The November 25, 1988 Saguenay earthquake in Quebec Province and its implications for seismic hazard estimates

The 25 November 1988, Ms=6.0, Saguenay earthquake is the largest in eastern North America since the 1935 Temiskaming earthquake, also in southeastern Canada. Ongoing studies of this important event have already produced a number of surprising results concerning earthquake hazard estimates in eastern North America. Preliminary observations at this point include: (1) The epicentral region is characterized by low historic seismicity; (2) the steeply-dipping rupture is confined to the lower crust (25-30 km deep) and yet it seems to be geometrically correlated with fracture controlled topographic lineaments; (3) several faults were activated in the aftershock sequence, possibly including one at a shallow angle; (4) attenuation of high-frequency seismic waves over hundreds of kilometers is very low and is lower along than across the structural grain of the Appalachians; (5) ground failure, including slope failures and liquefaction-related effects, were induced over a broad area, substantially larger than expected from the magnitude of the earthquake. Some of these points are discussed more in this paper