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Earthquakes and Plate Tectonics
Terms in this set (31)
Evidence for Plate tectonics?
puzzle pieces fit together (continents fit)
what drives plate tectonics?
-Occur along spreading centers where plates move apart
-New crust is created from magma pushing up from the mantle
-Example: Mid-Atlantic Ridge
3 types of convergent boundaries
Oceanic - continental
Oceanic - oceanic
Continental - continental
oceanic continental convergence
oceanic oceanic convergence
continental continental convergence
some cities near major faults
the application of force on an area
-compressive and tension
the response to stress
the weak link
All rocks have weaknesses such as faults, fractures, microcracks, and bedding planes.
When tectonic stresses build, these are the points where rupture occurs.
The past is the key to the future!
right-lateral strike-slip fualt
If surface waves only travel at the surface, how does an earthquake at depth generate them?
When a body wave (P or S) emerges at the surface some of the energy is converted into surface waves, which then propagate along the surface.
when do earthquakes occur?
when tectonic stresses build to the point where rock ruptures
when do ruptures occur?
along existing zones of weakness (normal, reverse and strike-slip faults)
where do seismic waves propagate?
from the earthquake focus (P, S and Surface waves)
purely descriptive based on damage observation (human accounts)
moment magnitude scale
new standard scale, presently preferred reporting system. It is based on amplitude AND size of slip area.
why are historical earthquakes so important
recurrance diagrams-past is key to the future
how did we rate the magnitude before seismographs?
man made structures
modified mercalli scale
-Earthquake severity is expressed on a logarithmic scale
-Each step is a factor of 10 in amplitude and about a factor of 30 in power.
A magnitude 8 earthquake is how many times more powerful than a magnitude 4?
Mercalli Scale Measures Damage not...
The message here is that it is the vulnerability we accumulate over time that makes our society susceptible to catastrophe.
How do earthquakes kill?
KNOW THE FACTS
Fires (power lines down, gas lines rupture)
Avalanches/Landslides triggered by EQ
Collapse of buildings (a Hollywood favorite)
Tsunami (can strike far from epicenter)
Subsidence (SETTLING) (ground liquifaction)
Earthquakes can cause the ground to liquefy and allow structures to subside (sink) or topple.
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