Abstract

Times of Increased Probability, TIPs, of magnitude 6.5 and above for earthquakes in eastern Tien Shan from 1963 through 1987 are identified, retrospectively, by the M8 algorithm. All parameters of the algorithm are fixed to standard values reported previously in 1986. The data available permitted to extend the analysis of regional seismicity for another 13 years compared to the previous study. Three earthquakes of magnitude above 6.5 occurred during the later time; all of them, as well as the fourth, magnitude 7.0 earthquake of 1978 considered previously, fall within the identified TIPs. None of the identified TIPs in the region is a false alarm, i.e. terminated without a large earthquake. Additional tests are performed to check stability of the results. These include modification of the magnitude scale and restriction of the analysis to the period considered previously. The magnitude modification (an {\it a priori} discretization of magnitudes) relates to artificial inhomogeneity of the catalog available which reports mainly integer values of energy class, K, and corresponding magnitudes before the mid-1960s. The results of additional tests ensure the stability and suggest a possibility of a real time earthquake prediction experiment in the region on the basis of the Kazakh Institute of Seismology file of earthquakes.