western quebec and southern ontario - Department of Geology

WQ8 is locatedin the north-western part of the Ottawa River from latitude 45.5 to46.4° and longitude -77.5 to -76.3° with five events at focal depths ranging from 13 to 26km. The events in this cluster to the north of the Ottawa River have different focalmechanism (reverse type) from those to the south of it (normal type). (Figure 5.16a). Theevents to the north of the river show mainly NW-SE strike for the nodal planes, while twoevents to the south of the river have almost N-S strike and one event E-W strike.Comparison of the strike of the nodal planes with the geological features in this areashows that most of the events have the same strike as the faults within the region (Figure5.5). Exceptionally, a few events have a N-S strike. The dip angles vary widely between24° and almost 80°. The P-axes show diverse orientation but most of them are subhorizontalwith trends varying from N-S to E-W. The regional stress field is oriented inNE-SW in this region which is comparatively similar to the average trend of P-axes of theWQ6, WQ7, and WQ8 in the study area.Comparison of the focal plane solutions (Figures 15.16) and the faults within thisregion (Figure 5.5) indicates that seismicity in this area could be related to reactivation offaults, although many researchers link the seismicity to the Great Meteor Hotspot Track(e.g., Crough, 1981).88