前言 自从60年代费多托夫提出空区概念以来,有关空区的研究一直受到人们广泛的重视,其研究也在不断深化。1979年茂木建议把空区分为第一类空区和第二类空区。第一类空区是板块消减带上的强震间隙地段,第二类空区是较大地震前震级较小的地震活动空区。陆远忠等人又把第二类空区分为背景空区和孕震空区。背景空区出现在主震 Introduction Since the concept of airspace was proposed by Fittov in 1960s, the research on theirspace has been widely valued by people and the research of it is also deepening. In 1979, Motegi suggested emptying into the first type of empty area and the second type of empty area. The first type of vacant area is the area of ​​strong earthquake clearance on the zone of plate depletion, and the second type of vacant area is the seismic activity vacant area of ​​smaller magnitude before the larger earthquake. Lu Yuanzhong et al. Divided the second type of empty area into a background empty area and a pregnant empty area. Background empty area appears in the main shock