Transcript Earthquakes

Aim: What are Earthquakes and their
characteristics?
I. Earthquakes – any vibrating, shaking, or rapid
motion of Earth’s crust.
A. Fault – zone of weakness or a break in the
rock.
1. When the stress exceeds the ability of the
crust to resist breaking, the crust shifts and
energy is released suddenly.
B. Focus – place underground where break
occurs.
C. Epicenter – the location at the surface just
above the focus.
D. Seismic waves (shock waves) – earthquake
waves
1. Primary (P) waves –the first waves to
arrive. Fastest wave that can travel
through any material.
2. Secondary (S) waves – second wave to
arrive. Slower than P wave and cannot
travel through liquids.
P wave motion
S wave motion
E. Measuring Earthquakes
1. Seismometers – detect vibrations of the
ground.
2. Seismograph – instrument that detects
and records seismic waves.
3. Richter scale – a scale from 1 – 10 that
measures the magnitude of an earthquake.
a. Each increase of one unit means a
ten-fold increase in shaking.
b. For example, an earthquake that measures
a 5 on the Richter scale is 10 times greater
than an earthquake that measures a 4 on the
Richter scale. An earthquake that measures a 5
on the Richter scale is 100 times greater than
an earthquake that measures a 3 on the
Richter scale. (5-3=2. 10 x 10 = 100)