Presentation on theme: "Earthquakes can be one of the most devastating natural disasters How Does an Earthquake Happen? Energy is Released."— Presentation transcript:
Earthquakes can be one of the most devastating natural disasters How Does an Earthquake Happen? Energy is Released
The Earth is made up of a number of layers (including the core) that radiate outwards at different depths and sizes. The surface of the Earth is the layer called the crust, and the crust is divided into many segments called plates. These plates are constantly in motion, though they move so slowly that any significant change in the plates will only be noticed after thousands of years.
Every now and then the movement of one plate over another builds up energy, and it is released at the point where the plates meet, called the fault line. This release of energy is the basis for an earthquake. Energy can also be released in other ways, such as when a volcano erupts with enough force. Manmade explosions can also release enough energy to cause an earthquake if they are strong enough. Whatever the catalyst is for a major release of energy in or against the Earth's crust, it is what triggers earthquakes to occur
Seismic Waves are Produced The point at which the mass amount of energy needed to start an earthquake originates is known as a focal point. These are usually found at shallow depths from the Earth's surface and go hand in hand with the point on the surface right above it, called the epicenter. As seismic waves travel through the Earth's crust, the effects of an earthquake we are familiar with occur. These seismic waves carry with them an enormous amount of energy, so whatever they travel through will be affected by that. This results in the quivering and shaking of the Earth during an earthquake
INTRODUCTION Natural disasters like earthquake, landslide, flood, drought, cyclone, forest fire, volcanic eruption, epidemic and major accidents are quite common in different parts of the globe. These lead to the loss of life, property damage and socio-economic disruption. Such losses have grown over the years due to increase in population and physical resources. It is believed that the natural disasters have claimed more than 2.8 million lives during the past two decades only and have adversely affected 820 million people with a financial loss of about million dollars. These losses are not evenly distributed and are more prevalent in the developing countries due to higher population concentration and low level of economic growth
Earthquakes are one of the worst among the natural disasters. About 1 lakh earthquakes of magnitude more than three hit the earth every year. According to a conservative estimate more than 15 million human lives have been lost and damage worth hundred billions of dollars has been inflicted in the recorded history due to these
Like any other natural disaster, it is not possible to prevent earthquakes from occurring. The disastrous effects of these, however, can be minimized considerably through scientific understanding of their nature, causes, frequency, magnitude and areas of influence. The key word in this context is "Mitigation and Preparedness". Earthquake disaster mitigation and preparedness strategies are the need of the hour to fight and reduce its miseries to mankind. Comprehensive mitigation and preparedness planning includes avoiding hazard for instance, by providing warning to enable evacuation preceding the hazard, determining the location and nature of the earthquake hazard, identifying the population and structures vulnerable for hazards and adopting strategies to combat the menace of these. In the light of the above, the author discusses the earthquake hazards in India with special reference to the northeastern region along with the mitigation strategies.
EARTHQUAKE PREDICTION It has been found that earthquakes are generally, but not necessarily, preceded by some signals like ground tilting, foreshocks, change in ground water levels, variations in the discharge of springs, anomalous oil flow from the producing wells, enhance emanations of radon and unusual animal behaviour. Perhaps the first successful prediction of earthquake in the world was made by the Chinese In India also efforts are going on for predicting earthquakes based on the statistical analysis of past events and their recurrence intervals, swarms activity and seismic gap. However, meaningful prediction is still alluding the seismologist
EARTHQUAKE RESISTANT STRUCTURES It is necessary to design and construct earthquake resistant dwellings in the seismic prone zones. The principles of a seismic design should be kept in mind in this regard. The important earthquake resistant features which are recommended in the latest BIS codes (IS 13828:1993) should be followed (Bhagwan and Sreenath, 1996).
Normally houses are built to withstand vertical load only and as a result they collapse when subjected to horizontal stresses produced by earthquake waves. The main requirements for preventing the collapse are a lateral load carrying system of enough residual capacity to safely resist lateral forces, a monolithic roof with sufficient in-place rigidity and a strong and durable vertical load carrying system (Shukla, 1998). It is said that the buildings made after 1981 basically had no damage due to Kobe event of 1995 in Japan because these fulfilled earthquake standards of construction (Struck, 1999). Besides, good quality construction materials should be used. The importance of quality material may be realised from the fact that almost all the individual houses in Jabalpur town withstood earthquake shaking, many government and private apartments built by contractors were badly damaged. It may be due to the reason that the contractors used substandard materials.
Strict enforcement of building codes for construction of masonry structures and even for small housing complex in the earthquake prone zones and strict legislation of landuse may help in fighting and reducing the miseries of earthquake hazard. However, it may never be possible for the mankind to live in "Zero Risk Situation" because even after full implementation of mitigation measures, there may be some unpredictable situation that may cause hazards (Acharrya, 1999). Satisfactory results may be obtained through pre, during and post event measures
Haiti devastated by massive earthquake Haiti earthquake On January 12, 2010, an earthquake with a magnitude of 7.0 struck the Caribbean nation of Haitijust 10 miles west of the capital, Port-au-Prince. Thousands of buildings and homes were destroyed. Millions of people were affected and more than 1 million people were left displaced or homeless.
A massive 7.0-magnitude earthquake has struck the Caribbean nation of Haiti. The extent of the devastation is still unclear but there are fears thousands of people may have died. Haiti's worst quake in two centuries hit south of the capital Port-au- Prince on Tuesday, wrecking the presidential palace, UN HQ and other buildings. The Red Cross says up to three million people have been affected. Describing the earthquake as a "catastrophe", Haiti's envoy to the US said the cost of the damage could run into billions. The quake, which struck about 15km (10 miles) south-west of Port-au- Prince, was quickly followed by two strong aftershocks of 5.9 and 5.5 magnitude. Relief Reconstruction Rehabilitation Recovery
Habitat for Humanity expects to help 50,000 families in Haiti who were affected by the devastating 7.0-magnitude earthquake that struck near Port-au-Prince on January 12. Through a multi-year effort that includes relief, rehabilitation and reconstruction, Habitat for Humanity announced today its plan to work with its partners and help improve shelter conditions In the rehabilitation phase, Habitat for Humanity will help families remove debris, salvage materials that can be recycled, repair homes that received minimal damage and build transitional shelters that meet basic needs In the reconstruction phase, Habitat will build core houses, each with a separate sanitation facility. These basic housing units are permanent and resistant to earthquakes and hurricanes. They are designed to be expanded over time by the homeowner families and meet international humanitarian standards.
With more than 200,000 houses severely damaged or destroyed and 1.2 million people homeless or displaced, there is a critical need for shelter in Haiti, said Reckford. Based on our responses to the Asian tsunami and hurricanes Katrina and Rita in the U.S. Gulf Coast, we are confident that we can empower families to improve their housing conditions by giving them the tools and then working alongside them. But Habitat for Humanity is in need of significant financial support so that we can help 50,000 families improve their lives.
The Indian Ocean Tsunami On December 26, 2004, the strongest earthquake felt on Earth in more than 40 years a magnitude 9.3 tremor off the coast of Indonesia's Sumatra island spawned unprecedented tsunami waves that leveled cities and villages across the region. Almost 230,000 people in 11 countries perished, with Indonesia the hardest hit, and millions were displaced.