earthquakes

faults

a fracture in crustal rock where one side is displaced with respect to the other side → causes an earthquake

earthquake

energy released as seismic waves

development of a fault

stress accumulation due to compression→development of a fold at the point of max stress→ stress release due to break in rock → create a fault and cause an earthquake

steps of an earthquake

stress applied to body of rock→ rocks deform while storing energy→ stress becomes greater than the strength of rock→ rock breaks→ energy released in the form of seismic waves→ waves travel in all directions 

focus

location where earthquakes originate (can be deep or shallow)

epicenter

point on surface directly above focus

magnitude

energy released

intensity

severity of shaking 

modified mercalli scale

qualitative measurement: scale based on damage

richter scale

quantitative measurement: scale based on amplitude of earthquake waves

majority of earthquakes occur where

along plate boundaries (greatest concentration along circum-pacific belt)

san andreas fault

transform fault with no vertical motion

strongest earthquakes occur where

subduction zones

tsunami

seismic sea waves caused by major earthquakes + usually centered on a subduction plate boundary (not wind derived + volcanic explosions can also cause them)

deep water tsunami

low height (1m), long wavelength, extremely fast

shallow water tsunami

shorter wavelength, slower wave, increased height

the largest, most destructive earthquakes occur along

subduction zones along continental-ocean boundaries

the modified mercalli scale…

measures the damage done by an earthquake

which of the following is true about tsunamis?

a. in the open ocean, they have a relatively small amplitude

b. they have very high velocities (800km/hr)

c. they can be produced by volcanic eruptions

d. they are often associated with movement on subduction faults 

e. all of the above 

e

intraplate earthquakes

earthquakes that do not occur along a plate boundary + can potentially cause more damage (ex: new madrid plate)