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Lecture

Lecture 2


Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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EESA06 Lecture 2
The deepest mine in the world is 4km underground, any deeper it will be too hot, hole will
begin to close due to temperature and movement
Geophysics application of physics to the world
Earthquakes generate energy
Fault plane surface (between moving bocks) which blocks have moved, we feel as an
earthquake
Focus is where the energy is released, the trigger of the earthquake, always
underground, can predict how much damage it can do how deep down the focus is
Epicenter directly above the focus on the earths surface
Seismic risk assessment gauge any movement along any fault, looks at fault scarp
& fault trace
Fault scarp cliff, bluff, the steep slope that results after earthquake (ex: 1891
Japan)
Fault trace fairly straight lines, many river valleys along traces of faults
oMorphological what shapes on earths surface created by faults
Not all faults create earthquakes, some creep dont result in earthquake, the lock
ones create earthquakes
Waves:
Body waves goes thru the interior
oPrimary and Secondary waves
Surface waves go around the surface
Primary waves the quickest 7km/sec, compression + extension spring
ocan go thru fluids, go all the way thru the interior of planet, thru the core
oRefraction effects create shadow zones no direct P waves
Secondary waves - are smaller 5km/sec, wave on a rope
oCannot go thru fluids, stops at core, very large shadow zone
Earth Core:
Outer most part of core is liquid preventing s-waves, refracting p-waves
Inner core is solid
Seismograph station closer to focus = time lag of arrival of P&S waves not much, farther
from focus = time lag from P&S wave is bigger
Allow to determine where the epicenter was
Networks was setup to determine nuclear bomb testing
Major Epicenters Circum-Pacific belt (most damaging, deepest), Indonesian belt,
Mediterranean-Himalayan belt (where India is colliding with China)
Deep focus earthquakes - Along the plate margins
Deepest earthquake is 7km down
Shallow-focus earthquakes, where plates are diverging, mid ocean drifts
Low magnitude earthquakes, magma coming up
Earthquakes can be in the middle of continents
Intracratonic earthquakes are very difficult to explain and predict (ex: Toronto)
Ancient China used missing farm animals to predict earthquakes
www.notesolution.com
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