The angle is 120 degrees. It may work its way around to 180 degrees. The whole planet shakes for several days after a major quake and they seem to resonate according to the natural frequencies as standing waves. 1/3 seems more sustainable than 1/2. Ask your local percussionist.
Unless I’m much mistaken, 65 MYA that was the angle between Chixulub and the Deccan Traps!
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.