what is earthquake, how to measure Earthquake, how are earthquakes measured and detected, different methods of measuring earthquake, different scales of measuring earthquake

1. How To Measure
Earthquake
BCT-VII
Guided By:
Prof. Deepali Hejib
Prof. Mugdha Bhave

2. CONTENT:
● What is Earthquake.
● How are earthquakes recorded and detected
● How to measure earthquake.

3. ● An earthquake is the sudden movement or
trembling of the earth’s tectonic plates, that
creates the shakes of the ground.
● This shaking can destroy building and break the
earth’s surface.
● Earthquake are caused by disturbances in the
balance of the earth.
● They are also caused by the reactions that are
result from invisible events operating beneath the
earth’s crust.
What is Earthquake

4. How are earthquakes recorded and detected ?
● When the earth trembles, earthquakes spread
energy in the form of seismic waves.
● A seismograph is the primary earthquake
measuring instrument.
● These seismograph produces a digital graphic
recording of the ground motion caused by seismic
waves. The digital recording is called a
seismogram.
● A network of world wide seismograms detects and
measures the strength and duration of the
earthquake’s waves.
● The seismograph produces a digital graphic
plotting of the ground motion of the event.

5. How to measure an earthquake ?
● Earthquakes are recorded by instruments called
seismographs. The recording they make is called a
seismogram.
● The seismograph has a base that sits firmly in the ground,
and a heavy weight that hangs free.
● When an earthquake cause the ground to shake, the base of
seismograph shakes too, but the hanging weight does not.
● Instead the spring or string that is hanging from absorbs all
the movement.
● The difference in position between both the parts of
seismograph is what is recorded.
Seismograph

6. There are two different ways to measure different
aspects of an earthquake:
Magnitude :
● Earthquake magnitude is a measure of the “size,”
or amplitude, of the seismic waves generated by
an earthquake source and recorded by
seismographs.
● It is measured in Richter Scale.
● It is measured as logarithm to the base 10 of the
maximum trace amplitude and it could even be
zero or even negative.
● It is a quantitative form of measurement.
Intensity :
● The intensity of earthquake at a place is a measure of the strength of shaking during the earthquake.
● More subjective of a measure of the destructive power of an earthquake and its effect.
● It is measured on a scale range of I to XII in Roman Capital Numerical.
● It is a qualitative form of measurement.

7. People have always tried to quantify the size of and damage done by earthquakes. Since early in the
20th century, there have been three methods.
● Mercalli Intensity Scale. Earthquakes are described in terms of what nearby residents felt
and the damage that was done to nearby structures.
● Richter magnitude scale. Developed in 1935 by
Charles Richter, this scale uses a seismometer to
measure the magnitude of the largest jolt of energy
released by an earthquake.
● Moment magnitude scale. Measures the total energy
released by an earthquake. Moment magnitude is
calculated from the area of the fault that is ruptured and
the distance the ground moved along the fault.

8. ● The Mercalli Intensity Scale was developed by the Italian volcanologist Giuseppe Mercalli in
1884 and expanded to include 12 degrees of intensity in 1902 by Adolfo Cancani.
● It was modified again by Harry O. Wood and Frank Neumann in 1931.
● It is known today as the Modified Mercalli Intensity Scale.
● The Mercalli Intensity Scale measures the intensity of an earthquake by observing its effect on
people, the environment and the earth’s surface.
The Mercalli Scale
● Mercalli ratings, which are given as Roman numerals, are based on largely subjective interpretations.
● A low intensity earthquake, one in which only some people feel the vibration and there is no significant
property damage, is rated as a II. The highest rating, a XII, is applied to earthquakes in which
structures are destroyed, the ground is cracked and other natural disasters, such as landslides or
tsunamis, are initiated.

10. The Richter Scale
● The Richter magnitude scale was developed in 1935 by Charles F.
● The magnitude of an earthquake is determined from the logarithm of the amplitude of waves
recorded by seismographs.
● On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions.
● Richter ratings only give you a rough idea of the actual impact of an earthquake.
● Richter scale ratings are determined soon after an earthquake, once scientists can compare the
data from different seismograph stations.
● Although modern scientific practice has replaced the original Richter scale with other,
more-accurate scales, the Richter scale is still often mentioned erroneously in news reports
of earthquake severity as the catch-all name for the logarithmic scale upon which
earthquakes are measured.

11. The Richter Scale
0-1.9
Can be detected only
By seismograph.
2-2.9
Hanging objects
(lampshade) may
swing.
3-3.9
Comparable to the
vibrations of a passing
lorry.
4-4.9
May break window or
cause small object in
your home to fall.
5-5.9
Furniture moves, chunk of plaster
may fall from wall
6-6.9
Damage is caused to well building
structures and severe damage to
poorly built structures.
7-7.9
Building are displaced from
foundations and there are visible
cracks in the earth.
8-8.9
Bridges are destroyed and few
structures are left standing.
9 and above
Near total distruction and seismic
wave are visible to naked eye.
(This rarely happen)

12. Moment magnitude scale
● The moment magnitude scale is based on the total moment release of the earthquake.
● Moment is a product of the distance a fault moved and the force required to move it.
● It is derived from modeling recordings of the earthquake at multiple stations.
● It was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori.
● it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both
scales.
● Moment magnitude is considered the authoritative magnitude scale for ranking earthquakes by size.
● It is more directly related to the energy of an earthquake than other scales, and does not
saturate—that is, it does not underestimate magnitudes as other scales do in certain conditions.

13. SUBMITTED BY:
Vishaka Bothra
Vishaka Patewar
Rajeshwari Sancheti
Mansi Sushir
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