NYC officials took 24 minutes to alert New Yorkers about earthquake
gothamist.com
gothamist.com
Also, I live on the coast where earthquakes are common, we have that advanced warning system mentioned in the article - there have been more misfires than valid warnings so far.
I guess the idea is if you didn't notice the initial quake then you should be warned there might be a follow up.
If you are manhatten, I suspect the tremor is probably not dissimilar to the vibrations felt when the Towers fell.
So knowing it’s a natural earthquake and not… something worse… is useful when something worse has already happened in recent memory.