Example essay. Question entails- "To what extent do physical factors contribute to hazards caused by earthquakes?"
Includes a range of named examples/ case studies.
To What Extent do Physical Factors contribute to Hazards caused by Earthquakes?
Earthquakes can cause a range of dangerous hazards, often measured in severity and defined by
the risk the hazard poses to humans whether individually or as a community. The main hazards
created by earthquakes include flooding, ground displacement, ground shaking and many more.
These hazards, often significantly dangerous, can often be enhanced or exacerbated by physical
factors and features of the individual location.
One of the major hazards created by earthquakes is flooding. During the 7.8 earthquake in
Ecuador, April 2016 many of the mountainous and coastal regions suffered significant levels of
flooding. As a result many sought shelter and relief services. The earthquake was caused by the
Nazca plate subducting beneath the pacific plate 17 miles offshore in a destructive collision
boundary. In one village situated near the Allurian river, over 600 homes were destroyed and 4
lives were lost. One of the predominant physical factors which enhanced the flooding was the relief
of the mountainous regions and alluvial plains surrounding many of the communities, causing
subsequent effects landslides, filling river banks with debris and causing an overland flow and
further flooding. Furthermore, the climate of Ecuador and effect of the La Nina phenomenon during
the period in which the earthquake occured, resulting in cool wet weather from the pacific and high
levels of rainfall additionally increased the volume of flooding that occurred. As well as this,
resulting in saturated soil such as the Andosols found within mountainous regions. Andosols high
capacity for water also makes it prone to liquefaction, another hazard which exacerbates flooding
and therefore the risk to villages in this type of region.
The hazard of ground displacement caused by earthquakes itself can also lead to flooding. The 9.0
magnitude earthquake in Tohoku, Japan 2011 resulted in an area of 300x100km around the city of
Sendai to tilt 41° and shift horizontally 3 metres eastward. The topography of Sendai is
predominantly low-lying plains, therefore already had the potential risk of flooding. However, the
displacement increased this risk, causing further areas of land to sink and become low-lying.
Additionally putting Sendai at risk of sea-level rise and coastal flooding, as well as greater
exposure to the Tsunami also generated by the earthquake. While the topography of the area had
influence over the flooding experienced, it had no direct effect on the ground displacement
experienced. Similarly, the brown forest soil and wet humid climate of Sendai influenced the risk of
hazards such as flooding and substantial liquefaction, however, has limited influence over ground
displacement as a hazard. The contribution of the pedology (brown forest soil) may have had on
displacement is through its easily liquefiable nature, allowing ease of displacement.
The main hazard generated by all earthquakes is ground shaking. In Italy 2016, a 6.2 earthquake
caused severe damage to infrastructure, especially in the Apennines mountains. The convergence
of the Eurasian plate subducting the African plate left 293-5 people dead, 400 injured and around
4,000 homeless. The village Pescara del Tronto was levelled to the ground. The topography of Italy
is mainly mountainous and its geology composed of hard rock. Seismic waves created by the
earthquake travel faster through harder rock suggesting why Italy was hit so quickly and without
proper warning. Furthermore increasing the risk of this hazard.
Overall, physical factors can (depending on hazard) contribute to hazards on both a small and
larger scale and enhance the risk of the hazard. However, as we can see certain hazards are more
affected than others such as the flooding seen in Ecuador. Meanwhile the physical factors including
geology of Japan and Italy had lesser extent on the hazards of ground displacement and shaking.
Therefore, it can be seen that physical factors contribute to a partial extent to these hazards.
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