A Seismogram of the 1906 Earthquake
![Seismogram recorded in Gottingen, Germany.](https://webarchive.library.unt.edu/eot2008/20081005003155im_/http://earthquake.usgs.gov/regional/nca/1906/18april/images/gotNS0_small.gif)
Above is a seismogram recorded in Gottingen, Germany, 9100 kilometers away. It shows how the ground moved in Germany as a result of the 1906 San Francisco earthquake. Time advances from left to right. Small wiggles, beginning 1/2 inch from left end, signal arrival of first compressional (P) waves. Large wiggles half way along represent arrival of slower-traveling shear (S) waves. The part of the record shown here spans about 1600 seconds or 26 minutes. The instrument subsequently went off-scale when surface waves arrived.
Compare the above 1906 seismogram to one recorded on the same instrument at the same location after the 1989 Loma Prieta earthquake.