This article discusses something Don and I took notice of in San Miguel at the Mission some years ago where we saw a tombstone which was broken at the center and the top part was upside down in the dirt. At the end of the article is mentions intense ground shaking in Bloomfield, CA. Bloomfield is a little burg just outside of Petaluma (south of Santa Rosa.) Santa Rosa was leveled during the 1906 earthquake and it's Rural Cemetary includes the graves of those who passed.

Roger Musson's oral at the AGU a few years ago covered retrieving information about earthquakes without the benefit of scientific equipment and thus this story further elaborates on this topic...Petra

Dead ringer

One of the most interesting ways geologists have measured the intensity of the 1906 earthquake is by visiting rural cemeteries.

"What tended to happen is the tombstones broke," explained Boatwright, who made several trips to cemeteries that previous surveyors had overlooked.

If Boatwright saw one or two pre-1906 headstones with damage, he assumed the area had felt an intensity of VII (or 7 in regular numbers) on the Modified Mercalli Intensity Scale. If a quarter to a third of the headstones were broken, the site was given a VIII (8), while anymore than that was a IX (9).

In Bloomfield, Calif., Boatwright was amazed to find three flat-lying footstones that were damaged. He gave that a 9.

Boatwright said he enjoyed this work, but "I'm hoping my cemetery tours are over."

• Crumbled Tombstones