Fault Line Notes
Fault Line Secrets
Student Guided Notes | How the Earth Was Made
Observer:
Date:
Vocabulary Field Guide
Plate Tectonics
The theory describing the large-scale motion of the plates making up Earth's outer shell.
Strike-Slip Fault
A fault where rocks slide horizontally past each other (no vertical motion).
Recurrence Interval
Define: __________________________________________________________________________
Guided Observations
Part 1: The San Francisco Disaster (1906)
1. Before 1906, scientists believed earthquakes were caused by _____________________ or _____________________.
2. Andrew Lawson noticed fences had moved _____________________ rather than up and down.
3. The two plates at the San Andreas are the _____________________ Plate and the _____________________ Plate.
Part 2: The Earthquake Capital (Parkfield)
4. Parkfield is the "Earthquake Capital" because quakes used to occur here every _________ years.
5. At Wallace Creek, the stream bed is offset by _____________________ feet.
6. The plates slide past each other at _________ inches per year (same speed as _____________________ grow).
Part 3: Ancient Evidence (Pallett Creek)
7. Kerry Sieh found evidence of ancient earthquakes by _____________________ in soil layers.
8. Scientists use _____________________ dating on organic material to determine the age of these quakes.
9. The average recurrence interval on the southern section is _________ years.
Recurrence Calculation
The last "Big One" on the southern San Andreas Fault was in 1857. Use the 150-year interval to calculate the next "due" date.
Calculation:
1857 + 150 = ___________________
Status:
Is the fault overdue? (Circle) Yes / No
Critical Thinking:
Why is it dangerous to rely on a "schedule" for earthquakes?
Plate Motion Sketch
Field Sketch Area
Draw the fault boundary line. Label the Pacific and N. American Plates.
Show movement arrows for each plate.
Fault Line Keys
Fault Line Secrets
Teacher Answer Key
Master Copy
Vocabulary Solutions
Recurrence Interval
The average time between successive occurrences of an earthquake on a given fault.
Guided Observations Solutions
Part 1: The San Francisco Disaster
- 1. Before 1906: Explosions or Volcanoes.
- 2. Fences moved: Horizontally (Sideways).
- 3. Massive plates: Pacific Plate and North American Plate.
Part 2: The Heart of the Fault
- 4. Capital: Parkfield / Every 22 years.
- 5. Offset: 430 feet.
- 6. Rate: 1.5 - 2 inches / Same speed your fingernails grow.
Part 3: Recurrence Intervals
- 7. Evidence: Trenches (Excavation).
- 8. Dating: Radiocarbon (Carbon-14) dating.
- 9. Interval: 150 years.
Data Analysis Solutions
Calculation:
1857 + 150 = 2007
The southern section became statistically "due" for a major rupture in 2007.
Overdue Analysis:
The fault is approximately 19 years overdue (as of 2026). This is an average because friction, plate stress, and rock density vary; some areas "stick" longer than others.
Sketch Reference
Pacific Plate: Moving Northwest
North American Plate: Moving Southeast
Student drawings should show horizontal displacement with clear arrows representing the relative motion across the fault line.
PACIFIC
N. AMERICAN
