High Resolution 1:10,000 scale Mapping Strategy of Multi ... - NDMA

Infact, magnitude is the measurement of the energy released by the earthquake
event, whereas the intensity are connected with effect of earthquake at epicenter to
location away from epicenter.
Richter magnitude of an earthquake is determined from the logarithm of the
amplitude of waves recorded by seismographs (adjustments are included to
compensate for the variation in the distance between the various seismographs and
the epicenter of the earthquake) as per the relationship
where A is the maximum excursion of the Wood-Anderson seismograph, the
empirical function A0 depends only on the epicentral distance of the station, δ. In
practice, readings from all observing stations are averaged after adjustment with
station-specific corrections to obtain the ML value.
Because of the logarithmic basis of the scale, each whole number increase in
magnitude represents a ten fold increase in measured amplitude; in terms of energy,
each whole number increase corresponds to an increase of about 31.6 times. The
energy released in an earthquake of magnitude 3 on Richter scale is equivalent 31.6
metric tons of TNT. An earthquake of magnitude 6 on Richter scale is equivalent 1
mega tons of TNT. An earthquake of magnitude 9 on Richter scale is equivalent 31.6
gigatons of TNT. This is an idea of strength of the energy released during the
earthquake.
SCALE FOR EARTHQUAKE HAZARD EVALUATION
INTENSITY- MODIFIED MARCALLI SCALE
The effect of an earthquake on the earth's surface is called the intensity. The
intensity scale consists of a series of certain key responses such as people
awakening, movement of furniture, damage to chimneys, and finally - total
destruction. Although numerous intensity scales have been developed over the last
several hundred years to evaluate the effects of earthquakes, the one currently used
is the Modified Mercalli (MM) intensity scale. This scale, composed of 12 increasing
levels of intensity that range from imperceptible shaking to catastrophic destruction,
is designated by Roman numerals. It does not have a mathematical basis; instead it
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