ENVIRONMENTAL SCIENCE : POLLUTION AND ITS FACTORS 185
(ii) Mid-Continental Belt: representing epicenters located along the Alpine-Himalayan
Chains of Eurasia and northern Africa and epicenters of East African Fault zones.
(iii) Mid Atlantic Belt: representing the earthquakes located along the mid-Atlantic
Ridge-and its offshoots.Effects of Earthquake hazardous
Earthquakes and their hazards are determined on the basis of the magnitude of seismic
intensity as determined by Richter scale but are decided in the basis of quantum of damages
done by a specific earthquake to human lives and property.
(i) Landslides
Weaker landmasses and tectonically sensitive land margins cause landslides and debris
falls, which damage settlements and transport systems on the lower slope segments.
(ii) Damage to Life and property
Structures such as buildings, roads, rails, factories, dams, bridges suffer a huge damage
thus causing a heavy loss of human life and property both. The vibrations of earthquakes
last longer and the amplitudes of seismic waves are greater artificially in filled and leveled
depressions, swamp deposits etc. than in the structures of consolidated materials and bedrocks.
Two major earthquakes of Bihar-Nepal border in 1934 and 1988 explain the impact of
earthquake disasters on human structures and human lives. The damage caused by the
Bihar earthquake of 15 January 1934, measuring 8.4 on Richter scale, include 10,700 human
deaths, landslides and slumping in an area of 250 km length and 60 km width, ruptures and
faults in the ground surface etc.
(iii) Damages to Government Infrastructure
Cities and towns are worst affected due to large concentration of human population,
commercial complexes and residential areas. Due to collapse of large buildings there is
greater loss of life and property. Due to collapse of buildings ground water pipes are bent
and damaged thus water supply is disrupted, electric and telephone poles are uprooted and
there is total disruption of power and communication. Other side effects are collapsed sewer
system causing epidemics, roadblocks etc.
(iv) Fire Hazard
Earthquakes strongly shake the buildings and thus strong oscillations cause severe
fires in houses, mines and factories because of overturning of cooking gas cylinders, contact
of live electric wires, churning of blast furnaces, displacement of other electric and fire-
related appliances.
(v) Landmass Deformation
Severe earth tremors and resultant, vibrations caused by severe earthquakes result in
the deformation of ground surface because of crusts and troughs in the ground surface and
faulting activity.
(vi) Flash Floods
Strong seismic events result in the damages of dams and cause severe flash floods.
Severe floods are also caused because of blocking of water flow of rivers due to rock blocks
and debris produced by severe tremors on the hill slopes facing the river valleys.