For a particle to survive tens of thousands of miles through dense rock and come out the other side and register with the detector makes me ask:
1. Just how many particles are discharged by the event and/or passing through the earth at the time of the reading?
2. What's so special about the composition of the detector that it's able to pick up particles that have not been stopped by the entirety of the Earth?
I'm not asking these questions dismissively. I'm keen to learn. I'm also aware I'm making many assumptions here. Please question or contradict all of my assumptions if possible.
What surprises me about this article is that catching neutrinos tunneling up through the earth is considered surprising. I had thought that neutrino detectors generally caught just as many neutrinos from below as from above; the earth is essentially transparent to them.
To answer your question #2: the detector is no better than anything else at stopping neutrinos (just as detecting their stoppage), but--even though the chance of any given neutrino stopping anywhere in the earth is almost nil--there are so very very many of them that the probabilities add up to a decent number impacting within the detector.
The surprising part is if other particles are observed coming in from below.
This is what I thought too, but apparently, the Earth is opaque to neutrinos at energies above 1 PeV. (That is, the Standard Model predicts so.)
The article states "The particles had energies that were high enough for the Standard Model to prohibit that kind of careless disregard for matter". Although I think it could have been explained better, explanation is there.
With enough particles, and enough time, it'll happen eventually at every point.