Abstract: The research on the quiescent fo reshock is of great theo retical and practical signi ficance. Through statistical analysis, it is demonstrated that the precursory waverelated to the quiescent foreshock is more universal than the fo reshocks. The precursory waveoccurs seven days earlier than the main shock, and it has ev er been observed befo reno t only the moderate but a lso strong earthquakes, which show sthat the mi ld slow fracture truly exists before large brit tle f racture. In na ture, it is common. According to the location tests applying the precursory waves before Bohai earthquake in 1969 and Tangshan ea rthquake in 1976, the approximate location is possible based o n go od o bserv atio n data. The precurso ry wave comes closely to the focus of strongear thquakes. The temporal and spa tial features mo tioned above show that the precursory waves related to quiescent fo reshock can be used fo rea rthquake prediction, especially they can provide important precursory information.

Key words: Precursory wave, Quiescent fore-shock, Slow fractures, Universality, Earthquake prediction