Arrival Time Estimates for Local Source Tsunami for Wellington Suburbs Xiaoming Wang Christof Mueller William Power Biljana Lukovic GNS Science Report 2016/03 February 2017 DISCLAIMER The Institute of Geological and Nuclear Sciences Limited (GNS Science) and its funders give no warranties of any kind concerning the accuracy, completeness, timeliness or fitness for purpose of the contents of this report. GNS Science accepts no responsibility for any actions taken based on, or reliance placed on the contents of this report and GNS Science and its funders exclude to the full extent permitted by law liability for any loss, damage or expense, direct or indirect, and however caused, whether through negligence or otherwise, resulting from any person’s or organisation’s use of, or reliance on, the contents of this report. BIBLIOGRAPHIC REFERENCE Wang, X.; Mueller, C.; Power, W.L.; Lukovic, B. 2016. Arrival time estimates for local source tsunami for Wellington suburbs, GNS Science Report 2016/03. 53 p. X. Wang, GNS Science, 1 Fairway Drive, Avalon, Lower Hutt, New Zealand C. Mueller, GNS Science, 1 Fairway Drive, Avalon, Lower Hutt, New Zealand W. L. Power, GNS Science, 1 Fairway Drive, Avalon, Lower Hutt, New Zealand B. Lukovic, GNS Science, 1 Fairway Drive, Avalon, Lower Hutt, New Zealand © Institute of Geological and Nuclear Sciences Limited, 2017 www.gns.cri.nz ISSN 1177-2425 (Print) ISSN 2350-3424 (Online) ISBN 978-0-908349-79-1 (Print) ISBN 978-0-908349-80-7 (Online) CONTENTS ABSTRACT ................................................................................................................ IV KEYWORDS ............................................................................................................... IV 1.0 INTRODUCTION ...............................................................................................1 2.0 TSUNAMI SOURCE MODELLING ....................................................................3 2.1 LOCAL SOURCES ......................................................................................3 2.1.1 Hikurangi Subduction Interface ............................................................... 3 2.1.2 Wellington Fault ....................................................................................... 4 2.1.3 Wairarapa Fault and Wharekauhau Thrust ............................................. 4 2.2 TSUNAMI SOURCE MODELLING ..................................................................5 2.2.1 Source Scenarios .................................................................................... 5 2.2.2 Fault Geometry, Non-uniform Slip and Slip Rate Deficit Weighting ........ 7 3.0 TSUNAMI MODELLING ..................................................................................11 3.1 TSUNAMI MODEL .................................................................................... 11 3.2 MODELLING GRIDS ................................................................................. 11 3.3 SEAFLOOR AND GROUND DISPLACEMENT CALCULATION ........................... 14 3.4 MODELLED DURATION AND ROUGHNESS CONSIDERATION ........................ 15 3.5 AUTOMATION OF TSUNAMI SIMULATIONS WITH TSUNAMI-API ..................... 16 4.0 TSUNAMI ARRIVAL TIME ESTIMATE ............................................................17 4.1 TIME HISTORY DATA MODELLING ............................................................ 17 4.2 ARRIVAL TIME IDENTIFICATION ................................................................ 19 4.3 ARRIVAL TIME ESTIMATES AND DISCUSSIONS ........................................... 21 5.0 LIMITATIONS ..................................................................................................31 6.0 CONCLUSIONS .............................................................................................. 33 7.0 ACKNOWLEDGEMENTS ................................................................................34 8.0 REFERENCES ................................................................................................35 FIGURES Figure 1.1 Coastal suburbs of the Wellington Harbour region. .......................................................... 2 Figure 2.1 Major local active faults and other structures in central New Zealand. ............................. 3 Figure 2.2 Overview of the geometry of the tsunami sources. ........................................................... 7 Figure 2.3 Subduction interface slip rate deficit for the Hikurangi subduction interface (credit: Wallace et al., 2012). ..................................................................................................................... 8 Figure 2.4 Comparison of non-uniform slip distribution ..................................................................... 9 Figure 3.1 Nested grid setup for tsunami generation and propagation modelling. ........................... 12 Figure 3.2 Nested grid setup for tsunami generation and propagation modelling. ........................... 12 Figure 3.3 Nested grid setup for tsunami propagation modelling. ................................................... 13 GNS Science Report 2016/03 i Figure 3.4 Nested grid setup for tsunami propagation and inundation modelling in Wellington region. ............................................................................................................................ 14 Figure 3.5 Examples of computed vertical seafloor/ground displacements resulting from scenario ruptures .......................................................................................................................... 15 Figure 4.1 Virtual tsunami gauges (black circles with red dots inside) for tsunami time history calculations, overlaid with the high-resolution DEM in Wellington Harbour region. ........ 17 Figure 4.2 Virtual tsunami gauges (red dots and red crosses with black dots at center), overlaid with Wellington suburb boundary map. .................................................................................. 18 Figure 4.3 Example of tsunami arrival time record (only the first 10 hours shown here) at the coastal front of Hataitai ............................................................................................................... 21 Figure 4.4 Distribution of first peak arrival times at the coastal front of Hataitai for all the Hikurangi subduction interface scenarios. ...................................................................................... 22 Figure 4.5 An illustration of time constraints for tsunami evacuation. .............................................. 28 TABLES Table 2.1 Tsunami observations in the 1855 Mw ~8.2 Wairarapa earthquake. ................................ 4 Table 2.2 Local seismic source scenarios for tsunami arrival time calculation. ................................ 6 Table 4.1 Virtual tsunami gauges for individual suburbs (see Figure 4.2). ..................................... 19 Table 4.2 Earliest tsunami arrival times at coastal fronts of Wellington Harbour suburbs for Hikurangi subduction interface scenarios (the start times and arrival times are measured in minutes after mainshock). ............................................................................................................ 23 Table 4.3 Earliest tsunami arrival times at coastal fronts of Wellington Harbour suburbs for Wellington Fault scenarios ............................................................................................. 24 Table 4.4 Earliest tsunami arrival times at coastal fronts of Wellington Harbour suburbs for Wairarapa Fault scenarios (the start times and arrival times are measured in minutes after mainshock). .................................................................................................................... 25 Table 4.5 Earliest tsunami arrival times at coastal fronts of Wellington Harbour suburbs for Wharekauhau Fault scenarios ........................................................................................ 26 Table 4.6 Statistical analysis of first peak arrival times at coastal fronts of Wellington Harbour suburbs considering all the four local fault sources ........................................................ 27 APPENDICES A1.0 SLIP DISTRIBUTIONS IN HIKURANGI SOURCE SCENARIOS ..................... 39 A2.0 ADDITIONAL TSUNAMI ARRIVAL TIMES ..................................................... 50 A2.1 ARRIVAL TIME STATISTICAL ANALYSIS FOR TSUNAMI FROM HIKURANGI SUBDUCTION INTERFACE ........................................................................ 51 A2.2 ARRIVAL TIME STATISTICAL ANALYSIS FOR TSUNAMI FROM WELLINGTON FAULT....................................................................................................53 A2.3 ARRIVAL TIME STATISTICAL ANALYSIS FOR TSUNAMI FROM WAIRARAPA FAULT .............................................................................................................55 A2.4 ARRIVAL TIME STATISTICAL ANALYSIS FOR TSUNAMI FROM WHAREKAUHAU FAULT....................................................................................................57 ii GNS Science Report 2016/03 APPENDIX FIGURES Figure A1.1 Source scenario 1 in Hikurangi subduction interface. ..................................................... 39 Figure A1.2 Source scenario 2 in Hikurangi subduction interface. ..................................................... 39 Figure A1.3 Source scenario 3 in Hikurangi subduction interface ...................................................... 40 Figure A1.4 Source scenario 4 in Hikurangi subduction interface. ....................................................