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Geology Test 4 Part 2
Terms in this set (75)
ground shaking caused by the sudden and rapid movement of one block of rock sliding past another
rocks slide past one another along fractures in the crust called
most earthquakes occur along..?
near plate boundaries , rock is stressed... convergent plate boundaries, mountains, rock is stressed. compressionally , rocks start to fracture, maybe move along fault... this is an earthquake
why would a fault develop?
anywhere crust is weakened
faults can develop..?
rock slippage orignates in the ground here, where rock has moved and caused an earthquake
stored up energy is released as this, it radiates in all directions from the focus
point on the ground surface directly above the focus
massive landslides, meteorites, and volcanic eruptions
these produce weak earthquakes
Over tens to hundreds of years, stress builds up from plate movement. Eventually, stress along the fault overcomes the frictional resistance, and slip initiates as the rocks break
deformed rocks snap back to original position in a process called elastic rebound
small earthquakes that follow a major earthquake
minor earthquakes that sometimes precede a major earthquake by days, weeks, or months
convergent plate boundaries generate what kind of stress on adjacent crust?
normal, reverse/thrust, strike-slip
name the 3 types of faults
associated with divergent plate boundaries
associated with convergent plate boundaries
in a subduction zone, the boundary between the subducting and overlying plate
these produce most of earth's powerful earthquakes
large faults associated with transform plate boundaries
small strike slip faults
small faults associated with divergent plate boundaries
most studied fault system in the world
slow, gradual displacement
other segments of a fault regularly slip, producing?
other segments of a fault remain stuck and store elastic energy for a few hundred years before they break loose, resulting in?
amount of displacement on the fault surface
Initial slip begins at hypocenter and propagates along the fault surface
Slippage adds strain to adjacent sections triggering more slippage
Slippage mainly travels in one direction
explain fault slippage
most are locked expect for small short movements
are faults always locked up?
study of earthquake waves
record the movement of earh in relation to a stationary mass on a rotating drum or magnetic tape
do you need more than one type of seismograph to record horizontal and vertical ground movement
records obtained from seismographs
surface waves, primary (p) waves, secondary (s) waves
list the types of seismic waves
travel in the rock layers just below earth's surface
travel through earth's interior
primary (p) waves
compression waves, travel through all materials
secondary (s) waves
shear waves, can only travel through solid material
which hits first --- s or p waves
what stops s waves?
secondary wave shadoq
lack of s waves
time it takes for s wave to hit seismograph after p wave hits
One causes the ground to move up and down, similar to the movement of ocean cells
The second causes the ground to move side to side, this causes the greatest destruction
surface waves have two general directions of motion. explain each.
the first to arrive at a recording station
the second to arrive at recording station
have the lowest velocity, are the last to arrive at a recording station, and have the highest amplitude. they also cause the greatest property damage
t/f: when lag time goes up, the distance goes up
intensity and magnitude
what two measurements are used to describe the size of an earthquake?
a measure of the degree of earthquake shaking at a given locale based on the amount of damage
an estimate of the amount of energy released at the source of the earthquake
if a magnitude 7 earthquake happens in one city, and another mag 7 eq happens elsewhere, will they cause the same amount of damage?
modified mercalli intensity scale
developed using california buildings as its standard. it is based on property destruction in a region. value change base on the distance from the epicenter
destruction may not be a true measure of the earthquake's actual severity
what is the drawback to intensity scales?
t/f: intensity is subjective
concept introduced by charles richter in 1935
calculated by measuring the amplitude of the largest seismic wave recorded on a seismogram (log scale that accounts for decrease in wave amp w/ inc distance)
10x the previous wave size amount
each segment of the richter scale is ...?
saturation: hard to tell apart fault to fault b.c there is little change from one fault to the next
downfall of richter scale?
measures the total energy released during an earthquake
the average amount of slip on the fault, the area of the fault surface that slipped, and the strength of the faulted rock
Can also be calculated by computer modeling data from seismograms
how is moment magnitude calculated?
Magnitude of the earthquake
Proximity to the epicenter
Amount of destruction attributable to an earthquake varies based on:
The earthquake intensity
The duration of the vibrations
The nature of the ground beneath the structures
The nature of building materials and construction practices of the region
The amount of damage to structures depends on
the process where loosely packed, waterlogged sediments behave as a fluid during the intense shaking of an earthquake
Soft sediments amplify seismic waves more than..?
Ground shaking causes loose sediments on a slope to ____, leading to landslides
Can start when gas and electrical lines are destroyed by an earthquake.
Broken water lines make ___ control problematic
series of large ocean waves; Most are generated by displacement from a megathrust fault
most tsunami activity is in...?
the circum-Pacific belt
95 percent of energy released from earthquakes originates along the..?
megathrust faults of convergent plate boundaries
Most earthquakes occur along ...?
Divergent plate boundaries are associated with frequent but weak ..?
-Monitor changes in ground elevation
- Measure strain in the rocks
-Measure changes in groundwater level
-Frequency of foreshocks
short-range predictions focus on monitoring possible precursors of major earthquakes. name them.
-Must have a small range of uncertainty in regards to location and timing
-Must produce few failures and false alarms
short range predictions must?
t/f: no reliable methods exist for making short-range earthquake predictions
useful for building codes; give the probability of earthquakes of a certain magnitude occurring on a time scale of 30 to 100 years
tectonically quiet zones along a fault where strain is currently building up (strain will be released in a future earthquake)
This set is often in folders with...
Geology test 4
Geology Test 4 Part 3
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