Studies have placed the source of this earthquake on two faults. The location and source have not been agreed on, with some researchers proposing that the epicenter was north of
Wrightwood or in the Santa Barbara Channel. Toppozada and others in 1981 proposed a location southwest of the
1925 Santa Barbara earthquake. Details of a possible tsunami would suggest a thrust-mechanism for the earthquake, similar to the
1978 Santa Barbara earthquake (>M5) which had a left-lateral and north-dipping thrust mechanism.
Coulomb stress scenarios were developed using models for the December 8 earthquake along the San Andreas Fault and indicate that there was an increase in stress on faults whose geometries may have been the source of the December 21 shock. This indicates that the latter shock was likely triggered by the December 8 earthquake. These trees took several years or decades to fully recover and return to their normal stage. These affected trees were found only in close proximity to the San Andreas Fault; in an event of a strong earthquake, trees at a considerable distance should also display evidence of trauma. A plausible cause might be that during slippage, the roots of these trees were severed, thus reducing the intake of nutrients and water required for growth. The seismic shaking may also knock off branches and parts of the trees. The rupture on December 21 initiated in the south, and progressed northwards to
Fort Tejon. Both events ruptured a total length of on the fault. However, if the earthquake was sourced from the San Andreas Fault, then the aftershocks should not have been felt around the coastal regions of California. The documented aftershocks were felt locally, and there were reports of "odd disturbances" in the sea. Another challenge to the San Andreas hypothesis is the lack of damage at Santa Barbara during the much more powerful 1857 earthquake. The section involved in the 1857 earthquake was closer to Santa Barbara and Ventura, but those regions were not affected as severely as in the 1812 earthquake.
San Cayetano Fault Located northwest of Los Angeles, the
San Cayetano Fault is a north-dipping reverse fault that extends from Ventura to the
Sespe Mountains. The fault comprises two segments separated by a right
stepover near
Fillmore. The eastern segment, known as the Modelo lobe, is expressed at the surface along the southern margin of the mountains west of Fillmore. Its surface rupture diminishes to the east of
Piru. The western segment's surface expression is located considerably above the mountain base because the segment lies atop the south-dipping Sisar Blind Thrust Fault and a north-dipping blind thrust. The compression rate along the Ventura area is estimated at per year and is accommodated by the San Cayetano and Oak Ridge faults. An epicenter proposed in the Santa Barbara Channel was based on reports of the large tsunami that flooded coastal communities. == Impact and aftermath ==