earthqu akes earthquake footage. epicenter the point on earth’s surface directly above where the...
TRANSCRIPT
EarthquakesEarthquake
Footage
Epicenter• The point on Earth’s surface directly above where the
energy is released in an earthquake.• Focus = point where energy is released• Energy that reaches the surface is greatest at the
epicenter.
• Seismic Waves: Energy spreads outward in all directions as vibrations.
• Seismograph: Instrument that measures and records seismic waves.
• Seismogram: Seismic record, looks like jagged lines on paper.
Triangulation• Identifies the epicenter of an earthquake. • How?– Get records from 3 seismograph stations.– Plot circles on map from the records.– Find point where all 3 circles intersect.– That's the epicenter.
How to find the epicenter using triangulation
• Measuring time btwn arrival of P & S waves determines the distance btwn the seismograph & the epicenter.
Earthquake Waves• There are 3 types…
Primary (P) Waves Secondary (S) Waves Surface Waves
P and S waves explained
Primary (P) Waves• Move out from EQ focus• Travel fastest of the 3 waves• Move thru solid and liquid layers of Earth• PUSH and PULL rock, creating a back-and-forth
motion in the direction the wave is moving• Longitudinal wave
Secondary (S) Waves• Move out from EQ focus• Move slower than P waves• Only move thru solid rock• Move at right angles to P waves, causing rocks
to move UP and DOWN and SIDE to SIDE• Transverse wave
Surface Waves• Form when P and S waves reach the surface.• Can cause ground to shake, making rock sway
from SIDE to SIDE and ROLL like an ocean wave.