The hypocenter was located at a depth of 26-km (16.2 miles) below the surface. The Japan Meteorological Agency gave it a magnitude of 7.8. Severe damage was done in Azad Kashmir and NWFP, as thousands of people died and the numbers of casualties are expected to rise, up to a formidable level. President Musharraf has termed the earthquake and its aftermath a "test for the nation."
Towns in Indian administered Kashmir are also affected. Till date, about 865 aftershocks have been recorded.
Over 100 international relief agencies and even a greater number of local groups are busy providing relief to the earthquake victims. In the worst hit nation, Pakistan, the Indian continental plate to the south is trying to subduct, or dive beneath, the Eurasian plate to the north.
This ongoing collision forces the Earth's crust to buckle, producing the Himalaya, Karakoram, Pamirs, and Hindu Kush mountain ranges. According to Geologists, the Indian subcontinent, which includes India, Pakistan, and Bangladesh, creeps northward at rate of about 1.6 inches (40 millimeters) per year.
It slammed into Eurasia about 50 million years ago, beginning the uplift of the Earth's crust that produces the regions lofty peaks. The collision of continental plates tends to produce shallower faults than when the crash involves a plate that forms part or all of an ocean basin. An oceanic plate consists of more dense material, so it slides beneath the continental plate much more willingly. When two continental plates collide, neither wants to be the one that goes underneath the other.
As a result, a highly active region of shallow thrust faults arc across the Himalayan foothills in the cross-border Kashmir region, which extends across northern India and northern Pakistan.
Other major quakes that have struck in the region include a magnitude 7.5 quake in north-east Afghanistan in 1842; a magnitude 7.8 quake in Kangra, India, in 1905; and a magnitude 7.5 earthquake in 1935 in Quetta, Pakistan, which killed at least 50,000 people.
An Earthquake is a sudden tremor or movement of the earth's crust, which originates naturally at or below the surface. The word natural is important here, since it excludes shock waves caused by French nuclear tests, man-made explosions and landslides caused by building work.
An earthquake can be likened to the effect observed when a stone is thrown into water. After the stone hits the water a series of concentric waves will move outwards from the center. The same events occur in an earthquake. There is a sudden movement within the crust or mantle, and concentric shock waves move out from that point.
Geologists and Geographers call the origin of the earthquake the focus. Since this is often deep below the surface and difficult to map, the location of the earthquake is often referred to as the point on the Earth surface directly above the focus. This point is called the epicenter.
When the ground shakes buildings respond to the accelerations transmitted from the ground through the structure's foundation. The inertia of the building (it wants to stay at rest) can cause shearing of the structure which can concentrate stresses on the weak walls or joints in the structure, resulting in failure or perhaps total collapse. The type of shaking and the frequency of shaking depend on the structure. Tall buildings tend to amplify the motions of longer nod motions when compared with small buildings.
Each structure has a resonance frequency that is characteristic of the building. Predicting the precise behaviour of buildings is complicated, a rule of thumb is that the period of resonance is about equal to 0.1 times the number of stories in the structure.
Taller buildings also tend to shake longer than short buildings, which can make them relatively more susceptible to damage. Fortunately many tall buildings are constructed to withstand strong winds and some precautions have been taken to reduce their tendency to shake. And they can be made resistant to earthquake vibrations.
The strength, or magnitude, of the shock waves determines the extent of the damage caused. Two main scales exist for defining the strength, the 'Mercalli Scale' and the 'Richter Scale'. Earthquakes are three dimensional events, the waves move outwards from the focus, but can travel in both the horizontal and vertical plains.
This produces three different types of shock-waves, which have their own distinct characteristics and can only move through certain layers within the Earth. There are three types of shock-waves.
P-WAVES: The P-wave is the fastest moving wave, travelling at about five kilometers a second, (three miles a second). Having the characteristic of sound waves, it moves longitudinally, creating a "push-pull" waves, it moves longitudinally, creating a "push-pull" effect on the rock as it passes. Primary Wages (P-Waves) are identical in character to sound waves. They are high frequency, short--wavelength, longitudinal waves, which can pass through both solids and liquids.
The ground is forced to move forwards and backwards as it is compressed and decompressed. This produces relatively small displacements of the ground. P-Waves can be reflected and refracted, and under certain circumstances can change into S-Waves.
S-WAVES: Secondary Waves (S-Waves) travel more slowly than P-Waves and arrive at any given point after the P-Waves. Like P-Waves they are high frequency, short-wavelength waves, but instead of being longitudinal they are transverse. They move in all directions away from their source, at speeds which de end upon the density of the rocks through which they are moving. They cannot move through liquids. On the surface of the Earth, S-Waves are responsible for the sideways displacement of walls and fences, leaving them 'S' shaped.
L-WAVES: Surface Waves (L-Waves) are low frequency transverse vibration with a long wavelength. They are created close to the epicenter and can only ravel through the outer part of the crust. They are responsible for the majority of the building damage caused by earthquakes.
This is because L-Waves have a motion similar to that of waves in the sea. The ground is made to move in a circular motion, causing it to rise and fall as visible waves move across the ground. Together with secondary effects such as landslides, fires and tsunami these waves account for the loss of approximately 10,000 lives and over $100 million per year.
Another form of the earthquake is the tsunami. Tsunamis are initiated by a sudden displacement of the ocean, commonly caused by vertical deformation of the ocean floor during earthquakes. Other causes such as deformation by landslides and volcanic processes also generate tsunamis.
The speed of this wave depends on the ocean depth and is typically about as fast as a commercial passenger jet (about 0.2 km/s or 712 km/hr). This is relatively slow compared to seismic waves, so we are often alerted to the dangers of the tsunami by the shaking before the wave arrives.
The trouble is that the time to react is not very long in regions close to the earthquake that caused the tsunami.
The cost of rehabilitation of the displaced is not estimated but it seems as if huge demand for monetary spending would create serious shortage of funds resulting the widening of the budget deficit, wrapping up of several projects and reduce the spending under the annual development plan.
Moreover, the indirect impact has already started appearing on the common life of people, as millions of people have donated their savings to help their brethren who are facing the devastation of the earthquake. Reports indicate that Eid shopping in the month of Ramazan, which is considered the best month for business, has slowed down.
A huge burden on government's spending can be perceived that would certainly hit a lot of new and ongoing projects. This would result in the slowing down of the economy, besides increasing the budget deficit.
Analysts estimated that the government has set the budget deficit at 3.8 percent (Rs 263 billion) of the GDP for the year 2005-06. It has been announced by the government that the aid committed by the international community is insignificant, which means that the government would have to bear the maximum load of spending for the rehabilitation of the quake-hit areas.
The importance of properly designing, constructing, and installing non-structural components in order to reduce the losses due to earthquakes cannot be overstated. As history has demonstrated, damage to nonstructural components in the past earthquakes has resulted in the majority of direct property losses. Additionally, the damage to nonstructural components can contribute to increased indirect losses due to business interruption and loss of market share.
It therefore becomes incumbent on the builder to understand the intended purpose of the safe building design pertaining to the expected, and acceptable, earthquake performance of the facility in establishing earthquake-risk tolerance.
We should not forget the example of the Kobe earthquake, Japan in which nearly 200,000 buildings collapsed, along with the elevated Hanshin Expressway, along with many bridges. Several bullet trains were derailed, and 120 of the 150 quays in the port of Kobe were destroyed.
The number of people that were homeless didn't decrease for days, even weeks, because people were afraid to go home because of the 716 aftershocks. In the end, there were 5,500 dead, 40,000 injured and 180,000 houses completely demolished.
However, in the months after the earthquake, Kobe picked up and began to work again. Industries that had been forced to close, like Mitsubishi or Panasonic, re-opened, and the public systems (telephones, electricity, gas, plumbing, etc) were 100% working by July.
The rubble had been cleared, and most of the business buildings in the central parts of Kobe had been fixed. All of the trains were working again by August. After a year, the port of Kobe was 80% functional. However, the Hanshin Expressway was still closed.
The people of Kobe learned from the catastrophe by improving the safety standards of their buildings, making sure they were made of both earthquake-proof and fire-proof materials, making sure that the buildings were built on solid rock, and ensuring that all houses and buildings would be able to absorb shocks well.
Also, there were more seismographs and other machines installed in order to better keep track of how the earth was moving, so that they would be better prepared next time.