be amenable to analysis with modern methods. The latter can supply locations ten to a hundred times more precise than traditional methods. Since good locations of seismic sources are needed as the starting point for so many user communities, and potentially can be provided due to current improvements in easily-accessible computational capability, we advocate wide-scale application of modern methods in the routine production of bulletins of seismicity. This effort requires access to waveform archives from well-calibrated stations that have long operated at the same location.