A zone between 105° and 140° from the epicentre is identified as the shadow zone for P and S waves because-
1. Generally, seismographs located at any distance within 105° from the epicentre, record the arrival of both Pwaves and S-waves.
2. However, the seismographs located beyond 140° from the epicentre; record the arrival of P-waves but not that of Swaves.
3. The shadow zone results from S-waves being stopped entirely by the liquid core and P-waves being bent (refracted) by the liquid core.
