Tuesday, March 2, 2010

Chilean Quake and Building Codes

We certainly are getting a reintroduction to earthquake risk.  This continues to bring home the direct economic benefits of strong building codes in danger areas and even elsewhere.  The cost of imposing resistant codes for new buildings in even those deemed as low risk areas is not prohibitive.  The benefit is clearly hugely economic if a disaster strikes.    The cost is simply worked into the cost of all building and is generally not significant enough to impede building and may provide a gain in terms of insurance costs.

The Pacific Northwest is on the ring of fire and the critical slip plane is out to sea off the coast.  Vancouver Island and the Olympic peninsula largely protect population centers from a major quake plausibly as a shock absorber.  Other fault structures exist in the populated and sunken valley now called the Salish Sea, but these are not likely to be as violent and are apparently deep.

California is not so protected and the major fault is on land in the population centers.  Yet serious quakes have been ridden through with modern building technology proving its worth.

I know that ground zero of a maximum quake is impossible to resist.  Yet is appears that good sense embodied in good codes can massively reduce exposure.  That is a great investment that the next century will certainly see implemented most everywhere.  It should include everywhere simply because the crust has plenty of hidden faults and we do not know if risk even exists until it is triggered.

In particular, the east coast of North America does have areas of interest that cannot be discounted.  Modern codes would protect from the likeliest risk type of mid range quakes.

Otherwise we have the New Madrid on the Mississippi and the Lisbon quake as nasty reminders of possibilities.

I think that this next generation in particular needs to go the extra mile to change all building codes.  A cost shared by all disappears.

Building codes, quake locations key to Chile-Haiti tolls

by Staff Writers

Washington (AFP) Feb 28, 2010

A combination of geography, comparative wealth and disaster readiness is why
Chile's massive earthquake won't come close to Haiti's calamitous toll even though it was much stronger, experts say.

Saturday's 8.8-magnitude quake, the seventh most powerful on record, struck central Chile some 325 kilometers (200 miles) south of the capital Santiago and 115 kilometers north-northeast of the second city of Concepcion.

So far the death toll is over 700 and rising, although President Michelle Bachelet in announcing the newest figures warned the toll would still rise with hundreds of people remaining missing.

Haiti, the poorest country in the Americas, was struck on January 12 with a 7.0-magnitude quake -- hundreds of times weaker than the one in Chile -- but the epicenter was just 24 kilometers from the overflowing capital Port-au-Prince.

The most recent estimates put the toll there at over 220,000 dead, with President Rene Preval warning the final figure could reach 300,000, making it the worst natural disaster in modern history.

Seismically speaking, comparisons between the tremors are irrelevant because the situations at their fault lines are so different, experts said.

But put in geographic context, the two earthquakes show how events of different strengths at varying distances from densely urban areas can have vastly different outcomes.

The epicenter of Chile's earthquake was 35 kilometers below the ocean floor, with the seabed absorbing a large portion of the shock -- although it did prompt a tsunami that threatened the entire Pacific region.

At a depth of only 10 kilometers, it was the Haiti quake's shallowness that proved so catastrophic, according to experts.

This proximity to the surface amplified the vibrations and caused far more damage to densely-packed urban areas near the Haitian capital.

The epicenter of Chile's quake was almost five times farther away from the second city of Concepcion than Port-au-Prince was to Haiti's quake.

"The difference between the Chile quake and Haiti was not only that the epicenter of the Haiti quake was closer... but also that Chile was better prepared than Haiti for a quake of this magnitude and intensity," Roger Bilham, a geology expert at the University of Colorado, told AFP.

Because Chileans live on an active fault line, with the experience of the largest recorded earthquake in history, the South American country was far more ready for a major seismic event than Haiti -- relatively unused to such quakes.

Since May 1960's record 9.5-magnitude quake that left over 2,000 dead, successive Chilean governments have ensured sensible moves towards robust construction standards.

While Saturday's quake still constitutes a major disaster, Chile's widespread adoption and enforcement of modern, seismic-resistant building practices "has mitigated the potential for devastation," according to US risk modelling firm EQECAT.

Sustainable building group Architecture for Humanity noted the differences between construction in the two countries by saying "stronger building codes and location/depth of the epicenter" resulted in less damage in South America.

Following Haiti's quake, engineering experts blamed lax building standards in the Caribbean nation for having exacerbated the disaster.

When the quake struck, apartment blocks and smaller homes simply crumbled to the ground, trapping thousands under rubble and burying thousands more alive.

"The quality of construction in Haiti, even in buildings that are supposedly engineered construction, is not good at all," Farzad Naeim, president of the board of directors of the Earthquake Engineering Research Institute (EERI), told AFP at the time.

From photographs he saw of the devastation in Haiti, Naeim said many of the larger buildings were built using non-ductile concrete.

This was described in a report presented at the World Conference on Earthquake Engineering in Beijing in 2008 as "arguably... the greatest seismic life safety hazard in many urban centers worldwide because of the collapse potential."

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