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Tsunami hazard in New Zealand due to South American
earthquakesWilliam Power, Gaye Downes, Mark StirlingWilliam Power, Gaye Downes, Mark StirlingInstitute of Geological and Nuclear SciencesInstitute of Geological and Nuclear Sciences
Napier, New Zealand, 1960
New Zealand tsunami sourcesNew Zealand tsunami sources
Figures from: Integrated Tsunami Database for Pacific
Magnitude/frequency of NZ Magnitude/frequency of NZ tsunami sources tsunami sources (approximate)(approximate)
Size of Tsunami (m)
Rec
urre
nce
Inte
rval
(yr
)
(ann
ual p
roba
bilit
y of
exc
eede
nce)
-1
1
10
100
1000
10000
1
10 100 1000
Distant Earthquakes
Local Earthquakes
Landslides
Asteroid Impact
Volcanoes
1933M8.3
1957M8.1
Which distant earthquakes caused tsunami which were damaging in New Zealand?Which distant earthquakes caused tsunami which were damaging in New Zealand?
Figures from: Integrated Tsunami Database for Pacific
1960M9.5
1877M9.0
1868M9.1
1906M8.6
1964M9.21952
M8.5
1919M8.3
?
?
1946M8?
?
?
?
?
19601960
Figure from: Integrated Tsunami Database for Pacific
South American subduction South American subduction zone earthquake sourceszone earthquake sources
Discretise by location and magnitudeDiscretise by location and magnitude
Ignore smaller earthquakes Mw < 8.5Ignore smaller earthquakes Mw < 8.5
Estimate typical uplift distribution for each Estimate typical uplift distribution for each location and magnitude combinationlocation and magnitude combination
Model tsunami propagation for each uplift Model tsunami propagation for each uplift distributiondistribution
Source ParametersSource Parameters
20º
2 km
130 km
Plate Boundary
Fault Plane
Refs: Abe (1975), Scholz (1982), Barrientos and Ward (1990) Refs: Abe (1975), Scholz (1982), Barrientos and Ward (1990)
Propagation modelPropagation model
Maximum heightsMaximum heights
10 cm
1m+
1 cm
Maximum wave height estimates, source 19, Mw 8.8
1 m
10 cm
1 cm
Maximum wave height estimates, source 19, Mw 8.8
Monte-CarloMonte-Carlo
Generate a synthetic catalogue of eventsGenerate a synthetic catalogue of events
For each source location:For each source location:
Select the number of earthquakes (Poisson)Select the number of earthquakes (Poisson)
For each earthquake:For each earthquake:
Select the magnitude (Gutenberg-Richter)Select the magnitude (Gutenberg-Richter)
For each point on the New Zealand grid:For each point on the New Zealand grid:
Accumulate exceedence countsAccumulate exceedence counts
End loop of pointsEnd loop of points
End loop of earthquakesEnd loop of earthquakes
End loop of sources End loop of sources
124 6 1082 14
2500 year return time peak-to-trough waveheights (metres)
124 6 1082 14
Gisborne
Napier
Wellington
AucklandChristchurch
Dunedin
Preliminary resultsPreliminary results. South American sources only.
500 year return time peak-to-trough waveheights (metres)
Gisborne
Napier
Wellington
Auckland
Christchurch
Dunedin
62 3 541 7 62 3 541 7Preliminary results. South American sources only.
DisaggregationDisaggregation
1
32
16
8
24
.
Improve geometrical and statistical modelsImprove geometrical and statistical models
Use further levels of nested grid, and model inundationUse further levels of nested grid, and model inundation
Study effects of non-uniform slip distributionStudy effects of non-uniform slip distribution
Consider other distant source regions, then local sourcesConsider other distant source regions, then local sources
What next?What next?
ConclusionsConclusions
South American earthquakes pose one of the South American earthquakes pose one of the most significant distant-source tsunami hazards most significant distant-source tsunami hazards for New Zealand.for New Zealand.
The hazard can be estimated using techniques The hazard can be estimated using techniques similar to seismic hazard modelling.similar to seismic hazard modelling.
A Monte-Carlo approach is a practical approach A Monte-Carlo approach is a practical approach to use for estimating tsunami hazard.to use for estimating tsunami hazard.
AcknowledgementsAcknowledgements
NOAA: Vasily Titov, Frank Gonzalez, Hal Mofjeld – MOST NOAA: Vasily Titov, Frank Gonzalez, Hal Mofjeld – MOST propagation model, many useful discussionspropagation model, many useful discussions
USC: Jose Borrero – general tsunami modelling adviceUSC: Jose Borrero – general tsunami modelling advice
GNS: John Beavan, Laura Wallace, Mauri McSaveney, GNS: John Beavan, Laura Wallace, Mauri McSaveney, Rafael Benites, Russell Robinson, Martin Reyners, Rafael Benites, Russell Robinson, Martin Reyners, Vaughan Stagpoole, Biljana Lukovic, Carolyn HumeVaughan Stagpoole, Biljana Lukovic, Carolyn Hume
Bathymetry: Smith & Sandwell, GEBCO, Seabed MappingBathymetry: Smith & Sandwell, GEBCO, Seabed Mapping(NZ contribution to GEBCO: NIWA)(NZ contribution to GEBCO: NIWA)
Tsunami hazard in New Zealand due to South American
earthquakes
William Power, Gaye Downes, Mark StirlingWilliam Power, Gaye Downes, Mark StirlingInstitute of Geological and Nuclear SciencesInstitute of Geological and Nuclear Sciences
Email: [email protected]