The future earthquake potential in New Zealand
Kekerengu fault rupture, Kaikōura earthquake, 14th Nov 2016
Kelvin Berryman Principal Scientist, GM Strategic Relationships GNS Science [email protected]
IPWEA conference, Wellington, April 2017 GNS Science Outline • Why are there earthquakes in New Zealand • Recent historical records of earthquakes • Past large earthquakes – history in geology • What does the future hold?
South Leader Fault, Hurunui District
IPWEA conference, Wellington, April 2017 GNS Science Why are there Earthquakes in NZ?
IPWEA conference, Wellington, April 2017 GNS Science New Zealand New Zealand EQ’s Deep Seismicity Shallow Seismicity Depths ≥ 40 km Depths < 40 km (a ten year snap-shot) (a ten year snap-shot)
IPWEA conference, Wellington, April 2017 GNS Science National Seismic Hazard Model (Stirling et al., 2012)
• Based upon historic & instrumental earthquakes and active faults
• Prior to Canterbury & Kaikōura EQ’s
• An ‘average’ model which only takes account of the time since last rupture on a few faults (e.g. Wellington, Alpine)
IPWEA conference, Wellington, April 2017 GNS Science Kaikōura Earthquake
IPWEA conference, Wellington, April 2017 GNS Science Kaikōura Earthquake
Litchfield et al., submitted Surface Fault Ruptures
GNS Science Kaikoura Earthquake Aftershocks, Nov 13th - 30th, depth <25 km Geodetic station displacements Hmax: 6m; Vmax: 2m
Seismology
IPWEA conference, Wellington, April 2017 GNS Science Kinematics in the transition zone
Wallace et al., 2012
IPWEA conference, Wellington, April 2017 GNS Science 2. Kaikōura Earthquake
Kaikōura earthquake & slow slip
Slow slip events started along the whole margin within 1 week of Kaikōura EQ
IPWEA conference, Wellington, April 2017 GNS Science Did the 2009 Dusky Sound Earthquake start a period of heightened activity?
IPWEA conference, Wellington, April 2017 GNS Science Or did the increase in activity start even earlier in 2003? 150 years of large earthquakes 1929-1942 2003-? 9 March 1929 22 August 2003 Arthurs Pass Fiordland Magnitude 7.1 Magnitude 7.1
17 June 1929 23 November 2004 Murchison Puysegur Trench Magnitude 7.8 Magnitude 7.1
3 February 1931 30 Sept 2007 Hawkes Bay Auckland Islands Magnitude 7.8 Magnitude 7.3
13 February 1931 15 July 2009 Hawkes Bay Dusky Sound Magnitude 7.3 Magnitude 7.8
5 March 1934 4 September 2010 Pahiatua Darfield Magnitude 7.6 Magnitude 7.1
24 June 1942 2 September 2016 Wairarapa East Cape Magnitude 7.2 Magnitude 7.1
2 August 1942 14 November 2016 Wairarapa Kaikoura Magnitude 7.0 Magnitude 7.8
GNS Science What are the scenarios following the Kaikōura Earthquake?
• Scenario One: Likely (70% within the next year) – Aftershocks will continue to decrease in frequency over the next year and no aftershocks of M7 or larger will occur, but a M6+ is very likely.
• Scenario Two: Unlikely (approximately 25% within the next year) – An earthquake smaller than the main shock but between M7.0 and M7.8 will occur.
IPWEA conference, Wellington, April 2017 GNS Science Scenario Three • Could we have a mega earthquake here? • Current thinking is about a 1 in 20 chance of a M8+ in the coming year
IPWEA conference, Wellington, April 2017 GNS Science More Broadly – what should we be preparing for ? Event Likelihood Possible economic loss in next 50 yrs (2012 estimates) Alpine fault - M8 earthquake 30% > $10bn? AF8 project – CDEM exercise and impact modelling Hikurangi subduction zone M8+ 10% > $10bn and tsunami Major national & international focus – NSF & IODP Hope fault M7.2 earthquake 50% ~$1bn ? Enhanced likelihood following Kaikōura earthquake NZ earthquake sequence like 1929-1942 50% >> $10bn Darfield and Kaikōura amounts to ~ $ 10bn so far Wellington fault earthquake 5% >> $10bn It’s Our Fault project, Wellington Resilient City initiative
Note: New Zealand GDP 277B NZD (2013)
IPWEA conference, Wellington, April 2017 GNS Science Alpine Fault
Wellington region faults
Hope Fault
IPWEA conference, Wellington, April 2017 GNS Science Also…………….. Our understanding of timing of past surface fault rupture and large (M6-7+) earthquakes suggest many faults are ‘late’ in their seismic cycle. These include: • Wairau, Clarence and Hope faults in Marlborough • coastal Wairarapa faults • Faults in the Ruapehu – White Island volcanic zone • Lake Heron, Irishman’s Creek, Ostler faults in eastern foothills of Southern Alps
Marine terraces record Ostler Fault coastal earthquakes Paeroa Fault excavation IPWEA conference, Wellington, April 2017 GNS Science Conclusions 1. We are known as the ‘Shaky Isles’ for good reason – earthquakes are our national wallpaper. 2. Earthquake knowledge and forecast (not prediction) ability is improving continuously, but there are funding constraints. 3. Policy settings (e.g. building codes, RMA, resilience improvements, risk transfer) are addressing quite a few elements of risk (but it could be better). 4. Public interest and education improving the ability to manage risk better (resilience). 5. Public Finance Act (national debt must not exceed 25% of GDP) means there is a national ability to weather earthquake crises.
IPWEA conference, Wellington, April 2017 GNS Science