Science Unit 4.1

Shear stress created the San Andreas Fault in Southern California. It is an example of a _____.

Strike-Slip Fault

Normal Fault

fault that occurs when two tectonic plates are moving apart from each other; the hanging wall drops relative to the footwall

Strike-Slip Fault

fault that occurs when two tectonic plates are sliding sideways against each other in opposite directions

Reverse Fault

fault that occurs when two tectonic plates collide; the hanging wall rises relative to the footwall

Magnitude

measure of the total amount of energy released during an earthquake

Mercalli Intensity Scale

measures effects of an earthquake; measurement can vary from place to place

Richter Scale

measures strength of an earthquake; measurement is based on the size of seismic waves

Moment Magnitude Scale

measures strength of larger earthquakes; measurement is based on multiple variables

Foreshocks

mini-quakes that usually occur before a major earthquake

Moment Magnitude Scale

newer magnitude scale that measures the amount of moved (displaced) rock along a fault to determine the strength of an earthquake

When a huge block of rock is pushed up at a normal fault, a ____ mountain is usually formed.

Fault-Block

The area where rock layers first move along a fault is the _____ of an earthquake.

Focus

Which of the following is the point underground where rock layers first move during an earthquake?

Focus

Which of the following represents the most powerful earthquake?

Great Chilean, 9.5

Normal faults that come in pairs usually display the geological feature of _____.

Horsts and Grabens

The cliff-like structure created from a normal fault is called a _____.

Scarp

Primary (P) waves

Shaking alllllllll around

Love (L) waves

Side to side

Richter Scale

scale of magnitude based on the size of seismic waves produced by an earthquake

Mercalli Intensity Scale

scale that measures the effects or severity of an earthquake

compressional stress

-> <-

A seismograph records an earthquake, but scientists do not feel it. The earthquake has a magnitude _____.

< 2.0

Shear stress

<- ->

tensional stress

<- ->

After an earthquake, additional adjustments can occur along the fault. These adjustments can cause damaging vibrations called _____.

Aftershocks

A fold is a ___ in rock and a fault is a ___ in rock

Bend, break

Tectonic plate movement is created by ____ in the underlying mantle.

Convection

Which of the following can occur during an earthquake? Select all that apply.

Crust can fold or wrinkle, part of the crust may sink under the ocean, cliffs and cracks form

You can tell normal and reverse faults apart because at a normal fault the hanging wall has _____ relative to the footwall.

Dropped

When tectonic plates pull apart from one another, tensional stress is placed on rock layers and a _____ fault occurs.

Normal

Liquefaction

Occurs when wet soil acts more like a liquid during an earthquake

The force that drives earthquake activity is _____.

Plate tectonics

Epicenter

Point on Earth's surface directly above an earthquake's focus

Compressional stress on rock can cause strong and deep earthquakes, usually at _____.

Reverse Faults

Focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake

Elastic Rebound

The sudden return of elastically deformed rock to its undeformed shape

Convection

The transfer of heat by the movement of a fluid

Syncline

U-shaped, downward fold in rock

Secondary (S) Waves

Up and down

Seismic Gaps

areas on active faults where a major earthquake hasn't occurred in a long time

Triangulation is a process to locate an earthquake. Which statements are true regarding this process?

You must know the difference in the times that S waves and P waves arrive at a seismograph station to determine the distance to the epicenter. Three seismograph distances must be mapped with circles and the point where they intersect is the epicenter.

Graben

a lower block of rock between two normal faults

Monocline

a ramp-like fold between flat rock layers at different elevations

Where does most seismic activity occur?

along tectonic plate boundaries

Horst

an uplifted block of rock between two normal faults

Anticline

arch-shaped, upward fold in rock

Hanging Wall

block of rock above the slant of a fault

Footwall

block of rock below the slant of a fault

Which of the following are signs that an earthquake may occur?

changes in water levels in wells, foreshocks, and changes in the magnetic properties of rocks

Scarp

cliff-like landform created by a normal fault

Earthquakes are the cause of other natural disasters, such as _____.

landslides, tsunamis, and liquefaction

Body Waves

seismic waves that travel through the Earth's interior

Aftershocks

smaller quakes produced after a major quake caused by rocks shifting to new positions