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
Objective: 2
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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
San Andreas Fault
1906 San Francisco Earthquake
1989 Loma Prieta Earthquake
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Pre-quiz
Do your best to answer the following questions.
1. What is a fault?
Answer:
2. What is a fault zone?
Answer:
3. What type of plate boundary is the San Andreas Fault?
Answer:
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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.
Bay Area
Lafayette
Link: Map of Bay Area Faults - http://gis.abag.ca.gov/website/FaultZones/
Explore the map. See if you can see where you live. Do you live near a fault line?
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 being
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.
San Andreas Fault
Areal View
1. Where does the San Andreas Fault pass through the Bay Area?
Answer:
Video Link: Intensity Map http://earthquake.usgs.gov/regiona`l/nca/simulations/1989/movies/lp1989plan.mov
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!
Hayward Fault
Arial View
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Video Link: Hayward Fault - http://science.kqed.org/quest/video/the-hayward-faultpredictable-peril/
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.
Bay Bridge
Nimitz Freeway
Video Link: 1989 Loma Prieta Earthquake:
http://www.dailymotion.com/video/x6lpds_nbc-news-on-1989-san-franciscoeart_shortfilms
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 is 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
A
B
B