The 2003 San Simeon earthquake struck at 11:15 PST (19:15 UTC) on December 22 on the

Central Coast of California The Central Coast is an area of California, roughly spanning the coastal region between Point Mugu and Monterey Bay. It lies northwest of Los Angeles County and south of San Mateo and Santa Clara counties, and includes the rugged, undeveloped ...

, about northeast of San Simeon. Probably centered in the Oceanic fault zone within the

Santa Lucia Mountains The Santa Lucia Mountains (sæntə luˈsiːə) or Santa Lucia Range is a rugged mountain range in coastal central California, running from Carmel southeast for to the Cuyama River in San Luis Obispo County. The range is never more than from t ...

, it was caused by

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

ing and the rupture propagated southeast from the

hypocenter In seismology, a hypocenter or hypocentre () is the point of origin of an earthquake or a subsurface nuclear explosion. A synonym is the focus of an earthquake. Earthquakes An earthquake's hypocenter is the position where the strain energy s ...

for 12 miles (19 km). The most violent ground movement was within 50 miles of the epicenter, though the earthquake was felt as far away as Los Angeles. With a moment magnitude of 6.6, it was the most destructive earthquake to hit the United States since the Northridge quake of 1994.

Damage

The area around the epicenter being sparsely populated, the most severe damage was in

Paso Robles Paso Robles ( ), officially El Paso de Robles (Spanish for "The Pass of Oaks"), is a city in San Luis Obispo County, California, United States. Located on the Salinas River approximately north of San Luis Obispo, the city is known for its hot ...

, 24 miles (39 km) east-southeast. Two women were killed when the Acorn Building, an unreinforced masonry structure built in 1892, collapsed. Other unreinforced masonry buildings, some more than a century old, were extensively damaged. No structure that had even partial retrofitting collapsed. Two sulfur

hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...

s in Paso Robles erupted after the earthquake. One was underneath the parking lot of the recently opened city hall/library building. There was formerly a bath house at the location, and the spring was capped after it closed down. Hot water and

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

were released at a rate of about 1,300 gallons per minute (4,900 liters per minute), forming a large

sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...

and endangering the building. Emergency efforts saved the building. However, it took until 2010 to fully repair the damage and fill in the hole. This was mainly caused by the requirement for a full Environmental Impact Study, and the inability to do any work on the project, other than the initial emergency work. Another hot spring flowed out of the embankment at the Paso Robles Street exit on

U.S. Route 101 U.S. Route 101, or U.S. Highway 101 (US 101), is a north–south United States Numbered Highway that runs through the states of California, Oregon, and Washington, on the West Coast of the United States. It is also known as (The Royal Roa ...

. Other unreinforced masonry buildings, some more than a century old, in the city's historic downtown area also had extensive damage. However, none of the buildings that had even partial retrofitting collapsed. There was a wrongful death lawsuit filed by the relatives of the 2 women killed in the earthquake against Mary Mastagni, and several trusts which owned the Acorn Building. The jury found Mastagni negligent in the care and maintenance of the Acorn Building, due to not retrofitting the building, in violation of city ordinances. The jury awarded nearly $2 million to the plaintiffs. Outside of Paso Robles the damage was less severe, with unreinforced masonry buildings taking minor to moderate damage. Buildings even 40 miles from the epicenter in San Luis Obispo suffered minor damage such as ceiling tiles falling.

Brick A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...

veneers were also disproportionately affected. In addition,

water tank A water tank is a container for storing water. Water tanks are used to provide storage of water for use in many applications, drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemi ...

s in Paso Robles, Templeton and

Los Osos Los Osos (Spanish for "the bears") is an unincorporated town and census-designated place (CDP) in San Luis Obispo County, California. Located on the Central Coast of California, Los Osos had a population estimated to be 16,533 in 2019. Histo ...

were damaged. Residential buildings, predominantly one- to two-story wood-frame structures, weathered the quake with little or no damage. The building that housed Atascadero's City Hall was damaged and vacated shortly after the quake. After extensive repairs, it reopened in August 2013. Some

wineries A winery is a building or property that produces wine, or a business involved in the production of wine, such as a wine company. Some wine companies own many wineries. Besides wine making equipment, larger wineries may also feature warehouses, b ...

, especially those near the epicenter along State Route 46, reported damage such as barrels toppling and bursting. The Mission San Miguel Arcángel had $15 million worth of damage. The earthquake also caused extensive damage to George H. Flamson Middle School. The main building was damaged and had to be demolished in 2004. A new building reflecting the original 1924 building was opened for use in August 2010. In Templeton, Bethel Lutheran Church (ELCA), sustained major damage to its 110+ year old building and the apse had to be rebuilt.

Aftermath

Following the event, California enacted A.B. 2533, amending the California Business and Professions Code § 8875.8, requiring that certain unreinforced masonry buildings that have not been seismically retrofitted have posted notice of the potential earthquake hazard. The law was called ''Jenna's Bill'', after Jennifer Myrick, who died in the quake.

Faulting

The area where the quake struck displays a complex faulting geometry, between the active

Oceanic Fault Oceanic may refer to: *Of or relating to the ocean *Of or relating to Oceania ** Oceanic climate ** Oceanic languages **Oceanic person or people, also called "Pacific Islander(s)" Places * Oceanic, British Columbia, a settlement on Smith Island ...

and the older

Nacimiento Fault Nacimiento may refer to: Settlements *Nacimiento, Chile, a municipality in the province of Bío Bío, region of Bío Bío, Chile * Nacimiento, Spain, a municipality in the province of Almería, Andalusia, Spain *Nacimiento, California, United State ...

, along with possible interaction from the Hosgri and San Simeon segments of the mainly offshore San Gregorio-San Simeon-Hosgri fault zone.

Notes

Sources
2003 San Simeon Earthquake: Preliminary Earthquake Analysis
– California Integrated Seismic Network
Preliminary Observations on the December 22, 2003, San Simeon Earthquake
–

Earthquake Engineering Research Institute The Earthquake Engineering Research Institute (EERI) is a leading technical society in dissemination of earthquake risk and earthquake engineering research both in the U.S. and globally. EERI members include researchers, geologists, geotechnical e ...

M6.6 - Central California
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

External links

San Simeon, California
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* {{DEFAULTSORT:San Simeon Earthquake, 2003

2003 File:2003 Events Collage.png, From top left, clockwise: The crew of STS-107 perished when the Space Shuttle Columbia disintegrated during reentry into Earth's atmosphere; SARS became an epidemic in China, and was a precursor to SARS-CoV-2; A des ...

2003 earthquakes History of San Luis Obispo County, California 2003 in California 2003 natural disasters in the United States Paso Robles, California Buried rupture earthquakes

Damage

Aftermath

Faulting

See also

Notes

External links