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▲ ▲ Figure 8. Misfit parameters (Anderson 2004) of simulated ground motion for the three components of motion, evaluated at the 23stations under consideration (see Table 1 and Figure 1) in the frequency band between 0.25 and 0.50 Hz. The results are shown for theA) INGV “step-like” , B) INGV “smooth” (center panel), and C) GNS “smooth” model (bottom panel).776 Seismological Research Letters Volume 82, Number 6 November/December 2011
▲ ▲ Figure 9. Comparison between recorded and simulated (GNS “smooth”) velocity time histories (in cm/s), on the EW, NS, and UDcomponent for the whole set of stations at R e < 40 km. The label on the left vertical axis reports the peak value of the correspondingtime history.tion of soil mechanical properties. To give a broad picture ofseismic wave propagation effects, Figure 10 depicts the spatialdistribution of PGV values obtained through GeoELSE alongwith the observed values (superimposed filled dots) for boththe INGV and GNS “smooth” models. Furthermore, Figure11 shows some representative snapshots of the simulated faultnormal velocity wavefield, in which the seismic wave propagationfield with the high contrast between rock and alluvial soiland the directivity toward the city of Christchurch is clearlydistinguishable. In particular, looking at Figure 10 it is possibleto notice that the GNS fault model better reproduces the variabilityof PGV values on the whole modeled area. From Figures10 and 11 it is apparent that the INGV source model producesstrong “up-dip” directivity effects in the central-eastern part ofChristchurch, in reasonable agreement with the spatial distributionof observed damage and liquefaction phenomena. Thewave propagation pattern obtained with the GNS fault modelproduces noticeable directivity off the sides of the fault due tothe relatively shallow hypocenter (around 6.5 km) and becausethe rake is oblique (145°). This leads to larger ground motionamplitudes in the southwestern portion of the city.Comparison with Observed Standard Spectral RatiosAs a concluding check of the quality of 3D numerical simulations,in this section we compare simulations with observationsin terms of standard spectral ratios (SSRs). Most of the 23 stationsincluded in the numerical model are located on alluvialsoil, while three of them lie on outcropping volcanic rock,namely HVSC, LPCC, and MQZ. For our purposes, we consideredthe four stations located in the Christchurch CBD, onsoft alluvial sediments, namely CCCC, REHS, CHHC, andCBGS. Station LPCC, located on rock around 15 km southeastfrom the CBD, is considered as reference rock station.The SSRs computed as the ratio of the Fourier spectrumof the recordings at CCCC, REHS, CHHC, and CBGS (geometricmean of the horizontal components), over that at LPCCreference station, are shown in Figure 12, for 4 September 2010Darfield earthquake, with the epicenter located around 40 kmwest of the considered set of stations. We refer to the Darfieldearthquake because we believe that this event is more reliablethan the Christchurch one in evaluating the SSR because ofthe strong nonlinear soil behavior verified in the latter and theshort distance (less than 10 km) between the epicenter and theconsidered stations. It is worth noting that stable resonancepeaks are found at around 0.3, 0.6, 1.3, and, more consistently,at around 1.7 Hz. The recorded SSRs are compared, on the onehand, with the 1D analytical transfer function obtained for asystem of four layers (layers 1, 2, 3, and 5 in Table 2) over a halfspace(layer 6 in Table 2), and, on the other hand, with the SSRsobtained through 3D numerical simulation (GNS “smooth”model). Compared with the 1D amplification function, the 3DSSRs show a better agreement with the records, pointing outresonance frequencies at about 0.4, 0.7, 1.3, and 1.7 Hz.CONCLUDING REMARKSThe main aim of this paper was to perform 3D numerical simulationsof the M W 6.2 Christchurch earthquake on 22 FebruarySeismological Research Letters Volume 82, Number 6 November/December 2011 777
Page 1: Volume 82, Number 6 November/Decemb
Page 7: News and Notes (continued)Nominatio
Page 11: Preface to the Focused Issue on the
Page 14 and 15: TABLE 1Peak ground acceleration (PG
Page 16 and 17: ▲▲Figure 2. A) Sketch of the
Page 18 and 19: ▲▲Figure 4. A) Adopted moment r
Page 20 and 21: ▲▲Figure 7. As in Figure 6 but
Page 24 and 25: ▲ ▲ Figure 10. Spatial variabil
Page 26 and 27: ▲ ▲ Figure 12. Standard spectra
Page 28 and 29: Quigley, M., R. Van Dissen, P. Vill
Page 30 and 31: slip on a 59-degree striking fault
Page 32 and 33: ▲▲Figure 4. Convergence of inve
Page 34 and 35: observations and other source studi
Page 36 and 37: -42. 5-43. 0-43. 5-44. 0-44. 5-43.2
Page 38 and 39: “Product CSK © ASI, (ItalianSpac
Page 40 and 41: TABLE 2Solutions for fault location
Page 42 and 43: -43.45(A)degrees N-43.50-43.552.52.
Page 44 and 45: is still a good fit to the horizont
Page 46 and 47: Coulomb Stress Change Sensitivity d
Page 48 and 49: mation takes on a larger strike-sli
Page 50 and 51: P 9.4267BLDU45P 20.1213CASY39P 2.62
Page 52 and 53: ERMJNUMAJOINUJHJ2CBIJMIDWJOWYHNBTPU
Page 54 and 55: (A)6.146.13(B)6.246.36Misfit6.156.1
Page 56 and 57: (A)(B)(C)(D)▲▲Figure 10. The co
Page 58 and 59: (A)(B)(C)(D)▲▲Figure 12. The co
Page 60 and 61: Luo, Y., Y. Tan, S. Wei, D. Helmber
Page 62 and 63: −44˚00' −43˚00'4-Sep-2010Mw 7
Page 64 and 65: TABLE 1Pairs of SAR imagery used in
Page 67 and 68: Depth (km)Coulomb Stress Change(bar
Page 69 and 70: Crippen, R. E. (1992). Measurement
Page 71 and 72: AlpineFaultHope Fault38 mm/yr0+ +-1
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σ 1dσ 3Nuσ 3CM w 7.1dw 6.2u70°M
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Right-lateral Faults(A) Range Front
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DISCUSSIONThe 2010-2011 Canterbury
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Large Apparent Stresses from the Ca
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▲ ▲ Figure 2. Observed vs. pred
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10Obs SA(1s)AS1AS+SDAB 2006AB+SDSA(
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Fine-scale Relocation of Aftershock
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−43.25°OXZ0 10 20km−43.5°−4
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A’0 km 4 8−43.5°B’B−43.6°
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REFERENCESAvery, H. R., J. B. Berri
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▲ ▲ Figure 2. A) shows three-co
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▲ ▲ Figure 4. Vertical accelera
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0.8PRPC Z0.40Normalized (Max PGA +
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Near-source Strong Ground MotionsOb
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(A)Magnitude, M w876542009 NZdataba
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Scale0.5 g5 seconds▲▲Figure 4.
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(A)(B)Spectral Acc, Sa (g)North/Wes
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Vertical-to-horizontal PGA ratio543
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(A)(B)Station:CCCCSolid:AvgHorizDas
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REFERENCESAagaard, B. T., J. F. Hal
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▲ ▲ Figure 1. Shear-wave veloci
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Spectral Acceleration (0.3 s), (g)I
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Spectral Acceleration (3 s), (g)In[
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TABLE 1Mean (μ LLH ) and standard
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Strong Ground Motions and Damage Co
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ings and the Modified Takeda-Slip M
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high, but there were no buildings d
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REFERENCES▲▲Figure 8. Heavily d
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(A)(B)(C)(D)(E)▲▲Figure 1. A) M
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(A) (B) (C)▲ ▲ Figure 3. A) Typ
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(A) (B) (C)▲ ▲ Figure 4. A) Typ
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Case StudyKey ParametersTABLE 1Key
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▲ ▲ Figure 9. Representative bu
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Soil Liquefaction Effects in the Ce
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▲ ▲ Figure 2. Representative su
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Location of structures illustrated
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Shading indicates areaover which pr
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1.8 deg15 cmGround cracking due to
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30 cm17 cm30 cmFoundation beam▲
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Comparison of Liquefaction Features
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(A)(B)▲▲Figure 2. A) Simplified
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(A)Acceleration (Gal)6004002000-200
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(A)(B)▲▲Figure 7. Distribution
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(A)(B)▲▲Figure 10. Damage to a
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(A)(B)▲ ▲ Figure 14. A) Subside
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▲▲Figure 17. A trench in a resi
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Ambient Noise Measurements followin
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▲▲Figure 1. Location of the noi
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▲▲Figure 5. Site N20 showing HV
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▲▲Figure 8. Comparison between
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Use of DCP and SASW Tests to Evalua
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▲ ▲ Figure 2. Aerial image of C
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(A)(B)▲▲Figure 4. DCP test bein
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▲▲Figure 7. SASW setup at a sit
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where X ~ N(μ X , σ X 2 ) is shor
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Using the same critical layers as s
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Performance of Levees (Stopbanks) d
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▲▲Figure 3. Typical geometry an
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TABLE 1Damage severity categories (
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(A)(B)▲▲Figure 6. A) Large sand
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(A)(B)▲▲Figure 8. A) Representa
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each of the Waimakariri River and a
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▲ ▲ Figure 2. Horizontal peak g
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only minor damage, mostly to their
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(A)(C)(B)▲▲Figure 5. Ferrymead
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(A)(B)▲▲Figure 7. Damage to sou
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(A)(B)▲▲Figure 11. Settlement o
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(A)(C)(B)▲▲Figure 14. Railway B
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Events Reconnaissance (GEER) Associ
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New PublicationsCanGeoRefThe Americ
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Wednesday, 18 AprilTechnical Sessio
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Verification of a Spectral-Element
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EASTERN SECTIONRESEARCH LETTERSReas
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(A)70°N100°W 60°W70°N(B)100°E1
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Mongolia SCRThe presence or absence
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the small horizontal relative motio
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80°100°120°140°EXPLANATIONBorde
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Chang, K. H. (1997). Korean peninsu
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Wheeler, R. L. (2008). Paleoseismic
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A significant outcome of this study
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TABLE 1 (continued)Earthquakes for
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▲▲Figure 2. Earthquakes used in
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Meeting CalendarM E E T I N GC A L
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201 Plaza Professional Bldg. • El
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Seismological Research Letters (SRL
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Christa von Hillebrandt-Andrade, Pr
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