Amplification of Strong Ground Motions at Heathcote Valley during the 2010–2011 Canterbury Earthquakes: The Role of 2D Nonlinear Site Response

Abstract

Research Article| September 25, 2017 Amplification of Strong Ground Motions at Heathcote Valley during the 2010–2011 Canterbury Earthquakes: The Role of 2D Nonlinear Site Response Seokho Jeong; Seokho Jeong aQuakeCoRE, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand, seokho.jeong@canterbury.ac.nz Search for other works by this author on: GSW Google Scholar Brendon A. Bradley Brendon A. Bradley bDepartment of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand, brendon.bradley@canterbury.ac.nzcCurrently at Department of Civil and Environmental Engineering, Stanford University, Stanford, California. Search for other works by this author on: GSW Google Scholar Author and Article Information Seokho Jeong aQuakeCoRE, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand, seokho.jeong@canterbury.ac.nz Brendon A. Bradley bDepartment of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand, brendon.bradley@canterbury.ac.nzcCurrently at Department of Civil and Environmental Engineering, Stanford University, Stanford, California. Publisher: Seismological Society of America First Online: 27 Sep 2017 Online Issn: 1943-3573 Print Issn: 0037-1106 Bulletin of the Seismological Society of America (2017) 107 (5): 2117–2130. https://doi.org/10.1785/0120160389 Article history First Online: 27 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 Seokho Jeong, Brendon A. Bradley; Amplification of Strong Ground Motions at Heathcote Valley during the 2010–2011 Canterbury Earthquakes: The Role of 2D Nonlinear Site Response. Bulletin of the Seismological Society of America 2017;; 107 (5): 2117–2130. doi: https://doi.org/10.1785/0120160389 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 SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract This article presents a quantitative case study on the site amplification effect observed at Heathcote Valley, New Zealand, during the 2010–2011 Canterbury earthquake sequence for 10 events that produced notable ground acceleration amplitudes up to 1.4g and 2.2g in the horizontal and vertical directions, respectively. We performed finite‐element analyses of the dynamic response of the valley, accounting for the realistic basin geometry and the soil nonlinear response. The site‐specific simulations performed significantly better than both empirical ground‐motion models and physics‐based regional‐scale ground‐motion simulations (which empirically account for the site effects), reducing the spectral acceleration prediction bias by a factor of 2 in short vibration periods. However, our validation exercise demonstrated that it was necessary to quantify the level of uncertainty in the estimated bedrock motion using multiple recorded events to understand how much the simplistic model can overestimate or underestimate the ground‐motion intensities. Inferences from the analyses suggest that the Rayleigh waves generated near the basin edge contributed significantly to the observed high‐frequency (⁠f>3 Hz⁠) amplification, in addition to the amplification caused by the strong soil–rock impedance contrast at the site fundamental frequency. Models with and without considering soil nonlinear response illustrate, as expected, that the linear‐elastic assumption severely overestimates ground motions in high frequencies for strong earthquakes, especially when the contribution of basin‐edge‐generated Rayleigh waves becomes significant. Our analyses also demonstrate that the effect of pressure‐dependent soil velocities on the high‐frequency ground motions is as significant as the amplification caused by the basin‐edge‐generated Rayleigh waves. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.