Lesson 4: Earthquakes

• PHILVOLCS stands for Philippine Institute of Volcanology and Seismology
• the Geological Disaster Agency in the Philippines is PHILVOLCS
• Earthquake is the weak or violent shaking of the Earth's surface caused by the sudden movement of rocks beneath it.
• earthquake commonly happens at a fault
• Convergent boundary creates mountains, volcanoes, and trenches
• Divergent Boundary creates rift valleys and seafloor spreading
• Transform Boundary creates fault lines
• three sliding of tectonic plates are: Reverse Fault, Normal Fault and Strike-split fault
• focus is the place where energy is released
• epicenter is the point immediately above the focus
• seismograph is a devices that measures Earthquakes: Magnitude and Intensity
• Magnitude is the measure of the total energy released by an Earthquake measured in a Richter Magnitude Scale
• Intensity is the perceived strength of an Earthquake based on relative effect measured in a Mercalli Scale
• The five earthquake hazards are : Groundshaking, Ground Rupture, Liquefaction, Ground Subsidence and Tsunami
• Groundshaking is caused by the passage of seismic waves beneath structures
• Ground Rupture is the displacement of the ground due to the violent shaking of the surface (vertical or horizontal)
• Liquefaction takes place when there is high water pressure in saturated soils because of ground shaking
• Ground subsidence is lowering the land surface due to the extraction of ground water and natural gas, mining and earthquakes
• Tsunami is a series of large waves resulting from the disturbance of sea water