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TABLE 1Comparison of peak ground accelerations recorded at strong-motion sites near the city during the 2010 Darfield earthquakeand 2011 Christchurch earthquake. Data are from GeoNet strong motion FTP site. The unit of acceleration is g (1 g = 9.80 m/s 2 ).SeismicStationsSite Name2010 Darfield Earthquake 2011 Christchurch EarthquakeEp. Dist.(km) Vert Hor-1 Hor-2MaxHorEp. Dist.(km) Vert Hor-1 Hor-2HVSC Heathcote Valley Primary School 43 0.28 0.56 0.62 0.66 1 1.47 1.46 1.19 1.50LPCC Lyttelton Port Company 45 0.16 0.33 0.23 0.37 4 0.41 0.78 0.88 1.00CCCC Chch Cathedral College 38 0.16 0.23 0.20 0.24 6 0.69 0.48 0.37 0.49CMHS ChCh Cashmere High School 36 0.25 0.25 0.24 0.26 6 0.80 0.35 0.38 0.42PRPC Pages Road Pumping Station 41 0.31 0.20 0.23 0.23 6 1.63 0.66 0.59 0.73CHHC Christchurch Hospital 36 0.16 0.20 0.15 0.20 8 0.51 0.34 0.36 0.46REHS Christchurch Resthaven 37 0.21 0.24 0.25 0.33 8 0.53 0.71 0.37 0.73CBGS Christchurch Botanic Gardens 36 0.11 0.15 0.17 0.18 9 0.27 0.53 0.43 0.64HPSC Hulverstone Dr Pumping Station 43 0.13 0.16 0.11 0.16 9 0.86 0.15 0.24 0.25SHLC Shirley Library 39 0.12 0.18 0.18 0.19 9 0.50 0.31 0.34 0.34Note: Ep. Dist – Epicentral distance; Vert – vertical acceleration; Hor-1 and Hor-2 – horizontal components of acceleration;Max. Hor – calculated maximum resultant acceleration of horizontal components. Unit of acceleration is g (1 g = 980 cm/s 2 ). Source:GeoNet 2011.MaxHormotion FTP site, the maximum recorded acceleration was onthe order of 0.95 g near the earthquake epicenter (GeoNet2010); however, no serious damage was reported in the area.In the city of Christchurch, the recorded peak ground accelerations(PGA) were on the order of 0.15–0.30 g, as shown inTable 1. The seismic stations indicated in the table correspondto those shown in Figure 3. Figure 4 shows a typical accelerationrecord obtained during the 2010 earthquake. Note thatthe duration of significant shaking at Christchurch Hospital(CHHC), located at the southwest edge of the CBD, is on theorder of about 25–30 sec.2011 Christchurch EarthquakeThe 2011 Christchurch earthquake occurred more than fivemonths after the 2010 Darfield earthquake, with an epicenterlocated on an unmapped fault different from the Greendalefault. Yet it is considered an aftershock because it was causedby a fault rupture within the zone of aftershocks that followedthe September 2010 mainshock (National Hazards ResearchPlatform 2011). Because the M 6.3 aftershock was much closerto the Christchurch CBD than the M 7.1 mainshock, theground accelerations experienced in the CBD as a result of the2011 earthquake were three to four times greater than during2010 event (see Table 1); in the eastern suburbs, they wereabout five times greater. The vertical PGA recorded was 1.47g at Heathcote Valley primary school (about midway betweenthe CBD and the epicenter) while in the CBD the PGA was0.5–0.7 g and in the eastern suburbs the maximum recordedvertical PGA was 1.63 g (GeoNet 2011). A feature of this earthquakewas the very strong vertical component of PGA, whichin general was greater than the horizontal components. Figure4 also illustrates the time histories of acceleration recorded atChristchurch Hospital on 22 February 2011. Because of theshorter distance to the epicenter, the acceleration records inthis earthquake have a higher frequency and shorter durationtime, as well as larger amplitude, in comparison with the onesrecorded on 4 September 2010.COMPARISON OF OBSERVED LIQUEFACTIONDAMAGEAlthough structural failure of commercial buildings led to thegreatest casualties in the M 6.3 Christchurch earthquake, byfar the most significant damage to residential buildings andlifelines in both Canterbury earthquakes was the result of liquefactionand associated ground deformations. Liquefactionoccurred in areas that are known to have high potential forliquefaction—former river channels, abandoned meanders,wetlands, and ponds. Immediately following some of the largestaftershocks from the M 7.1 earthquake, liquefaction reoccurredin some of these areas. During the M 6.3 earthquake,liquefaction was more widespread and vents continued to surgeduring the aftershocks immediately following this event. Theimpact of sand boils and cracks caused by lateral spreading wasthat parts of the eastern suburbs were inundated with sand andsilt—in places there were layers of ejected soil that were manytens of centimeters thick.As mentioned earlier, two large aftershocks, measuringM 5.6 and M 6.3, shook the city on 13 June 2011 and causedextensive re-liquefaction in many parts of the city. Streets wereagain flooded with water and ejected sands, reminiscent ofwhat happened immediately after the 22 February 2011 earthquake.Such reoccurrence of liquefaction indicates that the soildeposits in the area were still loose even after the intense shakingthey had been subjected to over the last nine months.908 Seismological Research Letters Volume 82, Number 6 November/December 2011
(A)Acceleration (Gal)6004002000-200-400-6006004002000-200-400-6006004002000-200-400-600Christchurch Hospital, 4 Sep 2010, MainshockN01W (Horizontal 1)S89W (Horizontal 2)Vertical0 10 20 30 40 50 60Time (sec)(B)Acceleration (Gal)6004002000-200-400-6006004002000-200-400-6006004002000-200-400Christchurch Hospital, 22 Feb 2011, MainshockN01W (Horizontal 1)S89W (Horizontal 2)Vertical-6000 10 20 30 40 50 60Time (sec)▲▲Figure 4. Acceleration time histories recorded at Christchurch hospital during the 2010 Darfield earthquake and 2011 Christchurchearthquake (data from GeoNet strong motion FTP Web site). Note: 1 g = 980 Gal.43°31′18″43°32′16″172°36′43″ 172°39′14″▲ ▲ Figure 5. Location of Avon River as well as wetlands and streams in 1850 superposed to the present-day map of the ChristchurchCBD.Eastern SuburbsLiquefaction and lateral spreading were extensive in areas adjacentto the Avon River, which follows a meandering coursethrough Christchurch from its source in the west throughthe CBD, then toward the east passing through Avonside,Dallington, Avondale, and Aranui, and finally flowing to thePacific Ocean via the Avon-Heathcote estuary.Figure 5 shows the locations of Avon River and otherstreams based on a 1850 map of the city superposed on thepresent map of Christchurch CBD. The meandering nature ofthe Avon is conspicuous as it flows from the west toward theeast. Also, it can be seen that several wetlands and streams crisscrossedthe future city center, some of which were later artificiallyreclaimed as the city grew. The locations of these formerriver channels had a significant effect on the damage observedfollowing the M 6.3 earthquake. Details of liquefactioninduceddamage observed in the central business district arepresented by Cubrinovski et al. (2011, page 893 of this issue).After the 2010 Darfield earthquake, Swedish weightsounding (SWS) tests were performed by the JGS-University ofCanterbury reconnaissance teams at numerous locations affectedby liquefaction and lateral spreading. The SWS test is a simplemanually operated penetration test under a dead-load of 100 kgin which the number of half-rotations required for a 25-cm penetrationof a rod (screw point) is recorded (Japanese StandardsAssociation 1995). As a result of the SWS test, the correspondingstandard penetration test (SPT) N-value can be obtainedthrough the following empirical equation (Inada 1960).Seismological Research Letters Volume 82, Number 6 November/December 2011 909
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Volume 82, Number 6 November/Decemb
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News and Notes (continued)Nominatio
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Preface to the Focused Issue on the
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TABLE 1Peak ground acceleration (PG
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▲▲Figure 2. A) Sketch of the
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▲▲Figure 4. A) Adopted moment r
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▲▲Figure 7. As in Figure 6 but
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▲ ▲ Figure 8. Misfit parameters
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▲ ▲ Figure 10. Spatial variabil
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▲ ▲ Figure 12. Standard spectra
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Quigley, M., R. Van Dissen, P. Vill
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slip on a 59-degree striking fault
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▲▲Figure 4. Convergence of inve
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observations and other source studi
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-42. 5-43. 0-43. 5-44. 0-44. 5-43.2
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“Product CSK © ASI, (ItalianSpac
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TABLE 2Solutions for fault location
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-43.45(A)degrees N-43.50-43.552.52.
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is still a good fit to the horizont
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Coulomb Stress Change Sensitivity d
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mation takes on a larger strike-sli
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P 9.4267BLDU45P 20.1213CASY39P 2.62
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ERMJNUMAJOINUJHJ2CBIJMIDWJOWYHNBTPU
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(A)6.146.13(B)6.246.36Misfit6.156.1
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(A)(B)(C)(D)▲▲Figure 10. The co
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(A)(B)(C)(D)▲▲Figure 12. The co
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Luo, Y., Y. Tan, S. Wei, D. Helmber
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−44˚00' −43˚00'4-Sep-2010Mw 7
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TABLE 1Pairs of SAR imagery used in
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Depth (km)Coulomb Stress Change(bar
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Crippen, R. E. (1992). Measurement
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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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Page 105 and 106: (A)(B)Spectral Acc, Sa (g)North/Wes
Page 107 and 108: Vertical-to-horizontal PGA ratio543
Page 109 and 110: (A)(B)Station:CCCCSolid:AvgHorizDas
Page 111 and 112: REFERENCESAagaard, B. T., J. F. Hal
Page 113 and 114: ▲ ▲ Figure 1. Shear-wave veloci
Page 115 and 116: Spectral Acceleration (0.3 s), (g)I
Page 117 and 118: Spectral Acceleration (3 s), (g)In[
Page 119 and 120: TABLE 1Mean (μ LLH ) and standard
Page 121 and 122: Strong Ground Motions and Damage Co
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Page 127 and 128: REFERENCES▲▲Figure 8. Heavily d
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Page 131 and 132: (A) (B) (C)▲ ▲ Figure 3. A) Typ
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Page 135 and 136: Case StudyKey ParametersTABLE 1Key
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Page 139 and 140: Soil Liquefaction Effects in the Ce
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Page 143 and 144: Location of structures illustrated
Page 145 and 146: Shading indicates areaover which pr
Page 147 and 148: 1.8 deg15 cmGround cracking due to
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Page 151 and 152: Comparison of Liquefaction Features
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Page 157 and 158: (A)(B)▲▲Figure 7. Distribution
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Page 165 and 166: Ambient Noise Measurements followin
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Page 173 and 174: Use of DCP and SASW Tests to Evalua
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Page 177 and 178: (A)(B)▲▲Figure 4. DCP test bein
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Page 181 and 182: where X ~ N(μ X , σ X 2 ) is shor
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Page 185 and 186: Performance of Levees (Stopbanks) d
Page 187 and 188: ▲▲Figure 3. Typical geometry an
Page 189 and 190: TABLE 1Damage severity categories (
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Page 197 and 198: ▲ ▲ Figure 2. Horizontal peak g
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Page 201 and 202: (A)(C)(B)▲▲Figure 5. Ferrymead
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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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