Fig. 2.(a) The Parkfield recurrences1 represents the failure stress of the fault. Most characteristic earthquakes occur at s1; the 1934 shock occurred at s2. A constant loading rate of 2.8 cm per year and a coseismic slip of 60 cm for the Parkfield earthquake sequences in 1881, 1901,1922,1934, and 1966 are assumed (56). (b) Series of earthquake sequences at Parkfield since 1850 [after (5)], The line represents the linear regression of the time of the sequence obtained without the 1934 sequence, The anticipated time of the seventh (that is, the next) Parkfield sequence for the regression is January 1988. (c) Shocks of ML greater than 4 since 1930 have tended to occur when the stress exceeds s2 .