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A commentary by William Burton of Ben Lomond
Why is earthquake design needed for us in Ben Lomond?
The Ben Lomond Fire House is 68 years old. It was built before much was known about how to protect buildings from earthquake forces. Since that time, civil engineers have studied structures worldwide, right after a large earthquake, to better understand why the building failed.
Each time a large earthquake is reported, teams of specialists fly to the location to study the damaged structures before any cleanup has begun and the evidence is removed. This has been going on more than 50 years. A lot has been learned during that time.
The study of earthquake damage is difficult, as there are so many variables. Here are a few the major ones:
A. The below-ground structure is not the same any place you study it. For instance, is it hard rock? What types of soils are there, and how deep down? Is it sand, or alluvial fills, subject to liquefaction? (That means turning into a jelly during an earthquake — what happened to the Marina District in San Francisco and to downtown Santa Cruz.)
B. Where in the Earth did the quake slippage take place? How deep down?
C. How strong was the energy release? The Richter number?
D. How far away from your building was the epicenter?
E. And the biggest one: How well was your building engineered to resist the energy release of the earthquake?
A lot has been learned and put into building practice since 1940.
National and local building codes have been changed as a result of the constantly improved knowledge of earthquake-resistant design. Many of the code changes are simple additions at low cost if incorporated at the time of the construction, but, unfortunately, very difficult and expensive if added to existing structures, often requiring major demolition.
We in Ben Lomond live on the “Ring of Fire,” the large circle of earthquake-prone locations around the Pacific Ocean — Japan, the Philippines, Chile and the west coast of South America, Mexico, LA, San Francisco, Washington and Alaska.
Most of the very large earthquakes have occurred and will occur here. This is where the large tectonic plates move against each other, causing the large energy releases — earthquake faults.
San Francisco’s 1906 earthquake was 8.3 on the Richter scale.
Anchorage, Alaska’s 1964 earthquake was 8.4.
Imperial Valley’s 1940 quake was 8.1.
The 1964 Nilgata, Japan, earthquake was also over an 8.
In 1976, Tianjin and Tangshan, port cities on the Pacific coast of China, had an earthquake of more than 8.
Please note that our local 1989 quake was only about a 7, which is less than one-tenth the power of the 1906 San Francisco quake — so we have not experienced a BIG earthquake in our lifetime!
The destructive power of a Richter 8, being 10 times the power of a 7, causes about 100 to 1,000 times the amount of damage, because the power is much too great for most buildings to resist.
The next very large earthquake near San Francisco is estimated by experts at between 75 to 150 years after the last. It has now been more than 100 years. Thus, we are now in the range of a likely return of a very large quake sometime in the remaining 50 years! It could be soon, or not for several decades. But it will come. We need to be prepared.
Knowing just how strong to build a structure is more a judgment figure than a science. However, a large number of experts have gathered a lot of data and experience in coming up with very likely probabilities, to which we need to pay attention. A lot of lives and property values are at stake.
“Code level” design (Richter 8) has been nationally determined as the degree of protection it is reasonable and economically feasible to require. However, the law does require that all hospitals, schools, major public assembly buildings — and fire houses — be designed 1½ times stronger than code level. The public needs to be protected.
That is a major reason why our new fire house will cost $10 million.
(Note: If this construction is delayed a year or two, the costs will greatly increase due to inflation in materials and oil prices and the falling value of the dollar.)
But there are many advantages in rebuilding. If we just tried to install all the required code-level improvements to the building, the cost turns out to be almost exactly the same.
Just making the required code-level changes would not gain any of the advantages of improved design, training facilities for volunteer firefighters, better communications, better organization and layout for all the new types of firefighter protection equipment developed in the past 50-plus years. Neither would it include the long list of organizational ideas suggested by our own firefighters in two large design meetings with the architect in the past two months. Excellent improved floor plans have resulted.
There have been two years of study: local contractors’ advice and study of the fire house, expert consultants’ input, investigations by our fire board, travel to newly built fire houses to find out what was learned and what not to do. There has been much volunteer input, as well.
This has been a long and thoughtful process by many.
We will get our money’s worth!
There will be improved service to Ben Lomond, even in a major disaster, when we all will need it the most.
William Burton is a retired civil engineer, life member of the American Society of Civil Engineers, retired lieutenant commander, Civil Engineer Corps, U.S. Navy, and member of the Yes on S Citizens Advisory Committee.
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