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San Francisco Earthquake

Theodore Roosevelt

San Francisco Earthquake: Theodore Roosevelt was the 26th American President who served in office from September 14, 1901 to March 4, 1909. One of the important events during his presidency was the San Francisco Earthquake.

Definition and Summary of the San Francisco Earthquake
Summary and definition:
On 5:12 a.m. on 18 April 1906 the city of San Francisco on the Pacific Coast was rocked by a violent earthquake. The devastating San Francisco earthquake was followed by a terrifying firestorm. The 1906 San Francisco earthquake and subsequent fire remains one of the most devastating natural disasters to have hit America.

It is believed that 3000 people were killed, countless numbers were injured and 225,000 (over half the population of the city) were made homeless by the firestorm fire.

1906 San Francisco Earthquake History: The Earthquake
Definition: An Earthquake is a terrifying geological phenomenon resulting from underground movement along a fault plane (or from volcanic activity). It is characterized by violent shaking and vibration of such tremendous force that it can destroy a city and kill thousands of people in minutes.

What caused the 1906 San Francisco Earthquake?
A rupture along the Tomales-Portola Fault line caused the earthquake. It was later re-named the San Andreas Fault line. The city of San Francisco lies along the San Andreas Fault line.

1906 San Francisco Earthquake History: The Fault Line
The San Andreas Fault extends roughly 810 miles (1,300 km) through California. Approximately 270 miles of ground surface was ruptured in Northern California. The epicenter was located near San Francisco.

1906 San Francisco Earthquake History: The Magnitude
The Great
San Francisco Earthquake caused the ground to shift at an estimated 4 - 5 feet per second, and the rupture traveled at about 5,900 miles per hour. The magnitude of the 1906 Great San Francisco Earthquake was estimated to be 7.8. on the Richter scale.

1906 San Francisco Earthquake History for kids: The Firestorm
The Great San Francisco earthquake was followed by a firestorm in which violent winds were drawn into a column of hot air rising over the severely damaged area created by the earthquake.  The high temperatures within the firestorm ignited anything that might possibly burn. The firestorm fire turned street tarmac into a flammable hot liquid and created an enormous ash cloud. 80% the destruction of the buildings in the San Francisco Earthquake were caused by the great fire.

1906 San Francisco Earthquake History for kids: Tectonic Plates
Earthquakes usually occur along fault lines, the lines where tectonic plates meet. Tectonic plates are the huge rocky plates that make up the surface of the earth. Tectonic plates can move apart or collide with each other due to great heat and pressure. This powerful movement tears apart the surface of the Earth releasing energy in the form of shock waves which cause earthquakes. The two tectonic plates that interacted to cause the 1906 San Francisco Earthquake were the Pacific Plate and the North American Plate on the boundary line that is now known as the famous San Andreas Fault.

San Francisco Earthquake History: Fast Facts for kids  via the Fact Sheet
Interesting description and brief facts about the San Francisco Earthquake History are detailed in the Fact Sheet.

The San Francisco Earthquake was caused by the rupture of ground surface along the San Andreas Fault plane (once referred to as the Tomales-Portola Fault line)

  • The intersection of a fault plane with the surface produces a feature called a "fault line"

  • Stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the rock which cause the shaking

The San Francisco Earthquake was estimated to be 7.8. on the Richter scale.  The Richter magnitude scale (also Richter scale) assigns a magnitude number to quantify the energy released by earthquakes. Seismic waves are also used to calculate the magnitude of earthquakes.

Liquefaction: Many streets destroyed by liquefaction during the San Francisco Earthquake. Liquefaction occurs when vibrations cause soil particles to lose contact with one another and as a result, the soil behaves like a liquid, unable to support any weight. Liquefaction had a devastating effect on the structures and buildings in the 1906 San Francisco Earthquake.

It was a major earthquake causing severe damage and felt in areas up to hundreds of miles from the epicenter. The activity of an earthquake is referred to as:

  • The Foreshock: A small earthquake heralding the arrival of a much larger one

  • The Mainshock: The largest, most violent shaking

  • The Aftershock: A small tremor that might follow a major earthquake or the effect or aftermath of the event

    • The 1906 San Francisco Earthquake was followed by a firestorm

The epicenter of the 1906 earthquake was located near the city of San Francisco.

At the time of the earthquake the city had a population of 400, 000. After the disaster 225,000 were left homeless

The area was subject to minor shakes but residents were not unduly worried as they had not caused great damage.

There was no warning of the disaster. The San Francisco Earthquake began before dawn at 5:12 a.m. when most of the inhabitants were still in bed. The date was 18 April 1906.

The Foreshock: People who were up and about, heard an ominous rumbling.  Then the shaking started. The foreshock tremor was a quick, terrifying warning of what was to come, and lasted for about 30 seconds. Then it stopped. It was the beginning of one of the worst natural disasters in the history of America.

The Mainshock: Approximately 20 seconds after the foreshock, the large earthquake hit - the mainshock. The Mainshock lasted for about 40 seconds and caused the entire city to rock. The effects of the 1906 San Francisco Earthquake were horrifying.

  • Buildings swayed

  • Trees were uprooted

  • Buildings crumpled and collapsed, bricks came crashing down

  • Walls caved in and chimneys toppled over

  • Streets were ripped open with hundreds of great cracks

  • Great, deep holes appeared in the ground

Many people were killed instantly, crushed to death by the collapsing masonry and falling debris. Animals meet the same fate and their carcasses lay on the streets. People and animals disappeared in an instant into deep holes opened by the earthquake. Those who survived were injured by showers of bricks and flying glass.

People watched in helpless horror as friends and family, including children, met their deaths in front of their eyes. The city was in chaos.

  • Gas mains ruptured

  • Electrical wires were broken

  • All telephone and telegraph services were cut off

  • Main water lines were broken

  • Many city chiefs were killed, so there was no leadership in the city

The Fire: The San Francisco Earthquake terrified the population but there was even worse to come. Fires immediately broke out across the city caused by the broken gas lines, broken electrical wires and the stoves and oil lamps that had fallen over during the shaking.

The Fire: Fires were also fueled by highly flammable, wood constructed buildings in the poorer, congested districts.

The Fire: There were more than 50 several separate major fires in the city that grew together. The fires spread at an alarming and rapid rate and were uncontrollable. There was:

  • Inadequate fire protection

  • Inadequate water supply

  • Inadequate direction - the fire chief had been killed in the earthquake

  • Broken gas lines

  • Inadequate man power and it was impossible to get extra help quickly

  • The firefighters desperately tried to combat the fires over an area of approximately
    21 square miles

The Fire:  Without water, without adequate leadership and the sheer enormity of the problem, the fires consumed the city.

The Fire: Most buildings were left to burn. The only way to stop the fires was to use a firebreak to create gaps between buildings to stop the progress of the fire. This method had been used in the Great Fire of London in 1666. But in 1906, over 350 years later, the firefighters had access to dynamite.

The Fire: The idea of creating a firebreak was good but the decision to use dynamite was bad.  None of the firefighters were trained in the use of dynamite which led to the useless destruction of even more buildings.

The Fire: The Fire, accompanied by deafening explosions, occurred all day long terrorized the people who were attempting to escape from the city.

The Fire: The explosions and the fire engulfed the city in smoke, leaving chemicals and ash clouds in its wake. Eye witnesses said you could hardly breath in the clouds of ash.

The Fire: The city burned for three days and three nights following the San Francisco Earthquake, some of the fires were as hot as 2,700°F. The fire eventually eased after 3 days, helped by a change in wind direction.

The Fire: The firestorm, the fires and the explosions were more catastrophic than the San Francisco Earthquake itself. When the fires finally burned out, more than 28,000 buildings had been destroyed attributing 80% - 85% of the damage in the city to the fire.

Aftermath: The terrified people left the shattered wreckage of their homes and the city. 98% of the city’s most populated 521 blocks lay in ruins.

The people left with nothing at first fleeing the nightmare by gathering together in parks, in vacant lots and on beachfronts. It is estimated that 250,000 residents fled the city by foot, ferry, horseback and train.

Over 100,000 other residents remained. A small number took advantage of the situation and looting occured.

An emergency, provisional government was formed and various announcements and edits were issued including one to shoot looters on sight. Soldiers, police, and vigilantes were empowered to carry out the needs of the city.

Aftermath: The City Hall and the County Courthouse were destroyed as were all records of the population. Property deeds, immigration records, marriage licenses, birth certificates were all destroyed.

Three days after the San Francisco Earthquake, the Governor of California, George C. Pardee appointed an 8 person Earthquake Investigation Commission.

It is estimated that the property loss due to the San Francisco Earthquake amounted to $524 million (in 1906 dollars)

Many insurance companies went bankrupt and shares on the Stock Market fell that triggered a nationwide financial Panic of 1907 that lasted for months.

It took nine years to rebuild the city following the San Francisco Earthquake.

The only comparable disaster at the time in America, in terms of the death toll, was the Galveston Hurricane of 1900.

The San Andreas fault has averaged 150 years between quakes.

US American History
1881-1913: Maturation Era

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