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|Name: | |

|Date: | |

|Subject: | |

|Bay Area Earthquakes |

Objectives

|Objective 1: ASWBAT identify the Hayward Fault and the San Andreas Fault on a map of the San Francisco Bay Area. |

|Objective 2: ASWBAT identify where the epicenter was of two historical earthquakes that occurred in the Bay Area and describe their effects on society. |

On a scale of 1 – 3 how well you can do on this objective now.

(1 – Not at all 2 – I know it a little bit 3 – I know it very well)

Highlight your choice.

|Objective: 1 |1 |2 |3 |

|Objective: 2 |1 |2 |3 |

Key Vocabulary Words

On a scale of 1 – 3 how well you know the vocabulary words below.

(1 – Not at all 2 – I know it a little bit 3– I know it very well)

|Hayward Fault |1 |2 |3 |

|San Andreas Fault |1 |2 |3 |

|1906 San Francisco Earthquake |1 |2 |3 |

|1989 Loma Prieta Earthquake |1 |2 |3 |

Pre-quiz

|Do your best to answer the following questions. |

| 1. What is a fault? |

|Answer: |

|2. What is a fault zone? |

|Answer: |

|3. Describe what the epicenter of an earthquake is. |

|Answer: |

Bay Area Fault Zone

The Bay Area is a wonderful place to live in fact it is home to over 7.3 million people. It also happens to be a major fault zone. A fault zone is an area where many faults, cracks in the Earth’s crust, exist relatively close to each other. The Bay Area has 10 major fault lines and many more if you count the small ones. For this lesson we are going to focus on 2 of the major Bay Area faults, the San Andreas Fault and the Hayward Fault. Scientists estimate that there is a 63% chance a 6.7 or greater magnitude earthquake will occur along one of the Bay Areas faults.

San Andreas Fault

The San Andreas Fault is the boundary between the pacific plate and the North American plate. The Pacific Plate (on the west) moves northwestward relative to the North American Plate (on the east), causing earthquakes along the fault. The entire San Andreas Fault system is more than 800 miles long and extends to depths of at least 10 miles within the Earth. Geologists believe that it has moved at least 350 miles since it came into existence about 15-20 million years ago. In the Bay Area the San Andreas Fault passes through the southern part of San Francisco and continues past the Golden Gate and into Marin County.

1. Where does the San Andreas Fault pass through the Bay Area?

|Answer: |

Video: 1989 Loma Prieta Earthquake Shake Map Animation

1. Why do you think the intensity is different in different areas?

|Answer: |

Hayward Fault

The Hayward Fault is considered one of the most dangerous in the world because scientists believe it is due for a large earthquake and because it runs under a densely populated area of California. The fault runs parallel to and east of the San Andreas Fault. The fault is in the East Bay and runs through cities like San Jose, Oakland, Fremont, Richmond, Berkeley, Hayward, San Leandro, San Lorenzo, El Cerrito, Emeryville, Kensington and Milpitas. The last major earthquake on the Hayward fault was an estimated magnitude 7.0 at 7:53 a.m. October 21, 1868. The fault moved northward an estimated 6 feet! Geologic records show that the fault produces a major earthquake about every 140 years. It has been over 145 years since the last big one!

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Video: The Hayward Fault

Review question – What can you do to be more prepared for the next earthquake on the Hayward fault?

1. Where is the Hayward fault?

|Answer: |

2. How often do scientists believe the fault produces a major earthquake?

|Answer: |

3. How long ago was the last major earthquake on the Hayward Fault?

|Answer: |

1906 San Francisco Earthquake

At 5:12 a.m. on April 18, 1906, a foreshock hit San Francisco. However, it offered just a quick warning, for massive devastation was soon to follow. Approximately 20 to 25 seconds after the foreshock, the large quake hit. With the epicenter being just outside the Golden Gate (under water) near San Francisco, the entire city was rocked. Chimneys fell, walls caved in, and gas lines broke. Asphalt that covered the streets buckled and piled up. Many people didn't have time to even get out of bed before they were killed by falling debris. The earthquake lasted for approximately 40 to 60 seconds. Almost immediately, fires broke out across the city from broken gas lines and stoves that had fallen over during the shaking. The fires spread ferociously across San Francisco. The quake ruptured a total of 290 miles of the earth's surface along the San Andreas Fault. Scientists are still trying to accurately calculate the magnitude of the quake. Since the scientific instruments used to measure the earthquake weren't as reliable as more modern ones, scientists have yet to agree on the size of the magnitude, but most scientists estimate it between 7.7 and 7.9 magnitude (a few have said as high as 8.3).

1. Where was the epicenter to the 1906 earthquake?

|Answer: |

2. What magnitude do scientists estimate the 1906 earthquake was?

|Answer: |

What did we learn?

When the 1906 earthquake struck on April 18, nearly all scientists in California began to assemble observations of the earthquake and its effects. Professor Andrew C. Lawson, of UC Berkeley was directed three days later to conduct a full study of the earthquake and its effects. The 1906 earthquake sparked a nationwide movement to study earthquakes. It caused society to begin to put a lot of resources into to studying earthquakes so that we could prevent another disaster like the 1906 earthquake. Much of what we now know about earthquakes we owe to this movement.

1. What did the 1906 earthquake cause society to do?

|Answer: |

1989 Loma Prieta Earthquake

On October 17, 1989 at 5:04pm local time, an earthquake with a surface magnitude of 7.1 occurred along the San Andreas Fault zone. The epicenter was in the Santa Cruz Mountains, 10 miles northeast of Santa Cruz. Although San Francisco and Oakland were located 60 miles northwest of the epicenter, these two cities suffered billions of dollars of damage. San Francisco’s Marina District suffered extensive damage. This was due to the unsteadiness of the ground. Following the 1906 San Francisco Earthquake, the debris and rubble was dumped into this area. Because this was filled land, the shockwaves were more severe. Buildings easily collapsed and buckled. Five people died. A portion of the Cypress Street Viaduct, a double decker highway, collapsed on the Nimitz Freeway where the upper deck collapsed and crushed the cars on the lower deck. There were 42 fatalities. On the San Francisco-Oakland Bay Bridge, a 50-foot section of the upper deck gave way and fell to the lower deck. One person was killed.

Video Link: 1989 Loma Prieta Earthquake:

1. What was the magnitude of 1989 Loma Prieta earthquake?

|Answer: |

2. Where was the epicenter of 1989 Loma Prieta earthquake?

|Answer: |

What did we learn?

Scientists and engineers learned a hard lesson from the damage the earthquake caused. Because of the 1989 Loma Prieta earthquake we no longer build double decker highways. Another result of this earthquake is that engineers realized the Oakland side of the Bay Bridge was not strong enough to withstand another large earthquake, so they built a new span. It was completed in 2013.

1. What two things have changed because of 1989 Loma Prieta earthquake?

|Answer: |

Quiz

Directions: Answer the following questions to see if you met the objectives.

1. Where was the epicenter of the 1906 San Francisco earthquake?

|Answer: |

2. What did the 1906 earthquake cause society to do?

|Answer |

3. Where was the epicenter of the 1989 Loma Prieta earthquake?

|Answer: |

4. What two things changed after the 1989 Loma Prieta earthquake?

|Answer: |

5. Identify which the name of the faults in the diagram below.

|A | |

|B | |

-----------------------

Bay Area

Lafayette

San Andreas Fault

Areal View

Hayward Fault

Arial View

Bay Bridge

Nimitz Freeway

B

A

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