Studied by 0 people
What causes an earthquake?
Earthquakes are caused by forces inside the Earth that cause rocks to move along faults. When rocks move past each other, their rough surfaces temporarily catch, creating stress. When this stress becomes too great, the rocks break, releasing energy in the form of seismic waves.
What does the Elastic Rebound Theory explain?
The Elastic Rebound Theory explains how energy is stored in rocks as they bend under stress. When the stress exceeds the rock's strength, it breaks and releases energy as seismic waves, causing an earthquake.
What are the three main types of faults?
Normal Faults - Caused by tension, the hanging wall moves downward. Reverse Faults - Caused by compression, the hanging wall moves upward. Strike-Slip Faults - Caused by shearing, plates slide past each other horizontally.
What is a Normal Fault?
A normal fault occurs when tension pulls the crust apart, and the hanging wall moves downward, commonly found at divergent plate boundaries.
What is a Reverse Fault?
A reverse fault occurs when compression pushes the crust together, and the hanging wall moves upward, often found at convergent plate boundaries.
What is a Strike-Slip Fault?
A strike-slip fault occurs when shearing forces cause plates to slide past each other horizontally, commonly found at transform plate boundaries.
What are seismic waves?
Seismic waves are energy released during an earthquake that travels through Earth’s interior and across its surface, causing the ground to shake.
What are P-waves?
P-waves are the fastest seismic waves, compressing and expanding the ground in the direction of travel. They can travel through solids, liquids, and gases, and are the first waves to arrive at seismic stations.
What are S-waves?
S-waves are slower than P-waves, traveling only through solids. They shake the ground side to side or up and down, causing more damage due to their vertical motion.
What are surface waves?
Surface waves are seismic waves that travel along the Earth’s surface. There are two types: Love waves and Rayleigh waves.
How do Love waves move?
Love waves cause the ground to move side to side in a horizontal motion, perpendicular to the direction of travel. They are the fastest surface waves and the most destructive.
How do Rayleigh waves move?
Rayleigh waves cause the ground to move in an elliptical, rolling motion similar to ocean waves, spreading out the most and giving them a long duration on seismograph recordings.
How is the epicenter of an earthquake located?
The epicenter is located using triangulation. Three seismograph stations measure the distance to the epicenter, and the intersection of the circles from these stations locates the epicenter.
What is a time-distance graph?
A time-distance graph shows the travel times for P-waves and S-waves, and the difference in arrival times helps calculate the distance from the seismograph to the epicenter.
What are shadow zones?
Shadow zones are regions where seismic waves are not detected due to the bending of P-waves and the inability of S-waves to travel through liquids. These zones help map Earth’s internal structure.
What is the relationship between depth, density, and pressure?
As depth increases, both density and pressure increase, causing changes in how seismic waves behave as they travel through different layers of Earth.
What is the Moho?
The Moho is the boundary between Earth’s crust and mantle, marked by a change in seismic wave speeds and densities.
What’s the difference between magnitude and intensity?
Magnitude measures the energy released by an earthquake, typically measured using the Richter scale. Intensity measures the observed effects and damage caused by the earthquake at specific locations.
What is the Richter scale?
The Richter scale measures the magnitude of an earthquake based on the height of seismic waves recorded on a seismograph. Each increase of 1.0 represents a 10-fold increase in wave size and 32 times more energy released.
What causes a tsunami?
Tsunamis are caused by underwater earthquakes that displace large amounts of water, creating massive waves that can travel across the ocean and reach heights of over 30 meters when they reach shore.
What is liquefaction?
Liquefaction occurs when shaking from an earthquake turns wet soil into a liquid-like state, destabilizing foundations and causing buildings to collapse or tilt.
What do seismologists study?
Seismologists are scientists who study earthquakes and seismic waves, using seismographs to record the intensity, duration, and location of seismic activity.
What are seismographs and seismograms?
Seismographs are instruments that register seismic waves and record the time of arrival for each wave. Seismograms are the printed records created by seismographs that show the intensity and time of seismic waves.
How can buildings be made more earthquake-resistant?
Buildings can be made more earthquake-resistant by constructing flexible foundations, such as rubber-steel cushions, that absorb the energy of seismic waves and allow movement during shaking.
How does fault behavior affect earthquakes?
Faults cause earthquakes by allowing rocks to move past each other. The type of fault influences the direction and nature of the earthquake's motion.
What is an aftershock?
An aftershock is a smaller earthquake that occurs after the main earthquake, caused by the adjustment of rocks around the fault zone.
Why do buildings sustain damage in an earthquake?
Buildings sustain damage in an earthquake as they vibrate from ground shaking. Damage occurs when the building cannot withstand these vibrations, especially high-frequency vibrations caused by P and S-waves.
What is the relationship between distance of a seismograph and an earthquake’s focus?
The farther a seismograph is from the focus of an earthquake, the longer the interval between the arrival of the P- and S-waves.
How do surface waves develop during an earthquake?
Surface waves develop when seismic waves from the focus reach the epicenter, moving more slowly than P and S waves but causing more severe ground movement.
How do seismic waves affect buildings of different heights?
Compressional (P) and shear (S) waves primarily cause high-frequency vibrations, affecting tall buildings, while surface waves cause low-frequency vibrations that affect low buildings.
How do primary (P) waves move?
P-waves move by compressing and expanding the ground in the direction of travel, similar to an accordion's motion.
How do secondary (S) waves move?
S-waves move in a shearing, crosswise motion, perpendicular to the direction of travel, causing more damage with vertical ground motion.
What is the focus and epicenter of an earthquake?
The focus (hypocenter) is the point inside Earth where the earthquake originates. The epicenter is the point directly above the focus on the Earth’s surface.
How do seismic waves behave during an earthquake?
Seismic waves travel outward from the focus in all directions, with P-waves arriving first, followed by S-waves, and then surface waves.
Can S-waves travel through liquids?
No, S-waves cannot travel through liquids, which is why there is a shadow zone for S-waves in the outer core.
Can P-waves travel through liquids?
Yes, P-waves can travel through liquids, but they are slowed and bent when passing through the Earth’s outer core.
How does a seismograph work?
A seismograph records earthquake waves by having a stationary marker trace vibrations on a moving drum as seismic waves reach it.
What happens when energy is released during an earthquake?
When rocks break due to stress, energy is released in the form of seismic waves, which radiate outward from the fault and are detected by seismographs.
How do earthquakes affect people?
Earthquakes can cause death, injury, and significant damage to infrastructure. Seismologists study them to predict and mitigate their effects.
Can earthquakes be reliably predicted?
Earthquakes cannot be reliably predicted; however, understanding seismic zones and preparation can help reduce risk and damage.
What type of fault is found at transform plate boundaries?
Strike-slip faults are found at transform plate boundaries, where plates slide past each other horizontally.
What type of fault occurs at subduction zones?
Reverse faults occur at subduction zones, where one tectonic plate is forced under another due to compression.
What type of fault occurs at divergent plate boundaries?
Normal faults occur at divergent plate boundaries, where tectonic plates pull apart due to tension.
What affects the duration of earthquake shaking?
The size of the earthquake, the distance from the epicenter, and the type of seismic waves affect how long the shaking lasts.
How do tectonic plate movements lead to earthquakes?
The movement of tectonic plates due to tension, compression, or shearing causes stress along faults. When this stress is released, it results in an earthquake.
What type of fault is associated with tension at divergent boundaries?
Normal faults are associated with tension at divergent boundaries where plates are pulling apart.
How does the type of fault influence earthquake strength?
The type of fault affects the direction of movement and the release of energy, influencing the size and impact of the earthquake.
How can earthquakes cause landslides?
Earthquakes can shake the ground, making unstable slopes collapse and leading to landslides, particularly in mountainous areas.
What happens to the energy released during an earthquake?
The energy released during an earthquake is transferred in the form of seismic waves that travel outward from the fault zone, causing the ground to shake.
What does the magnitude of an earthquake indicate?
The magnitude of an earthquake indicates the energy released at the fault and the potential for destruction. Larger magnitude earthquakes generally cause more damage.
