Hello VIvek,

There is no dedicated topic for Earthquake or Earthquake alarm in Physics class 12th. There is some portion about Earth in the Magnetism chapter. You may check CBSE class 12th Physics syllabus by heading to the official website of CBSE(Link below):

http://cbseacademic.nic.in/web_material/CurriculumMain20/SrSecondary/Physics.pdf

There is a chapter of Gravitaition in Class 11th Physics. You may search in that chapter.

Hope this helps