Unit 7 Earth Systems Test

What is an earthquake?

A natural shaking of the lithosphere caused by a release of energy stored in rocks.

What causes most earthquakes?

Movements along faults where potential energy is released as seismic waves.

What are the three types of faults?

Normal Fault, Reverse Fault, Strike-Slip Fault.

What is the definition of the epicenter?

The location on Earth's surface directly above the focus of an earthquake.

What is the focus in relation to an earthquake?

The point inside Earth where the earthquake originates.

What is a seismograph?

An instrument used to measure and record ground movements.

What is a seismogram?

The recorded output of a seismometer.

What are Primary Waves (P-Waves)?

The fastest seismic waves that travel through solids, liquids, and gases in a compressional motion.

What are Secondary Waves (S-Waves)?

Slower seismic waves that only travel through solids and move in a shear motion.

What are Surface Waves?

Seismic waves that travel along the Earth's surface and typically cause the most damage during an earthquake.

What is the Shadow Zone in seismic activity?

The area where no direct seismic waves are detected due to the absorption of S-waves and refraction of P-waves in the liquid outer core.

How do you determine the location of an earthquake epicenter?

By using both P-waves and S-waves data and triangulation from at least three seismic stations.

Who invented the first seismograph?

Chang Heng in 132 AD.

What scales measure earthquake magnitude and intensity?

The Mercalli Scale measures intensity; the Richter Scale and Moment Magnitude Scale measure magnitude.

What is the difference between magnitude and intensity of an earthquake?

Magnitude measures the energy released; intensity measures the observed effects.

What is the Richter Scale?

A logarithmic scale that measures earthquake magnitude based on wave amplitude.

What is the Mercalli Scale?

A scale that measures earthquake intensity based on observed effects.

What is the Moment Magnitude Scale?

A modern scale that measures the total energy released by an earthquake.

What is seismic activity?

The occurrences of earthquakes and related phenomena.

What is tremor in the context of seismic activity?

A tremor refers to a minor earthquake or tremulous motion of the ground.

What are aftershocks?

Smaller earthquakes that occur in the same area after a larger earthquake.

What is a megathrust earthquake?

A large earthquake that occurs at subduction zones, often with a magnitude of 7.5 or greater.

What is a seismic gap?

A section of a fault that has not produced earthquakes for a long time, potentially indicating a buildup of stress.

What is the relationship between tectonic plate movement and earthquakes?

Most earthquakes occur due to the movement of tectonic plates interacting at their boundaries.

What are tectonic plates?

Large sections of Earth's lithosphere that move and interact at their boundaries, causing geological activity.

What are the types of tectonic boundaries?

Convergent (colliding plates), Divergent (separating plates), Transform (sliding past each other).

What are earthquake hazards?

Tsunamis, liquefaction, landslides, and structural collapse.

What is liquefaction?

Saturated soil behaving like a liquid due to shaking.

What is a tsunami?

A large sea wave caused by seismic activity.

What is a landslide in the context of earthquakes?

A mass movement triggered by ground shaking.

What are historical major earthquakes?

Chile (1960) magnitude 9.5, Alaska (1964) magnitude 9.2, Japan (2011) caused a devastating tsunami.

What are the emergency preparedness steps for earthquakes and tsunamis?

Earthquake safety: Drop, cover, and hold; Tsunami safety: Move to higher ground.

What should you do during an earthquake?

Stay indoors, find cover under sturdy furniture, and stay away from windows.

How can building codes help reduce earthquake risk?

Building codes ensure structures can withstand seismic forces, reducing damage and casualties.

What is seismic retrofitting?

The process of strengthening existing structures to make them more resistant to seismic activity.

How does soil composition affect earthquake impact?

Soil composition influences how seismic waves travel; softer soils can amplify shaking and increase damage.

How do seismic waves travel through various materials, and what impacts their speed?

Seismic waves move faster through solids and slower through liquids and gases depending on material density and elasticity.

What is the importance of understanding seismic wave properties?

It helps in interpreting seismograms and understanding earthquake behavior.

What is the process for locating an earthquake epicenter?

Determine the time difference between P-waves and S-waves to triangulate the epicenter location.

How does the moment magnitude scale differ from the Richter scale?

The moment magnitude scale measures total energy released, while the Richter scale measures amplitude of seismic waves.

What is the difference between intraplate and interplate earthquakes?

Intraplate earthquakes occur within a tectonic plate, while interplate earthquakes occur at the boundaries between plates.

What contributes to the cause of an earthquake?

Faults, where rocks break and move along a fracture, release energy that causes earthquakes.

What are common earthquake hazard effects?

Hazard effects include structural damage, tsunamis, aftershocks, and landslides.

How do geologists use fault lines?

Geologists use fault lines to identify areas at risk for future earthquakes.

What is the Elastic Rebound Theory?

The idea that stress builds along a fault until the rock snaps and releases energy as an earthquake.

What is foreshock?

An earthquake that occurs before a larger seismic event, serving as a precursor.

What is an earthquake’s amplitude?

The maximum extent of a vibration or displacement from the rest position.

What is a fault trace?

The intersection of a fault plane with the Earth's surface.

What role do historical earthquake records play in predicting future seismic events?

Historical earthquake records help seismologists understand patterns, frequency, and the potential size of future earthquakes.

What strategies can communities implement for earthquake and tsunami preparedness?

Communities can create awareness programs, conduct drills, establish early warning systems, and plan evacuation routes.

How does liquefaction occur, and what conditions are necessary for it to take place?

Liquefaction occurs when loose, water-saturated sediments lose strength due to strong shaking.

What is seismic hazard assessment?

The study of earthquake risks in a given area based on historical and geological data.

How can you read a seismogram?

By analyzing the wave patterns on the seismogram, such as the arrival times of P-waves and S-waves.

How do tsunamis form?

Tsunamis form when an undersea earthquake displaces large amounts of water, creating massive waves.

What is the difference between an earthquake and a seismic event?

An earthquake is a specific type of seismic event characterized by ground shaking.

How does the understanding of the Shadow Zone help scientists in earthquake research?

It helps scientists determine Earth's interior structure, particularly the liquid outer core.

What are the potential economic and social impacts of significant earthquakes?

Earthquakes can lead to property loss, infrastructure damage, business disruption, and long-term displacement.

Discuss the differences in human response to earthquakes versus tsunamis.

Earthquakes require immediate protective actions, while tsunamis require rapid evacuation based on warnings.

What is the purpose of an early warning system for earthquakes?

Detects initial seismic waves and provides seconds to minutes of warning before shaking starts.

What is the process of structural collapse during an earthquake?

Weak structures fail due to shaking, often leading to significant damage and casualties.

Why are historical earthquake events significant?

They provide insights into seismic patterns, frequency, and potential risk in specific regions.

How do you use the Richter scale?

The Richter scale quantifies the amplitude of seismic waves to measure earthquake magnitude.

What is the purpose of earthquake drills?

To prepare people for real earthquakes by teaching proper safety actions and evacuation procedures.