Transcript 3A8 Week 06 Lecture 17-Earthquakes Part Two (Prediction)

Part Two
21/02/11: Christchurch Earthquake
21/02/11: Christchurch Earthquake
21/02/11: Christchurch Earthquake
Nicaragua Tsunami
September 1, 1992
Magnitude 7.0 earthquake
Shallow focus,
Subsea landslide
Waves 8-15m high
26 towns affected along
250 km of coastline
reached 1 km inland
116 dead
63 missing
489 injured
>40,000 lost home/income
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 on
W margin of Tenerife
Tsunami
threatens
eastern 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 crashing
northward into
stable 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
associated
with 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!
Before . . .
Repeat the calculations to
include the 1999 Izmit and
Duzce earthquakes
. . . 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