Part Two. 21/02/11: Christchurch Earthquake.
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Transcript of Part Two. 21/02/11: Christchurch Earthquake.
Part Two
21/02/11: Christchurch Earthquake
21/02/11: Christchurch Earthquake
21/02/11: Christchurch Earthquake
September 1, 1992Magnitude 7.0 earthquakeShallow focus,Subsea landslideWaves 8-15m high
26 towns affected along250 km of coastlinereached 1 km inland
116 dead63 missing489 injured>40,000 lost home/income
Nicaragua Tsunami
El Tranisto village
Population 1000,16 killed,151 injured
Most of village destroyed(> 200 houses)
3 main waves, highest > 9 m
Stone carried 50 m inland,1.9 m above sea level
Indonesia, December 1992 tsunami
Indonesia, December 1992 tsunami
1964 Alaska earthquake
Effect of resulting tsunami at Prince William Sound,
Volcanic rocks onW margin of Tenerife
Tsunami threatenseastern USA…
Earthquake Prediction?
How Often?
More smaller earthquakes than bigger ones
Similar spatial distribution
Case History: North Anatolian Fault
• * Historical earthquake data shows temporal & spatial patterns
• * Numerical modelling of regional stress changes
Probability of earthquake hitting Istanbul…
Driving tectonic force:
Arabia is crashingnorthward intostable Eurasia
Anatolia is squeezed out westwards as Arabia piles northward into stable Eurasia
Pattern of seismicity since 1950 is rather worrying for Istanbul!
Using historical records
1. Use modern earthquakes to explain historical events
2. Use historical earthquakes to make predictions for future events
Historical records of earthquakes go back over 1000 years in E Europe and the Middle East
Spatio-temporal progressions are not uncommon on the North Anatolian fault
First parameterise fault geometry and
regional plate motion...
Estimated stress change associatedwith 1939 earthquake
Cumulative stress change caused by large earthquakes and steady deep slip on the North Anatolian fault since 1939
Predictive power of model:
Stress situation after the 1939 and 1949 earthquakes.
The subsequent 1966 and 1971 fault breaks occurred in regions of high stress change.
“. . . During the next 30 years, we estimate a 15% probability of a M>=6.7 earthquake east of the major eastern center of Ercinzan, and a 12% probability for a large event south of the major western port city of Izmit. . .”
Stein et al., Geophysical Journal International, 1997
B A N G!
Repeat the calculations to include the 1999 Izmit and Duzce earthquakes
Before . . .
. . . After
“The probability of strong shaking affecting Istanbul is calculated as 62 +/- 15% (1 S.D.) during the next 30 years and 32 +/- 12% during the next decade.”
Parsons et al., Science, 2000
Mitigation
The USC University Hospital was built with base isolators to allow it to withstand strong earthquake shaking.
The success of the design strategy was demonstrated in the 1994 Northridge quake, when the hospital and its contents suffered no damage, despite the servere ground shaking produced by the quake.
Before . . . . . . After