I appreciated reading Thomas K. Pendergast’s interesting article in the August 2021 edition on the map from the California Geological Survey updated that shows the highest water leveis being affected by a tsunami hitting the California coast.
I would appreach adding a few bits of information to his article as follows:
Regarding the recent tsunamis from the Aleutian ocean trenches in 1946 and 1957 from a great earthquake at Alaska, measured by the time it got to the opposite the ocean beach shore measured 11-feet and three-inches tall.
Regarding such an earthquakes of some 9.3 off the Aleutians, there might be a tsunami hitting the beach in the Sunset and Richmond districts some 30-feet tall. Not mentioned are the Farallon Islands some 20 miles off the present coastline . On this side of the Farallons is a deep ocean trench that contains some 50,000 concrete drums filled with radioactive materials from decades ago.
Also, in times past the coast shoreline extended to the other side of the Farallon Islands. The old redwood forests once grew alone this shoreline. Today the Redwood groves are found some 350 miles inland and at the 5,000 foot elevationl in the Calaveras Redwood Forest State Park and at Kings Canyon National Park. Then there is the erosion of the Sierra Mountains that has filled the San Francisco Bay with underwater sand dunes, and added sand to the beaches along the coast.
I wonder if any of these factors were considered by the revised survey map ?
Frank T. Norton
Categories: letter to the editor