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