The characteristics of variation in inhomogeneity of temporal-spatial distribution of short to imminent precursors before strong earthquakes

C _v is used in this paper to describe the variation in inhomogeneity of spatial and temporal distribution of precursors. The inhomogeneous variation in the spatial and temporal distribution of the anomalies in water radon and electromagnetic waves before M _s≈6 earthquakes in northern North China is analyzed in detail. Results show that before a moderate to strong earthquake, the distribution of anomalies in water radon and electromagnetic waves changes inhomogeneously, i.e., C _v increases significantly. The inhomogeneity in spatial distribution of short-to-imminent precursors increases before a strong earthquake, which may relates to the enhancement of crustal strain field. The research will not only help us to know more about the process of seismogeny and to improve practical earthquake prediction, but also blaze a new way to do earthquake prediction with present precursor data. This work was sponsored by the Key Project 95-07-435 during Ninth “Five-Year” Plan from China Seismological Bureau.