U.S. Geological Survey research geophysicist Jack Boatwright became something of an historian while creating a "shake map" showing the intensity of ground shaking from the 1906 Northern California earthquake.

He extracted as much seismic data as he could from the 1908 Lawson report, the most authoritative account of the earthquake's damage, and then searched local newspaper archives and even visited cemeteries to see how many tombstones had toppled for clues as to how violently the earth shook.

The following images of the earthquake's damage and of the shake map itself are from the U.S. Geological Survey.

RealAudio: Boatwright describes some of the ways he collected the seismic information. (2:06)

USGS Northern California resources: More information on the 1906 quake, including shake maps and hazard protections