Transform Boundaries and Earthquakes
Transform Boundaries
•
Where plates ______________ ______________ each other
Earth’s Changing Surfaces
• Most earthquakes occur when rocks fracture, or break, deep within Earth.
• ______________ is the forces that ______________ and ______________ on the Earth’s surface.
• As rock of the crust undergo stress, they change ______________ and ______________. Also, they move up
and down.
• ______________ is the breaking, tilting and folding of ______________.
•
Stresses
• There are three kinds of stress that act on Earth’s rocks:
• ______________ is the stress that ______________ rocks together
• ______________ is the stress that ______________ materials apart
• ______________ is the stress that ______________ rocks in ______________ different directions
Faults
• A ______________ is a crack in a rock. (usually caused by one of the three stresses)
• A ______________ is the fracture or system of fractures along which ______________ occurs.
Folds
• A ______________ is a bend in a rock. There are two types.
• An anticline is an upward fold. A syncline is a downward fold
Foreshocks and Aftershocks
• A ______________ is a small earthquake that occurs ______________ or ______________ before the main
earthquake.
• An ______________ is an earthquake that occurs ______________ the main earthquake, usually a small
one.
•
•
Seismic Risk
…what’s the connection?
As with volcanoes, earthquakes are not randomly distributed over the globe
• At the ______________ between plates, ______________ causes them to stick together. When built up
energy causes them to break, ______________ occur.
Where do earthquakes form?
• Forces Within Earth
• An ______________ is a shaking and trembling of the earth’s surface that results from the sudden
movement of part of the earth’s crust at a fault.
• The shaking can last from 30 seconds up to a ______________.
Earthquake Waves
• Most earthquakes are caused by movements along faults
• A ______________ is a crack or break in the crust where movement occurs.
• Irregular surfaces in rocks can ______________ and ______________, causing stress to build in the
rocks.
• When the rocks reach their ______________ ______________ they break, and this produces an
______________.
• Most faults are between the ______________ and ______________.
San Andreas Fault
• Its ______________ long and ______________ deep.
Focus/Epicenter
• The ______________ of an earthquake is the point of failure of rocks at the depth where an earthquake
originates.
• The ______________ of an earthquake is the point on Earth’s surface directly above the focus.
• More than 1,000,000 earthquakes occur ______________ ______________.
• That’s an average of about one every ______________ seconds.
• Most (about 90%) are low in magnitude and aren’t even felt.
Earthquake Waves
Types of Seismic Waves
• Earthquake Waves
• The vibrations of the ground during an earthquake are called ______________ ______________.
• Every earthquake generates ______________ ______________ of seismic waves.
• ______________ ______________, or P-waves, squeeze and pull rocks in the same direction along
which the waves are traveling.
• S waves are Secondary waves
• They travel through ______________ only!
• They arrive ______________!
• ______________ ______________ travel along Earth’s ______________, moving in ______________
directions as they pass through rock.
Seismic Wave and Earth’s Interior
• ______________ is the study of earthquake waves.
• The ______________ ______________ that shake the ground during a quake also penetrate Earth’s
______________.
• This has provided information that has enabled Earth scientists to construct models of Earth’s
______________ ______________.
Seismometers and Seismograms
• ______________, or seismographs, are sensitive instruments that detect and record the ______________
sent out by earthquakes.
• A ______________ is the ______________ produced by a seismometer.
Earthquake Magnitude and Intensity
• ______________ is the measurement of the amount of energy released during an earthquake.
• The ______________ scale is a numerical scale based on the size of the ______________ seismic waves
generated by a quake that is used to describe its ______________.
• Each successive number in the scale represents an increase in seismic-wave size, or amplitude, of
a ______________ ______________ ______________.
• Each increase in magnitude corresponds to about a 32-fold ______________. in seismic energy.
• The ______________ ______________ scale, widely used by seismologists to measure earthquake
magnitude, takes into account the size of the ______________ ______________, the amount of ______________
along the fault, and the rocks’ ______________.
• Moment magnitude values are estimated from the size of several types of seismic waves produced
by an earthquake.
Modified Mercalli Scale
• The ______________ ______________ scale, which measures the amount of ______________ done to the
structures involved, is used to determine the intensity of an earthquake.
• This scale uses the Roman numerals I to XII to designate the degree of intensity.
• Specific effects or damage correspond to specific numerals; the ______________ the numeral, the
______________ the damage.
• Earthquake Magnitude and Intensity
• Earthquake Magnitude and Intensity
Depth of Focus
• Earthquake intensity is related to ______________ ______________.
• The depth of the quake’s focus is another factor that determines the ______________ of an earthquake.
• An earthquake can be classified as ______________, ______________, or ______________, depending on the
location of the quake’s focus.
• A deep-focus earthquake produces ______________ vibrations at the epicenter than a shallow-focus
quake.
Locating an Earthquake
• All epicenter locations, as well as times of occurrence, however, can be easily determined using
______________ and ______________ -______________ curves.
Seismic Belts
• The majority of the world’s earthquakes occur in relatively narrow seismic belts that are
associated with tectonic plate boundaries.
– Almost 80 percent of all earthquakes occur in the Circum-Pacific Belt.
– About 15 percent take place across southern
Europe and Asia.
– Most of the remaining earthquakes occur in narrow bands that run along the crests of ocean
ridges.
– A very small percentage of earthquakes happen far from tectonic plate boundaries and are
distributed more or less at random.