5 ms·
It says: "The echoes appear once to several times per day, from several weeks to a few days before the earthquake occurrence and do not appear on other time."
by psKama 3y ago
It says:
"The echoes appear once to several times per day, from several weeks to a few days before the earthquake occurrence and do not appear on other time."
- EdwardDiego 3y agoBut have they been looking for them at other times though?