Mean sea level before and after some great strike-slip earthquakes

Abstract

The annual mean sea levels of all permanently recording tide gauge stations along the North American west coast were inspected for evidence of elevation changes before and after large strike-slip earthquakes. The Yakutat earthquake, 1958 withM=7.9 was preceded by 3±3 cm of uplift 50 km west of the central part of the 400 km rupture. The Sitka earthquake, 1972 withM=7.1, was prceded by 3±3 cm of uplift at a station 40 km east of the center of the 170 km rupture. The Queen Charlotte earthquake, 1949 withM=8.1, was followed by 5±1 cm of subsidence 200 km east of the center of the 300 km rupture. This subsidence is interpreted as dilatance recovery. In this case the uplifted area had a radius of approximately 200 km, and the precursor time may have been about 30 years. The San Francisco earthquake, 1906 withM=8.3, was preceded by no uplift during seven years before it and was followed by no elevation change during 20 years after the event. The measurements were taken at the Presidio 6 km from the fault trace. The Long Beach earthquake, 1933 withM=6.3, was preceded by 1±1 cm of uplift at a point 7.4 km from the 50 km long aftershock zone.