Chapter-1 Basics of Earthquakes
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Transcript of Chapter-1 Basics of Earthquakes
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Chapter-1
Basics of Earthquakes
Class Two
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Where do Earthquake occurs
Elastic Rebound Theory
Faults
Plate Tectonics
Organization of Lecture
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Where do earthquakes Where do earthquakes occur?occur?
FaultsFaults
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Plate boundariesPlate boundaries
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Plate boundaries are often identified from the location of past earthquakes.
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Elastic Rebound Theory
• This theory was discovered by making measurements at a number of points across a fault.
• Prior to an earthquake it was noted that the rocks adjacent to the fault were bending. These bends disappeared after an earthquake suggesting that the energy stored in bending the rocks was suddenly released during the earthquake.
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Elastic Rebound Theory
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Sequence of elastic rebound: Stresses
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Sequence of elastic rebound: Bending
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Sequence of elastic rebound: Rupture
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Sequence of elastic rebound: Rebound
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Sudden Slip by Elastic Rebound
• Stresses (force/area) are applied to a fault.
• Strain (deformation) accumulates in the vicinity of friction-locked faults.
• Strain accumulation reaches a threshold and fault slips suddenly
• Rupture (slip) continues over some portion of the fault. Slip is the distance of displacement along a fault.
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FaultA fracture (crack) in the earth, where the two sides move past each other and the relative motion is parallel to the fracture.
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Different Fault TypesDifferent Fault Types
shear)
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hanging wall moves down
Normal Dip-slip faultNormal Dip-slip fault
A normal dip-slip fault
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Hanging wall moves upThis is also called a Thrust Fault.
Reverse Dip-slip Reverse Dip-slip faultfault
A Reverse dip slip fault
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A strike-slip fault
Displacement in horizontal direction
Strike-slip faultStrike-slip fault
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Blind/Hidden faultsBlind/Hidden faults
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Displacement in both vertical and horizontal directions
An oblique-slip fault
Oblique-slip faultOblique-slip fault
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THANK YOU