[Sundae]

If I was there with someone else I'd be talktalktalk too.
Are we in the safest place?
Hang on, does this mean there is an earthquake going on, I can't feel it?
Should we head off or do you think this is a test [yes, stupid response, but I might], the building doesn't appear to be shaking?

If I was on my mobile I would carry on talking:
Mum, are you okay? I'm in this weird place and there's a huge ball that's just started moving! It can't mean what I think it does!

My assumption is that if there were any normal indications of an earthquke these people would have exhibited all the screaming and running you hoped to see.
The fact that they didn't, and only the ball responded, meant that it was reacting to tremors that could have damaged the building, but weren't destroying anything at that point.

I might be wrong, no idea where Teipei lies in regards to the epicentre.
But it seems unlikely that even "tourists" would stand and talk if they felt the building shake on its foundations.