The Canterbury earthquake sequence triggered thousands of rockfalls in the Port Hills of Christchurch, New Zealand, with over 6,000 falling on 22 February 2011. Several hundred families were evacuated after about 200 homes were hit. We characterized the rockfalls by boulder-size distribution, runout distance, source-area dimensions, and boulder-production rates over a range of triggering peak ground accelerations. Using these characteristics, a time-varying seismic hazard model for Canterbury, and estimates of residential occupancy rates and resident vulnerability, we estimated annual individual fatality risk from rockfall in the Port Hills. The results demonstrate the Port Hills rockfall risk is time-variable, decreasing as the seismic hazard decreases following the main earthquakes in February and June 2011. This presents a real challenge for formulating robust land-use and reconstruction policy in the Port Hills.
BannisterS., and GledhillK., 2012. Evolution of the 2010–2012 Canterbury earthquake sequence. The New Zealand Journal of Geology and Geophysics55, 295–304.
3.
BellD. H., and TrangmarB. B., 1987. Regolith materials and erosion processes on the Port Hills, Christchurch, New Zealand, Fifth International Conference and Field Workshop on Landslides, 93–105.
4.
BradleyB. A., and CubrinovskiM., 2011. Near-source strong ground motions observed in the 22 February 2011 Christchurch earthquake. Seismological Research Letters82, 853–865.
5.
BradleyB. A., QuigleyM. C., Van DissenR. J., and LitchfieldN. J., 2014. Ground motion and seismic source aspects of the Canterbury earthquake sequence, Earthquake Spectra30, 1–15.
6.
BrideauM. A., MasseyC. I., ArchibaldG., and JaboyedoffM., 2012. Terrestrial photogrammetry and LiDAR investigation of the cliffs associated with the seismically triggered rockfalls during the February and June 2011 Christchurch earthquakes, in Landslides and Engineered Slopes: Protecting Society through Improved Understanding (EberhardtM. O. et al., Editors), Taylor & Francis Group, London.
7.
BunceC. M., CrudenD. M., and MorgensternN. R., 1997. Assessment of the hazard from rock fall on a highway, Canadian Geotechnical Journal34, 344–356.
8.
CoponsR., VilaplanaJ. M., and LinaresR., 2009. Rockfall travel distance analysis by using empirical models (Sola d'Andorra la Vella, Central Pyrenees), Natural Hazards and Earth System Sciences9, 2107–2118.
9.
CorominasJ., CoponsR., MoyaJ., VilaphanaJ. M., AltimirJ., and AmigoJ., 2005. Quantitative assessment of the residual risk in a rockfall protected area, Landslides2, 343–357.
10.
CrostaG. B., and AgliardiF., 2004. Parametric evaluation of 3-D dispersion of rockfall trajectories, Nat. Hazards Earth Syst. Sci. 4, 583–598.
11.
DellowG., YettonM., MasseyC., ArchibaldG., BarrellD. J. A., BellD., BruceZ., CampbellA., DaviesT., De PascaleG., EastonM., ForsythP. J., GibbonsC., GlasseyP., GrantH., GreenR., HancoxG., JongensR., KingsburyP., KupecJ, MacfarlaneD., McDowellB., McKelveyB., McCahonI., McPhersonI., MolloyJ., MuirsonJ., O'HalloranM., PerrinN., PriceC., ReadS., TraylenN., Van DissenR., VilleneuveM., and WalshI., 2011. Landslides caused by the 22 February 2011 Christchurch earthquake and management of landslide risk in the immediate aftermath, Bulletin of the New Zealand Society for Earthquake Engineering44, 227–238, available at http://www.nzsee.org.nz/db/Bulletin/Archive/44(4)0227.pdf.
12.
DorrenL. K. A., 2003. A review of rockfall mechanics and modeling approaches, Progress in Physical Geography27, 69–87.
13.
EvansS. G., and HungrO., 1993. The assessment of rockfall hazard at the base of talus slopes, Canadian Geotechnical Journal30, 620–636.
14.
FinlayP. J., MostynG. R., and FellR., 1999. Landslides: prediction of travel distance and guidelines for vulnerability of persons, in Proceedings, 8th Australia New Zealand Conference on Geomechanics1, Hobart, 105–113.
15.
ForsythP. J., BarrellD. J. A., and JongensR. (compilers), 2008. Geology of the Christchurch Area, scale 1:250000, Institute of Geological & Nuclear Sciences Limited, 1:250000 Geological Map 16, 1 sheet_67 p, GNS Science, Lower Hutt, NZ, ISBN 978-0-478-19649–8.
16.
FryB., BenitesR., ReynersM., HoldenC., KaiserA., BannisterS., GerstenbergerM., WilliamsC., RistauJ., and BeavanJ., 2011. Extremely strong shaking in the New Zealand earthquakes of 2010 and 2011, Eos92, 349–360.
17.
GerstenbergerM., McVerryG., RhoadesD., and StirlingM., 2014. Seismic hazard modeling for the recovery of Christchurch, Earthquake Spectra30, 17–29.
18.
GledhillK., RistauJ., ReynersM., FryB., and HoldenC., 2010. The Darfield (Canterbury) earthquake of September 2010: preliminary seismological report, Bulletin of the New Zealand Society for Earthquake Engineering43, 215–221, available at http://www.nzsee.org.nz/db/SpecialIssue/43(4)0215.pdf.
19.
HancoxG. T., MasseyC., and PerrinN. D., 2011. Landslides and related ground damage caused by the Mw 6.3 Christchurch earthquake of 22 February 2011, Geomechanics News (New Zealand)81, 53–67.
20.
HamptonS. J., 2010. Growth, Structure, and Evolution of the Lyttelton Volcanic Complex, Banks Peninsula, New Zealand, Ph.D. Thesis, University of Canterbury, Christchurch, NZ.
21.
HarpE. L., and JibsonR. W., 2002. Anomalous concentrations of seismically triggered rock falls in Pacoima Canyon: Are they caused by highly susceptible slopes or local amplification of seismic shaking?, Bulletin of the Seismological Society of America92, 3180–3189.
22.
HarpE. L., and WilsonR. C.1995. Shaking intensity threshold for rock falls and slides: Evidence from 1987 Whittier Narrows and Superstition Hills earthquake strong motion records, Bulletin of the Seismological Society of America85, 1739–1757.
23.
HeimA., 1932. Bergsturz und Menschenleben, Fretz and Wasmuth Verlag, Zurich, 218 pp.
24.
HungrO., CorominasJ., and EberhardtE., 2005. State of the Art Paper #4, Estimating landslide motion mechanism, travel distance and velocity, in Landslide Risk Management, Proceedings, Vancouver Conference (HungrO., FellR., CoutureR., and EberhardtE., Eds.), Taylor and Francis Group, London, 99–128.
25.
JaboyedoffM., DudtJ. P., and LabiouseV., 2005. An attempt to refine rockfall hazard zoning based on the kinetic energy, frequency and fragmentation degree, Nat. Hazards Earth Syst. Sci. 5, 621–632.
26.
KaiserA., HoldenC., BeavanJ., BeethamD., BenitesR., CelentanoA., CollettD., CousinsJ., CubrinovskiM., DellowG., DenysP., FieldingE., FryB., GerstenbergerM., LangridgeR., MasseyC., MotaghM., PondardN., McVerryG., RistauJ., StirlingM., ThomasJ., UmaS. R., and ZhaoJ., 2012. The Mw 6.2 Christchurch earthquake of February 2011: Preliminary report, New Zealand Journal of Geology and Geophysics55, 67–90.
27.
KaiserA., HoldenC., and MasseyC., 2013. Determination of site amplification, polarization and topographic effects in the seismic response of the Port Hills following the 2011 Christchurch earthquake, New Zealand Society for Earthquake Engineering, 26–28 April 2013, Wellington, NZ.
28.
KanariM., 2008. Evaluation of Rockfall Hazard to Qiryat Shemona - Possible Correlation to Earthquakes, M.S. Thesis, Department of Geophysics and Planetary Sciences, Tel Aviv University.
29.
KeeferD. K., 1984, Landslides caused by earthquakes, Geological Society of America Bulletin95, 406–421.
30.
KeylockD., and DomaasU., 1999. Evaluation of topographic models of rockfall travel distance for use in hazard applications, Antarctic and Alpine Research31, 312–320.
31.
KhajaviN., QuigleyM., McCollS. T., and RezanejadA., 2012. Seismically induced boulder displacement in the Port Hills, New Zealand during the 2010 Darfield (Canterbury) earthquake, New Zealand Journal of Geology and Geophysics55, 271–278.
MoonA. T., WilsonR. A., and FlentjeP., 2005. Developing and using landslide size frequency models, available at http://ro.uow.edu.au/engpapers/384.
38.
New Zealand Society for Earthquake Engineering (NZSEE), 2010. Special Issue: Preliminary observations of the September 2010 Darfield (Canterbury) earthquake sequence, Bulletin of the New Zealand Society for Earthquake Engineering43, 215–439.
39.
New Zealand Society for Earthquake Engineering (NZSEE), 2011. Special Issue: Effects of the 22 February 2011 Christchurch earthquake and its aftershocks, Bulletin of the New Zealand Society for Earthquake Engineering44, 181–430.
40.
ParkerR., PetleyD., DensmoreA., RosserN., DambyD., and BrainM., 2012. Progressive failure cycles and distributions of earthquake-triggered landslides, in Proceedings of the International Symposium on Earthquake-Induced Landslides, Kiryu, Japan, 755–762.
41.
QuigleyM., VillamorP., FurlongK., BeavanJ., Van DissenR., LitchfieldN., StahlT., DuffyB., BilderbackE., NobleD., BarrellD., JongensR., and CoxS., 2010. Previously unknown fault shakes New Zealand's South Island, Eos91, 469–470.
42.
SepulvedaS. A., MurphyW., JibsonR. W., and PetleyD. N., 2005. Seismically induced rock slope failures resulting from topographic amplification of strong ground motions: The case of Pacoima Canyon, California. Engineering Geology80, 336–348.
43.
Seismological Research Letters (SRL), 2011. Special Issue: The 22 February 2011 magnitude 6.2 Christchurch earthquake, Seismological Research Letters82, 765–964.
44.
StirlingM., McVerryG., GerstenbergerM., LitchfieldN., Van DissenR., BerrymanK., BarnesP., WallaceL., VillamorP., LangridgeR., LamarcheG., NodderS., ReynersM., BradleyB., RhoadesD., SmithW., NicolA., PettingaJ., ClarkK., and JacobsK., 2012. National seismic hazard model for New Zealand: 2010 update, Bulletin of the Seismological Society of America102, 1514–1542.
45.
TaigT., MasseyC., and WebbT., 2012. Canterbury Earthquakes Port Hills Slope Stability: Principles and Criteria for the Assessment of Risk from Slope Instability in the Port Hills, Christchurch, GNS Science Consultancy Report 2011/319, Lower Hutt, NZ, 41 pp.
46.
TownsendD., and RosserB., 2012. Canterbury Earthquakes 2010/2011 Port Hills Slope Stability: Geomorphology Mapping for Rockfall Risk Assessment, GNS Science Report CR 2012-015, Lower Hutt, NZ.
47.
Van HoutteC., KtenidouO.-J., LarkinT., and KaiserA., 2012. Reference stations for Christchurch, Bulletin of the New Zealand Society for Earthquake Engineering45, 184–195.
48.
VolkweinA., SchellenbergK., LabiouseV., AgliardiF., BergerF., BourrierF., DorrenL. K. A., GerberW., and JaboyedoffM., 2011. Rockfall characterisation and striuctural protection—a review, Natural Hazards and Earth System Sciences11, 2617–2651.
49.
WoodC. M., CoxB. R., WotherspoonL. M., and GreenR. A., 2011. Dynamic site characterization of Christchurch strong motion stations, Bulletin of the New Zealand Society for Earthquake Engineering44, 195–204.
