Chapter 12: Earthquakes and Earth's Interior

Match the earthquake with the description and damage caused by that event. Charleston, 1886

Tectonic cause is still not certain. Largest earthquake in the southeastern US. 60 people were killed.

The 2010 and 2011 earthquakes in New Zealand caused a lot of damage because they _____

were shallow and located near city centers

Match the type of body wave to the appropriate descriptions. P-wave

Compresses the rock in the same direction it propogates. Travels through solids and liquids. Travels at 6 to 14 km/s.

The 2004 Earthquake in ______ occurred due to a subduction of the Indian-Australian plate under the Eurasian plate, creating a ______ that killed over 220,000 people.

Indonesia, tsunami

Match the technique for studying earthquakes with its possible use. Study fault ruptures and topographic features.

Lower geophysical instruments deep into a fault to possibly record data on a large earthquake as it happens.

Steps taken to measure the local magnitude of a shallow earthquake.

Seismic data are gathered from several seismometers. Maximum amplitude of the S-wave is measured on each seismogram. Relationships between distance and S-wave amplitude are plotted on a nomograph. MI is the point where each line crosses the center column (magnitude) of the nomograph.

Match the situation with the movement of a seismic wave through that material. Wave continues on in a straight path.

Seismic ray passes through a material that does not change from place to place.

Why does the US have such varying risks of seismic activity?

Some areas are near plate boundaries, while others are not. Volcanic activity can cause seismic risk in some areas. Some regions in the continental interior have active fault systems.

What happened in and along the sea during the Great Alaskan Earthquake of 1964? (Choose all that apply.)

Some land that was below the sea was uplifed above sea level. Massive landslides were created. Faulitng and uplift of the seafloor occurred, creating a large tsunami in the Pacific Ocean. Some areas subsided and were flooded by seawater.

Match the technique for studying earthquakes with its possible use. Dig shallow trenches across faults.

Subsurface layers perceive the history of motion and some may be dated to give clues to magnitudes and recurrence of past earthquakes.

The image, indicating the path of a seismic wave through a segment of Earth, shows _________. Originates at surface, heading down and curving back up to surface.

Waves are eventually bent back towards the surface. Refraction causes seismic waves to take curves paths through Earth. Seismic waves are refracted to shallower and shallower angles at depth.

Hydraulic fracturing, filling reservoirs behind dams, and injecting wastewater underground are all ways in which humans create __________.

earthquakes

When rocks return to their original shapes after being strained, it is called _____ behavior

elastic

Landslides create earthquakes by causing the _____ to shake.

ground

An earthquake is generated at a location we call the ________ and releases energy in the form of ________ waves.

hypocenter seismic

The 9.0 magnitude earthquake that occurred northeast of Japan in March 2011 was the result of movement between two plates at a ____________.

subduction zone

Explosive eruptions, landslides, magma movement, and faulting are the causes of earthquakes associated with _______.

volcanoes

One method of studying faults uses __________ that map an area before and after an earthquake to measure how the surface was deformed.

satellites

The following are true for seismic waves:

Body waves travel within and through Earth. Surface waves only travel on the sfurface of Earth. Body waves include P-waves and S-waves

How are we able to limit risks from earthquakes?

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

Which may indicate the presence of fault scarp?

Freshly exposed, generally linear feature with little/ no vegetation. A "step" in the landscape. Break in slope along a hillside.

Match the type of surface waves to the appropriate descriptions

Rayleigh Waves: +Displace the surface vertically +Cause the most damage during an earthquake +Create a large rippling effect Love Waves: +Cause buildings to slide sideways off their foundations +Displace the surface horizontally

What features in the image help you identify the location of the fault? (Select all that apply.)

Scarp Stream channel running parallel with fault Linear ridges and valley

Seismic tomography has aided with which of the following regarding the interior of the Earth?

The existence of the D'' layer along the core-mantle boundary Modeling areas of hot plumes and cool subducted slabs Creation of flow models of the mantle

Match the fault type with its appropriate description. Reverse faults

The hanging wall moves up w.r.t. the footwall. Most common along convergent plate boundaries.

Long-range earthquake forecasting _____

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

Representing the huge thrust fault created by subduction, _______________ earthquakes are deadly and damaging, and commonly create tsunamis.

megathrust

Most Earthquakes occur along __________.

plate boundaries

Which of the following are true of earthquakes related to subduction zones?

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

Match the seismic wave type with appropriate descriptions of how that wave travels through the body of Earth. P-waves

Create two shadow zones where no direct waves of this kind are received. May travel through all layers of Earth. Drop in velocity as they enter the core.

In which ways may earthquakes be generated within a continental plate?

Continental rifting and normal faulting Intrusions of magma Movement of preexisting faults subjected to new stresses Transform faults

Match the seismic wave type with appropriate descriptions of how that wave travels through the body of Earth. S-waves

Create one large shadow zone where no direct waves of this kind are received. Cannot pass through the core of Earth.

A seismometer _________.

Detects and records ground motion during earthquakes. Is often placed with two others, oriented at 90-degrees to detect three components of motion. May create a graphic plot called a seismogram.

Match the tsunami event with its description. Papua New Guinea, 1998

Earthquake and underwater landslides in the southwestern Pacific generated three tsunamis, which destroyed villages, killing 2,200 people; wave at one location was 10 meters high.

Match the earthquake term with its correct description.

Epicenter Point on Earth's surface directly above where an earthquake is generated. Hypocenter Location where an earthquake is generated. Seismic wave Mode of earthquake energy transmission through Earth Seismic station Location of scientific instruments that measure earthquakes

Match the fault type with its appropriate description. Thrust faults

Gently dipping faults in which the hanging wall moves up w.r.t. the footwall. Most common along convergent plate boundaries.

Which factors influence the velocity of P-waves as they travel through Earth?

How rigid the material is. The density of the material. How easily the rocks are compressed.

If three seismic stations have the following P-S intervals: DUG = 57 sec, WUAZ = 73 sec, ISCO = 14 sec, place the stations in order from closest station (at the top) to the earthquake to the one farthest away.

ISCO DUG WUAZ

What evidence exists to indicate that the eastern US has earthquake risks

Major earthquakes have occurred in this area in the last 200 years Earthquake-hazard maps indicate two major zones of possible future activity Modern-day tectonic stresses, such as ridge push, may reactivate ancient faults in continental interiors

Match the location on the image with the best description for causes of earthquakes in that location. C

Plate cools, subsides, and bends as it moves away from the ridge. Stress from the bending forms steep faults. Magma is moving Thrust faults or reactived older faults may form within the interior of either continent. Magma intrusions may cause small earthquakes as molten material moves through rock.

Match the type of seismic waves with their descriptions.

Primary Waves: Type of body wave; compressional waves; fastest waves Secondary Waves: Type of body wave; movement is perpendicular to direciton of travel Horizontal Waves: Type of surface wave; material moves from side to side Vertical Waves: Type of surface wave; similar to ocean waves as material in a elliptical path

Which are true of reflection vs refraction?

Reflection sends a portion of the wave energy back away from the encountered boundary. Refraction bends a portion of the wave energy as the wave either slows or speeds up as it crosses the encountered boundary. Either may happen to a seismic wave as it encounters a boundary between materials of different physical properties.

Match the location on the image with the best description for causes of earthquakes in that location. D (lava pocket)

Spreading and slip between adjacent blocks occurs along normal faults. Earthquakes occur as magma intrudes into fissures. Shearing and downward-pulling forces produce deep earthquakes Oceanic plate material is detached, and deep earthquakes cease. Preexisting faults readjust and move as the plate is subjected to new stresses; may produce large earthquakes

Match the location on the image with the best description for causes of earthquakes in that location. B (horizontal fault)

Strike-slip earthquakes occur along faults that link adjacent segments of the spreading center. Shearing occurs within the accretionary prism. Megathrust forms along the the plate boundary and creates large earthquakes between the two plates. Moderate-size normal-fault earthquakes are created at a rift.

A large sea wave produced by uplift, subsidence, or some other disturbance of the seafloor, especially by a shallow submarine earthquake is called a

Tsunami

Which are true of earthquakes related to mid-ocean ridges?

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

Match the technique for studying earthquakes with its possible use. Use satellite data.

This can create an interferogram to show deformation of Earth

Match the seismic wave information with how it helps geologists determine the structure of the Earth. Presence of P-wave shadow zone

This helps determine the depth of the core-mantle boundary and diameter of the core. Some indirect waves of this type reach this area and may also be studied.

Match the tsunami event with its description. Hokkaido, 1993

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

Match the tsunami event with its description. Chile, 1960

Tsunami struck part of the shore of South America 15 minutes after the earthquake; 10-meter-high wave killed at least 2,000 people.

Which are potential sources of destruction that may be caused either directly or secondarily by earthquakes?

Tsunamis Aftershocks Fires Landslides and rockfalls

Match the fault type with its appropriate description. Strike-slip faults

Two sides of the fault move horizontally past one another; fault plane is near vertical. Most common along transform plate boundaries.

Satellites can be sued to study faults by ______

analyzing changes in elevation before and after earthquakes

The majority of people in the magnitude 7.0, 2010 Haitian earthquake died because __________.

buildings collapsed and crushed people

Short-term earthquake prediction __________.

is complex, but techniques are still developing that hold promise.

The Great Alaskan Earthquake of 1964 __________.

is the strongest ever recorded for North America ruptured a fault surface that was over 900km long and 250 km wide had an epicenter between Anchorage and Valdez

Based on the earthquake hazard map, which areas have a high risk for earthquakes?

the Middle East west coast of South America southern Alaska and the west coast of North America.

Match the location on the image with the best description for causes of earthquakes in that location. A (fault above lava pocket)

Deep rocks along this linear feature flow because they are too hot to fracture. Earthquakes are shallow, small, and numerous. The oceanic plate is bent and stressed as it moves toward the trench Thrust faults near the plate boundary and create large, shallow earthquakes. Strike-slip motion mostly causes shallow earthquakes; some may be large.

Match the situation with the movement of a seismic wave through that material. Wave is refracted away at a steeper angle.

Descending seismic ray passes from a fast material to a slower one.

Match the situation with the movement of a seismic wave through that material. Wave is refracted to a shallower angle.

Descending seismic ray passes from a slow material to a faster one.

Geologists look at rocks that were once at great depth, create high temperature and pressure conditions in the laboratory, and develop computer models in order to __________.

investigate deep conditions and processes within Earth

Prehistoric earthquakes may be studied by ___________.

Digging trenches along a fault in order to map the offset of layers of sediment and soil to provide a timeline for interpreting when the fault moved.

Match the technique for studying earthquakes with its possible use. Look for offset of both natural and human-made features.

In the field, provide reference points to measure motion, both how much and in what direction.

Which of these descriptions best explains earthquake activity in the New Madrid, Missouri area?

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

Match the situation with the movement of a seismic wave through that material. Wave is refracted upward toward the surface.

Rising seismic ray passes from a fast material to a slower one.

one of the most destructive hazards following an earthquake are _________, which are cause when both natural gas lines and then water mains (no water to fire hydrants) break due to shaking.

fires

Based on the map, what is true regarding earthquakes in the locations indicated?

A (Indian Ocean) Mostly shallow earthquakes occur along the mid-ocean ridge. Subduction zone causes earthquakes along the Aluetian Islands. B (Africa) This is a diffuse zone of seismic activity associated with continental rifting. Most earthquakes occur due to volcanic activity. C (Himalayas) This is a large zone of seismicity associated with a continental collision. Strike-slip earthquakes are common along the San Andreas fault. D (Japan) Shallow, intermediate, and deep earthquakes occur along a subduction zone. Shallow earthquakes folow the Mid-Atlantic Ridge E (North of everything) Very little seismicity occurs in this area, which is far from a plate boundary. Shallow, intermediate, and deep earthquakes occur along this subduction zone.

Rank the following in order from the start (at the top) of an earthquake rupture to the end of the earthquake event.

A small section of the fault begins to rupture. Rupture migrates outwards, generally following the actual fault surface. Rupture eventually amy tech Earth's Surface, creating a fault scarp. Rupture grows along the fault plane, and fault scarp lengthens. Earthquakes stops as remaining stress no longer overcomes friction along the fault.

Match the seismic wave feature indicated on the image with its appropriate descriptions.

Amplitude Characterized by how much the ground moves. Critical for estimating the strength and damage potential of an earthquake. Wavelength Along with velocity, determines the wave period. A critical component for assessing earthquake damage because a building's natural period may resonate with the period of the seismic wave.

Match the type of earthquake damage with the description.

Direct Damage: Fault scraps or ruptures destroy buildings and roads. Shaking collapses poorly constructed or rigid structures. Liquefaction of the ground causes building collapse. Secondary Effects: Flooding of dry land occurs as seawater inundates subsided areas. Ruptured natural gas lines cause explosions and fires. Flooding occurs due to failure of dams.

Match the terms associated with subsurface geology with their definitions.

Drill cores - Cylinder... Inclusions - Pieces... Geophysicists - Scientists... Geophones - Seismic... Gravity - Instruments...

Which are true of the Modified Mercalli Intensity Scale?

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

What actions can you take before or during an earthquake to reduce your chances of being hurt?

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

List the order of events that would lead to the formation of a tsunami due to an earthquake.

Megathrust is locked, causing the seafloor to bulge under stress. Megathrust ruptures, and bulging plate changes shape. Water above the plate lifts up toward the surface, forming a ridge of higher water. A tsunami radiates away from the disturbance; not noticeable in the open ocean. Tsunami approaches shore; energy concentrates in shallows to create a higher wave.

Match the type of body wave to the appropriate descriptions. S-wave

Movement perpendicular to the direction of travel. Cannot travel through liquids. Travels at about 3.6 km/s.

Rank the seismic waves in order of recording by a seismometer (from first to last).

P-wave S-wave Surface wave

Elastic behavior is when ________.

Rocks return to their original shape after being strained.

Secondary effects of earthquakes

Ruptured natural gas lines cause explosions and fires. Flooding occurs due to failure of dams. Flooding of dry land occurs as seawater inundates subsided areas.

Which fault, located in California, is both the world's best known and extensively studied? This fault is found along a transform plate boundary and will likely produce a significant earthquake in the next 30 years.

San Andres

Match the region/city of the US with its earthquake risk and the cause of that risk level.

San Francisco High risk; location near San Andreas fault. New Madrid High risk; location near reactivated ancient fault zone in the continental interior. Southern Alaska High risk; location near active subduction zone. Hawaii Medium to high risk; seismic activity associated with volcanism. Upper Midwest Low risk; few active faults in the continental interior. From Utah through Yellowstone Medium to high risk; intermountain seismic belt due to many active normal faults.

Match the technique for studying earthquakes with its possible use. Study fault ruptures and topographic features.

Scarps, troughs, ridges or steps may show the precise location of the faults at the surface, expressed as a linear feature.

Rank the steps in order for the process of locating an earthquake's epicenter.

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

Match the seismic wave information with how it helps geologists determine the structure of the Earth. Study of indirect waves

Since these waves have reflected off boundaries or changed wave type as they cross a boundary, geologists may learn more about Earth's interior by studying them.

Match the earthquake with the description and damage caused by that event. Yellowstone Area, 1959

Slip along a normal fault generated the Madison Canyon slide, which formed Earthquake Lake. 28 people were buried in the slide.

Rank the following in the best order, starting with the initial buildup of stress on top, to describe stick-slip behavior along a fault.

Stress builds up along the fault; elastic strain occurs in the rock. Stress increase to a point where it is greater than the strength of the faulted rock. Earthquake occurs as the fault slips; seismic waves radiate outward. The stress on the fault has been temporarily and partially relieved.

Short-term earthquake prediction may utilize which of the following?

Study of foreshocks and stress buildup. Monitoring activity along an earthquake-prone fault. Lasers that can record even slight movement along a fault.

Geologists can investigate the interior of the earth by

Subjecting rocks to high temperature and pressure in laboratory settings. Examining rocks that once resided at great depths. Creating computer and numerical model processes that occur at depth.

Match the fault type with its appropriate description. Normal faults

The hanging wall moves down w.r.t. the footwall. Most common along divergent boundaries.

Which are true of earthquakes related to continental collisions?

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

Match the seismic wave information with how it helps geologists determine the structure of the Earth. Presence of S-wave shadow zone

This helps determine that the outer core is molten, as this type of wave cannot travel through molten material.

Match the seismic wave information with how it helps geologists determine the structure of the Earth. P-wave velocity as a function of depth

This shows that rocks tend to become more dense with depth and that there is a dramatic change in material at the core-mantle boundary.

Match the earthquake with the description and damage caused by that event. Northridge, 1994

Thrust faulting lifted up a large section of land. Structural damage included a section of concrete and steel freeway. 60 people were killed.

Match the tsunami event with its description. Hawaii, 1960

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

Water-saturated sediment can lost its strength due to shaking during an earthquake in a process called _______.

liquefaction

The average time between repeating earthquakes along a certain fault is known as the ______________.

recurrence interval

A section of a fault that has had relatively little earthquake activity is called a ___________.

seismic gap

The two basic types of seismic waves include ________ waves, which are created when seismic wave energy reaches Earth's SURFACE and is transformed into new horizontal and vertical waves, and ________ waves, which are usually generated at faults and travel through Earth (primary and secondary).

surface body

An earthquake is _____

the sudden release of energy stored in rocks

Match the area within the Earth to the hypothesized flow processes occuring there.

A - Large upwelling are occurring from the core-mantle boundary B- Cold slabs of subducted material sink into the mantle C- Material in the inner core is flowing and generating Earth's magnetic field D- Mantle material is involved in convective flow

Direct damage from earthquakes

Fault scarps or ruptures destroy buildings and roads. Liquefaction of the ground causes building collapse. Shaking collapses poorly constructed or rigid structures.

What features may be common along active faults, like the San Andreas?

Offset stream channel Scarp Drainage channels running parallel to fault Linear ridge and/or valley

Ran seismic waves in order of recording by a seismometer (from first to last)

P-wave S-wave Surface Wave

Match the earthquake with the description and damage caused by that event. Alaska, 1964

Thrust faults generated landslides and a tsunami. Most of the 128 deaths were caused by the tsunami.

Most earthquake deaths are cause by _______.

collapse of structures