What is the current forecast for a major Hayward fault quake?
A. The 1996 NCEP (Northern California Earthquake Probability) working group came up with a 210-yr recurrence time for major earthquakes on both segments (northern and southern Hayward fault) which is the same as the best estimate of recurrence of Williams [1993] for the southern Hayward Fault based on trenching data at Tule Pond [TP] in Fremont. The NCEP did not know how the magnitude and length of the 1868 event compares to earlier events, because the paleoseismic record is not adequate to compare the size of events. If the entire 86-km length ruptured with 1.9 m slip, it would be Mw 7.1. Adding the southeastern extension would make it 112 km and Mw 7.2. The NCEP scenario involving the entire length is ranked equally likely. Petersen and others [1996a, b] chose to retain the 1.5 m slip and 167 yr recurrence time adopted by WGCEP [1990] for two Hayward fault segments, that also yields Mw 6.9 and an identical rate of moment release, but they felt it was a more cautious assumption given
