Bulletin of the New Zealand Society for Earthquake Engineering 2019-10-02T17:41:07+13:00 Rajesh Dhakal Open Journal Systems <p>Bulletin of the New Zealand Society for Earthquake Engineering</p> Guest editors foreword 2019-10-01T17:49:16+13:00 Misko Cubrinovski Michael Pender 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Misko Cubrinovski, Michael Pender Design ground motions near active faults 2019-10-02T17:40:55+13:00 Jonathan D. Bray Adrian Rodriguez-Marek Joanne L. Gillie <p>Forward-Directivity (FD) in the near-fault region can produce intense, pulse-type motions that differ significantly from ordinary ground motions that occur further from the ruptured fault. Near-fault FD motions typically govern the design of structures built close to active faults so the selection of design ground motions is critical for achieving effective performance without costly over-design. Updated empirical relationships are provided for estimating the peak ground velocity (<em>PGV</em>) and period of the velocity pulse (<em>T<sub>v</sub></em>) of near-fault FD motions. <em>PGV </em>varies significantly with magnitude, distance, and site effects. <em>T<sub>v</sub> </em>is a function of magnitude and site conditions with most of the energy being concentrated within a narrow-period band centred on the pulse period. Lower magnitude events, which produce lower pulse periods, might produce more damaging ground motions for the stiff structures more common in urban areas. As the number of near-fault recordings is still limited, fully nonlinear bi-directional shaking simulations are employed to gain additional insight. It is shown that site effects generally cause <em>T<sub>v</sub> </em>to increase. Although the amplification of <em>PGV </em>at soil sites depends on site properties, amplification is generally observed even for very intense rock motions. At soft soil sites, seismic site response can be limited by the yield strength of the soil, but then seismic instability may be a concern.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Jonathan D. Bray, Adrian Rodriguez-Marek, Joanne L. Gillie Analysis of dam response for foundation fault rupture 2019-10-02T17:40:57+13:00 Lelio Mejia Ethan Dawson <p>Considerable knowledge and experience has been developed over the past 40 years in the engineering profession regarding the seismic performance and analysis of dams for earthquake shaking. However, comparatively limited experience is available regarding the evaluation of dams for the effects of foundation fault rupture during earthquakes. This paper examines the factors to be considered in the evaluation of embankment dams for foundation faulting, and illustrates the analysis of dam response under foundation faulting by means of a case history, the seismic evaluation of Aviemore Dam.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Lelio Mejia, Ethan Dawson Probabilistic assessment of earthquake-induced sliding displacements of natural slopes 2019-10-02T17:40:59+13:00 Ellen M. Rathje Gokhan Saygili <p>The evaluation of earthquake-induced landslides in natural slopes is often based on an estimate of the permanent sliding displacement due to earthquake shaking. Current procedures for estimating sliding displacement do not rigorously account for the significant uncertainties present in the analysis. This paper presents a probabilistic framework for computing the annual rate of exceedance of different levels of displacement such that a hazard curve for sliding displacement can be developed. The analysis incorporates the uncertainties in the prediction of earthquake ground shaking, in the prediction of sliding displacement, and in the assessment of soil properties. Predictive models for sliding displacement that are appropriate for the probabilistic framework are presented. These models include a scalar model that predicts sliding displacement in terms of a single ground motion parameter (peak ground acceleration) and the earthquake magnitude, as well as a vector model that incorporates two ground motion parameters (peak ground acceleration and peak ground velocity). The addition of a second ground motion parameter results in a significant reduction in the standard deviation of the sliding displacement prediction. Comparisons are made between displacement hazard curves developed from the current scalar and vector models and previously developed scalar models that do not include earthquake magnitude. Additionally, an approximation to the vector hazard assessment is presented and compared with the rigorous vector approach. Finally, the inclusion of the soil property uncertainty is shown to increase the mean hazard at a site.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Ellen M. Rathje, Gokhan Saygili Pseudo-static analysis of piles subjected to lateral spreading 2019-10-02T17:41:00+13:00 Misko Cubrinovski Kenji Ishihara Harry Poulos <p>Soil liquefaction during strong ground shaking results in almost a complete loss of strength and stiffness in the liquefied soil, and consequent large ground deformation. Characteristics of the liquefied soils and loads on piles are significantly different during the cyclic phase and in the subsequent lateral spreading phase. Thus, it is necessary to separately consider these two phases in the simplified analysis of piles. This paper describes a practical procedure for preliminary assessment of piles subjected to lateral spreading. Effects of a crust of non-liquefied soil at the ground surface, properties of liquefied soils and pile groups are discussed in relation to their modelling in the simplified pseudo-static analysis approach. Particular attention is given to the treatment of unknowns and uncertainties involved in the simplified analysis and the need for parametric studies.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Misko Cubrinovski, Kenji Ishihara, Harry Poulos Full-scale shake table investigation of bridge abutment lateral earth pressure 2019-10-02T17:41:02+13:00 Patrick Wilson Ahmed Elgamal <p>During strong seismic excitation, passive earth pressure at the abutments may provide resistance to longitudinal displacement of the bridge deck. The dynamic pressure component may also contribute to undesirable abutment movement or damage. Current uncertainty in the passive force-displacement relationship and in the dynamic response of abutment backfills continues to motivate large-scale experimentation. In this regard, a test series is conducted to measure static and dynamic lateral earth pressure on a 1.7 meter high bridge abutment wall. Built in a large soil container, the wall is displaced horizontally into the dense sand backfill, in order to record the passive force-displacement relationship. The wall-backfill system is also subjected to shake table excitation. In the conducted tests, lateral earth pressure on the wall remained close to the static value during the low to moderate shaking events (up to about 0.5g). At higher levels of input acceleration, a substantial portion of the backfill inertial force started to clearly act on the wall.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Patrick Wilson, Ahmed Elgamal Model tests on behaviour of gravity-type quay walls subjected to strong shaking 2019-10-02T17:41:04+13:00 Ikuo Towhata Md. Jahangir Alam Tsuyoshi Honda Satoshi Tamate <p>Seismic stability of gravity-type quay walls and prevention of their large distortion are of major concern from a disaster prevention view point as well as in the sense of successful restoration after strong seismic events. There are, however, many existing walls which are of limited seismic resistance and would not be safe under increasing magnitude of design earthquakes. The present study conducted shaking model tests in both 1-g and 50-g centrifugal fields in order to demonstrate the efficiency of available mitigation technologies. Test results suggest that soil improvement in the loose foundation sand can reduce the quay wall damage to a certain extent when the intensity of shaking is around 0.30g. In contrast, under stronger shaking, the centrifugal tests manifested that those measures are not promising because of the increased effects of seismic inertia force.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Ikuo Towhata, Md. Jahangir Alam, Tsuyoshi Honda, Satoshi Tamate Undrained shear strength of partially saturated sand in triaxial tests 2019-10-02T17:41:05+13:00 Toshiyuki Kamata Yoshimichi Tsukamoto Kenji Ishihara <p>The undrained shear strength of partially saturated sand is examined based on a series of undrained triaxial compression and extension tests on Toyoura sand. The effects of partial saturation, density, and triaxial compression/extension modes are discussed in detail. The conditions of “flow” and “no flow” are categorised in terms of contractive and dilative behaviours. The threshold values of the undrained shear strength ratio dividing “flow” and “no flow” are found to be independent of the B-value and triaxial compression/extension modes. The empirical relations of the B-value against the initial state ratio r<sub>c</sub> and the undrained shear strength ratio S<sub>us</sub>/p’<sub>c</sub> are discussed in detail.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Toshiyuki Kamata, Yoshimichi Tsukamoto, Kenji Ishihara Fracture lineaments, fault mesh formation and seismicity 2019-10-02T17:41:07+13:00 Tariq I.H. Rahiman Jarg R. Pettinga <p>Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform, a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the SW Pacific. The upper crust of Viti Levu is dissected by numerous intersecting fault/lineament zones mapped from remote sensing imagery of the land surface (topography, radar and aerial photos) and basement (magnetic) and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field, and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineaments zones extend beyond the coastline to the offshore area from the SE Viti Levu study area. Multibeam bathymetry and seismic reflection data show the fault zones occur along and exert control on the location of a number of submarine canyons on the SE slope of Viti Levu. Evidence for Late Quaternary fault activity is only rarely observed in onshore SE Viti Levu (e.g. by displaced shoreline features), and in seismic reflection profiles from offshore.</p> <p>The principal fault sets in Viti Levu represent generations of regional tectonic faulting that pervade the Fiji Platform during and after the disruption of the proto Fijian arc in the Middle to Late Miocene (~15Ma). These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2-30 km wide. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (&lt;M4) occur regularly and may represent ruptures along short linking segments of the fault mesh, while infrequent larger earthquakes (&gt;M4) may result from complex rupture propagation through several linking fault segments of the mesh that lie close to optimum stress orientations. The interpreted model of distributed deformation through the fault mesh for the study area in SE Viti Levu is inferred to be characteristic of the style of active deformation that occurs throughout the entire Fiji Platform.</p> 2009-03-31T00:00:00+13:00 Copyright (c) 2009 Tariq I.H. Rahiman, Jarg R. Pettinga