One of the largest recorded earthquakes in the United States,[6] with an estimated moment magnitude of 7.9, it ruptured the southern part of the San Andreas Fault for a length of about 225 miles (350 km), between Parkfield and Wrightwood.

Accounts of the events' effects varied widely, including the time of the main shock as well as foreshocks that occurred at several locations earlier in the morning.

On the extreme northern end of the rupture zone, the surface cracking extended 80 kilometres (50 mi) north of Cholame into San Benito County.

[13] Evidence of uprooted and displaced trees south of Elizabeth Lake indicates surface faulting along a mole track (an "array of en echelon primary Riedel shears with linking compressional rolls and minor thrusts")[14] that ran directly under three Jeffrey Pines.

Seismologist Kerry Sieh determined that fault slip and the associated ground disturbance were the source of the mole track and subsequent tree tilt.

[19] Several mid-twentieth-century earthquakes had similar felt reports to the dawn and sunrise shocks, and with close inspection, Sieh theorizes that both events were local to coastal central California, probably between Point Conception and Monterey.

More buildings were destroyed along a twenty-mile stretch between Fort Tejon and southeast to Elizabeth Lake, a sag pond that was formed directly on the San Andreas fault.

[1] Central and southern California were thinly populated at the time and this likely helped limit the damage from the earthquake, but the lack of people present also reduced the number of perspectives to use in determining intensity estimates.

At downtown Los Angeles, with a maximum perceived intensity of VI, some homes and buildings were cracked, but no major damage was reported.

The largest aftershock occurred on the afternoon of January 16 with an estimated magnitude of about 6.7, a possible offshore location,[26] and high felt intensities in Southern California communities.

The last recorded major aftershock occurred on April 16, 1860, with an estimated magnitude of about 6.3, with an epicenter close to the Parkfield section of the San Andreas Fault.

[26] Scientists and public service officials have speculated on the threat of another very large earthquake occurring in southern California and what type and scale of damage might result.

Swaminathan Krishnan, assistant professor of civil engineering and geophysics at the California Institute of Technology, said that if a similar rupture from Parkfield to Wrightwood were to happen again, it would severely affect the Los Angeles area, with the San Fernando Valley being particularly hard hit.