Chapter 5 -Earthquakes
Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with a Richter magnitude of 5.5?
30 times
Major earthquakes are often followed by somewhat smaller events known as ________.
Aftershocks
In elastic rebound theory, what must occur to produce an earthquake?
Enough stress must build up over time on a fault to overcome friction.
The position on Earth's surface directly above the earthquake source is called the
Epicenter
When an earthquake occurs, energy radiates in all directions from its source. The source is also referred to as the ________.
Focus
The Mercalli Scale is a scale from ________.
I to XII that rates the structural damage due to an earthquake
Which of the following is determined by measuring the amplitude of waves recorded from an earthquake?
Magnitude
Which one of the following statements is correct?
P and S waves travel through solids and P waves travel through liquids.
________ have the highest
Primary Waves
On a typical seismogram, ________ will show the highest amplitudes
Surface Waves
Why is the Moment magnitude scale favored over the Richter magnitude scale
The Moment magnitude measures the total energy released by an earthquake.
The best building material to use in an earthquake prone region is ________.
Wood
________ is the maximum possible damage designation on the Mercalli scale.
XII
The Richter magnitude of an earthquake is determined from the
amplitude of the largest seismic wave
P waves ________.
are faster than S waves and surface waves
Which of the following is nota way that seismic waves travel in the earth
diffusion
Seismic gaps are places where scientists think that ________.
faults are storing elastic strain
Faults are "locked" because ________.
high confining pressure increases friction on the fault
Which of the following is determined by making direct observations in the area affected by an earthquake?
intensity
Long term earthquake prediction is based on ________.
measurements of the plate motions and rate of stress accumulation
Liquifaction, where normally solid material behaves more like a fluid during an earthquake, occurs because ________.
pore spaces between particles in unconsolidated sediments close and displace fluids
Earthquake prediction is
somewhat good for very long term statistical analyses based on ideas like mapping seismic gaps
Overall, this type of seismic wave is the most destructive.
surface wave
Aftershocks occur because ________.
the area surrounding a region that experienced a large earthquake needs time to adjust to the displacements on the main fault
One measurement that is widely used to determine how far the focus of an earthquake is from the seismograph where it is recorded is ________.
the difference in travel time between the P and the S wave
The earth's major layers formed because ________.
the earth was heated after its formation resulting in melting and redistribution of major chemical compositions
Megathrusts between subducting oceanic crust and an overriding plate are a potential source of tsunamis because ________.
the earthquakes on these faults are underwater and could displace large amounts of water from the oceans
Which of the following is nota significant factor contributing to the damage caused by an earthquake?
the proximity to a plate boundary
If you are on a beach, you might recognize that a tsunami is approaching because ________.
the water will withdraw from the beach farther than usual
A tsunami can occur ________.
when an earthquake occurs in the seafloor like along an oceanic plate boundary
