University:
Durham Technical Community College
Course:
GEL-111 | Geology
Academic year:

2024
Views:

252

Pages:

2
Author:

Amy TGT

earthquakes - very common and occur everyday usually occur at fault lines Earthquakes are caused by - stress forces - compressional (pushing) - tensional (pulling) - shear (scraping) An earthquake is a release of energy elastic rebound theory - once the stress of an earthquake is released, the plates will return to their starting positions hypocenter/focus - the location where fault motion occurs (usually on a fault surface) epicenter - the land surface directly above the hypocenter faults - planar breaks in the crust (usually sloping - vertical faults are rare) Normal Fault hanging wall - the block below the fault footwall - the block above the fault Reverse Fault hanging wall - above the fault footwall - below the fault Thrust fault - a type of reverse fault where the slope between the hanging wall and the footwall is less steep Strike-slip fault – one where two blocks move alongside each other (like a transverse fault in plate tectonics) Seismic Body Waves: P-wave (primary wave): the first waves sent out from the hypocenter; they move the fastest; can travel through all states of matter ; vibrate parallel to the direction in which they travel S-wave (secondary wave): much slower than P-waves; cannot travel through liquids; vibrate perpendicular to the direction in which they travel L-wave (Love wave): S-waves that travel along the surface, moving the ground back and forth like a snake R-wave (Rayleigh wave): P-waves that intersect the surface ; they cause the ground to ripple up and down like water Seismograph – an instrument that records ground motion Seismogram – the data record from a seismograph (shows P-waves first, then S-waves, then surface waves last) Magnitude – the amount of ground motion measured on a seismograph Richter scale – one of the scales on which the magnitude of an earthquake is measured (1 being lowest, 10 being highest) Intensity – the amount of damage observed in the field of an earthquake Mercalli Intensity scale – a scale that uses Roman numerals to describe differing degrees of damage done by an earthquake Effects of Earthquakes: Pancaking Topple Fires Tsunamis