 The mainshock generated a small tsunami that was recorded by the National Oceanic and Atmospheric Administration 's sea level gauge stations on the coasts of northern California , Oregon , and Hawaii . The series of waves first came ashore at the North Spit station in Eureka after a 26 @-@ minute travel time , but the largest surges were seen just to the north at Crescent City and arrived close to low tide , a condition that would have lowered the risk had the surges had a destructive capacity . The first packet of energy reached that location in 47 minutes and had a maximum wave height of 35 cm ( 14 in ) , and a second , larger packet arrived later with a maximum amplitude of 53 cm ( 21 in ) . The waves were also detected to the south in the interior of San Francisco Bay at Alameda , but with a considerable delay ( 135 minutes after the mainshock ) , due to the shallow waters of the bay and the shelf surrounding the bay 's entrance . The speed a tsunami travels is directly related to the depth of the water in which it is traversing . The tsunami was detected farther to the south in Monterey , for example , after just a 64 @-@ minute travel time , due to the deeper offshore waters and those in the Monterey Bay . 
