Hi All. Its not often that I apologize to anyone for being wrong, but in this case I think one is due. About 6 months ago Petra told me about a dream she had. The dream was about the San Gregorio fault and a tsunami. I told her I didn’t think that fault was capable of causing a tsunami, but she stuck to her guns and would not except my answer.

In doing some follow up research for her I came across this article from a newspaper. “1859 24 September - Slight shock at Half Moon Bay; waters of the bay receded 15 feet and returned suddenly; intensity IV. 18 October - Shock at San Francisco; at Half Moon Bay the water left for several seconds”.
My reasons for thinking that this was caused by the San Gregorio fault can be found in this report. “The San Gregorio fault, extends on land for about 27 kilometers from Point Ano Nuevo on the south to San Gregorio on the north. It trends out to sea at both Point Ano Nuevo and San Gregorio, and its position on the continental shelf has been studied by the U.S. Geological Survey using seismic profiling equipment.
Preliminary analysis of the U.S. Geological Survey data indicates a fault zone, rather than a single fault, that extends along the coast in the offshore area from Monterey to Half Moon Bay. Green, [13] in a U.S. Geological Survey open-file report on southern Monterey Bay, designated a zone of faulting approximately 5 miles wide trending N 50°W in the southern portion of the bay. More recently this zone has been traced from Point Ano Nuevo, where the San Gregorio fault zone trends out to sea, southeast-ward along the coast and across Monterey Bay where strands of it probably come ashore again on the Monterey peninsula [12]
The San Gregorio fault, which trends about N 20°W, may be related to the Seal Cove fault which is well exposed at Moss Beach, just north of Half Moon Bay. According to Glen, [11] the Seal Cove fault cuts the cliff face at Moss Beach where it brings horizontal overlying Pleistocene terrace sands into clearly exposed fault contact with the mid-Pliocene Merced Formation. This site is one of extensive recent land sliding and sea cliff erosion. A ban on any new construction in the immediate area was recently imposed (1972) by the San Mateo County Board of Supervisors”.
I apologies to you Petra for telling you that you were wrong. I’m the one who is wrong. Take Care…Don in creepy town.

• San Gregorio fault