Maria Javed
Active member
Earthquake is a sudden violent movement of the Earth, s surface. It occurs when a lot of energy, stored within the Earth is released.
The point within the earth where an earthquake originates is called the focus. The point on the earth, s surface directly above the focus is called the epicentre. If the focus is near the surface i. e. Between 0 and 70 km deep. A shallow focus earthquake is produced. If it is between 70 and 700 km deep a deep focus earthquake is produced.
There are many causes of earthquake
1. Faults:
The theory is that the earth crust is made of tectonic plates. These plates are lying side by side. The points where these plates meet are called faults. Sometimes the fault plain dips into the ground. The rock hanging over the dipping fault plain slips down ward into the ground. It is called a normal fault. Sometimes the tectonic plates slide horizontally in the fault plain. Such a slip in the fault plain produces horizontal displacement. The faults where such a movement takes place are are called strike slip faults.
2. Waves :
The sudden movement of rocks along a fault causes vibration. These vibrations transmit energy through the earth in the form of waves. These waves are called seismic waves. They are classified in to four types
1. S. Secondary waves
2. P. Primary waves
3. Love waves
4. Rayleigh waves
3. Effects :
Earthquakes results in land slides and other soils movement. These events cause an enormous loss of property and life. Earthquake waves shake buildings and cause weak structures totally collapse. If an earthquake occurs in oceans it may cause tsunami waves. Catastrophic earthquakes can spread contagious diseases. Damage to water supply lines and sewage lines may lead to conditions that spread infectious diseases.
The point within the earth where an earthquake originates is called the focus. The point on the earth, s surface directly above the focus is called the epicentre. If the focus is near the surface i. e. Between 0 and 70 km deep. A shallow focus earthquake is produced. If it is between 70 and 700 km deep a deep focus earthquake is produced.
There are many causes of earthquake
1. Faults:
The theory is that the earth crust is made of tectonic plates. These plates are lying side by side. The points where these plates meet are called faults. Sometimes the fault plain dips into the ground. The rock hanging over the dipping fault plain slips down ward into the ground. It is called a normal fault. Sometimes the tectonic plates slide horizontally in the fault plain. Such a slip in the fault plain produces horizontal displacement. The faults where such a movement takes place are are called strike slip faults.
2. Waves :
The sudden movement of rocks along a fault causes vibration. These vibrations transmit energy through the earth in the form of waves. These waves are called seismic waves. They are classified in to four types
1. S. Secondary waves
2. P. Primary waves
3. Love waves
4. Rayleigh waves
3. Effects :
Earthquakes results in land slides and other soils movement. These events cause an enormous loss of property and life. Earthquake waves shake buildings and cause weak structures totally collapse. If an earthquake occurs in oceans it may cause tsunami waves. Catastrophic earthquakes can spread contagious diseases. Damage to water supply lines and sewage lines may lead to conditions that spread infectious diseases.
