Transcript Should the tax payer fund earthquake research?

SEISMIC HAZARD
Presentation is based on:
•Allen, R., Earthquake hazard mitigation: New direction and opportunities, in
"Treatise on Geophysics”, 2007.
•Bilham, R., Earthquakes and urban growth, Nature 336, 625-626, 1988.
•Bilham, R., Urban earthquakes fatalities: A safer world, or worse to come?
Seis. Res. Lett. 75, 706-712, 2004.
Seismic risk versus seismic hazard
risk = hazard Ä vulnerability Ä cost
Seismic Hazard is the probability of occurrence of a specified level of
ground shaking in a specified period of time. (But a more general
definition includes anything associated with an earthquake that may
affect the normal activities of people, i.e. surface faulting, ground
shaking, landslides, liquefaction, tectonic deformation, and tsunamis.)
Vulnerability is the degree of damage caused by various levels of
loading. The vulnerability may be calculated in a probabilistic or
deterministic way for a single structure or groups of structures.
Seismic Risk is expressed in terms of economic costs, loss of lives or
environmental damage per unit of time.
It is the job of the geophysicists to provide hazard assessments (- but
not risk assessments.)
The US seismic hazard map
Highest hazard
PGA 2% in 50 years
64+
48-64
32-48
16-32
8-16
4-8
%g
0-4
Lowest hazard
Earthquakes are organized along belts
The spatial distribution of earthquake activity is correlated with
that of volcanic activity
Where do the largest earthquakes occur?
It is known from both historical and modern data that the largest
quakes strike in S. America, Alaska and throughout Asia.
The four largest most recent earthquakes are:
1. Chile, 1969, Mw9.5
2. Alaska, 1964, Mw9.2
3. Sumatra-Andaman, 2004, Mw9.1
4. Japan, 2011, Mw9.0
Global seismic hazard
(Figure from Allen, 2007)
Map prepared by the Global Seismic Hazard Assessment Program (Giardini, 1999).
Consequences of urbanization
Urbanization in developing
nations is rapid, but is flat in
industrial nations.
(Figure from Bilham, 2004)
''By the year 2025 more than 5500 million people will live in cities - more
than our entire 1990 combined rural and urban population.''
(from Roger Bilham’s web-page)
Consequences of urbanization
Note the slower
growth of cities in
N. America and W.
Euro. with respect
to cities throughout
Asia and S.
America.
Thus, the poor are
at greater risk than
the rich.
The location of the
largest cities in 1950 and
2000 superimposed on
the hazard map.
Consequences of urbanization
While cities in seismically
safe regions are removed
from the top 30 list, cities in
hazardous regions grow
more rapidly.
Question: why are big cities
built in areas of high seismic
risk?
(Figure from Allen, 2007)
Consequences of urbanization
Sumatra (2004)
Tangshan (1976)
(Figure from Allen, 2007)
Note that:
25,000 per year
8000 per year
1. The change in character pre- and post- 1940.
2. The two largest quakes did not cause many fatalities.
3. The new millennium started really bad…
Consequences of urbanization
• While the number of
fatalities is increasing, it
is not increasing as
global population.
• Thus, an individual risk
of dying has decreased
by a factor of 2 since
1950.
The chances of
dying of an
earthquake are very
small. Only 1 out of
200,000 people per
year!
(Figure from Allen, 2007)
Fatalities rate vs. growth rate
The conclusion that fatalities rate increase slower than population
growth is not true for Iran (and some other developing nations).
(Figure from Bilham, 2004)
• Earthquake fatalities rate in Iran is in pace with the population
growth.
• Fatalities rate in Iran is rising at an increasing rate.
Does fatalities rate rises at an increasing rate?
500 years of historical
and modern record
suggest that the fatalities
rate rises at an increasing
rate (Bilham, 2004).
(Figure from Bilham, 2004)
What to do?
Much of the risk may be mitigated by:
• Implementation of Early Warning Systems.
• Improvement and implementation of building codes.
• Fault mapping.
Early Warning System (EWS)
In many cases, the magnitude of an
impending earthquake may be estimated a
few tens of seconds prior to the arrival of the
destructive ground motion to the populated
area. In such cases, many lives may be
saved simply by:
• Automatic shutting down power supplies.
• Automatic shutting down of nuclear reactors.
• Automatic stopping or reducing the speed of fast trains.
• Individual actions
Early Warning System (ERS)
Early Warning System (EWS)
The October 17, 1989 M6.9 Loma Prieta, CA
CISN
California Integrated
Seismic Network
Alert
Shake
•Test system in CA is
now operational
•Alerts are delivered to a
few dozens of scientists
•About to start delivery to
public and private
partners
Early Warning System (EWS)
The March 11, 2011 M9 Tohoku-oki, Japan
JMA
Since 2007
15 sec warning
in Sendai ->
success
warning
region
Building codes
• Earthquake don’t kill - buildings do (but
also tsunami).
• Earthquake resistant construction costs
only 10% more than nonresistant
construction.
• Structures in CA built after 1976, when a
new building code was implemented,
suffered very little damage in the 1989
Loma Prieta and the 1994 Northridge.
• The implementation gap.
Fault mapping
* Earthquakes occur on faults.
* Yet, the location of some major faults is unknown.
* Examples for major earthquakes that ruptured unrecognized
faults include:
• 1989, Loma Prieta.
• 1994, Northridge.
But what about prediction?
Short term vs. long term prediction
The public wants this
Scientists provide this
Question: Will short term high probability prediction solve the
problem?
But what about prediction?
Lesson from the Hurricane Katrina example:
It is possible to make high probability short term predictions for
hurricanes, as was done in the case of hurricane Katrina. Still an
estimated 1800 people were killed in New Orleans and
neighboring areas. About 50% of New Orleans residences still
have not yet returned to the city.
Public funding for earthquake science
Should the tax payer fund earthquake research?
• Given that only 1 out of 200,000 people dies as a result of an
earthquake.
• Given that many (most?) scientists think the short term high
probability prediction will not be possible.
• The world has not yet experienced a major quake directly
beneath a mega-city, the economic and geopolitical
consequences of which are unimaginable. About 35% of
Tangshan population perished in the 1976 quake. Such a fatalities
rate in a city with a population of 3 million, would result in 1 million
fatalities!!!
• The two most damaging quakes in the U.S. were 1989, Loma
Prieta, and the 1994, Northridge, cause “only” 60 deaths each,
but cause financial loss of 10 and 46 billions dollars, respectively.
• Advancement in EQ physics will pave the way to advancements
in other fields, most notably material sciences and engineering.
Recommended readings:
• Allen, R., Earthquake hazard mitigation: New direction and
opportunities, in "Treatise on Geophysics”, 2007.
• Bilham, R., Earthquakes and urban growth, Nature 336, 625626, 1988.
• Bilham, R., Urban earthquakes fatalities: A safer world, or worse
to come? Seis. Res. Lett. 75, 706-712, 2004.