Geology: Unit 3, Day 6-10

In terms of strain, explain why an earthquake is more likely at a seismic gap than at another location.

A seismic gap lies along an active fault line. Therefore strain is accumulating at a steady rate and at some point, strain will become too great and an earthquake will occur.

Liquefaction of soils

Causes structures to sink into the ground.

Isostacy

Condition of equilibrium that describes the displacement of Earth's mantle by Earth's continental and oceanic crust.

False/landslides

Deaths associated with earthquake deaths in sloping areas can result from -tsunamis-.

Tsunami

Large, powerful, ocean wave generated by the vertical motions of the seafloor during an earthquake.

How does earthquake magnitude differ from intensity and which is more important in a community?

Magnitude is a measure of the energy released by the earthquake, while intensity is a measurement that reflects the damage done to structures, which may cause loss of life.

Magnitude

Measure of the energy released by a quake.

Magnitude

Measure of the energy released during an earthquake, which can be described using the Richter scale.

Modified Mercalli Scale

Measures earthquake intensity on a scale from 1 to 10.

Describe the global pattern of earthquakee distribution and what causes it.

Most of the world's earthquakes are located in relatively narrow seismic belts associated with tectonic plate boundaries. Forces that cause plate motions exert stress on the rocks making up the plates. To relieve this stress, the rocks bend and sometimes snap, causing earthquakes.

False/higher;warmer

Most rocks that exist in Earth's crust are brittle but become ductile at great depths where temperatures are -cooler-.

Richter Scale

Numerical scale used to measure the magnitude of an earthquake, using valves based on the size of the earthquake's largest seismic waves.

Seismic Gap

Place along an active fault that has not experienced an earthquake in a long time.

Modified mercalli scale

Rates earthquake intensity.

Vertical motions of the seafloor during an earthquake.

Results in a tsunami.

Explain how scientists have inferred the physical states of Earth's inner and outer cores using seismic data.

S-waves are not transmitted through liquid, and the observation that S-waves disappear as they strike the outer core led scientists to infer that the outer core is liquid. Studies of the refraction and reflection of P-waves by the inner core have indicated that the inner core is solid.

Moment Magnitude Scale

Scale used to measure earthquake magnitude using values that can be estimated from the size of several types of seismic waves.

Seismic gap

Section of an active fault that has not experienced a significant earthquake for a long time.

True

Seismic belts are relatively narrow and tend to follow -tectonic plate boundaries-.

Isostatic Rebound

Slow process of Earth's crust rising as the result of the removal of mass from the crust.

Compare and contrast the Richter scale and moment-magnitude scale.

The Richter scale rates magnitude based on the size of the largest seismic waves generated, while the moment-magnitude scale takes into account the size of the fault rupture, the amount of movement along a fault, and the stiffness of the rock.

False/intensity

The amount of damage done to structures as a result of an earthquake is the earthquake's -magnitude-.

Strain Accumulation

The amount of strain released during the last quake are used in earthquake probability settings.

True

The fact that a significant earthquake has not occured within a seismic gap indicates that an earthquake is -more likely- to occur in the near future.

What are two main factors that determine the probability that an earthquake will occur?

The probability of an earthquake is a function of the history of earthquakes in the area and the rate at which strain builds up in the rocks. Knowledge of these two factors aids in the study of earthquake predictions, which someday may be commonplace, thus reducing the numbers of injuries and deaths.

Collapse of higher, intact floors onto ground floors.

Type of structural failure called "pancaking"

Natural sway of intermediate buildings equals the period of vibration of the earthquake.

Type of structural failure related to building height.

Tsunami

Wave generated by vertical motions on the seafloor.