Earthquakes & Faults

• An earthquake refers to the shaking of Earth when energy stored in rocks deep inside earth is released.
• Earthquakes happen along tectonic plate boundaries or along active faults.
• The theory of plate tectonics explains the formation and movement of the plates of earth.
• Convection currents cause the movement of the lithosphere and the formation of tectonic plates.
• The Philippines has many trenches and active faults which are the sites of earthquakes.
• Active faults have a documented history of recent displacements.
• The Philippine Fault zone and the Valley fault system are examples of active faults.
• Faults are three types based on the direction of slippage: dip-slip, strike-slip, and oblique-slip.
• Earthquakes generated by movements along faults are all shallow-seated and very destructive.
• Tsunamis are often generated if strong shallow earthquakes occur under the sea.
• Earthquakes may be tectonic or volcanic in origin.
• Tectonic earthquakes happen because of displacements along fault fissures in the solid, rigid layers of earth.
• Volcanic earthquakes are induced by rising lava or magma beneath active volcanoes.
• The focus or hypocenter of the earthquake refers to the immediate area where the displacement of the plates takes place.
• The point directly above the focus is the epicenter.