Earthquake Hazards PDF - What is Geology?

EARTHQUAKE HAZARDS  Earthquake Hazards Objectives: At the end of the lesson, the learner is expected to: identify various potential earthquake hazards discuss the effects of different earthquake hazards categorize the hazard according to its type and explain its characte...

EARTHQUAKE HAZARDS  Earthquake Hazards Objectives: At the end of the lesson, the learner is expected to: identify various potential earthquake hazards discuss the effects of different earthquake hazards categorize the hazard according to its type and explain its characteristics and behaviors that produce disasters. CONCEPTS OF GEOLOGIC HAZARDS What is Geology? Definition the science that deals with the dynamics and physical history of the earth, the rocks of which it is composed, and the physical, chemical, and biological changes that the earth has undergone or is undergoing. What is Geology? Geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes the Earth and other terrestrial planets, as well as the processes that shape them. What is Geologic Hazard? Definition A geologic hazard is one of several types of adverse geologic conditions capable of causing damage or loss of property and life. Earthquake Hazards Earthquake Hazards What is Earthquake? An earthquake (also known as a quake, tremor or temblor) is the perceptible shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth’s crust that creates seismic waves. (US Geological Science - USGS) Earthquake Hazards Science of Earthquake Seismology - is the study of earthquakes and seismic waves that move through and around the earth. Seismography – is the scientific measuring and recording of the shock and vibrations of earthquakes. Seismologists - are scientists who study earthquakes and planetary activities as well as their effects, such as tsunamis. Earthquake Hazards Potential Earthquake Hazards Geologist explain that an earthquake is a type of hazards that depends on the strength of seismic activity, along with such factors as local topographic and built features, subsurface geology and groundwater. Classification of Earthquake Hazards 1. Primary Effects Permanent features an earthquake can bring out. Ex. Surface ruptures, offset of natural or human - constructed objects. Classification of Earthquake Hazards 2. Secondary Effects Happens when ground movement results to other types of destruction. Ex. Landslides, tsunami, liquefaction and fire. Earthquake Hazards 1. Ground shaking or Ground Motion The Earth shakes with the passage of earthquake waves, which radiate energy that had been “stored” in stressed rocks, and were released when a fault broke and the rocks slipped to relieved the pent-up stress. Earthquake Hazards 1. Ground shaking or Ground Motion The strength of ground-shaking is measured in the velocity of the ground motion, the acceleration of ground motion, the frequency content of the shaking and how long the shaking continues (“duration”). Earthquake Hazards 2. Ground or Surface Rupture Surface rupture is an offset of the ground surface when fault rupture extends to the Earth’s surface. Any structure built across the fault is at risk of being torn apart as the two sides of the fault slip past each other. Earthquake Hazards 3. Soil Liquefaction Soil liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. It normally occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. Earthquake Hazards 4. Earthquake – induced Ground Subsidence Subsidence or lowering of the ground surface, often occurs during earthquakes. This may be due downward vertical displacement on one side of the fault, and can sometimes affect a huge are of land. Earthquake Hazards 5. Earthquake – induced Lateral Spreading Lateral spreading occurs where sloping grounds starts to move downhill, causing cracks to open up, that are often seen along hill crests and river banks. Earthquake Hazards 6. Earthquake – induced Landslide Landslides are frequently triggered by strong ground motions. They are important secondary earthquake hazard. The term landslide includes a wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flow. Earthquake Hazards 7. Tsunami A tsunami, also known as a seismic wave, is a series of waves in a water body caused by displacement of a large volume of water, generally in an ocean or a large lake. Earthquake Hazards Natural Signs of an Impending Tsunami 1. Animal Behavior. Some zoologists hypothesize that some animal species like elephants have the ability to sense subsonic Rayleigh waves from an earthquake or tsunami. 2. Drawback. This is an observable natural sign of an impending tsunami that is noteworthy. Methods of reducing Earthquake Risks 1. Effective recording and interpretation of ground motion. Methods of reducing Earthquake Risks 2. Constructing Seismic Hazard Maps. Methods of reducing Earthquake Risks 3. Developing resistant structures. REFERENCES: Quebral, Villamor S. (2016). for Senior High School (Core Subject). Lorimar Publishing, Inc., Cubao, Quezon City Oliva, Mylene D.G. (2016). DIWA Senior High School Series: Module. Diwa Learning Systems Inc., Makati City.