Earthquakes

Effect of Earthquakes as a hazard  Vibrations themselves are not hazardous- it is the effect it has on buildings, etc. that poses risk.

Risk comes from:  Collapsing buildings, walls, bridges, falling furniture or objects, shattering glass windows and mirrors.  Debris from collapsing structures is one of the principal dangers during an earthquake since the impact of large, heavy objects can be fatal to human beings.  Earthquakes sometimes cause glass windows and mirrors to shatter and this is also quite dangerous.  Earthquake aftershocks can result in the complete collapse of buildings that were damaged during an earthquake

 Falling electricity lines. Earthquakes can cause electricity poles to fall and live wires to become exposed or to start fires.  Ruptured gas lines and spillage of flammable substances. Earthquake-generated fires can cause widespread destruction after a major earthquake.  Escaping gas from broken gas lines and the toppling of containers with flammable substances (e.g. kerosene, household chemicals, etc.) present a significant threat of explosions and fires, which can cause death and destruction of property.  Additionally, water pipes are sometimes ruptured during an earthquake and this compounds the problem of controlling such fires.

El Salvador  Rock slides and/or landslides on mountains and hillsides.  During an earthquake, large rocks and portions of earth high up in the hills can become dislodged and rapidly roll or slide down into the valleys.  This can cause damage to property and or if it slides into lakes or rivers can trigger localised tsunamis or flooding.

Floods caused by the collapse of dam walls. Earthquakes can cause dam walls to crack and eventually collapse, sending raging waters into surrounding areas and causing severe flooding. Taiwan Dam Failure 1999 Earthquake.

Tsunamis. A tsunami is a large sea wave or series of waves that can be generated by an earthquake. Large tsunamis can completely devastate low-lying coastal areas.

 Liquefaction- When sediments with a high water content are subjected to prolonged shaking, the pressure of the water held in pores in the sediment gradually increases eventually, the sediments lose all cohesive strength and begin to behave as if they were liquids. Building and other structures sink into the ground or overturn and buried tanks and other cavities rise to the surface.  Liquefaction occurred during the earthquake of 1692 in Jamaica and was responsible for the destruction of the town of Port Royal.  Over the past few decades, many parts of the Eastern Caribbean have become increasingly vulnerable to liquefaction because of the increased use of reclaimed land for urban development.

Assessment Assuming there is an earthquake in Trinidad felt along the Eastern Main Road. Which is the greatest risk do you think El Dorado faces? Give reasons for your answer.

Vulnerability to Earthquakes: Physical Vulnerability: 1. Not using building codes and the right type of material when constructing structures. Building codes are guides used to ensuring that structures can withstand the effects of earthquakes and hurricanes. Building structures according to building codes would ensure the integrity of the structure. 2. Not building structures on the correct type of foundation. Some soil types are more susceptible to ground movements than others. The soil type of the land upon which a structure is to be erected, would dictate the type of foundation the building should have; be it a shallow or deep foundation. Environmental Vulnerability: 1. Soil type. As previously mentioned different soil types are more susceptible to soil and ground movements. It is important to know the soil type before constructing. 2. Whether the area is located on or near a fault line. Areas away from fault lines can be affected by earthquakes; however areas located near or on fault line are more susceptible to the effects of an earthquake.

Economic Vulnerability: 1. Unemployment, livelihoods and debt. People may not be able to afford to use the best materials or adhere to building codes when constructing their homes. This makes them more vulnerable. 2. Increased population density. Due to lack of finances, the predominant density pattern in certain areas would be clusters; meaning that there would be a large number of houses being built very close together. Areas with a higher population density are more vulnerable to disasters. Social Vulnerability: 1. Lack of Information and beliefs. Citizens are unaware that there are six (6) seismogenic zones in Trinidad and Tobago; according to the University of the West Indies Seismic Research Centre. Some people still believe that Trinidad and Tobago would not be affected by a major earthquake.

Haiti 2010 The Earthquake Devastation

Epicentre near the town of Léogâne

The fault that lies under Haiti also runs through the Dominican Republic -the Enriquilla-Plantain Garden Fault

Haiti is situated to the north of the Caribbean Plate, on a transform (slip/conservative) plate boundary with the North American Plate. The North American plate is moving west. This movement is not smooth and there is friction between the North American Plate and the Caribbean Plate. Pressure builds between the two plates until it is released as an earthquake. The epicenter of the earthquake was 16km south west of Port-Au-Prince. The earthquake was caused by a slip along an existing fault in this area (Enriquillo-Plaintain Garden fault).

Impact As of Feb. 12, an estimated three million people were affected by the quake; the Haitian Government reports that between 217,000 and 230,000 people had been identified as dead, an estimated 300,000 injured, and an estimated 1,000,000 homeless. The death toll is expected to rise.They also estimated that 250,000 residences and 30,000 commercial buildings had collapsed or were severely damaged

What is Vulnerability Vulnerability describes the characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard. There are many aspects of vulnerability, arising from various physical, social, economic, and environmental factors. Examples may include:  poor design and construction of buildings,  inadequate protection of assets,  lack of public information and awareness,  limited official recognition of risks and preparedness measures, and disregard for wise environmental management.

What is Risk Risk (or more specifically, disaster risk) is the potential disaster losses (in terms of lives, health status, livelihoods, assets and services) which could occur to a particular community or a society over some specified future time period. (Reference UNISDR Terminology) It considers the probability of harmful consequences, or expected losses (deaths, injuries, property, livelihoods, economic activity disrupted or environmentally damaged) resulting from interactions between natural or human induced hazards and vulnerable conditions. Risk can be calculated using the following equation: Risk = Probability of Hazard x Degree of Vulnerability.

There are different ways of dealing with risk, such as: Risk Acceptance: an informed decision to accept the possible consequences and likelihood of a particular risk. Risk Avoidance: an informed decision to avoid involvement in activities leading to risk realization. Risk Reduction refers to the application of appropriate techniques to reduce the likelihood of risk occurrence and its consequences. Risk Transfer involves shifting of the burden of risk to another party. One of the most common forms of risk transfer is Insurance.

Links to Videos Seismic Waves Earthquake waves Christchurch Landslide Japan - Liquefaction Japan 2- Liquefaction

Additional Links: Haiti Today Haiti Case Study UWI Seismic Research ODPM