By: Christine Timpke

Earthquake: Lompoc, California
When: November 4, 1927
Time: 5:49am, PST
Location: 33̊ 43’N, 120̊ 46’W in the Lompoc area, about 16 km (10 miles) offshore
Magnitude: M 7. 1
Type of Faulting: uncertain
Fault Involved: uncertain, possibly the Hosgri Fault
Outcomes: Tsunami and damage to living areas

Facts of the Lompoc Earthquake: The Lompoc earthquake is known as the most powerful earthquake in Southern California near the San Andreas Fault in the last 100 years. Below (figure 1) you can see the general area of where Lompoc is located in the state of California.
lompoc.gif
Figure 1: State of California featuring Lompoc

http://earthquake.usgs.gov/earthquakes/states/events/1927_11_04.php
http://www.data.scec.org/chrono_index/lompoc.html

It affected Arroyo Grande, Berros, Guadalupe, Halcyon, Lompoc, Los Alamos, and Nipomo. The effects were severe damage to property, chimneys collapsed, the Southern Pacific Railroad bridge was thrown out of alignment, cracks in highways, small rock slides that left behind “sand craters”. The epicenter of the quake was near the coastal area by the town of Surf. The outcome of the earthquake caused a small tsunami of about 4-6 feet in height that spread from San Diego, CA to San Francisco, CA. Below (figure 2) is a picture of the aftermath of the Lompoc earthquake shown 8 years later.
lompoc3.jpg
Figure 2: Ruins of Mission La Purisima near Lompoc, California, circa 1935.

http://www.bing.com/images/search?q=lompoc+earthquake&FORM=BIFD#focal=08e4002dd1cb3cb0ccf4684f3d989b8d&furl=http%3A%2F%2Fprojects.crustal.ucsb.edu%2Fsb_eqs%2F1812%2F1812Ruins.1.jpg

Years later one can still see the damage was severe enough that rebuilding was almost impossible for some buildings. The Mission in Figure 2, still lies in ruins today.


The Tsunamis that occurred around Pismo and Port San Luis were small in height, about 6 feet high. Elsewhere, in San Francisco, Honolulu, Hilo, Hawaii, and La Jolla, the tsunamis effects were minimal, going between 1 and 4 inches.The Southern Pacific Railroad did have tracks near the coast. Several agents of the railroad reported seeing a small tsunami, estimated at six feet near Pismo and five feet at Port San Luis, break along the beach shortly after the earthquake. A lightkeeper near Port San Luis also reported seeing a four-foot wave. In at least one location, the tsunami was reported to have washed the beach clean of seaweed, driftwood, and other debris, and to have left a stretch of fine, smooth white sand. Fortunately for Californians, the earthquake took place in the ocean. Had it occurred on land, there could have been substantial damage done to homes, and building, and there could have been quite a high death rate due to the high Magnitude (7.1). On the Mercalli Intensity scale, the Lompoc earthquake was considered a IX. A 9 on the Mercalli Intensity scale means it has ruinous potential and could have shifted buildings off of its foundation as well as partially collapsing buildings while causing damage to the structures. Had this earthquake occurred on land, it could have been quite catastrophic for Southern California. *



Area Where it Took Place: The earthquake was said to have taken place about 10 miles offshore in the Pacific Ocean. The actual area of the epicenter is likely the reason there were no casualties in the cities that were affected. Though damage was reported to happen to property and buildings no one was hurt.From website,geoscienceworld.org, It says the deep of the ocean water is about 1000m and the depth of near shore beneath is less then 100m. We can use the equation from lecture: V= square root of g * D.
V is the velocity of the wave, g is the acceleration of gravity, and D is the depth of ocean water. The velocity of the wave in ocean is about 99.0 m/s and the velocity near shore shore beneath is about 31.3 m/s.
From tsunami travel times, the source location was estimated to be well offshore at about 34.2°N, 120.75°W, consistent with recent seismic waveform analysis. Waveform modeling of the tsunami also supports an outer continental shelf location. The seismic moment is estimated to be 3 x 1026 dyne · cm, corresponding to a moment magnitude of 7.0.

Another contributing factor is that Lompoc at the time was reasonably scarcely lived in. The fact that the earthquake did take place in the ocean is most likely the reason one of the main aftermaths was that fish were found stunned or dead floating on the water. The quake itself cause the tsunami that followed to reach as far as Honolulu, and Hilo, Hawaii the tides there reached only about 4 inches in height. Figure 3 below shows 3 main spots offshore that the earthquakes had originated from. The furthest star was the 7.1 magnitude; the middle star represented the earthquake at 3:10 a.m. and the star closest to shore the small earthquake at 1 a.m. in the morning.

lompoc2.jpg
Figure 3: The 4 November 1927 Lompoc earthquake.

http://bssa.geoscienceworld.org/cgi/figsearch?figtext=helmberger&resourcetype=HWFIG&sendit=Search

Prior to the 7.1 magnitude earthquake which was furthest from the shore residents of the coastal city of Casmalia had begun to feel a small earthquake around 1 a.m. in the morning this was followed by another around 3:10 that was followed by several aftershocks within 30 minutes. The Lompoc earthquake was the final quake for that morning as the most powerful and violently released.


Interesting Facts: On a ranch near Lompoc it was said that someone had put several pans of milk out over night to allow the cream to rise to the top. The earthquake was just powerful enough to knock the cream out of the pans and allow the milk to remain.
Dr. P. J. Bryson was said to have gone to his office to find damaged furniture and equipment that would have to be replaced. He also found his gold fish on the floor they had been knocked out of their bowl, he immediately placed them back into their bowl and they quickly revived.
In a bit of a hurry a man named Wallace Grossi had collided with a car driven by Mrs. Frank Jenks. Wallace Grossi’s car had been overturned and was unable to be driven. Wallace’s brother, Waldo, was cut in the head. Mrs. Jenks drove Waldo to the nearest hospital this was considered the most serious injury caused by the Lompoc earthquake.
Not only were there minor injuries and some structural damage, but some several hundred cubic feet of sand lying under the Southern Pacific Railroad were shaken down to the beaches below leaving the tracks impassible. The Lompoc earthquake also created a sea-quake, or, a compressional shock transmitted through water, which was so strong that it stunned and killed ocean fish off the coast. The sea quake also rocked two ships anchored off the coast, neither of which were damaged.


References:
Figure 1:
http://earthquake.usgs.gov/earthquakes/states/events/1927_11_04.php
http://www.data.scec.org/chrono_index/lompoc.html

Figure 2:
http://www.bing.com/images/search?q=lompoc+earthquake&FORM=BIFD#focal=08e4002dd1cb3cb0ccf4684f3d989b8d&furl=http%3A%2F%2Fprojects.crustal.ucsb.edu%2Fsb_eqs%2F1812%2F1812Ruins.1.jpg
Figure 3:
http://bssa.geoscienceworld.org/cgi/figsearch?figtext=helmberger&resourcetype=HWFIG&sendit=Search
http://www.johnmartin.com/earthquakes/eqsafs/safs_617.htm
http://projects.crustal.ucsb.edu/sb_eqs/1927/small_tsunami.html
http://projects.crustal.ucsb.edu/sb_eqs/1927/peculiar.html

1927 Lompoc Earthquakehttp://bssa.geoscienceworld.org

SCEDC: Lompoc Earthquake (1927)