Although animal and birds calls are evident as early warn, yet an unusual silence in the atmosphere were reported by general public just before Kashmir earthquake 2005 in Pakistan. Perhaps it opens new causes.
The problem is the same in most earthquake precursor candidates. It is to prove the relation beween the particular “ precursor” and the earthquake phenomenon, an other major problem is, one can never be sure that for the next earthquake the previous precursor will manifest itself again.
@ Ijaz Ahmad. My paper on the subject, published at RG, touches upon that. Science has not helped in predicting the timing of an earthquake; and, so far, it is an exercise in futility. The short-term precursors are the safest bet. May they be "unscientific" but some of them like rise in water level in wells, increased temperature in agricultural fields, sprouting muddy water springs on higher ground etc. etc are for sure scientific; though subtle, and require vigilant monitoring, as proposed in the paper. Just an opinion.