Assessment of liquefaction risk in the Hawke's Bay Volume 1: The liquefaction hazard model BJ Rosser and S Dellow (compilers) GNS Science Consultancy Report 2015/186 October 2017 DISCLAIMER This report has been prepared by the Institute of Geological and Nuclear Sciences Limited (GNS Science) exclusively for and under contract to Hawke’s Bay Regional Council. Unless otherwise agreed in writing by GNS Science, GNS Science accepts no responsibility for any use of or reliance on any contents of this report by any person other than Hawke’s Bay Regional Council and shall not be liable to any person other than Hawke’s Bay Regional Council, on any ground, for any loss, damage or expense arising from such use or reliance. Use of Data: Date that GNS Science can use associated data: October 2017 BIBLIOGRAPHIC REFERENCE Rosser BJ, Dellow GD, compilers. 2017. Assessment of liquefaction risk in the Hawke's Bay Volume 1: The liquefaction hazard model. Lower Hutt (NZ): GNS Science. 108 p. (GNS Science consultancy report; 2015/186). AUTHORS John Begg (GNS Science) Julia Becker (GNS Science) Rob Buxton (GNS Science) Sally Dellow (GNS Science) Sharn Hainsworth (Landcare Research) Andrew King (GNS Science) Virginie Lacrosse (Tonkin &Taylor Ltd.) Rob Langridge (GNS Science) Julie Lee (GNS Science) Sheng-Lin Lin (GNS Science) Iain Matcham (GNS Science) Mostafa Nayyerloo (GNS Science) Zara Rawlinson (GNS Science) Brenda Rosser (GNS Science) Wendy Saunders (GNS Science) Sjoerd van Ballegooy (Tonkin &Taylor Ltd.) Project Number 430W4083-00 Final 2017 CONTENTS EXECUTIVE SUMMARY ..................................................................................................... VII 1.0 INTRODUCTION ........................................................................................................1 1.1 PROJECT PURPOSE AND BACKGROUND .............................................................. 1 1.2 SCOPE..............................................................................................................2 2.0 BACKGROUND INFORMATION ................................................................................ 3 2.1 THE LIQUEFACTION PHENOMENON ..................................................................... 3 2.2 THE LIQUEFACTION PROCESS ............................................................................ 3 2.3 THE LIQUEFACTION VULNERABILITY ASSESSMENT PROCESS ............................... 4 2.3.1 Liquefaction Susceptibility ..................................................................................4 2.3.2 Liquefaction Triggering .......................................................................................5 2.3.3 Liquefaction Vulnerability ...................................................................................5 2.4 HISTORIC LIQUEFACTION IN HAWKE’S BAY ........................................................ 13 2.5 PREVIOUS LIQUEFACTION HAZARD STUDIES IN HAWKE’S BAY ............................ 16 3.0 DATASETS .............................................................................................................. 21 3.1 UNCONFINED GROUNDWATER SURFACE DATA .................................................. 21 3.2 SUB-SURFACE GEOLOGY ................................................................................. 24 3.3 GEOMORPHOLOGY .......................................................................................... 28 3.4 HISTORICAL OBSERVATIONS ............................................................................ 30 3.5 GEOTECHNICAL DATASETS .............................................................................. 32 4.0 GROUNDWATER MODEL ....................................................................................... 35 5.0 SEISMICITY AND EARTHQUAKE SHAKING .......................................................... 41 5.1 MAGNITUDE FOR TARGET RETURN PERIODS ..................................................... 42 5.2 PEAK GROUND ACCELERATION FOR TARGET RETURN PERIODS ......................... 43 6.0 LIQUEFACTION HAZARD MAPPING METHODOLOGY ......................................... 47 6.1 HERETAUNGA PLAINS ...................................................................................... 47 6.1.1 Geomorphic Zoning ......................................................................................... 47 6.1.2 Liquefaction Susceptibility ............................................................................... 49 6.1.3 Liquefaction Triggering .................................................................................... 56 6.1.4 Liquefaction Vulnerability ................................................................................ 58 6.2 WAIROA .......................................................................................................... 65 6.2.1 Geomorphic Zoning ......................................................................................... 65 6.3 CENTRAL HAWKE’S BAY ................................................................................... 70 6.3.1 Geomorphic Zoning ......................................................................................... 70 6.4 HASTINGS DISTRICT ........................................................................................ 75 7.0 LIQUEFACTION HAZARD MAPPING RESULTS .................................................... 79 7.1 HERETAUNGA PLAINS ...................................................................................... 79 8.0 LIQUEFACTION HAZARD PLANNING MAPS ......................................................... 85 8.1 HERETAUNGA PLAINS ...................................................................................... 85 GNS Science Consultancy Report 2015/186 i Final 2017 8.2 WAIROA .......................................................................................................... 88 8.3 CENTRAL HAWKE’S BAY ................................................................................... 90 8.4 HASTINGS DISTRICT ........................................................................................ 92 9.0 DIFFERENCES COMPARED TO THE 1999 MAP ................................................... 95 9.1 HERETAUNGA PLAINS ...................................................................................... 95 9.2 WAIROA DISTRICT ........................................................................................... 96 9.3 CENTRAL HAWKE’S BAY DISTRICT .................................................................... 96 9.4 HASTINGS DISTRICT (BEYOND THE HERETAUNGA PLAINS) .................................. 97 10.0 CONSTRAINTS ON USING THE LIQUEFACTION PLANNING MAPS .................... 99 11.0 CONCLUSIONS ..................................................................................................... 101 11.1 RECOMMENDATIONS ...................................................................................... 102 11.1.1 Data Quality and Quantity (all areas) ............................................................ 102 11.1.2 Heretaunga Plains ......................................................................................... 102 11.1.3 Central Hawke’s Bay District ......................................................................... 103 11.1.4 Wairoa District ............................................................................................... 103 11.1.5 Hastings District (beyond the Heretaunga Plains) ........................................ 103 12.0 ACKNOWLEDGEMENTS ....................................................................................... 105 13.0 GLOSSARY ............................................................................................................ 107 14.0 REFERENCES ....................................................................................................... 111 ii GNS Science Consultancy Report 2015/186 Final 2017 FIGURES Figure 2.1 Schematic representation of liquefaction and its effects ............................................................... 6 Figure 2.2 Liquefaction ejecta (sand boils) in Kaiapoi approximately 45 kilometres from the epicentre of the magnitude 7.1, 4 September 2010 Darfield earthquake. .............................................................. 7 Figure 2.3 Liquefaction ejecta in a suburban Christchurch Street. In the suburb of Bexley, approx. 10 km from the epicentre after the magnitude 6.3 Christchurch earthquake of 22 February 2011. ......... 7 Figure 2.4 Buoyancy of a pump-station floated up to 500 mm out of the ground by liquefaction adjacent to the Avon River near the eastern end of Morris Street, approx. 10 km form the epicentre after the magnitude 6.3 Christchurch earthquake of 22 February 2011. ..................................................... 8 Figure 2.5 Lateral spreading fissures run parallel to the Avon River in Avonside Drive, Christchurch, approx. 10 km from the epicentre after the magnitude 6.3 Christchurch earthquake of 22 February 2011. ............................................................................................................................. 8 Figure 2.6 Compression-induced buckling of a bridge over the Avon River near Medway Street due to lateral spreading displacement of the abutments approx. 10 km form the epicentre after the magnitude 6.3 Christchurch earthquake of 22 February 2011. ..................................................... 9 Figure 2.7 Liquefaction-induced lateral spreading through the foundation of a house in Kaiapoi approximately 45 kilometres from the epicentre of the