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