What is an Earthquake?

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacing the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity. The origin point of seismic waves is called epicenter of earthquake. If epicenter is located near the sea then it can cause the creation of Tsunami waves. Earthquakes lead to severe shaking of earth’s surface, landslides etc. Earthquakes are generally results of natural phenomena like geological stress, volcanic eruptions, landslides etc but earthquakes can also be induced by some human activities like mine blasts and nuclear experimentation etc. the first rupture point of earthquake is called focus hypocenter and epicenter is the point at ground level exactly above the hypocenter.

In its most generic sense, the word earthquake is used to describe any seismic event — whether a natural phenomenon or an event caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments. An earthquake's point of initial rupture is called its focus or hypocenter. The term epicenter refers to the point at ground level directly above the hypocenter.

Those earthquakes which occur due to some natural phenomena are generally more intensified and harmful. These Tectonic earthquakes can occur just anywhere in earth where enough elastic strain energy is stored to conduct fracture propagation at a fault plane. There are basically 3 types of faults, which cause creation of the earthquakes- reverse, strike-slip and normal. Reason of a certain displacement decides the intensity of the earthquakes. Earthquakes are classified as extreme destruction source of nature because an exact warning can’t be extracted about earthquakes. Even sometimes earthquakes can hit a region in a series. In this situation one new earthquake gets triggered due to displacement, shaking or stress induction by previous strike of earthquake. This situation is called earthquake storm. This is extremely detrimental for human life and property.

Shaking of ground causes severe damage to the buildings or other structures on the ground including houses etc. Shaking of ground at a particular place depends upon the distance of that place from the epicenter. Severe shaking of ground causes destruction of all the buildings of a city and many people die by burring into the building materials.

Typhoon Ketsana

Typhoon Ketsana (International designation: 0916, JTWC designation: 17W, PAGASA name: Ondoy) formed early on September 23, 2009, about 860 km (535 mi) to the northwest of Palau. The depression remained weak and was downgraded to a low pressure area later that day by the Japan Meteorological Agency. The low pressure area then reintensified early the next day and was named as Tropical Depression Ondoy by the Philippine Atmospheric, Geophysical and Astronomical Services Administration as the Joint Typhoon Warning Center issued a Tropical Cyclone Formation Alert on the depression. It was then reupgraded to a tropical depression by the JMA later that morning before the JTWC followed suit early on September 25, designating the depression as 17W.

The intensification of Ondoy was hampered throughout September 25 by the system moving into an area of moderate vertical windshear and an upper level trough of pressure which was moving over the system. It was then upgraded to a Tropical Storm and named as Ketsana before passing over the island of Luzon in the Philippines. As it moved into the South China sea later that day the system dramatically deepened and expanded whilst moving towards the west which lead to the JMA upgrading it to a Severe Tropical Storm.

Ketsana brought the worst rainfall to Metro Manila among recorded typhoons since the start of rainfall record keeping according by PAGASA, producing only moderate winds but hours of extremely heavy rain. President Gloria Arroyo declared a "state of calamity" encompassing most of Luzon after at least 86 people were initially reported dead in landslides and other incidents. Flood water levels reached a record 20 feet high in rural areas. As of October 24, 2009, at least 464 deaths were officially reported from the typhoon in the Philippines.

Reference : Wikipedia.org

Climate Change Definition

Climate change is a change in the statistical distribution of weather over periods of time that range from decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average (for example, greater or fewer extreme weather events). Climate change may be limited to a specific region, or may occur across the whole Earth.

In recent usage, especially in the context of environmental policy, climate change usually refers to changes in modern climate (see global warming). For information on temperature measurements over various periods, and the data sources available, see temperature record. For attribution of climate change over the past century, see attribution of recent climate change.

Factors that can shape climate are often called climate forcings. These include such processes as variations in solar radiation, deviations in the Earth's orbit, mountain-building andcontinental drift, and changes in greenhouse gas concentrations. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcing because of their large mass. Therefore, the climate system can take centuries or longer to fully respond to new external forcings.

Anthropogenic factors are human activities that change the environment. In some cases the chain of causality of human influence on the climate is direct and unambiguous (for example, the effects of irrigation on local humidity), whilst in other instances it is less clear. Various hypotheses for human-induced climate change have been argued for many years. Presently the scientific consensus on climate change is that human activity is very likely the cause for the rapid increase in global average temperatures over the past several decades. Consequently, the debate has largely shifted onto ways to reduce further human impact and to find ways to adapt to change that has already occurred.

Of most concern in these anthropogenic factors is the increase in CO2 levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere) andcement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation, are also of concern in the roles they play - both separately and in conjunction with other factors - in affecting climate.

Reference : Wikipedia.org