Earthquakes

1. Earthquakes Shanese Breitkreitz

2. 1906 San Francisco Earthquake • The Great San Francisco Earthquake is also known as The Great Quake and Fire, and The Great Shake. • The Great San Francisco Earthquake happened at 5:12 am on April the 18th 1906.This earthquake is one of the most significant earthquakes of all time. It ruptured 296 miles of the San Andreas fault, running from northwest of San Juan Bautista to the triple junction at Cape Mendocino. • A foreshock with sufficient force was felt widely throughout the San Francisco Bay area at almost precisely 5:12 am. The earthquake occurred about 20 – 25 seconds later, and last for approximately 45 – 60 seconds. This great earthquake was felt from southern Oregon to south of LA and inland to central Nevada. • The Great San Francisco Earthquake is remembered most for the fire it spawned in San Francisco. Most of the deaths occurred in San Francisco caused by the earthquake and fire, as well as 189 reported elsewhere. However the commonly quoted number of deaths ‘700’ is not believed to be underestimated.

3. 1906 Earthquake (Cont’d) • Fires broke out across the city almost immediately, caused by broken gas lines and stoves that had fallen over. These fires spread ferociously. During the shake most of the water mains had also been broken, and the fire chief was killed early on by the falling debris. Is was amazing that the fire was under control within just three days considering the little water they had along with no leadership. • The ground is thought to have moved at a speed of 4 – 5 ft/sec or approximately 3 miles/hr. • The disaster left half of San Francisco’s population homeless, and destroyed 28 thousand buildings, with an estimated property damage of $400 million from the earthquake and fire, and $80 million from the earthquake alone. • Mostly the magnitude of the quake is between 7.7 and 7.9 on the Richter scale. • This earthquake led to the formation of the elastic-rebound theory, and was the first large, natural disaster whose damage was photographed.

4. 1964 Alaska "Good Friday" Earthquake • At 5:36 pm Good Friday, March 27, 1964 the Alaskan earthquake occurred, and was the largest earthquake ever recorded in North America, and the second largest earthquake ever recorded. The quake last for about 3 – 5 minutes and was eventually rated with a magnitude of 9.2, that is 10 time more power then the bomb that hit Hiroshima. • The quake occurred on a thrust fault, and the first slip occurred at a depth of 25km deep. • This sudden uplift of the seafloor caused a tsunami, and propagated speeds of over 400 miles/hr. It even reached the Hawaiian Islands and Japan. Continuing waves is Valdes occurred at 30 minute intervals until 2 am. • Ground liquefaction was also caused, the soil and sand temporarily turned from a solid to a liquid state. This caused rockslides and avalanches, destroying 75 homes. The property damage was about $311 million.

5. 1964 Earthquake (Cont’d) • For the first 10 seconds of the shake the ground rocked gently. Most people did not think to much of it because small Alaskan quakes were a normal part of life. But very soon the gentle rocking increased, the ground started to open and close, buildings twisted and collapsed, trees uprooted, and the people clung to lamp posts, cars, and each other to keep from falling over. A quarter-mile section of 4thave was ripped apart and the north side dropped 11 feet. On the coast of Valdes the S.S. Chena, a 10,000 ton cargo freighter that was moored at the dock, destroyed the dock and killed several dockworkers, as giant waves carried and deposited it on dry land before returning and carrying it back out to sea. 32 people died from this. 12 people were killed in the city of Seward, and 8 more people died on Kodiak Island. The entire town of Chenega was wiped out of existence, along with 23 of its inhabitants. 199 of the 131 deaths recorded were caused by the tsunami.

6. 1994 Northridge Earthquake • The Northridge earthquake happened early in the morning at 4:31 am on January 17,1994. The epicentre was a suburb of LA in the San Fernando Valley of Northridge, California. The magnitude of the quake was rated at 6.7. In 1971 the same general area had been hit by a earthquake with a magnitude of 6.6. because of this previous quake people in the area awareness in California was high, and this was one of the best prepared areas in the world. Luckily because of the timing most people were safe sleeping in their bed, lowering the death rate substantially. 57 people were killed and approximately 9000 were injured.

7. 1994 Earthquake (Cont’d) It caused extreme damage to parking structures and freeway overpasses. At the California State University, a 2500-car parking garage collapsed. The quake also caused landslides in the Santa Susana Mountains, Santa Monica Mountains, and western San Gabrial Mountains. The slides blocked roads and damaged water line, along with homes. The quake lasted for about 10 – 20 seconds. Since the San Fernando earthquake in 1971, the Northridge earthquake was the worst in the LA basin.