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DDC:
550 - Earth sciences
Abstract:
An earthquake near Ottawa (45.20"SUP o"N, 75.75"SUP o"W, focal depth 12 km) of unusualy large size for the region's seismicity (m"SUB b"(Lg) = 4.1) provided good P-wave first-motion data for a focal-mechanism solution. The mechanism is thrust faulting with a predominantly horizontal pressure axis trending 154"SUP o". The nodal planes have strike 71"SUP o", dip 75"SUP o", and strike 221"SUP o", dip 17"SUP o". The spatial distribution of aftershocks suggests the gently-dipping nodal plane could be the fault plane. There is uncertainty about the seismotectonics of the region, and the orientation of neither nodal plane correlates with known geological features. More earthquake fault-plane solutions are required to interpret the seismotectonics and the stress regime. -from Authors
