Researching the distribution of small earthquakes with M_L≥2, we have discovered that before the Luhuo earthquake with magnitude 7.9 on Feb. 6, 1973, the Liyang earthquake of M=5.5 on April 22, 1974 and the Longling earthquake of M=7.3, 7.4 on May 29, 1976, during about three months, the small shocks with M_L≥2 occurred one by one along a circle migrating turn left(for the Luhuo earthquake of M=7.9 and the Longling earthquake of M=7.3, 7.4) or right(for the Liyang earthquake of M=5.5). The Liyang and Longling main shocks happened inter or near their circles, but the Luhuo main shock happened outside its circle. The Luhuo main shock and its small earthquakes circle located in the same tectonic zone.
According to that the sum of square roots of energy for small earthquakes at circles has partly increased quickly with time nonlinearly, we may conside it as a short-term foreshock.