On the use of the parameter τ for long-term and medium-term earthquake prediction

Results of the use of the parameter τ as a precursor for long-term and medium-term earthquake prediction are considered using traveltimes of P- and S-waves from local earthquakes within a fixed area as the initial data. The parameters studied are Δτ which characterizes fluctuation of this parameter with respect to the long-term mean values, ξτ which denotes variations in the dispersion of Δτ in units of mean square deviation (στ) over a period of time Δt, and F(σgt) which is a function of the dispersion of the parameter Δτ. The latter characterizes rapid variations in the parameter over time. The data analyzed are the spatial and temporal fluctuations of the parameter Σ(Δτij), ξτ. Zones are selected in which during the period of time Δτ positive and negative anomalies of the parameter Σ(Δτij) and ξτ were accumulated. The significant anomalies are those where ¦ξτ¦⩾ 3. The extent of the preparedness of the anomalous zone is determined from the plot ξτ = F1, (T) and the variation in the curve of the real time function F(στ) = F2(t). The time intervals where the curve rises above the experimentally determined level are considered as intervals in which an alarm begins.