The Canterbury Earthquake Sequence: major geologic and social impacts - Kelvin Berryman

The Canterbury Earthquake Sequence:
major geologic and social impacts
Kelvin Berryman – Director, Natural Hazards Research Platform

22 Feb, 2011

Natural Hazards Research Science
GNS Platform

Ruaumoko, the Maori god of earthquakes & volcanoes, has
surprised us in Canterbury
This talk:
•Geologic context and characteristics of the earthquake sequence and
impacts
•Affects of the prolonged sequence
•Impacts on the city, the people, and the regional economy
•Soil liquefaction and rockfall
•Land zoning, insurance and communities

Natural Hazards Research Platform
GNS Science

Barnes et al, 2011
Regional Hikurangi
Fault Subduction
margin
Patterns

Wellington

Christchurch
Alpine
Fault

Jongens et al, 2012
GNS Science

Evolution of the earthquake sequence

GNS Science

GNS Science

Highfield Road,
Sept 4th 2010

Quigley et al, UoC & GNS

4.5 m dextral & < 1 m vertical
GNS Science

Strike-slip component of surface slip on the 30 km long Greendale Fault. Very
good fit with rupture models from seismology and geodesy
GNS Science

Boxing Day and
subsequent

Chances of a M6+ in 1 year = This number was widely communicated but
25% in the aftershock region what did it mean – no scenario models in
terms of impact were developed

GNS Science

February and June fault slip inversions from GPS data
– can also be compared with seismology and InSar

Interpretation by Beaven et al., GNS
GNS Science

Comparison of four CBD records
against code requirements

22 Feb 2011

GNS Science

Magnitude vs Time ( up to February 2013 )
Magnitude

generally felt

often not felt

incomplete detection

• More than 2 years of aftershocks have had major psycho-social impacts
GNS Science

The Impacts - Ground Motion (code level ~ 0.3g)
4 Sept 2010 26 Dec 2010

22 Feb 2011 13 June 2011

GNS Science

A couple of perspectives ………………….
1.The Sept 2010 Darfield earthquake was near design level in the city
•Damage wasn’t too bad except for unreinforced masonry (as expected)
•Services were restored reasonably quickly (24 hrs for electricity, a few
days in most places for water & waste water, liquefaction and lateral
spread damage in a few places (future red zone)
•But was there significant hidden damage to structures (CTV, for example)?

2. The Feb 2011 event was near to a 2500 yr return period event for the city
•Damage was largely as would be expected
•Most engineered structures performed quite well
•Infrastructure was badly damaged, especially in future red zones & TC 2 &3
•The people and the city did very well, considering, but there is now an
expectation in some quarters to have little or no damage in extreme events
•Was performance good enough for an extreme event? What are acceptable
levels of safety and economic resilience – red zoning implies unacceptable,
what about repairability and functionality in extreme events
GNS Science

Features of the earthquake sequence in the NZ context
A large (for NZ) natural hazard event in a small economy
•10% of NZ’s 4.5 million people directly impacted
•Total loss estimates c. $35b NZD – about 8-10% GDP
•NZ’s economy about the same size as Munich-Re or IBM annual revenue

Events such as this have the possibility of irreparably damaging the economy
of small or developing nations

Regional economy is strong (based on agriculture)
•Port, airport, road and rail networks had very little downtime
•95% of businesses are still operating albeit with downturn in tourism, education,
and hospitality
•Some migration away from Canterbury especially initially, now about 9,000
persons, but 30,000 new workers needed for rebuild – communities remained
largely intact
•Early government support for local business continuity and workforce

A city cannot operate in isolation from its hinterland. Supply chains and
infrastructure are critical. There was no need for widespread evacuation in
Christchurch and this is a key tipping-point in regional economic resilience

GNS Science

Insurance Perspectives - Recent major earthquake events
USD billion (at 2011 prices)

Event Date Country Economic Economic losses Insured Insurance
Losses as %GDP Losses Industry
Contribution
11 March 11 Japan up to 300 up to 5.4% 35 up to 17%
27 Feb 11 Chile 30 18.6% 8 27%
22 Feb 11 NZ 15 10% 12 80%
12 Jan 10 Haiti 8 121% 0.1 1%
04 Sept 10 NZ 6 5.3% 5 81%
06 April 09 Italy 4 0.2% 0.5 14%
23 Oct 11 Turkey 0.75 0.1% 0.03
4%
04 April 10 Mexico 0.95 0.09% 0.2 21%

Source: Swiss Re sigma catastrophe database
NZ presents the highest ratio of insured to economic losses. Residential earthquake
insurance virtually mandatory through the EQ Commission, so insurance plays a
much greater role in reconstruction efforts than in other examples

GNS Science

Legend

Repairs > $100k (houses which Residential Building Damage Map
had significant damage but
could be economically repaired

Rebuilds (houses which are
beyond economic repair)

Confirmed rebuilds (houses
which were confirmed to be
beyond economic repair)

Building damage after the 4 September 2010 event
GNS Science

Residential Building Damage Map
Building Damage Ratio
(Repair cost estimate / replacement
cost)
0% (no building damage)
0% - 20%
20% - 40%
40% - 60%
60% - 80%
80% - 100%
100% (rebuild because it is
uneconomic to repair the
building)

Building damage after the 22 February 2011 event
GNS Science

Sept 4, 2010

GNS Science

Feb 22, 2011

GNS Science

Rockfall Hazard

GNS Science

Liquefaction

GNS Science

6.5 Ka New Zealand Historical Atlas 1997
7 Ka
5 Ka
8 Ka 3 Ka
2 Ka
1 Ka

Why is liquefaction such an
issue in eastern Christchurch?

GNS Science

Time-Varying Earthquake Hazard Forecast
• Used to inform update of building
codes
• Accounts for different earthquake
clustering scales
• Combines four different models
• Used to estimate probabilities of
ground shaking

• Short-term clustering model –
STEP - Days to Year(s)
• Medium-term clustering model
– EEPAS - Years to decades
• Long-term average model –
PPE - Average earthquake rate
since 1960
• NSHM fault model - Longest-
term mostly time-independent
Yearly number of earthquakes greater than M 5 from
four models
Gerstenberger, Rhoades, et al, GNS
GNS Science

Refined Forecast for Canterbury region (whole of Canterbury Plains)
starting April 15th, 2012
1 Month 1 Year 5 years 20 years 50 years
Prob Prob Prob Prob Prob
5.0-5.4 15% 76% 5.0-5.4 99% 100% 100%

5.5-5.9 5% 34% 5.5-5.9 75% 97% 100%
<3% 6.0-6.4 34% 64% 83%
6.0-6.4 1% 11%
for city
6.5-6.9 <1% 3% 6.5-6.9 11% 27% 51%

7.0+ <1% 1% 7.0+ 4% 13% 21%

The ground motions associated with these earthquakes are part of the revised building
code requirements, but not as a direct hit, and for about the next 5yrs the hazard level
is higher than the 50 yr average reflected in the code

GNS Science

Major lessons emerging
1. Land use planning controls to limit exposure to known liquefaction
susceptibility were not enacted – failure to deflect development pressure
and failure by science to spell-out likely impacts or consequences.
2. Failure to find a solution to known earthquake prone building risk –
this is largely a URM and older concrete inventory, not the
two multistory buildings that collapsed. The built environment
generally performed as expected or better than expected under
extreme ground motions.
3. Poor communication of what building codes and rapid building
inspections mean, and in risk communication. Engineers and scientists
should talk to the public in terms of possible impacts, not “safe”, and not
earthquake magnitudes.
4. High stress drop, extremely energetic earthquakes with higher than
expected vertical accelerations may be a characteristic of some low
strain rate parts of NZ – implications for hazard and code requirements
5. Code is for life safety but a cities future depends on functionality – how
to achieve this in the code or city planning process ?
GNS Science

Rebuilding – challenges, impediments and opportunities
• Getting people back into homes, businesses, and feeling secure
• Building standards (life risk + serviceability?)
• Insurability
• Investment capital
• Technical considerations (short term EQ risk, liquefaction)
• The biggest build NZ will ever do (we hope) – a major urban
renewal project

GNS Science

Many, many acknowledgments……………

The science response to the Canterbury earthquakes has involved
major contributions from many professions and institutions, including:

GNS Science, University of Canterbury, New Zealand’s geotechnical &
structural engineering capacity, Auckland University, Victoria University,
and international collaborators from USA, Japan, Canada and elsewhere.

The science has been communicated to:

Civil Defence, CERA, Christchurch City Council and adjacent local
government authorities, Environment Canterbury, central government
departments (social development, education, justice, treasury, building &
housing), government Ministers, the insurance industry, and the business
community.

Making a difference - absorbing lessons learned as a memorial to the 185
persons that lost their lives in the February 22nd earthquake – requires
ongoing cooperation between science and policy. It is a work in progress.
GNS Science

The Canterbury Earthquake Sequence: major geologic and social impacts - Kelvin Berryman

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