Harry Fielding Reid developed the earthquake cycle to explain the 1906 San Francisco earthquake.
Reid examined survey data of the area from the 1880s and again immediately after the earthquake, revealing the surface deformation caused by an earthquake for the first time. He found it had caused an average of four to five meters surface slip along 450km of the San Andreas Fault (another strike-slip fault).
The survey data revealed that points on the southwest side of the San Andreas Fault had moved to the northwest compared with points on the other side. Reid also found that the points close to the fault had moved much more than those further away. When he used the survey data to extrapolate the surface slip, his calculations matched the distance the ground had broken apart at the fault.
Reid also compared survey data of California from the 1860s and 1880s. He found that the Farallon lighthouse, located a long way to the southwest of the fault, had moved north-west over a 20-year period.
These observations led Reid to propose his elastic rebound theory.