About a hundred miles north of San Francisco is Point Arena and its lighthouse. The current lighthouse was built after the previous one was destroyed in the 1906 earthquake. Point Arena is along the same San Andreas fault as San Francisco. A keeper was on duty at the time of the quake and he reported that the lighthouse first swung twelve feet one-way and then twelve feet back the other way. The keeper survived the quake with only minor scrapes.
The reason for his survival was the steel spiral staircase that bended, but did not break during the quake. The original lighthouse had to be rebuilt, but the stairs were reusable. We toured the lighthouse and its top is now an empty room. At the time there was huge Fresnel up there that is now on display in the museum. The lens turned, because it rode on a table that was floating in a vat of mercury. All that weight at the top makes the lightkeepers survival even more amazing.
I bicycled in the park today. I was hardly quicksilver fast. I think that I was passed by about half-a-dozen other cyclists. Still, I was out there on the bike.