Assessment of the Spatial Variability of Site Response in Southern Ontario

Abstract

Research Article| July 12, 2017 Assessment of the Spatial Variability of Site Response in Southern Ontario Sebastian Braganza; Sebastian Braganza aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Search for other works by this author on: GSW Google Scholar Gail M. Atkinson; Gail M. Atkinson aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Search for other works by this author on: GSW Google Scholar Sheri Molnar Sheri Molnar aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Search for other works by this author on: GSW Google Scholar Author and Article Information Sebastian Braganza aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Gail M. Atkinson aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Sheri Molnar aDepartment of Earth Sciences, Western University, Biological & Geological Sciences Building, 1151 Richmond Street, London, Ontario, Canada N6A 5B7, sbraganza53@gmail.com Publisher: Seismological Society of America First Online: 15 Sep 2017 Online Issn: 1938-2057 Print Issn: 0895-0695 © Seismological Society of America Seismological Research Letters (2017) 88 (5): 1415–1426. https://doi.org/10.1785/0220170042 Article history First Online: 15 Sep 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Sebastian Braganza, Gail M. Atkinson, Sheri Molnar; Assessment of the Spatial Variability of Site Response in Southern Ontario. Seismological Research Letters 2017;; 88 (5): 1415–1426. doi: https://doi.org/10.1785/0220170042 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search ABSTRACT In southern Ontario, Canada, site amplification plays a major role in the interpretation of ground motions and felt shaking during earthquakes. Sediments in the region vary from soft to stiff and overlie very hard glaciated bedrock, providing a strong impedance contrast that results in pronounced amplification of horizontal‐component motions. Generally, the peak frequency of amplification (⁠fpeak⁠) is inversely related to the depth to bedrock. In southern Ontario and many other parts of eastern North America, fpeak is the most important site‐response parameter. In this study, we measure the spatial variability of fpeak within a 1 km distance of 10 seismograph stations in southern Ontario. Establishing spatial variability of fpeak is useful for assessment of regional site response and its uncertainty; we can estimate site response if fpeak is known, and thus it is important to know to what distances the value of fpeak is spatially stable.Using ambient noise records, fpeak is measured from horizontal‐to‐vertical (H/V) spectral ratios at a number of locations at increasing distance from each seismograph site. Ambient noise H/V amplification ratios are compared with those obtained using weak‐motion earthquake recordings at the station. We find that, on average, log10(fpeak) as measured by microtremor survey observations is within 0.13 units of the value recorded at the seismograph station (using H/V from earthquake records) for survey sites within 1 km of the station. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.