21 December 1812 M7.1

Santa Barbara: Senan (1813) wrote to the Bishop of Sonora about the effects of this earthquake at Santa Barbara: . . . "there are so many cracks in the houses, church, and other buildings, and a chapel of Saint Michael, which was in the Rancheria of Mescaltitan, fell down completely, and the land was opened up in the vicinity, to such an extent that it causes horror. The Presidio of Santa Barbara is all on the verge of falling down, and there is not one room in it that can be used. People from the Rancheria are living on the plains around the Mission, to where they withdrew since they were very close to the ocean, which threatened to flood them."

La Purisima Concepcion: The damage at Mission La Purisima Concepcion was described in the 1812 annual report of Payeras and Ripoll: "The extraordinary and horrifying earthquake which this mission suffered on the memorable day of the glorious Apostle Saint Thomas [Dec. 21] completely ruined the church. It destroyed the name, several statues and paintings, and ruined most of the adornments. The ecclestical vestments were not damaged since they were in drawers. Some of the buildings have been flattened to the ground, and others, after extensive repair, will be useable (if the damage does not continue), and as living quarters, but for activities which do not require great safety. A hundred of the neophytes' houses and the pozolera kitchen (?), buildings of adobe (__ ?___) and roofed with tile, cannot be used; even the adobe wall of the garden, covered with tile, has either fallen down or is out of line to such an extent that the damage parts will provide scarcely any material which may be used for later reconstruction. The possessions and furnishings of the mission have also suffered; some are smashed, others broken, and all are damaged, not to mention the inclement weather and copious rains which fell immediately afterwards, allowing us no time to dig out or to reroof what is still precariously standing."

The original mission was on the edge of a marsh and on sloping ground, which probably contributed to the extent of damage. Ripoll and Payeras (1813) recommended moving the mission to a dry and level location (Los Berros) because, among other reasons: " . . . those structures which leaned to the south, fell to the south, those which leaned to the north, fell to the north, and those that had a naturally flat floor, and were even, were not damaged at all, like the houses and the large, tall granary of our Rancho de San Antonio."

This indicates that buildings on level ground, in the general vicinity of the mission, were not damaged.

Santa Inez: The damage at Santa Inez is given in the 1812 annual report of Uria and Olbes: "On Dec. 21 at approximately 10:00 a.m. there were two earthquakes with a fifteen minute interval between shocks. The first made a considerable aperture in one corner of the Church; the second tore down another corner. A room next to the Church, of the new homes, fell down to its very foundation; it cracked the upper interior walls of other homes, knocked down all the tiles from the Mission roof, and many main walls (support walls) were opened up. But all will be usable if there are no new shocks, seeing as how everything has been repaired as far as circumstances have permitted."

San Buenaventura: The 1812 annual report from Mission San Buenaventura (Vitoria and Senan) describes the damage at that mission: "The buildings have suffered a great deal as a result of three horrible tremors, or earthquakes, during which it seemed to us that the mission was coming down. About 3 varas (8.4 feet) of the uppermost part of the facade of the church were knocked out of plumb and the front wall of the presbytery has a sizeable crack. This wall should be rebuilt; the rest can be repaired and we are confident that with reinforcements of stone and mortar and with strong braces, it will be stronger than before. The tower was rendered useless and we are going to tear it down. The other buildings of the mission have several cracks, but they can be repaired and will be in good condition with the rebuilding of some of the back walls and partitions which are the parts which suffered the most damage. Only one room needs to be completely rebuilt."

San Fernando: The damage at San Fernando necessitated "thirty beams to support the walls of the church due to the strong and repeated earthquakes" (Munoz and Nuez, 31 Dec. 1812). As indicated under the previous earthquake, this damage was probably initiated on the 8th when San Gabriel, only 37 km away, was damaged, and the description above permits additional damage on the 21st, even though San Gabriel reports no additional damage on the 21st. San Luis Obispo. The 1812 annual report of Mission San Luis Obispo does not mention any earthquakes, indicating that the effects of the December 1812 earthquakes at San Luis Obispo were not significant enough to mention in that report.

Double Earthquake: The damage on 21 December 1812 resulted from two earthquakes separated by about a quarter of an hour. This was the case at Santa Inez as indicated above. At Purisima, according to Engelhardt (1897), "there was an earthquake while the Fathers were making their examination of conscience. The earth shook so violently that it was difficult to stand. A brief examination showed that the church walls had been thrown out of plumb. Just before 11 o'clock, there came another more violent shock which brought down the church and nearly all the mission buildings, besides about 100 nearby houses of adobe." At Santa Barbara, the commander of the Presidio equated the strength of the two earthquakes (Arguello, 28 Dec. 1812): "there occurred at this Fort two horrible earthquakes between which no notable difference could be discerned beside the fact that they were a quarter of an h our apart." This circumstance probably accounts for two of the three horrible earthquakes reported at San Buenaventura, the third earthquake possibly being that of 8 December. Also, the two shocks on 21st December might have contributed to the damage at San Fernando, that is not attributed to a particular shock in December 1812.

Aftershocks: Aftershocks caused concern at Mission Santa Barbara as reported by Arguello (28 Dec. 1812): "The continuous tremors that even until now [28 December] have followed to such an extent that thirty have been counted on a given night, not to mention the fact that some days they have recurred every quarter of an hour, have helped to paralyse everything." Later aftershocks are reported at Santa Barbara by Geiger (1965): "As long as the quakes lasted ( and these did last until April of 1813) the priests refrained from conducting services in the damaged church because of danger to life and limb." A suggestion of damage from aftershocks comes from Gil 6 Taboada and Amestoy's 1812 annual report at Santa Barbara: "With the terrible earthquakes of December 21 and following days, the mission is in quite a ruined condition, and everything needs to be examined carefully with extensive repairs to be made." A similar suggestion of damage from aftershocks comes from Payeras and Ripoll's 1813 annual report at Purisima: "Purisima . . . ruined by the horrendous earthquakes, which it suffered since December 21 until the end of the same month."

Sea Waves: There are several reports of sea waves following the earthquakes. Senan (1813), in describing the effects of the earthquakes at Santa Barbara and the Rancheria de Mescaltitan, wrote: "People from the Rancheria are living on the plains around the Mission [Santa Barbara], to where they withdrew since they were very close to the ocean, which threatened to flood them." In the same document, in describing the effects at San Buenaventura, Senan (1813) wrote: " , , , it has been necessary for us to withdraw for now, for somewhat more than a half a league inland, for fear of the ocean, which knew had flooded in two parts."

From Santa Barbara, Arguello (28 December 1812) wrote: "In the bay of the Presidio, the sea has changed from its natural condition", suggesting a possible change in elevation. An apparent change in level occurred at San Buenaventura as related by Engelhardt (1897): "The whole mission site appeared to settle, and the fear of being engulfed by the sea drove all away to San Joaquin y Santa Ana, where they remained until April 1813". A graphic description of a sea wave occurs in Ord's Occurrences in Hispanic California: "In speaking to Padre Luis Gil Taboada, he told me that in 1812 there had been very strong earthquakes at Santa Barbara while he was there. That on the 8th of December while he was at the Presidio there occurred an earthquake so violent that the sea receded and rose like a high mountain. He, with all the people of the presidio, went running to the Mission chanting supplications to the Virgin. I asked him humorously, why he had not gone to see if there were a ship at the foot of the mountain of water. He also assured me that they had placed a pole with a ball tied to it. It was fastened in the ground at a place where the air would not move it, and that it was in continual movement for 8 days. After the 8 days the ball was still for 2 or 3 hours then started to move again, and this lasted for about 15 days." This conversation occurred in 1833, twenty years after the earthquake, which might account for the date of 8 December instead of 21 December and any possible romanticism in the report.

According to Bancroft (1888), Padre Gil y Toboada reported that a ship at Refugio was carried up a canyon by the wave and returned to sea (Townley and Allen, 1939). Trask (1856, 1864b), giving an erroneous date of September 1812, describes the sea receding and returning in an immense wave which flowed half a mile to a mile inland "doing but little damage, destroying only three small adobe buildings." These later reports of a sea wave (Bancroft, 1888; Trask, 1856) might be romanticized, and are not as reliable as the reports written following the earthquake. There is no reliable report of catastrophic flooding or of loss of life resulting from the sea waves. The only fatality reported for this earthquake was that of a neophyte from Santa Barbara who was killed by a boulder at Agua Caliente (Arguello, 28 December 1812).

The commander of Santa Barbara Presidio (Arguello, 28 December 1812) states that, after the earthquake, they moved to Mission Santa Barbara: "fearing that the place where were could, at any time, be wiped out by the sea [by watching the waves] and our refuge being some coverings made with branches." This indicates a fear of sea waves after the refuge was made with branches and suggests that sea waves occurred somewhat after the earthquake and might have been related to the storm which followed the earthquake at Mission Purisima (Payeras and Ripoll, 1812). However, there is no reference to a storm anywhere other than that at Purisima.

We conclude that sea waves followed the earthquake, but were not reported to have caused loss of life or any substantial damage. Possible sources of sea waves are a tsunami or a seiche in the Santa Barbara Channel or a submarine landslide. Finally, any waves that might have occurred after 21 December could have been related to the storm that was reported at Purisima.

Comparison to 1925 Santa Barbara Earthquake: In comparing this earthquake to the 1925 Santa Barbara earthquake (Willis, 1925), we find that the intensity at Ventura was a unit higher than at Lompoc (Purisima) in 1925 but not in 1812 (the intensity in 1812 being probably influenced by the slop and marsh at Purisima). This suggests a source for the 1812 earthquake slightly westward of the source of the 1925 earthquake. If this were the case, then the intensity at San Fernando on 21 December 1812 would have been distinctly lower than at Ventura, as was the case in 1925. This supports the hypothesis that the damage at San Fernando started on 8 December, not on 21 December 1812. The intensity in the Santa Barbara area was distinctly higher than at Ventura and Lompoc in 1925, but the intensity was about the same at Santa Barbara, Ventura, and Lompoc in 1925. However, the source (fault) cannot be too far from Santa Barbara, because of the extensive sequence of aftershocks felt there. It thus appears that a source near that of the 1925 earthquake, and 10 to 20 km more distant from Santa Barbara, toward the south west, is appropriate for the 21 December 1812 earthquake. The area damaged at intensity VII MM on 21 December 1812 ext ended at least from Ventura to Purisima, whereas in 1925 Purisima had intensity only V to VI MM; This, combined with the suggestion that the 1812 earthquake was farther offshore than the 1925 earthquake, indicates that the 1812 earthquake was substantially larger than the 1925 earthquake.

From: Toppozada, T. R., C. R. real, and D. L. Parke, 1981. Preparation of isoseismal maps and summaries of reported effects for pre-1900 California earthquakes. California Division of Mines and Geology Open-File Report 81-11, pp. 136-140.

CDMG References to 21 December 1812 earthquake