Seismic Sphere

Real-time propagation from IASP91 travel times — P reaches 90° in ~13 min, S ~24 min, surface waves ~45 min. Rings dim with distance (geometric spreading + attenuation) and dissolve near their magnitude-scaled reach. Big quakes add reflected multiples (PP, SS, SSS); direct S dies off past 103° (liquid outer core); P dims in the 103–143° shadow zone.