GLG 112 Lecture Round 2 (Exam 2) – Flashcards

The block of rock above an inclined fault

The block of rock below the fault

STRIKE & DIP

Hanging wall moves down relative to footwall, most common along divergent boundaries

Hanging wall moves up relative to footwall, most common along convergent plate boundaries

Fault motion is parallel to the strike

This is a type of strike-slip; opposite side displaced to the left

This is a type of strike-slip; opposite side displaced to the right

1.) Is calculated from the amount of fault displacement & size of the fault area that slipped 2.)Is useful for both large & small earthquakes 3.)For energy released by earthquakes is almost always greater than the energy of the lightning strikes but is less than that of an average hurricane

Seismograph (works by measuring ground motion in 3 directions)

-A megathrust between 2 plates creates large earthquakes -Earthquakes are widely distributed along the collision zone -They may occur in either continental plate -They may occur in large thrust faults created near the plate boundary

-Use maximum S-wave amplitude on a seismogram -Most commonly mentioned -Use a nomograph to relate distance, magnitude & amplitude

-Most have hypocenters less than 20 km deep -They may be due to strike-slip motion along transform faults -They may occur along steep faults away from the ridge axis as the new crust cools & bends -Many occur along the axis of the ridge due to normal faulting or magma intrusions

1-Seismic data are gathered from several seismometers 2-Maximum amplitude of the S-wave is measured on each seismogram 3-Relationships between distance and S-wave amplitude are plotted on a nomogragh 4-MI is the point where each line crosses the center column (Magnitude) of the nomogragh

1.) P-waves 2-S-waves 3-Surface waves

Type of body wave; compressional waves; fastest waves

Type of body wave; movement is perpendicular to direction of travel

Type of surface wave; material moves from side to side

Type of surface wave; similar to ocean waves as material moves in an elliptical path

-Is often placed with 2 others, oriented at 90 to detect 3 components of motion (contains 3 seismometers) -May create a graphic plot called a seismogram -Detects & records ground motion during earthquakes

Elastic

Plate boundaries

1.) Select records from at least 3 seismic stations 2.) Determine the P-S interval for each station 3.) Estimate station distances from the epicenter using P-S intervals on a time-travel curve 4.) Draw circles around each station, with a radius equal to distance from the epicenter 5.)Locate the intersection of all of the circles to determine the epicenter of the earthquake

Earthquake

TRUE

Earthquakes

The average time between repeating earthquakes

-A value of XII indicates complete destruction of buildings -It describes the effects of shaking in everyday terms -It may be used to describe earthquakes that occurred before seismometers were invented

Ground

Gently dipping faults in which the hanging wall moves up with respect to the footwall, most common along convergent plate boundaries

2 sides of the fault move horizontally past one another, fault plane is near vertical; most common along transform plate boundaries

-Body waves include P-waves & S-waves -Body waves travel within & through earth -Surface waves only travel on the surface of earth

-Seismometer; Seismogram

-Hypocenter; seismic

1.) A small section of the fault begins to rupture 2.) Rupture migrates outward, generally following the actual fault surface 3.) Rupture eventually may reach Earth's surface, creating a fault scarp 4.) Rupture grows along the fault plane & fault scarp lengthens 5.) Earthquake stops as remaining stress no longer overcomes friction along the fault.

-10, 30

-Less than 100 km, up to 700 km

-They may be due to magma movement -A megathrust earthquake may be very damaging -These are typically the only place to produce deep earthquakes -They may occur either in front of or behind the trench

-Movement of magma within the volcano -Landslides on unstable slopes -Explosive eruptions

-Wave amplitude, period

-Surface; body

-Megathrust

1.) ISCO 2.)DUG 3.) WUAZ

1.) Stress builds up along the fault, elastic strain occurs in the rock 2.) Stress increases to a point where it is greater than the strength of the faulted rock 3.) Earthquake occurs as the fault slips, seismic waves radiate outward 4.) The stress on the fault has been temporarily & partially relieved

Collapse of structures

Liquefaction

SAN ANDREAS

FIRES

-Measures patterns of seismic activity along a fault to determine locations & recurrence intervals -Uses tectonic settings & historical records -Is based mainly on the knowledge of when & where earthquakes occurred in the past

-Occurred due to subduction -9.1 -Created a destructive tsunami

-Activity associated with volcanic eruptions -Earthquakes that cause the seafloor to shift -Landslides that displace large amounts of water

-The wave height is around a meter, the wave doesn't become high until reaching the shallow seabed near the coast -Travels at 600-800km/hr that is 370-500mi/hr -Wavelength is more than 700 km

A fault segment that has had fewer earthquakes than other sections

Shallow & located near city centers

-Install warning systems to shut down gas system & pipelines -Engineer buildings with systems to dampen seismic energy -Use earthquake hazard maps to determine areas of least risk

Tsunami struck part of the shore of South America 15 minutes after the earthquake; 10-meter-high wave killed at least 2k people

Tsunami reached the middle of the Pacific 15 hours after a South American earthquake; 11-meter-high wave killed 61 people & damaged buildings

Tsunami in the western Pacific hit 5 minutes after the 7.8 magnitude earthquake; wave killed at least 100 people & swept boats across a concrete barrier on the shoreline

Earthquake & underwater landslides in the southwestern Pacific generated 3 tsunamis, which destroyed villages, killing 2.2k people; wave at one location was 10 meter high.

-Use seismic information to determine an earthquake's potential to cause a tsunami -Help detect potential tsunamis in the Pacific & Indian Oceans -Have buoys & ocean bottom sensors to detect small changes in sea level

1-Mega-thrust is locked, causing the seafloor to bulge under stress 2-Mega-thrust ruptures & bulging plate changes the shape 3-Water above the plate lifts up towards the surface, forming a ridge of higher water 4-A tsunami radiates away from the disturbance; not noticeable in the open ocean 5-Tsunami approaches shore; energy concentrates in shallows to create a higher wave.

-Ridge push from the Mid-Atlantic Ridge is activating ancient faults associated with a rift basin

Subduction zone

-Stand clear of buildings -Stay away from glass & heavy objects that could fall -Seek cover under a heavy piece of furniture -Stand on a door frame or next to an inner wall

-Landslides & rock falls -Fires -Tsunamis -Aftershocks

-Seek cover under a heavy desk or door frame -Keep 72 hours worth of food, water & supplies -Avoid using open flames, since there may be gas leaks -Stand clear of buildings or objects that may fall

-one of the five largest ever recorded -The earthquake occurred due to the subduction of the Pacific plate -It created a very destructive tsunami

High risk; location near the San Andreas fault

High risk; location near a reactivated ancient fault zone in the continental interior

High risk, location near an active subduction zone

Medium to high risk, seismic activity associated with volcanism

Low-risk; few active faults in the continental interior

Medium to high risk; intermountain seismic belt due to many active normal faults

An active mega-thrust exists along the west coast of South America

Collision of the Arabian plate causes thrust & strike-slip faults

Continental collision zone continues to build the Himalaya Mountains

This area straddles active plate boundaries in the southwestern Pacific Ocean

Thrust faults associated with the Aleutian Island subduction zone

470KM of the San Andreas fault ruptured; devastating fires after the earthquake

Tectonic stresses reactivated an ancient fault zone

Subduction zone, seismic waves amplified by geologic setting of lake sediments in a bowl-shaped basin

TSUNAMI