Chapter 9 Earthquakes

the point within the earth where an earthquake takes place is termed the

focus

periods of intermittent sliding on a fault because of stress release during episodes of slip, followed by stress buildup to the point that the fault is reactivated, is termed

stick slip behavior

the quantity of motion that occurs along a fault is termed

displacement

a primary force opposing motion on all faults is

friction

the vast majority of earthquakes occur

along all types of plate boundaries

earthquakes often occur along

fault zones

_______ travel with a compressional motion

P waves

vertical motion seismographs record earthquakes by producing a squiggly diagram called a

seismogram

an increase in size of one unit of magnitude translates to ____ the ground motion

10 times

at a minimum, how many seismic stations are necessary to locate the epicenter of an earthquake?

3

the moment magnitude is based on the ____ and ___ of the earthquake

amplitude; rupture area

an earthquake occurs with an epicenter in the town of New Madrid, Missouri in the interior of the north american plate, where might the hypocenter of this earthquake plausibly be found?

20 km beneath New Madrid

The Mercalli intensity scale tends to be very subjective and thus is generally only used for historical earthquakes that were near people but were not recorded by seismometers. Why might the Mercalli scale be subjective?

it relies on testimony from people

________ occur(s) when earthquakes causes pore pressure to increase, which in turn causes grains to separate and compact.

liquefaction

a tsunami is

a sea wave generated by a displacement of water

The Denali Pipeline in ________ was designed to withstand displacement from earthquakes in order to prevent oil spills.

Alaska

______ are smaller earthquakes of lesser magnitude that follow a major earthquake

aftershocks

Which tectonic boundary is responsible for the most powerful and destructive earthquakes recorded?

convergent

What is the term used to describe slow, gradual displacement along a fault without the accumulation of significant strain?

fault creep

Which of the following best describes a seismic gap?

unusually quiet zones along typically active faults

The ________ is a newer scale that measures the total energy released during an earthquake by determining the average amount of slip on the fault, the area of the fault surface that slipped, and the strength of the faulted rock

moment magnitude scale

Which of the following would be the most unstable during an earthquake?

unconsolidated sediments

You are monitoring a seismograph in Seattle. One morning, your instrument records an earthquake approximately 2000 km away. From that information, can you determine where the earthquake occurred?

no, because you would need information from more than one seismograph to plot it

Seiches are dangerous to begin with, but which of the following situations is particularly dangerous during seiche formation?

reservoir behind an earthen dam

Which of the following zones has the greatest seismic activity on Earth?

circum pacific belt

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 ground shaking produced by large earthquakes is not only ________, but takes a ________ time than shaking produced by slippage along small fault segments.

stronger; longer

Earthquake A is classified as a 3 on the Richter Scale. Earthquake B is classified as a 6. How many times more energy has Earthquake B released than Earthquake A?

33,000 times

As of 2015, what was the strongest earthquake on record, and when did it occur?

1960 Chilean Earthquake

What is the highest level on the Mercalli Intensity Scale?

XII