. "1928 earthquakes" . . "Chirpan earthquake" . . . "7.0 magnitude earthquake" . . "great earthquake in 1928" . "earthquake on 18 April 1928" . . . "earthquake occurs in Chirpan" . "1928 Chirpan\u2013Plovdiv earthquakes" . . . . . . ":1928 Chirpan\u2013Plovdiv earthquakes" . . . . "127" . . . "1928 Chirpan\u2013Plovdiv earthquakes" . "sequence of two earthquakes" . . .