Wouldn’t the P and S Shadow zones actually determine the spherical angle transmittable? Look at coordinates for the Chengdu big one(s) and the subsequent 6.x in Iceland. (something like 100 around and 35 up)
I don’t have the math, data or knowledge to calculate it, but it seems like any next quake could fall on a line from the first quake point along the edge of the liquid core to the surface (twin circles)(as the S wave would go)and ‘generally’ across the earth center-solid core for the P wave. (so ~180+/- deg) And if the arriving power found a susceptibility there, a quake would be generated. Which could be smaller or maybe bigger depending on the situation there.
USGS uses tensors and displays them graphically in their world chart. Also, I just discovered that if you click the world map at the pole it will display a hemispherical map and you can see a little easier how the earthquakes form lines along, I assume great circles rather than through the core. If the planet were a uniform sphere the patterns might be easier to develop. I attended Real Analysis class and Complex Analysis class with some of these competitive personnel, quite a challenge.