Understanding Earthquakes: Terms and Definitions, Quizzes of Geology

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TERM 1 What happens during an earthquake DEFINITION 1 during earthquakes elastic limit is reached- start of brittle failure- start of earthquakelike an elastic band TERM 2 Hypocenter DEFINITION 2 start of brittle failureactual point where earthquake begins TERM 3 Epicenter DEFINITION 3 map view of the hypocenter (so it is above it) TERM 4 What is an earthquake DEFINITION 4 - a brittle strain event- sudden slip on a fault- causes seismic shaking TERM 5 4 actions of the energy released by an earthquake DEFINITION 5 1) moves rocks2) grinds rocks3) creates heat (friction)4) creates vibrations TERM 6 P- waves DEFINITION 6 Travelling elastic normal- strain vibrationscompression waves- fastest in fluids it is the speed of sound- causes little shaking TERM 7 S- waves DEFINITION 7 travelling elastic shear-strain vibrations2nd fastest wavesmedium shakingnot in fluid TERM 8 surface waves (love and rayleigh waves) DEFINITION 8 waves that travel along the surfaceslowestlargest shaking TERM 9 seismic wave DEFINITION 9 - traveling elastic strain vibrations TERM 10 seismometer DEFINITION 10 - mass on a spring- measuring seismic waves TERM 21 Ground rupture DEFINITION 21 land movesmyth: ground swallowing people/oobjects. its under compression it cant just open TERM 22 Creep DEFINITION 22 - continuous motion without earthquakes bends structions- (no large earthquake) very little earthquake TERM 23 landslide DEFINITION 23 - unstable slopes can be triggered by earthquakes TERM 24 Liquefaction DEFINITION 24 muds and wet soils can become liquid when shaken (can cause mud volcanos) TERM 25 tsunami DEFINITION 25 water wave created by verticle motion of a fault TERM 26 Prediction DEFINITION 26 specific damaging earth location (within km)time period of a few days TERM 27 forecasting DEFINITION 27 - probability of exceeding- a certain magnitude or ground shaking- location (within 100 km- time period of a decade- based on known earthquake patterns- stress build up TERM 28 seismic hazard map DEFINITION 28 - major faults only- expected earthquakes-probability of strong ground shaking- 30 year forcast > 65% for san francisco > 99% chance for california TERM 29 Possible earthquake precursors DEFINITION 29 - foreshocks- ground deformation- groundwater lvl and chemistry- electromagnetic (peizo electric) signals TERM 30 What affects slop stability DEFINITION 30 - slope angle- shear force- shear strength- stress vibration TERM 31 slope angle DEFINITION 31 steepen --> less stable- build mountains by tections- erosion at base TERM 32 mass movement DEFINITION 32 - down slope movements driven by gravity= mass wasting TERM 33 what happens as the slope of a surface gets steeper DEFINITION 33 - shear stress on the surface increases- normal stress decreases- friction decreasesmovement on the surface is more likely TERM 34 tectonics DEFINITION 34 builds mountains (change slope- makes steeper) TERM 35 erosion undercutting DEFINITION 35 removal of lateral supportmakes steeper TERM 46 things humans should not do to reduce risk of mass movement DEFINITION 46 - undercut slop- steepen for landscaping- add mass to top of hill- add water- increases wet-dry cycle- remove vegetation (increase erosion) TERM 47 Principal stress DEFINITION 47 it is always possible to roatate the coordinate system to an orinatation in which the cube has no shear stress on its faces TERM 48 stress DEFINITION 48 force per unit areastress measured inside a volume of material in geocompression TERM 49 Lithostatic stress DEFINITION 49 stress due to weight of overlaying rock TERM 50 principle stress at oceanic spreading center, continental collision zone, transform plate boundary DEFINITION 50 oceanic spreading center: regional horizontal extensioncontinental collision zone: regional horizontal compressiontransform plate boundary: regional transform faulting TERM 51 strain DEFINITION 51 defromation: change in size or shapestress causes strain TERM 52 normal strain DEFINITION 52 change in length per unit length TERM 53 shear strain DEFINITION 53 change in angle TERM 54 elastic strain DEFINITION 54 small stress => elastic strainoccurs immediatly (by changing size)temporary(hooke's law) elastic strain is linearly proportional to stressstress- modulus(strain) TERM 55 elastic limit DEFINITION 55 larger stress= permanet strain (rock breaks or flows) TERM 56 strength DEFINITION 56 stress at failure point TERM 57 what happens when rocks go under brittle and ductile strain DEFINITION 57 brittle = rock breaksductile = rock flows TERM 58 for a plan that might break what does shearing and normal stress do? DEFINITION 58 Shear: tries to make the plane slip= break rock along the planeNormal: increases friction= tries to prevent breaking TERM 59 examples or geologic features that can act as planes of weakness DEFINITION 59 - preexisting creacks (fractures)- bedding folliation- contacts between rocks TERM 60 water under pressure do to the brittle strength of rock DEFINITION 60 water pressure p in pores N is replaced by N -Pweakens rock (lubricates) decreases normal stresswater is an incomprehensible fluid TERM 71 fault DEFINITION 71 facture with motion along it TERM 72 normal fault DEFINITION 72 net norizontal extension hang wall moves down and outwardextension stress TERM 73 reverse fault DEFINITION 73 footwall moves up mountain buildinghorizontal shorting and tallercompression stress TERM 74 how do folds form DEFINITION 74 compression forces. at subduction and collision zones TERM 75 syncline DEFINITION 75 bowl shaped TERM 76 anticline DEFINITION 76 hat shaped TERM 77 strain at the microscopic scale produce what in metamorphic rocks DEFINITION 77 flow metamorphic texturesfoliationlineationshearing as metamorphosing and recrystallizing