[EAS] WEA used in NYC bombings

[Alan Kline]

On 9/25/2016 2:54 PM, John Willkie wrote:

> We have data points that we can apply against this concern.  Transit has very low ridership numbers in California, with the Bay Area leading the pack.  In the 1989 Loma Prieta quack, which I "experienced" in Washington, DC on live TV, there were several BART derailments, but I don't remember any loss of life or serious injuries underground or even above ground.  There were serious concerns about passengers trapped in underwater tunnels, and BART already had automatic train-stop mechanisms which more or less went into effect.  BART is a third rail system.  There would be zero advantage to sending out alerts in that scenario, because the epicenter is too close to the population center; the waves will travel and do damage before electrons have had a chance to put on their socks.

As a blanket statement, that's incorrect. The largest cities, 
particularly the LA, SF and San Diego areas, have quite healthy transit 
ridership. In other areas, particularly in suburban areas and smaller 
cities, ridership is less--but that's common across the country.

> The Cypress structure had been built upon alluvial fill, and even at the time, it was suspected that areas over alluvial fill suffered worse in earthquakes than areas built upon rock.  The term is "liquefaction" of terra firma.  I think that is a perfect and cautionary term.  There were some building collapses in the Loma Prieta quake in the Mission District of San Francisco.

I don't think the Cypress was built on fill--it was far enough inland 
and in long-established neighborhoods. It was simply designed in the 
1950's, when that kind of structure was both new and not engineered for 
earthquakes as they would be now. The Cypress wasn't the only 
double-deck freeway structure which suffered significant damage; it just 
happened to be the one with the loss of life.

Finally, while there may have been damage in the Mission district, the 
building collapses were in the *Marina* district on the northern 
waterfront. The Marina *was* built on fill.

ak