Below is the text of an editorial written by Prof. John G. Anderson
at the request of the local newspaper, the Reno Gazette Journal. It
ran on the front page of the Business section, on Sunday, Jan 25,
1998, and altogether they gave it about a quarter of a page. Next
to it, their reporter Mike Henderson wrote an article about the seismic
code, with a large photo of the steel reinforcements from when the
Silver Legacy Casino was being constructed.
Opinion
Exceeding Seismic Code Pays in the Long Run
John G. Anderson
Associate Director
Professor of Geophysics
Seismological Laboratory
University of Nevada, Reno
Past Chairman (1992-1997), Nevada Earthquake Safety Council; Continuing
Member
The Reno - Carson City region has an earthquake
hazard. We have had 13 earthquakes since 1852 with magnitude over
6.0. Among urban areas in the US, only California cities along the
San Andreas fault system have more earthquakes. Whether you are
in Reno, Sparks, Carson City, Gardnerville or Fallon, there is a
fault nearby. More research is needed before we will know if any
of these communities have significantly higher earthquake hazards
than the others. Although most of the large historical earthquakes
were near misses for our communities - like the one south of Gardnerville
in 1994 - sooner or later a fault directly beneath us will rupture.
Then, we can expect shaking as strong as in the Northridge, California
or Kobe, Japan quakes.
It is important for all of us, individuals and organizations, to
have good emergency plans and to follow the checklists of what to
do before an earthquake. But this takes place in the context of
what the community decides to require for earthquake resistance
of its structures. Fortunately, we have adopted a building code
which places the entire region in either zone 4, which has the highest
standards, or zone 3, which still provides significant earthquake
resistance. My opinion is that this region should require zone 4
standards now, and under future codes should choose standards that
exceed the recommendation of the national code-writing agencies.
Unfortunately, there is no simple answer to the question of how
much more it costs to build to zone 4 than to zone 3 standards,
or to the question of how much less it will cost to repair a zone
4 building after a severe earthquake. Both levels seek to assure
life safety, but damage can occur. All we can say is that a structure
built to zone 4 standards will often cost a few percent more, and
will perform better.
Although a rigorous economic assessment of the alternatives is
not available, I have two reasons to favor exceeding the recommendation
of the national code-writing agencies. First, in my judgment, as
the largest scientific uncertainties are solved, our estimates of
the hazard here are more likely to go up than down. The second involves
the trade-off in the code. The agencies that write the codes decide
on the value of more earthquake resistance vs. the value of lower
construction costs. Perhaps this trade-off is about right for an
average city, but our region has some special circumstances: an
economy that depends on our good reputation with potential tourists
worldwide, more severe winters, and greater physical isolation.
Damage hurts us more than an average community. Thus we should face
the earthquake hazard more aggressively.
Here are a few more considerations:
The building code is not the only place to prepare for earthquakes.
For instance, everyone dealing with tourism, from the executive
to the desk clerk, should anticipate what tourists want to know
immediately after the earthquake, where to get the information,
and what they should do for the next few hours. Bracing furniture
against earthquake forces is also very important - if a slot machine
falls on a tourist, he will not agree that the buildings survival
is adequate.
A change in our code makes an increasing difference as time goes
on. Our population is growing fast. At the current pace, in 2050
about nine out of ten buildings will be post 1998.
Building codes aim to assure life safety, but may not prevent damage.
The cost of repair can easily exceed the initial cost of more earthquake
resistance. But the earthquake might not happen soon, in which case
the gamble to decrease the earthquake resistance seems to pay off.
Putting more money into earthquake resistance might mean you have
less to spend on other things. The person who builds a stronger
house ends up with a higher mortgage, so he has a few dollars less
every month for movies or car repairs, except that he might realize
that earthquake insurance is not necessary. For a company, higher
expenses for earthquake resistance could contribute to pressures
to locate elsewhere or raise prices. And the government, when building
bridges, has to either raise taxes a bit or spend less on other
programs.
Setting higher earthquake standards than the national code-writers
recommend thus will take a courageous political act. The seismologists,
geologists and earthquake engineers at UNR and the Nevada Earthquake
Safety Council believe that a community dialogue on appropriate
seismic standards is warranted, and are eager to take part.
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