Exam 2

What do you think? Earthquake magnitudes, timing, location and amount of shaking are predictable.

False

Earthquakes are a release of energy when rocks snap, or fracture. What rheological layer do most earthquakes occur in?

Lithosphere

Which of the following is NOT likely to cause an earthquake?

Flood (Earthquakes can be generated by any disruption that sends energy through rocks. Most common is release of energy from rocks stored by plate movement.)

What location is at the least risk for an earthquake?

East coast of South America (The east coast of South America is the only location on this list that is not a plate boundary, it is a passive margin)

What is the best definition of a fault?

Faults are fractures upon which the rocks have moved

Which of the following DOES NOT determine the magnitude of a quake?

The distance between you and the epicenter

How many earthquakes are shown? Fill in the events shown.

Choose the correct order of processes that generate an earthquake.

Stress is applied, strain is stored, rocks break, and then rocks rebound, after every earthquake the process begins again

How many types of seismic waves are there?

Three, P waves, S waves, Surface waves

What type of seismic wave causes a vertical jolt?

P wave, p=primary; P waves are compressional waves which cause a vert

How does wave amplitude relate to shaking?

The higher the amplitude shown on the seismogram the stronger the shaking

What approximate length of fault will rupture during a Mw8 earthquake?

400 km (249 mi)

Three measurements are needed to calculate Moment Magnitude (Mw) of an earthquake. Which one of the following is not used?

Which of these TRUE statements is not a description of earthquake intensity?

Which of the following locations has not had a major eq (>Mw 7.0) in the last 10 years?

Chile = 2010 (Mw 8.8)

Central Mexico = 2017 (Mw 7.1)

Nepal = 2015 (Mw 7.8)

Japan = 2011 (Mw 9.0)

All of these locations have had major earthquakes

What is liquefaction?

The process of wet sediment fluidizing during an earthquake

What is an aftershock?

Why is ground shaking amplified in less dense rock and sediment?

Here is a picture from Arches National Park in Utah. What is this telling you about earthquakes in this area?

How do geologists study earthquakes in the geologic record?

Tsunami are created by earthquakes only.

False, Tsunami can be generated by landslides, asteroid impacts, and volcanic eruptions

Earthquakes occur under Earth’s oceans frequently, but tsunami are only generated by some of them…not all.

True, High magnitude earthquakes ~M7 or greater (on dip-slip faults), may generate a tsunami. Smaller magnitude earthquakes dont move the seafloor enough.

Tsunami can travel across all oceans (e.g. from one side of the Pacific Ocean to the other)

True, This has been documented many times, particularly when tsunami result from high magnitude earthquakes

The water from the beach can withdraw before a tsunami arrives.

True, When the trough of the wave approaches the shore, it will quickly draw in water, leaving boats and fish stranded. This is an important warning sign.

How high was the highest tsunami ever recorded?

524 m, This was caused by an earthquake-induced landslide into a small bay in Alaska, 1958

Tsunami are caused by seismic energy moving through the ocean

False, This is a common misconception. Tsunami are created when a large amount of water is displaced by (1) movement on a fault & elastic rebound due to an earthquake, (2) landslides, (3) an asteroid impact or (4) volcanic eruption

Most Waves are generated by….

Wind, Particles in the air collide with the surface of the water and transfer energy. The faster the wind, the bigger the wave.

What is wavelength?

The horizontal distance between two consecutive wave crests = wavelength

Choose the best statement that describes the tsunami shown in the animation.

How is wave height different from run-up height?

Wave height is the height of the wave before it breaks; run-up height is vertical distance between sea level and the maximum height of the water on land

Which mountain range is formed by subduction of the Nazca plate underneath the South American plate?

What is the rupture length of a fault?

the magnitude of a quake does not depend on which of the following?

Why is ground shaking amplified in less dense rock and sediment?

What controls how much water will be drawn back into a tsunami when it approaches shore?

Slope of the seafloor, wavelength of the tsunami

Why does tsunami wave height increase as it moves towards shore?

The tsunami slows down in shallow water

Which of the following characteristics does not contribute to run-up height?