I once thought that the man made catastrophe that has consumed every sphere of our lives in Nigeria is worse than having a natural disaster. When people say that we are lucky to be in an area not prone to earthquakes I wonder if they realize that an earthquake will be far better than the curse our government placed on her citizenry.
However watching excerpts from the Haiti earthquake disaster of 2010 that killed about 220,000 people, I knew I wouldn’t even wish that for my enemies.
What could be worse than that?
Following the tremor that occurred on September 11, 2009, which affected western parts of the country, researchers have said that the incident was a sign that Nigeria is no longer safe as far as earthquake is concerned.
The general belief that Nigeria is outside the seismic region should no longer exist. When it comes to earthquakes, Nigeria is not as safe as we think. Information has it that, some parts of Nigeria especially the South-West appear not to be safe, this much was gathered from the Centre for Geo-dynamics and Geodesy (CGG) network in Nigeria. Therefore there is a need to monitor how structures respond to earthquakes and applying the knowledge gained in the event that the unexpected happens. Scientists and engineers are improving the ability of structures to survive major earthquakes.
Designing and building large structures is always a challenge, and that challenge is compounded when they are built in earthquake-prone areas. More than 60 deaths and about $ 6 billion in property damage resulted from the 1989 Loma Prieta earthquake that occurred in North California. As earth scientists learn more about ground motion during earthquakes and structural engineers use this information to design stronger buildings, such loss of life and property can ultimately be reduced.
Building codes provide the first line of defense against future earthquake damage and help to ensure public safety. Records of building response to earthquakes, especially those from structures that failed or were damaged, have led to many revisions and improvements in building codes.
Earth scientists began recording earthquakes about 1880, but it was not until the 1940’s that instruments were installed in buildings to measure their response to earthquakes. The number of instruments installed in structures increased in the 1950’s and 1960’s. The first abundant data on the response of structures came from the devastating 1971 San Fernando, California, earthquake, which yielded several dozen records. These records were primitive by today’s standards. The first records from instruments sophisticated enough to measure twisting of a building were obtained during the 1979 Imperial Valley, California, earthquake.
The majority of deaths and injuries from earthquakes are caused by the damage or collapse of buildings and other structures. However, these losses can be reduced through documenting and understanding how structures respond to earthquakes. Gaining such knowledge requires a long-term commitment because large devastating earthquakes occur at irregular and often long intervals. Recording instruments must be in place and waiting, ready to capture the response to the next temblor whenever it occurs. The new information acquired by these instruments can then be used to better design earthquake-resistant structures. In this way, earth scientists and engineers help reduce loss of life and property in future earthquakes.
Different types of building materials respond differently to the shaking caused by seismic waves. Materials such as brick and stone break easily during an earthquake. The mortar that typically holds these materials together shakes loose because it is not strong. Brick, stone, and mortar structures are very unsuitable dwellings for “earthquake country.” In addition, non-bearing walls of bricks or stone are extremely dangerous because they are not structurally part of a house. Wood and steel are much better at withstanding seismic waves. Both of these materials flex as the earth shakes.
Weak materials can be reinforced to make them relatively safe. Reinforcing structures with a steel frame, or driving beams through a structure will help support it during shaking.
Architects and engineers can also design and construct buildings that can withstand intense ground shaking. For example, designs that are broader at the base than at the top or homes that are not more than two stories high survive earthquakes fairly well. Ornate pillars or facades (fake fronts) on a home do not survive shaking well. Engineers need to consider the rigidity of the building material. The material should be able to bend or flex without damage in an earthquake. For instance, wood bends but brick and mortar does not. Engineers need to reinforce brick masonry by putting steel beams through the structures. Many buildings were built prior to strict earthquake codes, so in many places such reinforcement is necessary. Bracing a structure is an alternative way to prevent damage. Engineers and architects can make structures earthquake resistant, but they cannot make them earthquake proof.
Most of the damage we associate with earthquakes involves human-built structures: people trapped by collapsed buildings or cut off from vital water or energy supplies.
How a quake will affect the people of a city has a lot to do with how the city, its residents, and nearby governments have engineered structures and pipelines. It might seem obvious to say that earthquakes do most of their damage by shaking the ground. But ground-shaking is actually a complex phenomenon. Engineering the seismic safety of a structure involves the same considerations as any real estate venture—design, construction, and location.
When the ground beneath a building shakes, it makes the building sway as the energy of a quake’s waves moves through it. You might think that a skyscraper would be more dangerous than a smaller office building, but in fact, the opposite is often true. Here’s why:
The taller a structure, the more flexible it is. The more flexible it is, the less energy is required to keep it from toppling or collapsing when the earth’s shaking makes it sway. Because shorter buildings are stiffer than taller ones, a three-story apartment house is considered more vulnerable to earthquake damage than a 30-story skyscraper. When planning the seismic safety of a building, structural engineers must design the support elements of shorter buildings to withstand greater forces than those of taller buildings.
Let’s draw lessons from these scenarios:
When a magnitude 7.0 quake hit Haiti on January 12, 2010 about 220,000 people died, over 300,000 people got injured while about 300,000 homes got damaged. Haiti, also a poor country, had no national building code and hence was notorious for shoddy construction works.
In contrast, when an earthquake of 6.9 magnitude hit San Francisco on October 17, 1989, only 63 people died and 3,700 people got injured. Building system, ethics and enforcement of codes are pertinent to reduction of losses in an earthquake occurrence.
The difference in those death tolls comes from building construction and technology. In Haiti, the buildings were constructed quickly and cheaply. San Francisco, a richer and more industrialized nation, adheres to more stringent building codes.
We can only pray that we never witness such devastating mishap in Nigeria. But in the event that it happens, what becomes of our fate?
They say when faced with two evils choose the lesser. Now that it is been widely reported that Nigeria is susceptible to an earthquake, won’t the disaster in San Francisco be a better option?
Albeit, our building system, ethics and enforcement of codes is not any better from that obtainable in Haiti.
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