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Images, eqnz.chch.2010

Collapsed silos at David Bell Daffodil Farm in Leeston; aftermath of the magnitude 7.1 earthquake that struck mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

The faultline cuts across Telegraph Road, leaving a kink in its originally straight alignment; aftermath of the magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

On the previously unknown faultline on Highfield Road in mid-Canterbury! This was where two tectonic plates slipped, causing the magnitude 7.1 earthquake on Saturday 4 September 2010.

Images, eqnz.chch.2010

The faultline cuts across Telegraph Road, leaving a kink in its originally straight alignment; aftermath of the magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

Slipping of the tectonic plates caused tension cracks on this previously unknown faultline that runs through this paddock; magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

Slipping of the tectonic plates caused tension cracks on this previously unknown faultline that runs through this paddock; magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

This originally straight farm fence has been laterally displaced at least 2 metres where it crosses the previously unknown faultline from which the Saturday 4 September 2010 earthquake originated.

Images, eqnz.chch.2010

This originally straight farm fence has been laterally displaced at least 2 metres where it crosses the previously unknown faultline from which the Saturday 4 September 2010 earthquake originated.

Images, eqnz.chch.2010

Looking along this previously unknown faultline that runs through this paddock, note how the ground had heaved and subsided; magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

The faultline cuts across Telegraph Road, leaving a kink in its originally straight alignment; aftermath of the magnitude 7.1 earthquake in mid-Canterbury on Saturday 4 September 2010.

Research papers, University of Canterbury Library

In this paper, the characteristics of near-fault ground motions recorded during the Mw7.1 Darfield and Mw 6.2 Christchurch earthquakes are examined and compared with existing empirical models. The characteristics of forward-directivity effects are first examined using a wavelet-based pulse-classification algorithm. This is followed by an assessment of the adequacy of empirical models which aim to capture the effect of directivity effects on amplifying the acceleration response spectra; and the period and peak velocity of the forward-directivity pulse. It is illustrated that broadband directivity models developed by Somerville et al. (1997) and Abrahamson (2000) generally under-predict the observed amplification of response spectral ordinates at longer vibration periods. In contrast, a recently developed narrowband model by Shahi and Baker (2011) provides significantly improved predictions by amplifying the response spectra within a small range of periods surrounding the directivity pulse period. Although the empirical predictions of the pulse period are generally favourable for the Christchurch earthquake, the observations from the Darfield earthquake are significantly under-predicted. The elongation in observed pulse periods is inferred as being a result of the soft sedimentary soils of the Canterbury basin. However, empirical predictions of the observed peak velocity associated with the directivity pulse are generally adequate for both events.

Images, eqnz.chch.2010

Damage to the St John The Evangelist Catholic Church in Leeston suffered during the magnitude 7.1 earthquake that struck mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

Hehehe ..... did the surveyors get the road setout wrong? This previously straight road is now kinked across this previously unknown faultline along which the Saturday 4 September 2010 magnitude 7.1 earthquake originated.

Images, eqnz.chch.2010

Hehehe ..... did the surveyors get the road setout wrong? This previously straight road is now kinked across this previously unknown faultline along which the Saturday 4 September 2010 magnitude 7.1 earthquake originated.

Images, eqnz.chch.2010

The farmers in this area swore that this road was straight when they were returning from the pub on Friday 3 September 2010, the night before the magnitude 7.1 earthquake struck.

Images, eqnz.chch.2010

The farmers in this area swore that this road was straight when they were returning from the pub on Friday 3 September 2010, the night before the magnitude 7.1 earthquake struck.

Audio, Radio New Zealand

Spud Hilton knows what it's like to feel the fear of a large scale earthquake. As the Travel Editor of the San Francisco Chronicle newspaper, he lives in a city on a fault line. Spud Hilton has just published an article in the San Francisco Chronicle about the status of Christchurch as a tourist destination and as a city that must rebuild, rethink and reinvent itself.

Images, eqnz.chch.2010

The St John The Evangelist Catholic Church in Leeston was cordoned off due to damage suffered during the magnitude 7.1 earthquake that struck mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

The St John The Evangelist Catholic Church in Leeston was cordoned off due to damage suffered during the magnitude 7.1 earthquake that struck mid-Canterbury on Saturday 4 September 2010.

Images, eqnz.chch.2010

The farmer swore that his fence was erected in a straingt line, but mother nature had other ideas! Aftermath of the Saturday 4 September 2010 magnitude 7.1 earthquake at the previously unknown faultline along which the quake originated.

Images, eqnz.chch.2010

The farmer swore that his hedge was planted in a straingt line, but mother nature had other ideas! Aftermath of the Saturday 4 September 2010 magnitude 7.1 earthquake at the previously unknown faultline along which the quake originated.

Images, eqnz.chch.2010

The magnitude 7.1 earthquake that struck mid-Canterbury on Saturday 4 September 2010 broke the tip of the spire of the St John The Evangelist Catholic Church in Leeston

Images, eqnz.chch.2010

The farmer swore that his fence was erected in a straingt line, but mother nature had other ideas! Aftermath of the Saturday 4 September 2010 magnitude 7.1 earthquake at the previously unknown faultline along which the quake originated.

Research papers, University of Canterbury Library

This dissertation addresses a diverse range of topics in the physics-based broadband ground motion simulation, with a focus on New Zealand applications. In particular the following topics are addressed: the methodology and computational implementation of a New Zealand Velocity Model for broadband ground motion simulation; generalised parametric functions and spatial correlations for seismic velocities in the Canterbury, New Zealand region from surface-wave-based site characterisation; and ground motion simulations of Hope Fault earthquakes. The paragraphs below outline each contribution in more detail. A necessary component in physics-based ground motion simulation is a 3D model which details the seismic velocities in the region of interest. Here a velocity model construction methodology, its computational implementation, and application in the construction of a New Zealand velocity model for use in physics-based broadband ground motion simulation are presented. The methodology utilises multiple datasets spanning different length scales, which is enabled via the use of modular sub-regions, geologic surfaces, and parametric representations of crustal velocity. A number of efficiency-related workflows to decrease the overall computational construction time are employed, while maintaining the flexibility and extensibility to incorporate additional datasets and re- fined velocity parameterizations as they become available. The model comprises explicit representations of the Canterbury, Wellington, Nelson-Tasman, Kaikoura, Marlborough, Waiau, Hanmer and Cheviot sedimentary basins embedded within a regional travel-time tomography-based velocity model for the shallow crust and provides the means to conduct ground motion simulations throughout New Zealand for the first time. Recently developed deep shear-wave velocity profiles in Canterbury enabled models that better characterise the velocity structure within geologic layers of the Canterbury sedimentary basin to be developed. Here the development of depth- and Vs30-dependent para-metric velocity and spatial correlation models to characterise shear-wave velocities within the geologic layers of the Canterbury sedimentary basin are presented. The models utilise data from 22 shear-wave velocity profiles of up to 2.5km depth (derived from surface wave analysis) juxtaposed with models which detail the three-dimensional structure of the geologic formations in the Canterbury sedimentary basin. Parametric velocity equations are presented for Fine Grained Sediments, Gravels, and Tertiary layer groupings. Spatial correlations were developed and applied to generate three-dimensional stochastic velocity perturbations. Collectively, these models enable seismic velocities to be realistically represented for applications such as 3D ground motion and site response simulations. Lastly the New Zealand velocity model is applied to simulate ground motions for a Mw7.51 rupture of the Hope Fault using a physics-based simulation methodology and a 3D crustal velocity model of New Zealand. The simulation methodology was validated for use in the region through comparison with observations for a suite of historic small magnitude earthquakes located proximal to the Hope Fault. Simulations are compared with conventionally utilised empirical ground motion models, with simulated peak ground velocities being notably higher in regions with modelled sedimentary basins. A sensitivity analysis was undertaken where the source characteristics of magnitude, stress parameter, hypocentre location and kinematic slip distribution were varied and an analysis of their effect on ground motion intensities is presented. It was found that the magnitude and stress parameter strongly influenced long and short period ground motion amplitudes, respectively. Ground motion intensities for the Hope Fault scenario are compared with the 2016 Kaikoura Mw7.8 earthquake, it was found that the Kaikoura earthquake produced stronger motions along the eastern South Island, while the Hope Fault scenario resulted in stronger motions immediately West of the near-fault region. The simulated ground motions for this scenario complement prior empirically-based estimates and are informative for mitigation and emergency planning purposes.

Research papers, University of Canterbury Library

The Porter's Pass-Amberley Fault Zone (PPAFZ) is a complex zone of anastomosing faults and folds bounding the south-eastern edge of the transition from subducting Pacific Plate to continental collision on the Australia Plate boundary. This study combines mapping of a 2000 km2 zone from the Southern Alps northeast to the coast near Amberley, 40 km north of metropolitan Christchurch, with an analysis of seismicity and a revision of regional seismic hazard. Three structural styles: 1) a western strike-slip, and 2) a more easterly thrust and reverse domain, pass into 3) a northwest verging fold belt on the northern Canterbury Plains, reflecting the structural levels exposed and the evolving west to east propagation. Basal remnants of a Late Cretaceous-Cenozoic, largely marine sedimentary cover sequence are preserved as outliers that unconformably overlie Mesozoic basement (greywacke and argillite of the Torlesse terrain) in the mountains of the PPAFZ and are underlain by a deeply leached zone which is widely preserved. Structure contouring of the unconformity surface indicates maximum, differential uplift of c.2600 m in the southwest, decreasing to c.1200 m in the coastal fold belt to the northeast. Much lower rates (or reversal) of uplift are evident a few kilometres southeast of the PPAFZ range-front escarpment. The youngest elements of the cover sequence are basement-derived conglomerates of Plio-Pleistocene age preserved on the SE margin. The source is more distant than the intervening mountains of the PPAFZ, probably from the Southern Alps, to the west and northwest. The absence of another regional unconformity on Mesozoic basement, older than Pleistocene, indicates that this uplift is post-Pliocene. Late Pleistocene(<100 kyr) differential uplift rates of c.0.5-2.7 m/kyr from uplifted marine terraces at the east coast, and rates of 2.5-3.3 m/kyr for tectonically-induced river-down cutting further west, suggest that uplift commenced locally during the last 1 Ma, and possibly within the last 0.5 Ma, if average rates are assumed to be uniform over time. Analysis of seismicity, recorded during a 10 week regional survey of micro earthquakes in 1990, identified two seismic zones beneath North Canterbury: 1) a sub-horizontal zone of activity restricted to the upper crust (≤12 km); and 2) a seismic zone in the lower crust (below a ceiling of ≤17 km), that broadens vertically to the north and northwest to a depth of c.40 km, with a bottom edge which dips 10°N and 15°NW, respectively. No events were recorded at depths between 12 km and 17 km, which is interpreted as a relatively aseismic, mid-crustal ductile layer. Marked differences (up to 60°) in the trend of strain axes for events above and below the inferred ductile layer are observed only north of the PPAFZ. A fundamental, north-to-south increase in the Wave-length of major geological structures occurs across the PPAFZ, and is interpreted as evidence that the upper crust beneath the Canterbury Plains is coupled to the lower crust, whereas the upper crust further north is not. Most of the recorded micro earthquakes <12 km deep beneath the PPAFZ have strike-slip mechanisms. It is probable that faults splay upward into the thrusts and folds at the surface as an evolving transpression zone in response to deep shear in basement. There have been no historic surface ruptures of the PPAFZ, but the zone has been characterised historically by frequent small earthquakes. Paleoseismic data (dated landslides and surface ruptures) compiled in this study, indicate a return period of 1500-1900 years between the last two M>7-7.5 earthquakes, and 500-700 years have elapsed since the last. The magnitudes of these events are estimated at c.M7.5, which represents a probable maximum magnitude for the PPAFZ. There are insufficient data to determine whether or not the frequency of large earthquakes conforms to a recognised model of behaviour, but comparison of the paleoseismic data with the historic record of smaller earthquakes, suggests that the magnitudes of the largest earthquakes in this zone are not exponentially distributed. A seismicity model for the PPAFZ (Elder et al., 1991) is reviewed, and a b-value of 1.0 is found to be consistent with the newly acquired paleoseismic data. This b-value reduces the predicted frequency of large earthquakes (M≥7.0) in this zone by a factor of 3.5, while retaining a conservative margin that allows for temporal variations in the frequency of large events and the possibility that the geological database is incomplete, suggesting grounds for revising the hazard model for Christchurch.

Research papers, University of Canterbury Library

The purpose of this thesis is to conduct a detailed examination of the forward-directivity characteristics of near-fault ground motions produced in the 2010-11 Canterbury earthquakes, including evaluating the efficacy of several existing empirical models which form the basis of frameworks for considering directivity in seismic hazard assessment. A wavelet-based pulse classification algorithm developed by Baker (2007) is firstly used to identify and characterise ground motions which demonstrate evidence of forward-directivity effects from significant events in the Canterbury earthquake sequence. The algorithm fails to classify a large number of ground motions which clearly exhibit an early-arriving directivity pulse due to: (i) incorrect pulse extraction resulting from the presence of pulse-like features caused by other physical phenomena; and (ii) inadequacy of the pulse indicator score used to carry out binary pulse-like/non-pulse-like classification. An alternative ‘manual’ approach is proposed to ensure 'correct' pulse extraction and the classification process is also guided by examination of the horizontal velocity trajectory plots and source-to-site geometry. Based on the above analysis, 59 pulse-like ground motions are identified from the Canterbury earthquakes , which in the author's opinion, are caused by forward-directivity effects. The pulses are also characterised in terms of their period and amplitude. A revised version of the B07 algorithm developed by Shahi (2013) is also subsequently utilised but without observing any notable improvement in the pulse classification results. A series of three chapters are dedicated to assess the predictive capabilities of empirical models to predict the: (i) probability of pulse occurrence; (ii) response spectrum amplification caused by the directivity pulse; (iii) period and amplitude (peak ground velocity, PGV) of the directivity pulse using observations from four significant events in the Canterbury earthquakes. Based on the results of logistic regression analysis, it is found that the pulse probability model of Shahi (2013) provides the most improved predictions in comparison to its predecessors. Pulse probability contour maps are developed to scrutinise observations of pulses/non-pulses with predicted probabilities. A direct comparison of the observed and predicted directivity amplification of acceleration response spectra reveals the inadequacy of broadband directivity models, which form the basis of the near-fault factor in the New Zealand loadings standard, NZS1170.5:2004. In contrast, a recently developed narrowband model by Shahi & Baker (2011) provides significantly improved predictions by amplifying the response spectra within a small range of periods. The significant positive bias demonstrated by the residuals associated with all models at longer vibration periods (in the Mw7.1 Darfield and Mw6.2 Christchurch earthquakes) is likely due to the influence of basin-induced surface waves and non-linear soil response. Empirical models for the pulse period notably under-predict observations from the Darfield and Christchurch earthquakes, inferred as being a result of both the effect of nonlinear site response and influence of the Canterbury basin. In contrast, observed pulse periods from the smaller magnitude June (Mw6.0) and December (Mw5.9) 2011 earthquakes are in good agreement with predictions. Models for the pulse amplitude generally provide accurate estimates of the observations at source-to-site distances between 1 km and 10 km. At longer distances, observed PGVs are significantly under-predicted due to their slower apparent attenuation. Mixed-effects regression is employed to develop revised models for both parameters using the latest NGA-West2 pulse-like ground motion database. A pulse period relationship which accounts for the effect of faulting mechanism using rake angle as a continuous predictor variable is developed. The use of a larger database in model development, however does not result in improved predictions of pulse period for the Darfield and Christchurch earthquakes. In contrast, the revised model for PGV provides a more appropriate attenuation of the pulse amplitude with distance, and does not exhibit the bias associated with previous models. Finally, the effects of near-fault directivity are explicitly included in NZ-specific probabilistic seismic hazard analysis (PSHA) using the narrowband directivity model of Shahi & Baker (2011). Seismic hazard analyses are conducted with and without considering directivity for typical sites in Christchurch and Otira. The inadequacy of the near-fault factor in the NZS1170.5: 2004 is apparent based on a comparison with the directivity amplification obtained from PSHA.

Articles, UC QuakeStudies

This study updated the 1999 Earthquake hazard and risk assessment study Stage 1 Part B: Probabilistic seismic hazard assessment and Earthquake scenarios for the Canterbury region, and historic earthquakes in Christchurch report. It incorporated new fault data, a new distributed seismicity model and new methods for estimating Modified Mercalli intensities. See Object Overview for background and usage information.

Articles, UC QuakeStudies

This study updated the 1999 Earthquake hazard and risk assessment study Stage 1 Part B: Probabilistic seismic hazard assessment and Earthquake scenarios for the Canterbury region, and historic earthquakes in Christchurch report. It incorporated new fault data, a new distributed seismicity model and new methods for estimating Modified Mercalli intensities. See Object Overview for background and usage information.

Images, Canterbury Museum

One print on paper of an artwork titled "There Came a Day" featuring the text "There came a day, the earth did say, I've had enough, of this fault's fray, so up it lift, a Christchurch rift, a seven point one, of rattle and tip, still here we are, too strong to split" in white and red ink on a black background.