 Now let's look at the same record section, but a different station. I'm going to look at the station PAYG, which is almost 180 degrees away from the earthquake. I've drawn it down here and what you'll notice right away is that the number of arrivals are fewer. There's no direct P wave and there's no direct S wave. And the reason for that is that the core gets in the way. Remember on our earlier station that P waves and S waves take kind of a curving path through the mantle that I'm showing you right now with the mouse. If you're farther away than about 104 degrees, then these waves will bounce off the core or they'll be refracted within the core if P waves, and so you won't get a direct arrival. In fact, this is how the core was discovered. So what are the arrivals that are coming into the station? Well, the first one is this this one here and that one is labeled PKIKP. So what that wave does is it's a P wave in the mouth. It comes down here. It gets refracted in the outer core and the inner core and back through the outer core, back out through the mantle to the station. So the path is called a P wave when it's in the mantle and then a P wave in the outer core is called K. I don't know why that is. In the inner core, it's called I and then it goes back out it's K and then it is P for this last part of the path. So the whole thing together is called PKIKP. So the next arriving wave is the double P and that's our old friend. We know how that works, right? It just goes through the mantle and it bounces and goes to the station. So each of these paths is a P wave in the mantle. It's called PP. The last arriving wave is the double S, which follows the same path as double P except shear waves are slower, so it takes it longer to get there.