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terms of velocity time histories and corresponding Fourieramplitude spectra, respectively. The comparison is presentedfor four representative stations: HVSC, which lies on outcroppingrock; REHS, located on alluvial soil in the CentralBusiness District (CBD); SHLC, situated on alluvial soil at epicentraldistance R e = 9 km, close to the CBD; and SLRC, lyingon alluvial soil at R e = 33 km, southwest of the epicenter. Bothobserved and simulated waveforms have been processed with abandpass acausal Butterworth filter between 0.1 and 2 Hz.A quantitative estimation of the overall quality of thenumerical analyses can be inferred evaluating the misfitparameters proposed by Anderson (2004). Stating that a singleparameter is incomplete to assess the correspondence betweensimulated and observed time-histories, Anderson (2004) introduceda set of 10 parameters, each one evaluated for a specificfrequency band of interest: Arias duration (AD), energy duration(ED), Arias intensity (AI), energy integral (EI), peakacceleration (PA), peak velocity (PV), peak displacement (PD),response spectra (RS), Fourier spectra (FS), and cross-correlation(CC). A score between 0 and 10, with 0 indicating noagreement and 10 perfect agreement, is calculated for each ofthese parameters, yielding an overall goodness of fit.Figure 8 depicts the goodness of fit parameters computedin the frequency band 0.25–0.50 Hz for the three modelsunder study, “step-like” INGV, “smooth” INGV, and “smooth”GNS, and for three components of motion (EW, NS, and UD).The scores of the aforementioned parameters are shown for the23 stations summarized in Table 1.Dependence of Results on the Geometry of theCanterbury PlainsIn this section we address the issue regarding the role of the3D geometry of the Canterbury Plains, i.e., the “step-like” vs.“smooth” model, on the simulated waveforms. Referring toFigures 6 and 7, we note that, in spite of the rough approximationsbehind the “step-like” model, the overall agreementis fairly satisfactory. For most of the considered stations, the“step-like” model reproduces the first arrivals and the PGVswith reasonable accuracy. The agreement between syntheticsand observations is satisfactory for the stations located in thecentral-western portion of the Canterbury Plains, while it deterioratesfor the station located on the southern volcanic region.Nonetheless, such model tends to overestimate PGV valuesmeasured in the eastern area of Christchurch, where majorliquefaction effects were observed. This effect may be due tothe rough representation of the interface between the volcanicmaterial and the soft soil of the basin, leading to an excessivelylarge concentration of energy toward the city of Christchurchas a consequence of the high impedance contrast between thevolcano region and the surrounding soft sediments.The introduction of the “smooth” model yields significantimprovements of the simulated waveforms, in particular forthe reproduction of the coda-waves inside the alluvial plain.The smooth interface between volcanic rock and alluvial soilleads to a better agreement in terms of PGV; nonetheless, themodel still tends to overestimate the peak values measured inthe CBD and in the eastern-coastal area of Christchurch andto underestimate the peak values recorded far from the epicenter,especially in the southwestern region of the model.Figure 8 allows us to have a quantitative criterion to assessthe performance of the different numerical simulations. Whilethe “step-like” model shows at least six stations with goodscores for the whole set of parameters (Figure 8A), the INGV“smooth” model, with at least nine stations with good averagescores (Figure 8B), yields actual improvements of the numericalanalyses. As a general remark, for both simulations integralmeasures of Arias and energy duration (AD and ED) and peakground acceleration, velocity, and displacement values (PA, PV,and PD) present a good fit for all the considered stations, whilea poor score is achieved for intensity measures (AI and EI),spectral amplitudes, and cross-correlation (RS, FS, and CC).Effect of the Kinematic Seismic SourceAfter having illustrated the results obtained for the “step-like”and “smooth” model, we now turn to evaluating the effect ofdifferent kinematic seismic sources. To this end, we will showa comparison of the numerical results obtained for the INGVand GNS fault solutions (see Figure 3), relying on the “smooth”model, which turns out to produce satisfactory results as discussedin the previous section.The comparison in Figures 6 and 7 shows that the GNSfault model leads to a better agreement between recorded andsimulated ground motion velocities at the four stations underconsideration. For this kinematic source model, a good agreementis found both at stations located on alluvial soil a fewkilometers from the epicenter and at those stations locatedseveral kilometers farther away in the southwestern portion ofthe model. In spite of the rough assumptions behind the GNS“smooth” model, numerical simulations are able to reproducewith reasonable accuracy the PGVs within the CanterburyPlains. Nonetheless, the agreement between synthetics andobserved values is still quite poor for the station located in thevolcanic region. This is most likely due to the simplified modelassumed for the topography of the Banks Peninsula, which isapproximated as a smooth surface and does not capture thecomplex geometry of bays and coves that may play an importantrole in seismic wave propagation phenomena. Furthermore, ahomogeneous soil profile is assumed for the volcano region, sothat erosion and weathering phenomena of the surface rock layersare not taken into account.The analysis of the Anderson misfit criteria (Figure 8C)confirms the quality of the numerical simulations, showinggood average scores for almost all the stations under consideration.As mentioned previously, the figure highlights a goodagreement in terms of PGVs (parameter PV) for many stationsinside the computation domain. Figure 9 shows a comprehensivecomparison between recorded and simulated (GNS “smooth”model) velocity time histories at the entire set of accelerometricstations inside the computational model, ordered by epicentraldistance. A good agreement is found in terms of arrivaltimes, peak ground values, and attenuation with distance, inspite of the rough assumptions concerning the characteriza-Seismological Research Letters Volume 82, Number 6 November/December 2011 775