geology chapter 11
Which one of the following statements concerning foci and epicenters is correct?
The epicenter is at the surface directly above the focus where the earthquake initiates.
What is the definition of the focus?
The exact location on the fault where slippage occurs
Which seismic waves are released first during an earthquake?
p waves
The ________ earthquake was accompanied by extensive fire damage.
san Fransisco 1906
What is the term for stored-up energy released by earthquakes?
seismic
_______ are records of seismic waves.
seismograms
The ________ is used to record ground shaking and the earthquake-magnitude scale was invented by ________.
seismograph; Richter
The strongest earthquakes occur primarily at _____.
subduction zones
The epicenter of an earthquake is the ________.
surface location directly above the point where the fault slip initiates
Generally speaking, which seismic waves will have the greatest amplitude on a seismogram?
surface waves
________ have the highest velocities.
Primary waves (P-waves)
The ________ magnitude scale is a measure of the energy released. It does not directly measure the extent of building damage.
Richter
______ are instruments that sense earthquake waves and transmit them to a recording device
Seismographs
You are watching TV with a friend when there is a special bulletin about a city in California being devastated by an earthquake. The news anchor reports that the epicenter of the earthquake is 45 miles east of Los Angeles. How would you explain the definition of the epicenter to your geologically impaired friend?
The location on Earth's surface directly above the point of slippage
Which of the following would be the most unstable during an earthquake?
Unconsolidated sediments
Which one of the following regarding the San Andreas Fault in California is true
a sliver of continent west of the fault is moving northward with the Pacific plate
are smaller earthquakes of lesser magnitude that follow a major earthquake.
aftershock
hat are the smaller magnitude quakes that follow a major earthquake?
aftershock
P waves ________.
are faster than S waves and surface waves
What are the two categories of seismic waves?
body waves and surface waves
Which tectonic boundary is associated with megathrust faults?
convergent
which plate boundary along the Circum-Pacific Belt is responsible for the majority of that belt's earthquakes?
convergent
Deep-focus earthquakes happen at _____.
convergent plate boundaries
S waves can travel through solid and liquid media.
false
Unconsolidated, water-saturated soils or sediments provide good foundation materials for buildings and other structures.
false
P waves arrive at the seismograph _____ and are _____ waves.
first and compressional
The ________ is the point of origination for an earthquake.
focus
During an earthquake, energy waves radiate outward in all directions through the interior from the ________ whereas energy waves radiate outward in all directions along the surface from the ________.
focus; EPICENTER
The largest lateral, ground displacement is produced by ________.
horizontally vibrating surface waves
refers to the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking.
liquefaction
The point of origin of an earthquake at depth is called
the focus
To locate the epicenter of an earthquake, you need information from at least _____ seismic station(s).
three
Most faults are locked in place, except for brief, abrupt movements when sudden slippage produces earthquakes.
true
The epicenter of an earthquake is on the surface of the Earth directly above the focus.
true
arthquakes with a Richter magnitude less than 2.0 are generally not felt by humans.
true
________ is the maximum possible damage designation on the Mercalli scale.
xii