Building officials consider lessons learned from November quake
It’s been six months since the Nov. 30 earthquake, but municipal building official Bob Doehl said there are still plenty of lessons to be learned, including some things that have been a bit surprising, like the amount of damage in Chugiak and Eagle River versus Anchorage.
“Anecdotally, we knew the numbers were higher, so I’m surprised at how much higher it is,” said Doehl.
For homes built after 1990, the percentage of reported damage in Eagle River and Chugiak was five times higher than in Anchorage. Nearly 4% of the homes in Anchorage had earthquake damage, compared to nearly 20% in more northern communities.
Doehl said that comes despite the fact that ground sensors did not show the earthquake was any more severe in those northern communities.
“We’ve partnered with [the Federal Emergency Management Agency] and the state of Alaska to continue analyzing the data to see what we can learn there in terms of why the reported damage rate is five times higher in Eagle River and Chugiak than it is in the traditional city of Anchorage boundaries,” he said.
One reason may be because the city’s building codes aren’t enforced in Chugiak and Eagle River. Those communities, along with a small part of the Anchorage Hillside, are not part of what’s called the Building Safety Service Area, meaning it’s not required to have a municipal inspection to make sure homes and businesses are properly built. Doehl said they are finding some structures that clearly weren’t.
“We’ve encountered plans that did not have the seismic-required components that our codes require for building inside the Municipality of Anchorage,” said Doehl. “In at least one other case, we found a large structure where the plans called for certain seismic features to make the building more resilient, and they were not added during construction.”
Doehl said the administration can’t force residents in Eagle River and Chugiak to become part of the BSSA. They would have to vote to enter it and agree to pay for it. So far, they have not done so.
Another thing Doehl found a bit surprising was ground failure that occurred in parts of Sand Lake in Anchorage. According to an Anchorage seismic map based on research after the 1964 earthquake, that area of town is designated a “yellow zone” where the ground is considered relatively safe.
“The number, particularly of the red soil failures, the red-tagged buildings in that area, isn’t something you would predict. You would expect those to be more prone to an area of higher risk.”
Doehl said investigations are ongoing, to try and learn more.
“This is kind of level one of an investigation we are doing to try to compare that with soil movement in different areas, different construction, different codes, to look at what we can do better in the future in terms of making our buildings better and safer for all.”
He said, at this point, that research is still a work in progress.
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