"Core" Concepts
This is the point inside the Earth where an earthquake begins.
What is the focus?
In this type of fault, the hanging wall moves downward relative to the footwall.
What is a normal fault?
These are the fastest seismic waves and the first to arrive at a recording station.
What are P-waves?
This instrument is used to detect and record seismic waves.
What is a seismograph?
This occurs when saturated soil temporarily behaves like a liquid during shaking.
What is liquefaction?
This is the point on Earth’s surface directly above the focus.
What is the epicenter?
In this type of fault, the hanging wall moves upward due to compression.
What is a reverse fault?
These surface waves move in a rolling, ocean-like motion along the ground.
What are Rayleigh waves?
This is the recorded output produced by a seismograph.
What is a seismogram?
This hazard can result from ruptured gas lines during an earthquake.
What are fires?
This is a fracture in Earth’s crust where movement occurs.
What is a fault?
This type of fault involves horizontal motion as blocks slide past each other.
What is a strike-slip fault?
These seismic waves cannot travel through liquids.
What are S-waves?
This is the minimum number of seismic stations needed to locate an earthquake’s epicenter.
What is three?
This large ocean wave is caused by the sudden displacement of water during an earthquake.
What is a tsunami?
This force resists motion between two surfaces in contact.
What is friction?
This type of fault is a low-angle reverse fault commonly formed by strong compression.
What is a thrust fault?
These waves usually cause the most damage due to their large ground motion.
What are surface waves?
This scale measures the total energy released by an earthquake.
What is magnitude (Moment Magnitude, Mw)?
These structures are often heavily damaged by strong surface wave motion.
What are buildings?
This term describes the total amount of movement along a fault during an earthquake.
What is displacement?
This type of stress causes rocks to be pushed together, often forming reverse or thrust faults.
What is compressional stress?
These waves are detected first by earthquake early warning systems.
What are P-waves?
This scale uses Roman numerals from I to XII to measure observed damage and intensity.
What is the Modified Mercalli Intensity Scale?
This hazard occurs when slopes fail due to earthquake shaking.
What is a landslide?