1927 Lompoc earthquake

The Lompoc earthquake of 1927 occurred at 5:49 a.m. Pacific Standard Time (PST), on November 4 with an epicenter off the coast of Lompoc, Santa Barbara County in Southern California.[1] It is one of the largest earthquakes to have occurred off the coast of California, measuring a surface-wave magnitude of 7.3.[2][3][4] The earthquake may have originated along the Hosgri Fault, an entirely offshore structure.[5] Shaking from the earthquake and an unusually large tsunami caused some damage to communities near the earthquake. Due to its location and the area being sparsely populated at the time, there were no human fatalities reported. It is the only California-generated tsunami recorded in Hawaii.[6]

1927 Lompoc earthquake
1927 Lompoc earthquake is located in California
1927 Lompoc earthquake
Los Angeles
Los Angeles
UTC time1927-11-04 13:51:03
ISC event909604
Local dateNovember 4, 1927 (1927-11-04)
Local time5:49 P.M. PST
Magnitude7.3 Ms
Depth10.0 km
Epicenter34°48′47″N 120°46′26″W / 34.813°N 120.774°W / 34.813; -120.774
FaultPossibly the Hosgri Fault
TypeUnknown (possibly thrust or reverse and/or with some strike-slip component)
Areas affectedCalifornia
Total damageLimited
Max. intensityMMI X (Extreme)
Tsunami2 meters (6.6 feet)


Map showing the location of the Hosgri Fault.

The San Simeon-Hosgri Fault is an approximately 140 km long, complex thrust or reverse fault that runs offshore, with an 18 km section that is on land. The fault has an almost north-south strike and east dip. It is a system of interlaced and parallel faults that form this structure. It lies sub-parallel to the San Andreas Fault and is part of a system of faults that accommodate motion between the North American and Pacific Plate.[7] The fault poses a hazard to the Diablo Canyon Power Plant, which sits a few kilometers from the fault.[8] Following the Fukushima Daichi nuclear accident, caused by an earthquake, there have been concerns of a nuclear disaster involving the power plant. The onshore San Simeon Fault triggered the 2003 earthquake that killed two people.



The epicenter was located 80 km west of Point Arguello. Large landslides happened along coast around the Santa Barbara district and railway services were suspended. Flues and chimneys were damaged at Lompoc and other surrounding towns. In the town of Surf, people were thrown from standing and reclining positions, a concrete road cracked, a rail bridge was thrown out of position, and sand and water erupted from sand blows, indicating that liquefaction took place because of the earthquake.[9] Shaking intensity reached a maximum of X (Extremely high intensity tremor) on the Rossi-Forel scale, while intensities VIII–VI covered a larger region.[3][10][11] Shock from the earthquake apparently stunned and killed many fishes near the epicenter.[9][12]



The earthquake triggered a tsunami that reached a maximum height of 2 meters was seen at Surf and Pismo beach, and was 1.2 meters at Port San Luis.[6] The tsunami measured 7 cm at La Jolla, San Diego. A positive wave was sent in the direction towards the California coast, as reported by eyewitnesses that there was no receding of the seawater before the waves hit. Tide gauges in Hawaii measured the tsunamis at 2 cm at Honolulu and 10 cm at Hilo.[6]

See also



  1. ^ "M 6.9 - offshore Central California". US Geological Survey. Retrieved 24 November 2020.
  2. ^ William Gawthrop (1978). "The 1927 Lompoc, California earthquake". Bulletin of the Seismological Society of America. 68 (6): 1705–1716. Retrieved 2 July 2021.
  3. ^ a b "Significant Earthquake Information". NOAA NCEI. Retrieved 24 November 2020.
  4. ^ "Preferred Magnitudes of Selected Significant Earthquakes" (PDF). USGS. 24 June 2013. Retrieved 24 November 2020.
  5. ^ Helmberger, D. V.; Somerville, P. G.; Garnero, E. (August 1992). "The Location and Source Parameters of the Lompoc, California, Earthquake of 4 November 1927" (PDF). Bulletin of the Seismological Society of America. 82.
  6. ^ a b c Satake, Kenji; Somerville, Paul G. (August 1992). "Location and Size of the 1927 Lompoc, California, Earthquake from Tsunami Data". Bulletin of the Seismological Society of America. 82. CiteSeerX
  7. ^ Willingham, C. Richard; Rietman, Jan D.; Heck, Ronald G.; Lettis, William R. "Characterization of the Hosgri Fault Zone and Adjacent Structures in the Offshore Santa Maria Basin, South Central California". U.S. Geological Survey Bulletin 1995-CC. doi:10.3133/b1995cc – via United States Geological Survey.
  8. ^ McGinnis, Ronald N.; Morris, Alan P.; Ferrill, David A.; Smart, Kevin J.; Stamatakos, John A.; Juckett, Miriam R. "Independent Evaluation of the Hosgri Fault Slip Rate Based On A Structural Analysis of the Pull-Apart Basin Linking the Hosgri and San Simeon Fault Systems" (PDF). U.S. Nuclear Regulatory Commission Contract No. NRC–HQ–50–14–E–0001 – via Nuclear Regulatory Commission.
  9. ^ a b "Lompoc Earthquake". Southern California Earthquake Data Center. Retrieved 24 November 2020.
  10. ^ Evernden, J. F.; Kohler, W. M.; Clow, G. D. "Seismic Intensities of Earthquakes of Conterminous United States Their Prediction and Interpretation" (PDF). Geological Survey Professional Paper (1223): 27–30 – via USGS.
  11. ^ McCulloch, D. S.; Greene, H. G.; Heston, K. S.; Rubin, D. M. "A Summary of the Geology and Geologic Hazards in Proposed Lease Sale 53, Central California Outer Continental Shelf" (PDF). United States Department of the Interior Geological Survey: 25 – via USGS.
  12. ^ "Significant Earthquakes and Faults Lompoc Earthquake". Southern California Earthquake Data Center. Retrieved 24 November 2020.