If you live in New York and were on Twitter about an hour ago, something like this probably happened to you: you read a tweet about an earthquake from someone in DC. Then, moments later, you felt it. Here’s why.
Basically, as XKCD explained some time back, the fibre signals that usher your beeps and bops over the internet move at a much, much faster rate than seismic waves. Which means that your quake-related texts, tweets and emails can sprint to their targets faster than the quake itself, assuming your missives are travelling more than 100km.