Plate Tectonics
These enormous sections of Earth's outer shell move slowly over the planet's surface.
Tectonic plates
This geological feature is a break in Earth's crust where rocks have moved relative to one another.
Fault
This instrument detects and records vibrations produced by earthquakes.
Seismograph
This term describes the amount of energy released by an earthquake.
Magnitude
This massive ocean wave can form when an undersea earthquake suddenly displaces a large volume of water.
Tsunami
At this type of plate boundary, two plates move away from each other, allowing new crust to form in some locations.
Divergent boundary
Unlike a fault, this crack in rock forms when the rock breaks but no significant movement occurs along the break.
Joint
These seismic waves travel fastest through Earth's interior and generally arrive at recording stations first.
P waves (primary waves)
This term describes the observed effects and degree of shaking or damage an earthquake causes at a particular location.
Intensity
These structures are designed with flexible materials and engineering features that help them withstand strong ground shaking.
Earthquake-resistant buildings
When two tectonic plates push toward one another, they meet at this type of boundary, where mountains or deep ocean trenches may form.
Convergent boundary
At this type of fault, one block of rock moves downward relative to the other because the crust is being pulled apart.
Normal fault
Unlike P waves, these body waves cannot travel through liquids because they involve shearing motion.
S waves (secondary waves)
This point lies underground where an earthquake begins and seismic energy is first released.
Focus
A building collapses during an earthquake, trapping people beneath bricks and concrete. This illustrates why falling debris and structural failure can be more dangerous than the shaking itself.
This type of stress pulls rocks apart and can cause the crust to stretch and thin.
Tension
This type of fault forms when compression pushes one block of rock up and over another block.
Love waves and Rayleigh waves belong to this group of seismic waves that travel along Earth's exterior and can cause significant damage.
Surface waves
This location on Earth's surface lies directly above the underground starting point of an earthquake.
Epicenter
Scientists cannot reliably tell people the exact date and time of a future earthquake, but they can estimate this long-term likelihood for a region.
Earthquake risk/probability
Two blocks of rock are pushed horizontally in opposite directions, causing them to grind past each other. What type of stress is acting on the rocks?
Shear stress
A geologist discovers that a large slab of older rock has been pushed over younger rock along a low-angle fault. What type of fault could explain this arrangement?
Overthrust fault
A large earthquake occurs, and several smaller earthquakes follow in the surrounding area over the next few days. What are these later earthquakes called?
Aftershocks
Scientists use recordings from at least three seismic stations to determine this location because each station provides a distance estimate that helps narrow down where the earthquake occurred.
Epicenter
A coastal city experiences a powerful earthquake offshore. Officials warn residents to move to higher ground rather than wait by the beach. What dangerous event are they preparing for, and why is moving uphill important?
Tsunami. Moving higher helps people escape the flooding