Chapter 7 Earthquakes Section 1 and 2 What Are Earthquakes? Flashcards
What is a fault?
A fault is a break in Earth’s crust along which blocks of rock slide relative to one another
Define earthquake
A movement or trembling of the ground that is caused by sudden release of energy when rocks along a fault move
Where do most earthquakes happen?
Most earthquakes take place near the boundaries of tectonic plates
Describe earthquakes at divergent boundaries
Plates pull away from one another. Locks drop down. Earthquakes happen along normal faults. example: mid Ocean Ridge.
Describe earthquakes at convergent boundaries
Tectonic plates collide. This causes mountain building or subduction. Compression causes the lithosphere to break into fault blocks. Earthquakes happen along reverse faults.
Describe earthquakes at transform boundaries
As plates move past each other horizontally, the rocks on both sides of the fault are sheared. Quakes happen at strike-slip faults Schooley at shallow depths.
Why do earthquakes happen at transform boundaries?
Rock some both sides of the fault of our broken as they grind past one another
What is a fault zone?
Places along plate boundaries when large numbers of interconnected faults are located.
What is elastic rebound?
The sudden return of elastically deformed rock to its undeformed shape.
What is a seismic wave?
Hey wave of energy that travels through the earth and away from an earthquake in all directions.
How does the elastic rebound cause earthquakes?
During the sudden return of elastically deformed rock to its original shape, large amounts of energy are released. This energy travels the rocks of seismic waves. The waves cause the ground to move.
What is the other name for a P-wave?
Primary wave because they are always the fastest, and the first waves of an earthquake to be detected.
What is an S wave?
An S wave or secondary wave is the second fastest seismic waves. S waves are body waves that sheer rock horizontally from side to side.
What are surface waves and why they cause the most damage?
Surface waves can move the ground with the rolling up-and-down motion. Because their energy is focused on earth surface, surface waves tend to cause the most damage.
What is a seismometer or seismograph?
Earthquake sensing instruments that record seismic waves
What is an earthquake’s focus?
The location within Earth along a fault at which the first motion of an earthquake occurs.
What is an epicenter?
The point on Earth’s surface directly above an earthquake starting point or focus
What is lag time and why is it important?
The time between the arrival of the P waves and the arrival of the S waves is called lag time and tells scientist how far the waves have traveled.
What is triangulation?
A process where at least three seismometer stations are used to calculate the Epicenter up and earthquake.
What is magnitude?
Magnitude is the measure of the earthquake’s strength. In the past scientist use the Richter scale. now, they use the moment magnitude scale.
What is intensity?
Amount of damage caused by an earthquake.
What is the modified Mercalli scale?
A scale used to describe earthquakes intensity. The scale ranges from one to twelve
What four factors determine the effect of an earthquake?
Size of the earthquake, distance from the epicenter, local geology, and type of construction
How does distance from the epicenter effect in earthquake?
The farther in area is from the epicenter the less destructive earthquake will be
How does local geology how to determine that affects of an earthquake on a given area?
Seismic waves are particularly dangerous when they travel through loose soils and sediments that contain large amounts of water.
What is liquefaction?
When water saturated soil is shaken by seismic waves the grains the make up the sentiment lose contact with one another and are surrounded by water. This process is called liquefaction.
What is earthquake resistant construction?
Wouldn’t steal her more flexible, and flexible structures are more likely to survive shaking. Bricks and concrete are not flexible, and are easily damaged by earthquakes.
