4. measuring activity
Transcript of 4. measuring activity
M E A S U R I N G M AG N I T U D E
TECTONIC LANDSCAPES
SPECIFICATION DETAIL
• 3.1d The measurement of earthquake magnitude (the Mercalli and Richter scales).
• Diagrams showing the characteristics of focus and epicentre.
LEARNING OBJETIVES
• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.
• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.
DEFINITIONS
• Watch Seismograph: Here
• Mercalli scale: (intensity)Uses seismic scale to measure the intensity of an earthquake. It is used to measure the effects of an earthquake.
• Richter scale: (magnitude)A logarithmic scale used to express the total amount of energy released by an earthquake(It is a base 10 logrimithic scale: e.g. 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0, )assign a single number to quantify the energy released during an earthquake.
The Richter scale can be used to measure the magnitude (power) of a tremor using an instrument called a seismograph.
HOW ARE EARTHQUAKES MEASURED?
It is a logarithmic scale which means that a size ‘6’ earthquake on the Richter scale is 10 times larger than a size ‘5’ and 100 times larger than a size ‘4’.
HOW DOES A SEISMOGRAPH WORK?
The Mercalli scale rates an earthquake's magnitude based on observations of the damage it causes on a scale of 1 to 12.
THE MERCALLI SCALE
Items shake from shelves:
scale 5
Buildings collapse: scale 10
Intensity
(Mercalli)
Observations (Mercalli)
Richter Scale Magnitude (approx.
comparison)
I No effect 1 to 2
II Noticed only by sensitive people 2 to 3
III Resembles vibrations caused by heavy traffic 3 to 4
IV Felt by people walking; rocking of free standing objects 4
V Sleepers awakened; bells ring 4 to 5
VI Trees sway, some damage from falling objects 5 to 6
VII General alarm, cracking of walls 6
VIII Chimneys fall and some damage to building 6 to 7
IX Ground crack, houses begin to collapse, pipes break 7
X Ground badly cracked, many buildings destroyed. Some landslides
7 to 8
XI Few buildings remain standing, bridges destroyed. 8
XII Total destruction; objects thrown in air, shaking and distortion of ground
8 or greater
TASK: SORTING
• Using the following statements, sort them into which best describes the scales.
• Here
Intensity
(Mercalli)
Observations (Mercalli)
Richter Scale Magnitude (approx.
comparison)
I No effect 1 to 2
II Noticed only by sensitive people 2 to 3
III Resembles vibrations caused by heavy traffic 3 to 4
IV Felt by people walking; rocking of free standing objects 4
V Sleepers awakened; bells ring 4 to 5
VI Trees sway, some damage from falling objects 5 to 6
VII General alarm, cracking of walls 6
VIII Chimneys fall and some damage to building 6 to 7
IX Ground crack, houses begin to collapse, pipes break 7
X Ground badly cracked, many buildings destroyed. Some landslides
7 to 8
XI Few buildings remain standing, bridges destroyed. 8
XII Total destruction; objects thrown in air, shaking and distortion of ground
8 or greater
TASK: WATCH THESE CLIPS
• Tachoma, Japan earthquake: Here• Chilean earthquake: Here• Kashima, Japan earthquake: Here• Tokyo, Japan earthquake: Here• Maryland, USA earthquake: Here
Which scale was the most easy to use? Why?
EXAM PRACTISE
• Describe 2 differences between the Mercalli and Richter scale. (2 marks)
One difference is …………
A second difference is that……………
LEARNING OBJETIVES
• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.
• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.
EPICENTRE
• Epicentre on google earth: here• Interactive : Here
EPICENTRE AND FOCUS
EXAM QUESTION
• Outline a difference between the focus and epicentre of an earthquake. (2marks)
LEARNING OBJETIVES
• Know the differences between the Mercalli (intensity) and Richter (magnitude) scales.
• Explain how earthquakes occur with reference to the epicentre and focus of earthquakes.