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Images, eqnz.chch.2010

The now vacated Christchurch City Council building suffered some damage in the magnitude 7.1 earthquake that struck Christchurch on Saturday 4 September 2010.

Images, eqnz.chch.2010

The now vacated Christchurch City Council building suffered some damage in the magnitude 7.1 earthquake that struck Christchurch on Saturday 4 September 2010.

Research papers, University of Canterbury Library

This study explicitly investigates uncertainties in physics-based ground motion simulation validation for earthquakes in the Canterbury region. The simulations utilise the Graves and Pitarka (2015) hybrid methodology, with separately quantified parametric uncertainties in the comprehensive physics and simplified physics components of the model. The study is limited to the simulation of 148 small magnitude (Mw 3.5 – 5) earthquakes, with a point source approximation for the source rupture representations, which also enables a focus on a small number of relevant uncertainties. The parametric uncertainties under consideration were selected through sensitivity analysis, and specifically include: magnitude, Brune stress parameter and high frequency rupture velocity. Twenty Monte Carlo realisations were used to sample parameter uncertainties for each of the 148 events. Residuals associated with the following intensity measures: spectral acceleration, peak ground velocity, arias intensity and significant duration, were ascertained. Using these residuals, validation was performed through assessment of systematic biases in site and source terms from mixed-effects regression. Based on the results to date, initial standard deviation recommendations for parameter uncertainties, based on the Canterbury simulations have been obtained. This work ultimately provides an initial step toward explicit incorporation of modelling uncertainty in simulated ground motion predictions for future events, which will improve the use of simulation models in seismic hazard analysis. We plan to subsequently assess uncertainties for larger magnitude events with more complex ruptures, and events across a larger geographic region, as well as uncertainties due to path attenuation, site effects, and more general model epistemic uncertainties.

Research papers, University of Canterbury Library

1. Background and Objectives This poster presents results from ground motion simulations of small-to-moderate magnitude (3.5≤Mw≤5.0) earthquake events in the Canterbury, New Zealand region using the Graves and Pitarka (2010,2015) methodology. Subsequent investigation of systematic ground motion effects highlights the prediction bias in the simulations which are also benchmarked against empirical ground motion models (e.g. Bradley (2013)). In this study, 144 earthquake ruptures, modelled as point sources, are considered with 1924 quality-assured ground motions recorded across 45 strong motion stations throughout the Canterbury region, as shown in Figure 1. The majority of sources are Mw≥4.0 and have centroid depth (CD) 10km or shallower. Earthquake source descriptions were obtained from the GeoNet New Zealand earthquake catalogue. The ground motion simulations were performed within a computational domain of 140km x 120km x 46km with a finite difference grid spacing of 0.1km. The low-frequency (LF) simulations utilize the 3D Canterbury Velocity Model while the high-frequency (HF) simulations utilize a generic regional 1D velocity model. In the LF simulations, a minimum shear wave velocity of 500m/s is enforced, yielding a maximum frequency of 1.0Hz.

Research papers, University of Canterbury Library

This poster presents work to date on ground motion simulation validation and inversion for the Canterbury, New Zealand region. Recent developments have focused on the collection of different earthquake sources and the verification of the SPECFEM3D software package in forward and inverse simulations. SPECFEM3D is an open source software package which simulates seismic wave propagation and performs adjoint tomography based upon the spectral-element method. Figure 2: Fence diagrams of shear wave velocities highlighting the salient features of the (a) 1D Canterbury velocity model, and (b) 3D Canterbury velocity model. Figure 5: Seismic sources and strong motion stations in the South Island of New Zealand, and corresponding ray paths of observed ground motions. Figure 3: Domain used for the 19th October 2010 Mw 4.8 case study event including the location of the seismic source and strong motion stations. By understanding the predictive and inversion capabilities of SPECFEM3D, the current 3D Canterbury Velocity Model can be iteratively improved to better predict the observed ground motions. This is achieved by minimizing the misfit between observed and simulated ground motions using the built-in optimization algorithm. Figure 1 shows the Canterbury Velocity Model domain considered including the locations of small-to-moderate Mw events [3-4.5], strong motion stations, and ray paths of observed ground motions. The area covered by the ray paths essentially indicates the area of the model which will be most affected by the waveform inversion. The seismic sources used in the ground motion simulations are centroid moment tensor solutions obtained from GeoNet. All earthquake ruptures are modelled as point sources with a Gaussian source time function. The minimum Mw limit is enforced to ensure good signal-to-noise ratio and well constrained source parameters. The maximum Mw limit is enforced to ensure the point source approximation is valid and to minimize off-fault nonlinear effects.

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110173 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110202 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110176 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011.CCL-2011-02-22-Earthquake-P1110182 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110177 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken at the Lyttelton Community briefing held on March 7 2011 following the magnitude 6.3 earthquake on 22 February 2011. File Ref: CCL-2011-03-07-Lyttelton-Community-Briefing-P1110625 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110179 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110211 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110203 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken at the Lyttelton Community briefing held on March 7 2011 following the magnitude 6.3 earthquake on 22 February 2011. File Ref: CCL-2011-03-07-Lyttelton-Community-Briefing-P1110622 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110172 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110178 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110209 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken at the Lyttelton Community briefing held on March 7 2011 following the magnitude 6.3 earthquake on 22 February 2011. File Ref: CCL-2011-03-07-Lyttelton-Community-Briefing-P1110619 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011.CCL-2011-02-22-Earthquake-P1110175 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110174 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011.CCL-2011-02-22-Earthquake-P1110180 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken at the Lyttelton Community briefing held on March 7 2011 following the magnitude 6.3 earthquake on 22 February 2011. File Ref: CCL-2011-03-07-Lyttelton-Community-Briefing-P1110621 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110171 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. CCL-2011-02-22-Earthquake-P1110170 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, and let us ...

Images, eqnz.chch.2010

Photos taken following the magnitude 6.3 earthquake in Christchurch on 22 February 2011. File ref: CCL-2011-02-22-Earthquake-P1110168 We all have earthquake stories to tell — and we’d like to hear yours. Please submit your story on our website, a...