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Earthquake Hazards - Coggle Diagram
Earthquake Hazards
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Liquefaction
When an earthquake strikes an areas with surface materials made of fine grained sands, alluvium and landfill with high water content, the vibrations can cause these minerals to behave like liquids.
These materials lose their strength; slops collapse and structures tilt and sink as their foundations give way.
This was a major issue during the Kobe earthquake as much of the port was destroyed at Osaka Bay affecting the Japanese economy and trade throughout the world.
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Tsunamis
Underwater earthquakes can cause the sea bed to rise vertically which displaces the water above producing powerful waves at the surface which spread out at a high velocity from the epicentre.
Wave height increases when they reach shallow water near the shore. The height of a tsunami is greatly affected by the shape of seabed and coastline. The steeper the coastline, the less distance the tsunami can travel.
Examples: Sumatra, 2004 - 1000 tonnes/m of shore line, Papua New Guinea, 1998 - 2200 villagers died living in coastal communities.
Flooding
Can be caused by tsunamis, difficult to prevent and can displace many people as houses are destroyed, transport routes become blocked and communication is cut off.
Can also be caused by build-ups of water in rivers due to natural damming by material from landslides.
CAUSALITY: the agency that connects one process (cause) with another process or state (effect) where the 1st is partly responsible for the 2nd and the 2nd is dependent on the 1st.
THRESHOLD: occurs when a relatively small stimulus within a system suddenly forces a rapid change of that system. Thresholds are often thought of as tipping points after which a system shifts dramatically and potentially irreversibly into a different equilibrium state.