I recently wrote about two new downtown highrises ("Genuflecting to the High Rises"), and the article prompted this interesting email from a San Francisco reader, Charles M. Marsteller, who identifies himself as formerly with Seismic Safety in that city. His worry is about falling glass, in earthquake-prone cities such as Seattle, particularly when they are almost entirely glass-clad, as the project at Fifth and Columbia would be: I note with interest your article on Slender Glass Towers. They too are coming to San Francisco. Make no mistake that economics is the engine that drives this phenomenon and not the need for eco-friendly development. Why do I say this? No one seems to mention public safety. Why public safety? Glass breaks in seismic zones, and I can assure you that a major quake will cause the glass to shatter and sheer into the streets. The effect, albeit very brief, will be the effect of a waterfall cascading off the size of these buildings, burying the streets below in 20 feet of glass. This is what the engineers here advise. Yet, no one discusses this aspect of SGTs. I am not opposed to tall buildings per se; I do question the wisdom of constructing them in certain areas like barrier islands (hurricanes) and seismic zones. You Seattle experts: should we be worried? And is this the kind of issue that was reviewed as the Fifth and Columbia building went through City Hall approval?