earthquakes (LEC 8) Flashcards
earthquakes occur when rocks return to their original, stress-free shape after overcoming the frictional forces exhibiting _________ _________
elastic rebound
the _____________ is the point of where rock slippage occurs. also called the focus.
hypocenter
the _________ is the location on the EARTH’S SURFACE, directly above the hypocenter
epicenter
_______ are small earthquakes that often occur before major earthquakes by days or even by as much as several years
foreshocks
__________ are earthquakes of lesser magnitude that occur after a strong earthquake
aftershocks
what is a seismograph and how does it work
an instrument used to detect and record earthquakes, the main idea is that the base moves and the mass does not
what are body waves
body waves are the waves that travel through the earth’s interior
what are the two types of BODY WAVES
primary waves and secondary waves
there are two types of body waves: P-waves and S-waves
what are the differences between them
primary waves are a push-pull waves: compressing and expanding the rocks in the direction of waves travel
secondary waves are when the rocks shake perpendicular to the direction of wave travel
what are surface waves
surface waves are the waves that travel in the rock layers just below the earth’s surface i.e. travelling only through the crust
surface waves cause the earth to move ______________ or _______________
up and down
side to side
___________ have even greater amplitudes than S waves and retain their maximum amplitude for much longer
surface waves
what is is the intensity of an earthquake vs the magnitude
intensity is a measure of the degree of ground shaking at a given location
based on the amount of property damage
magnitude is the amount of energy released at the source of the earthquake based on the data provided by seismographs
what is the Modified Mercalli Intensity Scale
a scale to estimate
the intensity of an earthquake
what are the drawbacks of the Modified Mercalli Intensity Scale
destruction may not be a true measure of the earthquakes’ actual severity because it depends only on the ground shaking and the building destruction. it does not take into consideration the population intensity, building design, and the nature of surface materials
what is the Richter Scale
it is based on the amplitude of the largest seismic wave recorded on a seismogram and the distance to the epicenter
what are some factors affecting earthquake destruction
*magnitude
*duration of shaking
*local geology
*population density where the earthquake occur
*distance from epicenter
*construction practices
*disaster response planning
*time: earthquakes during working hours in populated urban areas are
most destructive and cause most injuries.
what are some major destructive forces that earthquake vibrations can trigger
*seismic vibrations
*liquefaction
*tsunami
*fire
*landslides and subsidence
(true or false)
the effects of vibrations cause more injuries than any other earthquake
effect
TRUE
what is liquefaction
a process in which unconsolidated materials that are saturated with water act like a liquid due to earthquakes
(true or false)
a tsunami has more effect on a steep shore compared to a flat one
FALSE
a tsunami has more effect on a flat shore
95% of the energy released by earthquakes originates in a few, narrow locations. where are these places
Circum-Pacific belt
Alpine-Himalayan belt
Transform faults
Intraplate earthquakes
