Understanding Earthquakes and Faults

What is a fracture in the Earth’s crust where significant movement has taken place?

• Earthquake

• Fault

How are faults formed? Faults are formed______.

• when volcanic activity pushes magma to the surface, causing the Earth’s crust to split and form fractures.

• when stress from the movement of tectonic plates causes the Earth’s crust to bend and eventually break, creating a fracture where rocks can slide past each other.

Refer to the figure below; to explain how compressional stress produces a reverse fault?

• pulling the two plates away from each other.

• pushing or squeezing the two plates against each other.

Consider the diagram below which shows the section of the Earth’s crust, and the arrow represents the movement of the tectonic plate. Which is TRUE in the formation of reverse fault?

• I and II

• II and III

• II and IV

• I and III

Refer to the illustration. Rocks deform plastically, and they tend to fold. What force squeezes rocks together that causes rocks to fold or break along faults?

• Fault

• Stress

What is the likely effect on rocks along a fault when they bend due to tectonic stress? The rocks will bend _______.

• continuously without breaking, preventing any earthquake from occurring.

• elastically, storing energy, but will eventually break and cause an earthquake when the energy is released.

In an area near a fault, scientists measure the movement of two large blocks of rock along the fault. Over many years, one block moves horizontally past the other block with little vertical movement. Which type of fault is most likely to be present in this area?

• 
• 

Why does a continuous movement along a fault cause an earthquake? There is a continuous movement along a fault cause an earthquake because the rocks_____.

• suddenly move and kept on trembling.

• are no longer moving and just stop adjusting its position.

An earthquake was detected in Nasugbo, Batangas with a magnitude of 4.1. The aftershocks are expected to be stronger than the main shock. Based on the diagram, what do you call Point A, where slip or sudden movement occur?

• epicenter

• focus

Which statements CORRECTLY describe the difference between the epicenter and the focus of an earthquake? The epicenter is the point ______ while the focus is ______.

• where seismic waves travel fastest; the point where the earthquake is felt most strongly.

• beneath the Earth’s surface where the energy is first released; the point on the Earth’s surface directly above the epicenter.

• on the Earth’s surface where the earthquake starts; is the location deep beneath the surface where the energy is first released.

• deep beneath the surface where the earthquake starts; the point on the Earth’s surface where the earthquake is felt most strongly.