TOPIC 4:
DEVELOPING COST-EFFECTIVE EARTHQUAKE HAZARD
MITIGATION POLICY
Mitigating hazard (reducing risk) from earthquakes or
other natural disasters involves economic and policy
issues as well as the scientific one of estimating the hazard
and the engineering one of designing safe structures.
$100M seismic retrofit
of Memphis hospital,
removing nine floors,
bringing it to California
standard
Does this make sense?
How can we help
society decide?
Because most earthquake-related deaths result from the
collapse of buildings, the primary defense against
earthquakes is designing structures that should not collapse.
We want to assess the seismic hazard and chose a level of
safety that makes economic sense, because such design
raises construction costs and diverts resources from other
uses.
”Earthquakes
don't kill
people;
buildings kill
people.”
Building codes should not be too weak, permitting unsafe
construction and undue risks, or too strong, imposing
unneeded costs and promoting evasion.
Deciding where to draw this line is a complex issue for which
there is no unique answer.
”Earthquakes
don't kill
people;
buildings kill
people.”
1999
Chi-Chi
earthquake
Taiwan
Tsai et al,
2001
”Earthquakes
don't kill
people;
buildings kill
people.”
There’s no clear division between economic/policy
and science/engineering issues
In particular, the definition of “hazard” (number of
years/probability over which to plan for maximum
shaking) is economic/policy based
Challenge is to develop sensible policies that balance
costs and benefits, given what we know and don't
know about future earthquakes and their effects.
There’s no right answer, so society has to chose what
to do.
Difficulties:
1) Estimating hazards requires assumptions about
the size, recurrence, and shaking from future
earthquakes, which often are poorly known.
2) Need to chose definition of seismic hazard,
which is even more arbitrary and at least as
significant as assumptions about future
earthquakes.
3) Mitigating risks involves economic and policy
issues as well as the scientific one of estimating
the hazard and the engineering one of designing
safe structures
U.S. average 10-20 deaths per year, but can be
many more for large earthquake
Some foreign countries much more (more people
living along plate boundary, different construction)
U.S. EARTHQUAKES
Infrequent, but occasionally
major, fatalities and damage
Moderate (M 6.7) 1994
Northridge earthquake: 58
deaths, $20B damage
Challenge: find mitigation
strategy that balances cost of
safer construction with
benefits, given other possible
uses of resources
Tough problem!
ORGANIZATIONAL ISSUE (in US)
Because
There are no unique or correct mitigation strategies
There’s no clear division between economic/policy and
science/engineering issues
Different public and private organizations with different
perspectives - none of which are charged with looking at the
problem as a totality - take different approaches.
Organizations
(public or
private)
focusing on
economic
development
tend to
discount
hazards
San Andreas Fault not
mentioned
NASA
SOME EMERGENCY MANAGEMENT Can get huge range of
GROUPS EXAGERATE HAZARD probabilities, depending
on assumptions of
magnitude and recurrence
“Seismologists have
predicted a 40-60% chance
of a devastating earthquake
in the New Madrid seismic
zone in the next ten years.
Those odds jump to 90%
over the next 50 years. The
potential magnitude of a
catastrophic New Madrid
quake dictates that we
approach the preparedness
on a regional basis"
Stein et al., 2003
“Catastrophic” & “devastating”
defined as M>6 … which occurs ~
every 150 years somewhere in the
New Madrid zone - most of which
isn’t densely populated
The largest in the past century,
1968 (M 5.5) Illinois earthquake,
caused no fatalities. Damage
consisted of fallen bricks from
chimneys, broken windows,
toppled television aerials, and
cracked or fallen brick & plaster.
Organizations with quasi-regulatory duties (BSSC, FEMA,
USGS) focus on reducing losses in future earthquakes without
considering cost of mitigation measures or how this use of
resources should be balanced with alternative uses
HOW CAN WE
TAKE A BROADER,
INTEGRATED,
VIEW?
Post-tsunami cleanup,
Banda Aceh
THOUGHT EXPERIMENT: TRADEOFF
Your department is about to build a new building.
The more seismic safety you want, the more it will
cost.
You have to decide how much of the construction
budget to put into safety.
Spending more makes you better off in a future
large earthquake. However, you’re worse off in
the intervening years, because that money isn't
available for office and lab space, equipment, etc.
THOUGHT EXPERIMENT: TRADEOFF
Deciding what to do involves benefit-cost
analysis. You try to estimate the maximum
shaking expected during the building's life, and
the level of damage you will accept.
You consider a range of scenarios involving
different costs for safety and different benefits in
damage reduction.
You weigh these, accepting that your estimates
for the future have considerable uncertainties,
and somehow decide on a
balance between benefit and cost.
THIS PROCESS, WHICH SOCIETY FACES IN
PREPARING FOR EARTHQUAKES,
ILLUSTRATES TWO PRINCIPLES:
“There's no free lunch”
Resources used for one goal aren’t available
for another
This is easy to see in the public sector, where there
are direct tradeoffs. Funds spent strengthening
schools aren’t available to hire teachers,
upgrading hospitals may mean covering fewer
uninsured (~$1 K/yr), stronger bridges may
result in hiring fewer police and fire fighters
(~$50 K/yr), etc...
THIS PROCESS, WHICH SOCIETY FACES IN
PREPARING FOR EARTHQUAKES,
ILLUSTRATES TWO PRINCIPLES:
“There's no such thing as other people's
money”
Costs are ultimately borne by society as a
whole
Imposing costs on the private sector affects
everyone via reduced economic activity (firms
don't build or build elsewhere), job loss (or
reduced growth), and the resulting reduction in
tax revenue and thus social services.
Retrofitting California Hospitals
Following hospital collapses in 1971 San Fernando
earthquake, California required seismic retrofits
Law assumed retrofits would be cheap
In fact, retrofit cost close to that of new buildings
At least $24 B needed !
No funding available
After 37 years, slow progress
Deadlines already extended
Won’t be done before at least 2030
20% of Californians - 6.6 M people have no health insurance
1) RECOGNIZE THAT ALTHOUGH SCIENCE AND
ENGINEERING ARE IMPORTANT, ISSUES ARE
ULTIMATELY ECONOMIC & SOCIETAL
There are no unique or correct strategies, so society has to make
tough choices.
A few % cost increase may decide whether a building is built or
renovated, or whether other worthy programs are conducted.
Our goal is to use what we know about earthquake hazards and
recurrence to help society decide how much to accept in additional
costs to reduce both the direct and indirect costs of future earthquakes.
This involves detailed analysis, which we don't have yet, of the costs
and benefits of various policies.
The strategy chosen shouldn't be a technocratic decision to be imposed
from above, but one made openly through the democratic process on
the community level - where the costs and benefits of the policy accrue.
SHOULD MEMPHIS BUILDINGS MEET CALIFORNIA
STANDARD?
New building code IBC 2000, urged by USGS/FEMA, would raise to
California level (~ UBC 4)
Essentially no analysis of costs & benefits of new code
Initial estimates suggest cost likely to exceed benefits
Detailed study needed to see if justified
Memphis Seismic
Hazard Abatement
40
Code Year
Code
Year
'2000
60
17.5
'94
110
25
20
'88
15
'84
10 (Not Req'd by code)
J. Tomasello
Pre 84 0
S.E. Shelby
Ctr Shelby
N.W. Shelby
0
20
40
60
80
100
120
Level of Hazard Abatement
in terms of PGA (%g)
INITIAL BENEFIT/COST ESTIMATES: MEMPHIS
I: Present value: FEMA estimate of annual
earthquake loss for Memphis area ($17 million/yr),
only part of which would be eliminated by new
code
~ 1% of annual construction costs ($2 B)
Seismic mitigation meeting new code might cost
more
INITIAL BENEFIT/COST ESTIMATES: MEMPHIS
II: Life-of-building: FEMA estimates annual
earthquake loss ratio (AELR), ratio of annualized
earthquake loss to the replacement cost of all
buildings in the area = 4 x 10-4.
Equivalent to average annual loss in building value,
so in 50 yr building loses 2% of value.
If loss halved by new code, than over 50 yr new code
saves 1% of building value.
If seismic mitigation cost increase for new code
>> 1%, probably wouldn't make sense.
FEMA BUILDING RISK COMPARISON
Uses Frankel et al. map hazard (high end of possible values) to
estimate annual earthquake loss ratio (AELR), ratio of annualized
earthquake loss to the replacement cost of all buildings in the area.
Memphis and St. Louis values ~1/5 - 1/10 of those for San Francisco
and Los Angeles. Memphis 32nd among major U.S. cities; St. Louis
34th.
Since ratios are
equivalent to the
fractional risk of
building damage,
estimate predicts
NMSZ buildings 510 times less
likely to be
damaged during
their lives than
ones in California.
Searer et
al, 2005
2) THOUGHTFULLY ADDRESS LIFE SAFETY
ISSUES
The issue is how to balance this benefit with alternative
uses of resources (flu shots, defibrillators, highway
upgrades, etc.) that might save more lives for less.
Estimated cost to save life (in U.S.) varies in other
applications:
~$50 K highway improvements
~$100 K medical screening
~$5 M auto tire pressure sensors
Different strategies are likely to make sense in different
areas both within the U.S. and elsewhere, depending on
the earthquake risk, current building codes, and
alternative demands for resources.
3) EXPLAIN
UNCERTAINTIES
Individuals and society
are used to making
decisions in the
presence of uncertainty:
we buy life insurance
and decide how much to
spend on safety features
in cars.
Business and political
leaders routinely
consider risks in
deciding whether and
how to invest large
sums.
One way to present uncertainty - show hazard for
different assumed magnitudes & ground motion
models
Stein et al, 2012
Newman et
al, 2001
4) AVOID OVERESTIMATING HAZARD
Estimates biased toward high ("conservative") values
distort policy decisions by favoring seismic safety over
other resource uses.
Don’t want poor education in earthquake-safe schools,
or to turn away patients from earthquake-safe hospitals
Need careful balance
5) HAZARD ASSESSMENTS AND MITIGATION
POLICIES SHOULD UNDERGO DISINTERESTED
PEER REVIEW
Best results come when review process is at
arm's length.
Hazard estimates prepared by one organization
should be reviewed by a different one.
This would ensure that crucial economic and
societal issues are fully explored before a
decision is made.
6) TAKE THE TIME TO GET THINGS RIGHT
Because major earthquakes in a given area are infrequent
on human timescale, we generally have time to formulate
strategy carefully (no need to rush to the wrong answer)
Time can also help on both the cost and benefit sides.
As older buildings are replaced by ones meeting newer
standards, a community's overall earthquake resistance
increases.
Similarly, even where retrofitting structures isn't costeffective, higher standards for new ones may be.
Technological advances can make additional mitigation
cheaper and hence more cost-effective.
Eventually, if our understanding of earthquake
probabilities becomes sufficient to confidently
identify how large earthquake probabilities vary
with time, construction standards could be
adjusted accordingly where appropriate.
Hebden & Stein, 2008
7) DON’T RELY ON
UNFUNDED
MANDATES
Society - who
benefits from more
safety - should
assume cost rather
than impose cost
on property
owners who don’t
benefits (can’t
charge higher rent)
and thus resist
Can then decide if
worthwhile - is
public willing to
pay higher taxes
for safety?
8) BENEFIT FROM RESEARCH ON OTHER ISSUES
WHERE SOCIETY FORMULATES HAZARD MITIGATION
STRATEGIES IN SITUATIONS WITH LARGE
UNCERTAINTIES
There's increasing recognition of the need to make
policy more rationally. The challenge, summarized by a
joint project of Brookings Institution and American
Enterprise Institute is that
“The direct costs of federal environmental, health, and safety
regulations are probably on the order of $200 billion annually,
or about the size of all federal domestic, nondefense
discretionary spending. The benefits of those regulations are
even less certain. Evidence suggests that some recent
regulations would pass a benefit-cost test while others would
not.”
Using seismology, engineering,
economics and policy in an
integrated approach to hazards
mitigation will best for society
We will do better as we learn
more about earthquakes and their
effects in different areas