SCHOOL OF ENVIRONMENT
From science to practice: bridging the gap through the Determining Volcanic Risk in Auckland (DEVORA) project
Jan Lindsay1 and Gill Jolly2 1School of Environment, The University of Auckland, New Zealand; 2GNS Science, Taupo, New Zealand
volcano volcano volcano volcano volcano volcano volcano
volcano volcano
volcano
Photo courtesy of Lloyd Homer, GNS Science
Auckland population: 1.5 million, ca. 1/3 of national population AVF: one of 3 potentially active intraplate volcanic fields in NZ
Other fields: Kaikohe-Bay of Islands and Whangarei Fields
SCHOOL OF ENVIRONMENT · Geology Auckland Volcanic Field ca. 50-55 small “monogenetic” basaltic centres
Hayward et al. (2011)
SCHOOL OF ENVIRONMENT · Geology Types of volcanoes
Maars or explosion craters (e.g. Lake Pupuke, Orakei basin, Onepoto Domain)
Scoria/cinder cones (e.g. Mt. Eden, Mt. Wellington, Mt. Albert)
SCHOOL OF ENVIRONMENT · Geology Spatio-temporal relationships
Rangitoto: 550 – 600 years ago
Pupuke erupted about 250,000 years ago
SCHOOL OF ENVIRONMENT · Geology Will the AVF erupt again?
• Such fields can be long- lived (> 1 million years), AVF ~ 250,000 yrs
• Last eruption 550 yrs ago
Horspool et al. (2006)
Mantle anomaly 70-90 km beneath Auckland = partially molten mantle??
SCHOOL OF ENVIRONMENT · Geology Slide courtesy Greg Auckland CBD Holland, Auck. Council SH1 Parnell Grafton Newmarket Epsom SH16 Remuera Greenland Mt Eden One Tree Hill Oranga Royal Oak Three Kings Mt Eden Sandringham St Lukes Balmoral Population: 223,000 Morningside West’n Springs Businesses: 38,000 Kingsland Grey Lynn Employees: 204,000 Ponsonby
SCHOOL OF ENVIRONMENT · Geology Herne Bay Volcanic Risk = (hazard, vulnerability)
Auckland is vulnerable. So, even though the probability of the “hazard” of an AVF eruption is low – the risk is not low.
An eruption in Auckland would be a low probability, high consequence event “DEtermining VOlcanic Risk in Auckland” A UoA-GNS Science collaborative project
Project aim: a much-improved assessment of volcanic hazard and risk from the Auckland Volcanic Field & ash fall from Central North Island volcanoes
Core Funding: EQC, Auckland Council, MBIE, GNS Science, UoA Co-funding: Massey, Victoria, Canterbury Universities, Marsden, VORiSA
Regular engagement with all partners (e.g. EQC, Civil Defence, Lifelines) Determining Volcanic Risk in Auckland (DEVORA) A UoA-GNS Science collaborative project
Three main themes: Geological Model Probabilistic Hazard Model Risk and Social model
currently in 6th year of a 7 year project.
30 Researchers & 10 PhD students across 9 institutions Theme 1: Geological model
• Using geochemistry to understand how volcanic systems work
Determining the conditions of magma genesis – depth, degree of partial melting, source characteristics.
Defining trends within individual volcanoes to establish the type of processes that have modified rising magma and provide constraints on the rates of magma ascent
• Using structural geology to identify volcanic pathways
Statistical analysis of vent locations
Using geological (incl. borehole) and geophysical data
• Integration and development of geological model
SCHOOL OF ENVIRONMENT · Geology Theme 2: Hazard model
Refining hazard knowledge
• Field studies and modelling of base surge, lava flows, gas, ash
Determining magnitude-frequency relationships
• Reassessing old ages (C14, K-Ar, Ar-Ar) • New C14, Ar-Ar and Paleomag proxy ages • Tephrochronology • Correlation of ash layers with source volcanoes
Spatio-temporal modelling
• BET VH/EF • Scenario probability matrix • Refine all models and develop for RiskScape
SCHOOL OF ENVIRONMENT · Geology Theme 3: Risk and Social Model
Impacts (determining vulnerability) • Exposure database (assets) • Fragility of Auckland’s infrastructure, buildings, and population • Intangible and indirect impacts
Societal response • Determine best risk assessment and risk communication methods • Development of tools for improved societal response
Calculate Volcanic Risk!
SCHOOL OF ENVIRONMENT · Geology Recent discovery !! Thin basaltic tephra layers in Lake Pupuke that are 1,500 years old suggest Rangitoto may have erupted several times over 1,000 years
Not reworked The Volcanoes, the City and the Borehole Database
#0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0#0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0#0 #0 #0 #0 #0 #0 #0 #0 #0 #0 #0#0 #0 #0#0 #0 #0#0 #0 Eruption Types and feeding systems - Auckland Jeju - magma evolves due to crustal/mantle modification
Brenna et al., 2012, Lithos Controls on Auckland hazards
Magma Volume, rise rate, ejection rates Magma properties: composition, gas, temperature, crystalinity etc.
Environmental Properties Water, surface, saturation Country rock, structure, strength Topography
Orakei Basin Study Nemeth et al. 2012 Bull Volcanol External vs. internal factors for eruption hazard
increasingMagma magma Supply supply rata,Rate magma flux
steady stage volcanic hazards dominate: internal forcing Saturation supply Water Depthsoft of sediment
initial volcanic hazards dominate: external forcing increasing water saturation of Plio-Miocene strata ofPlio-Miocene saturation water increasing increasing thicness of Plio-Miocene strata Plio-Miocene of thicness increasing increasing probaility of water filled fractures filled of water probaility increasing increasing probability of embedded pressurised ground water in Miocene rock untis rock in Miocene water ground pressurised of embedded probability increasing increasing standing water depth water standing increasing Substrate matters
Central-Nth Auckland – Waitemata Group – firm, dense rocks
South Auckland – Soft, saturated sediments
Play a major role in how volcanic eruptions occur Spatial classification of eruption scenario probabilities
Substrate geology/water Past eruption type Volcano substrate is a critical factor for hazard
Maungataketake, South Auckland
Magma ponded in wet soft rock
Eruptions low-energy “excavations” What about submarine volcanism?
One of the few submarine volcanoes – North Head
Most of the rest of the volcanoes erupted at periods of low-sea levels
Agustin-Flores et al, in prep Lava flow hazards
1. Geomorphic modelling approach – using high precision LiDAR
Kereszturi, et al., 2012 Remote Sensing of Environment Lava flow simulation codes (MAGFLOW)
Best fit scenario (5000h) Three Kings Duration ~208 days volcano effusion rate = 5 m3/s
Input into hazard scenarios…
Kereszturi et al., in prep Auckland Civil Defence Emergency Where are we going with Management (CDEM) Group Plan 2011-2016 all this?
1 Oct 2009
www.stuff.co.nz
SCHOOL OF ENVIRONMENT · Geology RiskScape
Moving towards a quantitative volcanic risk assessment framework
SCHOOL OF ENVIRONMENT · Geology Thanks to the team