The shock was felt over an area of 120,000 km2 , from Chico in the north to Monterey in the south , and to Carson City in western Nevada . compared the isoseismal map from the event to those of earthquakes that occurred during the instrumental period to resolve the magnitude . The intensity VI isoseismals for the 1969 Santa Rosa and 1984 Morgan Hill earthquakes were markedly smaller ; only the 1989 Loma Prieta earthquake covered a larger area than that of the 1898 event . The isoseismals for intensity V , VII , and VIII were also compared for additional calibration , and 6.7 was presented as the magnitude of the event , which was presumed to have occurred on the southern Rogers Creek Fault . This estimate was later reduced to M6 .4 in
1989 Loma Prieta earthquake
1989 Loma Prieta earthquake
1898 Mare Island earthquake