scholarly journals Soil profile characterisation of Christchurch Central Business District strong motion stations

2015 ◽  
Vol 48 (3) ◽  
pp. 146-156 ◽  
Author(s):  
Liam M. Wotherspoon ◽  
Rolando P. Orense ◽  
Brendon A. Bradley ◽  
Brady R. Cox ◽  
Clinton M. Wood ◽  
...  
Keyword(s):  
Soil Profile ◽  
Site Response ◽  
Strong Motion ◽  
Central Business District ◽  
Site Classification ◽  
Surface Wave Dispersion ◽  
Close Vicinity ◽  
Short Period ◽  
Business District ◽  
Site Classes

This paper presents an overview of the soil profile characteristics at strong motion station (SMS) locations in the Christchurch Central Business District (CBD) based on recently completed geotechnical site investigations. Given the variability of Christchurch soils, detailed investigations were needed in close vicinity to each SMS. In this regard, CPT, SPT and borehole data, and shear wave velocity (Vs) profiles from surface wave dispersion data in close vicinity to the SMSs have been used to develop detailed representative soil profiles at each site and to determine site classes according to the New Zealand standard NZS1170.5. A disparity between the NZS1170.5 site classes based on Vs and SPT N60 investigation techniques is highlighted, and additional studies are needed to harmonize site classification based on these techniques. The short period mode of vibration of soft deposits above gravels, which are found throughout Christchurch, are compared to the long period mode of vibration of the entire soil profile to bedrock. These two distinct modes of vibration require further investigation to determine their impact on the site response. According to current American and European approaches to seismic site classification, all SMSs were classified as problematic soil sites due to the presence of liquefiable strata, soils which are not directly accounted for by the NZS1170.5 approach.

scholarly journals Systematic Ground Motion Observations in the Canterbury Earthquakes and Region-Specific Non-Ergodic Empirical Ground Motion Modeling

2015 ◽  
Vol 31 (3) ◽  
pp. 1735-1761 ◽  
Author(s):  
Brendon A. Bradley
Keyword(s):  
Standard Deviation ◽  
Ground Motion ◽  
Strong Motion ◽  
Central Business District ◽  
Motion Modeling ◽  
Strong Motion Station ◽  
Systematic Effects ◽  
Canterbury Earthquake Sequence ◽  
Business District ◽  
A Site

This paper presents an examination of ground motion observations from 20 near-source strong motion stations during the most significant ten events in the 2010–2011 Canterbury earthquake sequence to examine region-specific systematic effects based on relaxing the conventional ergodic assumption. On the basis of similar site-to-site residuals, surfical geology, and geographical proximity, 15 of the 20 stations are grouped into four sub-regions: the Central Business District; and Western, Eastern, and Northern suburbs. Mean site-to-site residuals for these sub-regions then allows for the possibility of non-ergodic ground motion prediction over these sub-regions of Canterbury, rather than only at strong motion station locations. The ratio of the total non-ergodic vs. ergodic standard deviation is found to be, on average, consistent with previous studies, however it is emphasized that on a site-by-site basis the non-ergodic standard deviation can easily vary by ±20%.

Nonlinear shear stress reduction factor (rd) for assessment of liquefaction potential in Christchurch Central Business District

2014 ◽  
Vol 47 (1) ◽  
pp. 1-14
Author(s):  
James N. Dismuke
Keyword(s):  
Shear Stress ◽  
Stress Reduction ◽  
Site Response ◽  
Ground Motions ◽  
Limit State ◽  
Central Business District ◽  
Reduction Factor ◽  
Response Models ◽  
Business District ◽  
Nonlinear Shear

Simplified procedures for evaluating liquefaction triggering potential use the nonlinear shear stress reduction factor, rd, to estimate the peak earthquake-induced cyclic shear stress within the soil strata. Previous studies have derived rd by considering the response of representative ground profiles subjected to input ground motions with a range of ground motion characteristics. In this study, site–specific rd for serviceability limit state (SLS) and ultimate limit state (ULS) design ground motions are developed using site response models of the Christchurch Central Business District (CBD). The site response models are generated for typical geologic conditions of Christchurch CBD with shear wave velocity, Vs, profiles developed from the results of multichannel analysis of surface waves (MASW) surveys conducted across Christchurch CBD. A total of 528 simulations were conducted using 1D nonlinear time domain site response analyses using a suite of input ground motions that are representative of controlling ground motion scenarios for seismic hazard of Christchurch. The results of the ground response analyses are used to determine Christchurch CBD-specific rd relationships for liquefaction triggering assessments. The proposed relationships provide a better estimate of the cyclic stress ratios induced below Christchurch CBD when subjected to design SLS and ULS ground motions as compared to typical practice using generic liquefaction assessment methodologies.

scholarly journals Lake Parramatta

1970 ◽  
Vol 2 (2) ◽  
pp. 55-59
Author(s):  
Matti Keentok
Keyword(s):  
Drinking Water ◽  
Water Reservoir ◽  
Central Business District ◽  
Short History ◽  
European Settlement ◽  
Short Period ◽  
History Of ◽  
Business District

Lake Parramatta is about two kilometres north of Parramatta's central business district, on Hunts Creek. The reserve in which Lake Parramatta lies has gone through significant changes in its short history of European settlement. Originally a place of Aboriginal habitation by the Burramattagal clan, it has since seen occupation by people engaging in illicit production of spirits and by bushrangers (as was the case for neighbouring Darling Mills Creek); a short period of farming; a water reservoir supplying drinking water for Parramatta; and subsequently a place of recreation including swimming. These and other uses have left a number of relics still visible, although not obvious.

Seismic site response in the greater Vancouver, British Columbia, area: spectral ratios from moderate earthquakes

1999 ◽  
Vol 36 (2) ◽  
pp. 195-209 ◽  
Author(s):  
John F Cassidy ◽  
Garry C Rogers
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
River Delta ◽  
Data Sets ◽  
Fraser River ◽  
Spectral Ratios ◽  
Data Set ◽  
Seismic Site Response ◽  
Fraser River Delta ◽  
S Period

Three-component, digital recordings of two recent moderate earthquakes provide valuable new insight into the response to seismic shaking in the greater Vancouver area, particularly on the Fraser River delta. The 1996 M = 5.1 Duvall, Washington, earthquake (180 km southeast of Vancouver) triggered strong-motion seismographs at seven sites and the 1997 M = 4.3 Georgia Strait earthquake (37 km west of Vancouver) triggered instruments at 13 sites in the greater Vancouver area. The latter data set is especially important because it contains the first three-component recordings made on bedrock in greater Vancouver. Both data sets represent weak ground motion, with peak horizontal accelerations of 0.5-1.5% gravity (g) for the Duvall earthquake, and 0.2-2.4% g for the Georgia Strait earthquake. Using the method of spectral ratios, we estimate the site response for each of the strong-motion instrument soil sites. On the Fraser River delta amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period), with peak amplification of 4-10 (relative to competent bedrock) for the thick soil delta centre sites, and about 7-11 for the delta edge sites. Relative to firm soil, the peak amplification ranges from 2 to 5 for the thick soil delta centre sites, and 2 to 6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation, is observed.Key words: seismic site response, Fraser delta, earthquakes.

scholarly journals Analysis of Urban Effects in Oklahoma City using a Dense Surface Observing Network

2016 ◽  
Vol 55 (3) ◽  
pp. 723-741 ◽  
Author(s):  
Xiao-Ming Hu ◽  
Ming Xue ◽  
Petra M. Klein ◽  
Bradley G. Illston ◽  
Sheng Chen
Keyword(s):  
Metropolitan Area ◽  
Land Surface ◽  
Critical Role ◽  
Central Business District ◽  
Temperature Inversion ◽  
Oklahoma City ◽  
Near Surface ◽  
Open Questions ◽  
The Stability ◽  
Business District

AbstractMany studies have investigated urban heat island (UHI) intensity for cities around the world, which is normally quantified as the temperature difference between urban location(s) and rural location(s). A few open questions still remain regarding the UHI, such as the spatial distribution of UHI intensity, temporal (including diurnal and seasonal) variation of UHI intensity, and the UHI formation mechanism. A dense network of atmospheric monitoring sites, known as the Oklahoma City (OKC) Micronet (OKCNET), was deployed in 2008 across the OKC metropolitan area. This study analyzes data from OKCNET in 2009 and 2010 to investigate OKC UHI at a subcity spatial scale for the first time. The UHI intensity exhibited large spatial variations over OKC. During both daytime and nighttime, the strongest UHI intensity is mostly confined around the central business district where land surface roughness is the highest in the OKC metropolitan area. These results do not support the roughness warming theory to explain the air temperature UHI in OKC. The UHI intensity of OKC increased prominently around the early evening transition (EET) and stayed at a fairly constant level throughout the night. The physical processes during the EET play a critical role in determining the nocturnal UHI intensity. The near-surface rural temperature inversion strength was a good indicator for nocturnal UHI intensity. As a consequence of the relatively weak near-surface rural inversion, the strongest nocturnal UHI in OKC was less likely to occur in summer. Other meteorological factors (e.g., wind speed and cloud) can affect the stability/depth of the nighttime boundary layer and can thus modulate nocturnal UHI intensity.

Sign in / Sign up

Export Citation Format

Share Document