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5:12 AM - April 18, 1906

The California earthquake of April 18, 1906 ranks as one of the most significant earthquakes of all time. Today, its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size. Rupturing the northernmost 296 miles (477 kilometers) of the San Andreas fault from northwest of San Juan Bautista to the triple junction at Cape Mendocino, the earthquake confounded contemporary geologists with its large, horizontal displacements and great rupture length. Indeed, the significance of the fault and recognition of its large cumulative offset would not be fully appreciated until the advent of plate tectonics more than half a century later. Analysis of the 1906 displacements and strain in the surrounding crust led Reid (1910) to formulate his elastic-rebound theory of the earthquake source, which remains today the principal model of the earthquake cycle.

At almost precisely 5:12 a.m., local time, a foreshock occurred with sufficient force to be felt widely throughout the San Francisco Bay area. The great earthquake broke loose some 20 to 25 seconds later, with an epicenter near San Francisco. Violent shocks punctuated the strong shaking which lasted some 45 to 60 seconds. The earthquake was felt from southern Oregon to south of Los Angeles and inland as far as central Nevada. The highest Modified Mercalli Intensities (MMI's) of VII to IX paralleled the length of the rupture, extending as far as 80 kilometers inland from the fault trace. One important characteristic of the shaking intensity noted in Lawson's (1908) report was the clear correlation of intensity with underlying geologic conditions. Areas situated in sediment-filled valleys sustained stronger shaking than nearby bedrock sites, and the strongest shaking occurred in areas where ground reclaimed from San Francisco Bay failed in the earthquake. Modern seismic-zonation practice accounts for the differences in seismic hazard posed by varying geologic conditions.

As a basic reference about the earthquake and the damage it caused, geologic observations of the fault rupture and shaking effects, and other consequences of the earthquake, the Lawson (1908) report remains the authoritative work, as well as arguably the most important study of a single earthquake. In the public's mind, this earthquake is perhaps remembered most for the fire it spawned in San Francisco, giving it the somewhat misleading appellation of the "San Francisco earthquake". Shaking damage, however, was equally severe in many other places along the fault rupture. The frequently quoted value of 700 deaths caused by the earthquake and fire is now believed to underestimate the total loss of life by a factor of 3 or 4. Most of the fatalities occurred in San Francisco, and 189 were reported elsewhere.

Excerpted from Ellsworth, 1990.

Aerial view of the city taken from a series of kites five weeks after the earthquake and fire (154K).

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The California earthquake of April 18, 1906 ranks as one of the most significant earthquakes of all time. Today, its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size.

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Why do earthquakes happen and what are the different kinds of quakes? Caltech scientists explains the science behind the shaking.

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A list of the 20 largest earthquakes in the world.

View 20 Largest Earthquakes in the World on Map
References

Duputel, Z., Rivera, L., Kanamori, H., & Hayes, G. (2012). W phase source inversion for moderate to large earthquakes (1990-2010). GJI, 189(2), 1125-1147.

Johnson, J. M., Tanioka, Y., Ruff, L. J., Satake, K., Kanamori, H., & Sykes, L. R. (1994). The 1957 great Aleutian earthquake. Pure and Applied Geophysics, 142(1), 3-28.

Kanamori, H. (1971). Seismological evidence for a lithospheric normal faulting-The Sanriku earthquake of 1933. Physics of the Earth and Planetary Interiors, 4(4), 289-300.

Kanamori, H. (1976). Re-examination of the earth's free oxcillations excited by the Kamchatka earthquake of November 4, 1952. Physics of the Earth and Planetary Interiors, 11(3), 216-226.

Kanamori, H. (1977). The energy release in great earthquakes. Journal of geophysical research, 82(20), 2981-2987.

Kanamori, H., & Anderson, D. L. (1975). Theoretical basis of some empirical relations in seismology. BSSA, 65(5), 1073-1095.

López, A. M., & Okal, E. A. (2006). A seismological reassessment of the source of the 1946 Aleutian 'tsunami'earthquake. Geophysical Journal International, 165(3), 835-849.

Okal, E. A. (1992). Use of the mantle magnitude Mm for the reassessment of the moment of historical earthquakes. Pure and Applied Geophysics, 139(1), 17-57.

Okal, E. A., & Reymond, D. (2003). The mechanism of great Banda Sea earthquake of 1 February 1938: applying the method of preliminary determination of focal mechanism to a historical event. earth and planetary science letters, 216(1), 1-15.

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A list of the 20 largest earthquakes in the world. View 20 Largest Earthquakes in the World on Map Duputel, Z., Rivera, L., Kanamori, H., & Hayes, G. (2012). W phase source inversion for moderate to large earthquakes (1990-2010). GJI, 189(2), 1125-1147. Johnson, J. M., Tanioka, Y., Ruff, L.

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On May 22, 1960, the largest earthquake in recorded history-magnitude 9.5-struck southern Chile.

On May 22, 1960, the most powerful earthquake in recorded history-magnitude 9.5-struck southern Chile. Estimates were the rupture zone stretched anywhere from 500 kilometers (311 miles) to almost 1,000 kilometers (621 miles) along the country's coast. The event was named after the city most affected by the quake, Valdivia.

The Valdivia earthquake left two million people homeless, injured at least 3,000, and killed approximately 1,655. The economic damage totaled $550 million (more than $4.8 billion, adjusted for 2020 inflation).

The Valdivia earthquake triggered a massive tsunami that raced across the Pacific. Waves wracked coastal communities as far away as New Zealand, Japan, and the Philippines. In Hawai'i, the tsunami devastated the coastal town of Hilo, killing 61 people.

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National Geographic Society

Producer

Mary Crooks, National Geographic Society

other

Last Updated

March 2, 2023

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On May 22, 1960, the largest earthquake in recorded history-magnitude 9.5-struck southern Chile. On May 22, 1960, the most powerful earthquake in recorded history-magnitude 9.5-struck southern Chile. Estimates were the rupture zone stretched anywhere from 500 kilometers (311 miles) to almost 1,000 kilometers (621 miles) along the country's coast.

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A magnitude 6.0 earthquake at the California Nevada border felt July 8, had residents reflecting on past California quakes

SACRAMENTO COUNTY, Calif. - A magnitude 6.0 earthquake -- felt across hundreds of miles across California and Nevada -- occurred Friday, July 8, resulting in no major damages or injuries.

The United States Geological Survey (USGS) said the quake's epicenter was near the California-Nevada border, southeast of Markleeville in Antelope Valley. Dozens of aftershocks followed, including some of magnitude 4.0 or greater.

The magnitude 6.0 earthquake was the largest to hit the area since the magnitude 6.1 quake in 1994.

Some viewers shared their reaction to the recent earthquake, many comparing it to the 1989 Loma Prieta earthquake in San Francisco.

"The earthquake was shaking my couch I was sitting on in Modesto. My daughter and granddaughter felt it in Oakdale at 3:50 p.m. I am 80, so was a little scared. We remember the big one in San Francisco," Kathy and John Weaver from Modesto texted ABC10.

"I felt the quake it jarred me out of very very deep sleep and it seemed as if my house would not stop shaking. I lived in Oakland during the 1989 earthquake and I was working in San Francisco at the time and I thank God that I called off work that day otherwise I would have been on the bridge, and God knows what would have happened," Don texted ABC10.

"Felt it good in Modesto. Had about one-foot wave on the pool! Shook the house for about 30 seconds. Nothing like 1989 thank God," another viewer texted in.
Here are the major quakes over 7.0 magnitude, according to the California Department of Conservation:
7.9- April 18, 1906
San Francisco
3,000 killed, $524 million in property damage, including fire damage

7.3 - Jan. 31, 1922
West of Eureka
37 miles offshore

7.3 - Nov. 4, 1927
SW of Lompoc
No major injuries, slight damage

7.2 - April 25, 1992
Cape Mendocino
6.5 and 6.6 aftershocks

7.1 - Oct. 16, 1999
Ludlow (Hector Mine Quake)
Remote, so minimal damage

7.1 - May 18, 1940
El Centro
9 killed, $6 million in damage

WATCH MORE: Experts say to expect aftershocks for days following Thursday's earthquake

ABC10: Watch, Download, Read

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Largest earthquakes in California history

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A magnitude 6.0 earthquake at the California Nevada border felt July 8, had residents reflecting on past California quakes SACRAMENTO COUNTY, Calif. - A magnitude 6.0 earthquake -- felt across hundreds of miles across California and Nevada -- occurred Friday, July 8, resulting in no major damages or injuries.

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The Earth's lithosphere, which includes the crust and upper mantle, is made up of a series of pieces, or tectonic plates, that move slowly over time.

A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth's mantle to the surface, solidifying to create new oceanic crust. The Mid-Atlantic Ridge is an example of divergent plate boundaries.

When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench. A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. The Pacific Ring of Fire is an example of a convergent plate boundary.

At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.

Two plates sliding past each other forms a transform plate boundary. One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater. Natural or human-made structures that cross a transform boundary are offset - split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. Earthquakes are common along these faults. In contrast to convergent and divergent boundaries, crust is cracked and broken at transform margins, but is not created or destroyed.

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What are the different types of plate tectonic boundaries?

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The Earth's lithosphere, which includes the crust and upper mantle, is made up of a series of pieces, or tectonic plates, that move slowly over time. A divergent boundary occurs when two tectonic plates move away from each other.