The 1957 San Francisco earthquake (also known as the Daly City earthquake of 1957) occurred on March 22 at 11:44:22 local time with a moment magnitude of 5.7 and a maximum Mercalli Intensity of VII (''Very strong''). It was located just off the

San Francisco Peninsula The San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is Mountain View, south of Palo Alt ...

near the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal) ...

and was felt in a limited portion of

Northern Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United States * Northern Province, Sri Lanka * Northern Range, a r ...

and

Central California Central California is generally thought of as the middle third of the state, north of Southern California, which includes Los Angeles, and south of Northern California, which includes San Francisco. It includes the northern portion of the S ...

. There was a non-destructive foreshock and aftershock sequence that lasted for several months. With financial losses of around US$1 million, damage was considered minimal, with one death and forty injuries.

Tectonic setting

The San Andreas Fault System (SAFS) is a collection of faults that accommodates differential motion between the Pacific and North American Plates and extends from the

Mendocino Triple Junction The Mendocino Triple Junction (MTJ) is the point where the Gorda plate, the North American plate, and the Pacific plate meet, in the Pacific Ocean near Cape Mendocino in northern California. This triple junction is the location of a change in ...

in the north to the

Salton Sea The Salton Sea is a shallow, landlocked, highly saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California. It lies on the San Andreas Fault within the Salton Trough that stretches to the Gul ...

in the south. While the majority of movement occurs as right-lateral strike-slip on the significant branches of the system, including the San Jacinto and Hayward faults that are relatively near the main San Andreas Fault, other types of faults (including left-lateral strike-slip, reverse, thrust, and to a lesser extent, normal) are also present. These various fault types have been observed well east into the

Basin and Range Province The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...

Earthquake

Eight foreshocks (with a maximum magnitude of 3.8) preceded the main event. The first motion method was used to determine the focal mechanism of the mainshock. It was found to be dissimilar from the strike-slip movement of the 1906 earthquake, and instead showed oblique movement on a steeply-dipping thrust fault, with the eastern side of the fault rising relative to the western side. The strike-slip component was minimal and was only about half as much as the thrust component.

Damage

Damage was non-structural and was limited to content within buildings and cracked plaster and was estimated at $1 million, not including loss to building content. The most significant effects were seen in the western portion of

Daly City Daly City () is the second most populous city in San Mateo County, California, United States, with population of 104,901 according to the 2020 census. Located in the San Francisco Bay Area, and immediately south of San Francisco (sharing its ...

and in the Lake Merced area of San Francisco. The minimal losses were attributed to the short duration and lack of high intensity shaking.

Strong motion

The event was felt over an area of 12,000 square miles. Its scientific value was reinforced because it was captured on 13 strong motion instruments. A maximum (free field) peak ground acceleration of 0.13 '' g'' was recorded in

Golden Gate Park Golden Gate Park, located in San Francisco, California, United States, is a large urban park consisting of of public grounds. It is administered by the San Francisco Recreation & Parks Department, which began in 1871 to oversee the developm ...

and .18 ''g'' was recorded on the fourteenth floor of a building in San Francisco.

References

External links

M 5.7 – offshore Northern California
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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, ...