“The two largest tsunamis known to have been generated on the western coast of the United States formed in the Santa Barbara Channel region. The earthquake of 1812 near Santa Barbara caused waves that reportedly flooded the lower part of town, and the 1927 shock off Point Arguello caused waves at least six feet high.”
— U.S. Geological Survey professional paper (1969)
Although relatively minimal in their height and inland reach, and wholly incomparable to the Japanese tsunami, the California earthquakes of 1812 and 1927 near Santa Barbara generated record-sized tidal waves in the region. Both temblors are estimated to have been 7.1 in magnitude.
According to one publication, the oceanic surge resulting from the 1812 earthquake may have reached “15 feet at Gaviota, 30-35 feet at Santa Barbara, and 15 feet or more at Ventura.” Yet, while contemporary accounts make it clear that earthquakes did occur and that there was purportedly some change in the ocean, conflicting statements and a lack of corroborating evidence make it impossible to confirm whether or not a tsunami occurred, and if it did what its actual size or height may have been.
“The sea was observed to recede from the shore during the continuance of the shocks, and left the harbor dry for a considerable distance, when it returned in five or six heavy rollers, which overflowed the plain on which Santa Barbara is built. The inhabitants saw the recession of the sea, and being aware of the danger on its return, fled to the adjoining hills near the town to escape the probable deluge. . . .The sea, on its return flowed inland little more than half a mile, and reached the lower part of town, doing but a trifling damage, destroying three small adobe buildings.”
— Dr. John Boardman Trask, appointed president of the California Academy of Sciences in 1864, recounting the tsunami of 1812 based on the testimony of local residents.
“In 1812 the great earthquake occurred on the California coast and at that time every [Indian] soul left the island of Santa Rosa. The waters receded from the island several hundred yards. This so alarmed the Indians that, fearful that the island was about to be engulfed, they departed and were settled in bands of three or four hundred at the several missions. The above is the story told by the Indian.”
— Ethnographer H. W. Henshaw in 1884 relating the story told to him by Anisetto Pajilacheet, one of the last remaining Chumash.
The tsunami generated by the temblor of November 4, 1927 was apparently of little consequence if it was noticed at all by coastal residents, because the reportage in the local papers had nothing to say about it at the time:
“‘QUAKE IS FELT ON STEAMSHIP
SAN PEDRO, Nov. 4.— The steamer Floridan, of the American-Hawaiian line, today reported to the federal radio here that it experienced four distinct earth shocks shortly after 11 a. m. off Point Arguello. The message said the sea appeared to ‘shimmy.'”
—Ventura County Star November 4, 1927
“Long-Dry Artesian Wells in Lompoc Canyon Flow Anew
Shimmying earth in the Lompoc region yesterday brought joy to ranchers in and near Lompoc canyon where artesian wells, dry for many years, broke forth from the ground and started a flow that increased throughout the day.
The water will be used for the irrigation of a number of acres in and about the mouth of the canyon.
So copious was the flow from several of the wells that the grounds of the Lompoc canyon school were flooded and school was suspended for the day while workmen built canals to divert the water.
The Santa Ynez river also rose in its banks, probably being supplied from freshly gushing springs in the vicinity.”
—Santa Barbara Morning Press, Saturday, November 5, 1927
The official wave heights, as recorded in a U.S. Geological Survey Professional Paper (1993) (PDF):
A tsunami was recorded on tide gages at San Francisco, La Jolla, San Diego, and Fort Point, and waves were observed at Pismo, Port San Luis (1.5 m), and Surf (1.8 m). Many aftershocks occurred.
Geology, Petroleum Development, and Seismicity of the Santa Barbara Channel Region, California [U.S. Geological Survey professional paper 1969], 64.
Many more accounts of the earthquake and tsunami of December 1812 have been compiled by Dr. George Pararas-Carayannis, as part of a 1967 study conducted at the behest of government regulators in connection with the San Onofre nuclear power plant. An excerpt of the study can be found at the following link: The Santa Barbara, California, Earthquakes and Tsunami(s) of December 1812.
UCSB Santa Barbara Earthquake History Page: