they knew that there was a major earthquake in 1812 (OK, two of them in different places 13 days apart), but they did not know where it was. Then, they noticed some deformed trees standing on the San Andreas fault, and they did tree ring work and found that something happened in 1812. The earthquake would have actually sheared the trees. Also related to 1812 was the one 13 days later, which may have been on the San Cayetano fault (Dolan, Rockwell etc. trench, which I visited), but I think it was near Santa Rosa Island, where there is an indirect oral history of the sea retreating: could be permanent uplift or just the tsunami.

there is a landslide that may or may not have slid in 1812. There are oaks that are growing in the disturbed ground at the toe of the landslide. Someone else and I each independently though one might date the oaks to see if they started to grow around 1812 (protected from grazing?).

Chris