Earthquakes PDF

Earthquake by Janine Hilario & Allen Lauson  EARTHQUAKE An earthquake is the shaking of the Earth's surface caused by the sudden release of energy in the Earth's crust. This release of energy creates seismic waves that cause the ground to shake. TYPES OF EARTHQUAKES BASED ON THEIR CA...

Earthquake by Janine Hilario & Allen Lauson  EARTHQUAKE An earthquake is the shaking of the Earth's surface caused by the sudden release of energy in the Earth's crust. This release of energy creates seismic waves that cause the ground to shake. TYPES OF EARTHQUAKES BASED ON THEIR CAUSES 1. Tectonic earthquake 2. Volcanic earthquake 3. Man-made earthquake  TYPES OF EARTHQUAKES BASED ON THEIR CAUSES 1. Tectonic earthquake occurs when there is a sudden release of energy in the Earth's crust due to the movement of tectonic plates 95% of all earthquakes are tectonic earthquakes  TYPES OF EARTHQUAKES BASED ON THEIR CAUSES 2. Volcanic Earthquake Volcanic earthquakes are associated with volcanic activity and are caused by vibrations generated by the movement of magma or other fluids within the volcano  TYPES OF EARTHQUAKES BASED ON THEIR CAUSES 3. Man-made Earthquake Also called induced seismicity, can occur due to human activities such as fluid extraction and mining.  TREMOR VS EARTHQUAKE Tremors are generally regarded as milder seismic vibrations that occur as a result of minor stress adjustments within the Earth’s crust. The main difference between an earthquake and a tremor is in their magnitude.  TECTONIC EARTHQUAKES MECHANISM TECTONIC PLATES Tectonic plates are large, rigid pieces of the Earth's lithosphere (the outer layer of the Earth consists of upper mantle and crust) that fit together like a puzzle, covering the entire planet's surface. These plates move slowly over the semi-fluid asthenosphere, which lies beneath them. Their movement is driven by forces such as convection currents in the Earth's mantle, gravity, and the Earth's rotation. Tectonic plate boundaries are the edges where two or more tectonic plates meet, and they are classified based on how the plates interact. Over geological time, the movement of the mantle beneath the plates causes them to shift, break, and interact, leading to the creation of faults at their boundaries.  STRESS AND STRAIN Stress is the force applied per unit area on a material. It quantifies how much force is acting on a given area of a rock or material, causing deformation. There are three kinds of stress that act on Earth’s rocks: Tensive Stress - occurs when forces pull apart Compressive Stress - occurs when forces push together Shear Stress - occurs when forces slide past each other Strain is the deformation that results from the applied stress. It represents the change in shape or size of a material compared to its original dimensions. STRESS AND STRAIN  ELASTIC REBOUND THEORY The gradual accumulation and release of stress and strain is now referred to as the "elastic rebound theory" of earthquakes. Most earthquakes are the result of the sudden elastic rebound of previously stored energy. FAULTS A fault is a fracture or zone of fractures in the Earth's crust along which there has been movement of the rock. Fault is the area directly above where two tectonic plates interact.  TYPES OF FAULTS 1. NORMAL FAULT This is the most common type of fault. It forms when rock above an inclined fracture plane moves downward, sliding along the rock on the other side of the fracture. Normal faults are often found along divergent plate boundaries.  TYPES OF FAULTS 2. REVERSE FAULT The opposite of a normal fault. A reverse fault forms when the rocks on the “uphill” side of an inclined fault plane rise above the rocks on the other side. Reverse faults often form along convergent plate boundaries.  TYPES OF FAULTS 3. STRIKE-SLIP FAULT Sometimes referred to as a lateral fault, this type forms when the blocks of rock on either side of a vertical (or nearly vertical) fracture move past each other. A visible normal faulting. Example of reverse faulting. Example: The San Andreas Fault is a strike-slip fault that marks the boundary between two major tectonic plates: the Pacific Plate and the North American Plate FOCUS AND EPICENTER  FOCUS The point inside the Earth where an earthquake originates. Causes seismic waves to propagate in all directions. Indicates the point of origin and releases energy during an earthquake.  epicenter The point on the Earth's surface directly above the origin of an earthquake. Indicates the point of maximum damage on the Earth's surface. SEISMIC WAVES  SEISMIC WAVES Seismic waves are the waves of energy that travel through the Earth as a result of a sudden release of energy in the Earth's crust. These waves cause the ground to shake and are the reason we feel earthquakes. Two Types: Body Waves and Surface Waves  body waves Body waves travel through the interior of the Earth and are the first waves to be detected by seismographs during an earthquake. Two types: P (Primary) Waves: Compressional waves that push and pull the ground in the direction the wave is traveling. S (Secondary) Waves: Shear waves that move the ground side-to-side, perpendicular to the direction of wave travel.  SURFACE WAVES Surface waves travel along the Earth's surface and cause the most damage during an earthquake. They travel more slowly than body waves but produce larger ground movements. Two types: Love Waves: They only move through the Earth's crust and cause horizontal shearing of the ground. Rayleigh Waves: They cause the ground to move in an elliptical, rolling motion, with both vertical and horizontal displacement.  earthquake measurement Magnitude: Magnitude measures the energy released at the source of the earthquake. Magnitude is typically measured using seismographs, which record the seismic waves produced by an earthquake. Intensity: Intensity measures the effects of an earthquake at specific locations, assessing how much shaking is felt and the resulting damage. It is a qualitative measure and can vary significantly from place to place. thank you