Is Chaturdashi Shradh the same as Sarvapitru Amavasya?

No, they are different. Chaturdashi Shradh (Ghata Chaturdashi) on October 9 is specifically for ancestors who died unnatural deaths. Sarva Pitru Amavasya on October 10 is the universal day for ALL ancestors, regardless of their manner of death. Some families perform both — Chaturdashi for the specific akal mrityu ancestor, and Amavasya for the broader family line.