Earthquake

• An earthquake is the result of sudden release of energy in the Earth’s crust that create seismic waves.

TYPES OF AN EARTHQUAKE:
• Tectonic earthquake is one that occurs when the earth’s crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.
• Volcanic earthquake is any earthquake that results from tectonic forces which occur in conjunction with volcanic activity.
• Landslips/Landslide Earthquake is caused by a landslide. It is a wide range of ground movement such as rock falls, deep failure of slopes and shallow debris flow.
CAUSES:
• Earthquakes are caused by faulting, a sudden lateral or vertical movement of rock along a rupture (break) surface. The surface of the Earth is in continuous slow motion. This is plate tectonics – the motion of immerse rigid plates at the surface of the Earth in response to flow of rock within the Earth. The plates cover the entire surface of the globe. Since they are all moving they rub against each other in some places, sink beneath each other at such places, the motion isn’t smooth – the plates are stick together at the edges but the rest of each plate is continuing to move so the rock along the edge distorted. As the motion continues the strain builds up to the point where the rock cannot withstand any more bending. With a lunch, the rock breaks and the two sides move. An earthquake us the shaking that radiates out from the rock.
FOCUS & EPICENTER:
Focus is the location where the earthquake begins the ground rupture this spot, the seismic waves radiate outward in all directions while Epicenter is the point of the Earth surface located directly above the focus of earthquake.
FORESHOCK & AFTERSHOCK:
Foreshock is an earthquake which precede larger earthquake in the same location while Aftershock is the smaller earthquake in the same general area during the day following a larger event or main shock as within 1 – 2 faults lengths away and during the period of time before the background seismicity level has resumed.
SEISMOGRAPH:
• A seismograph is an instrument used to detect and record earthquakes. During an earthquake the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper magnetic tape or another recording medium. This record is proportional to the motion of the seismometer mass relative to the earth but it can be mathematically converted to a record of the absolute motion of the ground. It records the motion of the mass relative to the frame or the force needed to keep it from moving. Any movement of the ground moves the frame. The mass tends not to move because of its inertia and by measuring the movement between the frames of the mass, the motion of the ground can be determined.
MAGNITUDE & INTENSITY:
Magnitude is the energy released at the source of an earthquake while Intensity is the strength of shaking produced by the earthquake at a certain location.
RICHTER & ROSSI-FOREL SCALE:
Richter Magnitude Scale has developed to assign a single number to quantify the energy released during an earthquake while Rossi-Forel Scale is one of the first seismic scales to reflect earthquake intensities. Developed by Michele Stefano Corte de Rossi of Italy and Francois – Alphonse of Switzerland in the late 19th century.

What to do Before an Earthquake:
• Learn first aid
• Learn how to turn of the gas, water and electricity
• Learn the earthquake plan at your school or workplace
What to do During an Earthquake:
• Don’t use elevators
• Don’t use matches or candles or any flame.
• If you are in a car, stop the car and stay inside the car where it stop.
What to do After an Earthquake:
• Check yourself and others for injuries.
• Stay out of damaged buildings.
• Turn on radio. Don’t use phone unless it’s an emergency.