Development of an NEHRP map for the Orleans suburb of Ottawa, Ontario

Abstract

The average shear-wave velocity to a depth of 30 m (Vs30) has been obtained for 73 sites in the Orleans area in the northeast part of the City of Ottawa. Measurements of Vs30 were made using both ground surface reflection and refraction methods. In addition, borehole data was used to estimate Vs versus depth profiles using average Vs values assigned to distinct geological units. High values of Vs (>1500 m/s) were obtained in areas of thin surficial sediments overlying Paleozoic bedrock, and low Vs values (<180 m/s) were calculated in areas of thick late–post-glacial clay. The Vs30 values have been used to prepare an NEHRP map for the study area. Much of the suburb of Orleans is classified as NEHRP zone E, whereas the perimeter areas and some isolated central areas are classified as zones ranging from zone D to zone A. The presence of thick unconsolidated late–post-glacial sediments deposited in the Champlain Sea is the main contributing factor to the wide range of average shear-wave velocities in the study area.

Earthquake-triggered slumps (1935 Timiskaming M6.2) in Lake Kipawa, Western Quebec Seismic Zone, Canada

“…Such issues loom large across the Shield terrain of eastern Canada in connection with the safe design of mines and nuclear facilities including waste disposal sites. The stability of urban infrastructure on lateglacial marine sediments (Leda Clays) along the Ottawa and St. Lawrence Valleys is also a concern as these Leda Clays exhibit 'quick' behaviour when disturbed (Ma et al, 2008;Motazedian and Hunter, 2008;Rosset and Chouinard, 2008;Lundstrom et al, 2009). Attention focuses on the geologic and geomorphic record of seismic activity in eastern North America such as liquefaction structures, faults, sedimentary dikes and landslides (e.g., Kelson et al, 1996;Ouellet, 1997;Aylsworth et al, 2000;Talwani and Schaeffer, 2001;Tuttle, 2001).…”

Detailed gravity survey to help seismic microzonation: Mapping the thickness of unconsolidated deposits in Ottawa, Canada

“…Fig. 3 presents the interpolated thickness of unconsolidated deposits based on these sources of information (Crow et al, 2007;Motazedian and Hunter, 2008).…”

Seismic site classification and site period mapping of Chennai City using geophysical and geotechnical data

“…The above correlation between SPT-N value and shear wave velocity is used to obtain the (V s ) 30 where shear wave velocity profile is not available. Similar kind of merging MASW tests with the borehole data has been carried out for the development of the NEHRP maps for Orleans suburb of Ottawa, Ontario (Motazedian and Hunter, 2008).…”