Lecture 8 - Earthquakes/Tectonics Flashcards by sabindero .

What is the driving force of plate movement

Gravity

How well did you know this?

Not at all

Perfectly

What is slab pull?

pulling of crust into mantle by down-going slab during subduction

How well did you know this?

Not at all

Perfectly

what is slab-push

Pushing of crust resulting from elevated position of oceanic ridge system, causing crust to gravitationally slide down flanks of ridge

How well did you know this?

Not at all

Perfectly

Divergent margins can occur where and lead to what?

can occur within ocean or within continent but always leads to creation of ocean basin

How well did you know this?

Not at all

Perfectly

Divergent margins are marked by

faults, volcanoes, and uplift

How well did you know this?

Not at all

Perfectly

What are faults?

Faults are fractures in bedrock along which movement has occurred.

How well did you know this?

Not at all

Perfectly

What are joints?

fractures or crack in bedrock along which essentially no movement has occurred

How well did you know this?

Not at all

Perfectly

What type of fault is formed exclusively in divergent plate margins?

Normal fault

How well did you know this?

Not at all

Perfectly

Normal faults result in thinning of the crust =

extension

How well did you know this?

Not at all

Perfectly

True or false: There is igneous activity at transform margins

False

How well did you know this?

Not at all

Perfectly

What happens at transform margins?

Plates slide horizontally past one another

How well did you know this?

Not at all

Perfectly

What type of fault happens at transform margins?

Transform fault

How well did you know this?

Not at all

Perfectly

Convergent margins are where plates move toward each other. What type of faults happen there?

Reverse faults

How well did you know this?

Not at all

Perfectly

What happens at ocean-ocean convergence

Marked by depe ocean trench and volcanic island arc (subduction zone)

How well did you know this?

Not at all

Perfectly

What happens at ocean-continent convergence

Marked by ocean trench, volcanic arc and mountain belt (subduction zone)

How well did you know this?

Not at all

Perfectly

What happens at continent-continent convergence?

Marked by mountain belts and thrust faults

How well did you know this?

Not at all

Perfectly

Not al rocks break (fault). THey can also undergo

ductile deformation (flow) and folding

How well did you know this?

Not at all

Perfectly

If fold happens in two directions at the same time it can gives us:

Domes: unwarped displacement of rocks
Basin: downwarped displacement of rock

How well did you know this?

Not at all

Perfectly

How are earthquakes produced?

By the movement of rock bodies past other. THe stress has to exceed the strength of the rocks in brittle manner (cohesion is lost)

How well did you know this?

Not at all

Perfectly

The loci of the earthquake movements are

faults

How well did you know this?

Not at all

Perfectly

what is fault creep

slow migration of crust along fault plane; weak vibrations

How well did you know this?

Not at all

Perfectly

Rocks bend and store elastic energy which builds-up strain. How is frictictional resistance holding the rocks together overcome?

Earthquakes

What is an earthquake

Vibration of earth produced by rapid release of energy stored in rock subjected to stress

What is the focus or hypocenter?

Energy released radiates in all directions from its source

What is the epicenter

Location on the surface directly above the focus

What is magnitude

Energy measured in in the form of waves

What is intesity

Energy felt/observed

What is seismology

Study of earthquake waves

What are seismograms

Records of seismic waves from seismographs

What do seismograms rely on

inertia of suspended weight to record motion

What's a P wave

Compressional, 6-8km/s parallel to direction of movement (slinky)

What an S-wiave

shear. 4-5 lm/s. Perpendicular to direction of movement (rope)

What do s waves not pass through

Liquids

What do surface waves result in

horizontal and vertical orbital motions with long period and great amplitude; travel along outer parts of Earth

What are the 2 types of surface waves

Love waves: side to side | Rayleigh (R) waves: like an ocean wave.

What are the most destructive waves

R waves

How is the epicenter located

Using the difference in velocites of P & S waves . The point where all 3 circles of the different stations interesect is the earthquake epicenter

Major earthquake zones include

Circum-pacific belt, alpine-himilayan chain, and oceanic ridge system..... aka plate boundaries

90% of quakes happen at what depths

<100 km depth

What scale was developed using Califormnia buildings as its standard

Modified Mercalli Intensity Scale

what is the 1st magnitude number that comes out

Richter scale

What is the richter scale

Based on the amplitude of the largest seismic wave recorded 100km from epicenter

What is the moment-magnitude scales

Gauges quake total energy

What 3 factors influence the amount of damage attributable to earthquakes

intensity/duration of vibration natural of material upon which the structure rests design of the structure

What is liquefaction

unconsolidated materials saturated with water converts into mobile fluid

What is seiches

The rhythmic sloshing of water in lakes, reservoirs, and enclosed basins

what 3 rock behaviour forces are used to try and predict the way earthquakes will happen/behave

1) If deformed materials return to original shape after stress removal, they are behaving elastically (however once the stress exceeds the elastic limit of a rock, it deforms permanently 2) Ductile deformation involves bending plastically 3) Brittle deformation involves fracturing/rupture

In terms of rock behaviour, what is stress?

Results in irreversible changes in shape or size of rock (applied force)

In terms of rock behaviour, what is strain

Change in size or shape in response to stress (deformation)

How can we predict earthquakes in terms of physical changes in crust?

Rocks under stress begin to dilate (expand in volume)

What are some short term earthquake preidctions

``` Swarms of foreshocks tilt/bulge in crust/land surface changes in seismic wave velocity strain monitors plaeoseismology ```

What are some long term earthquake predictions

``` Seismic gaps (locked segments of a fault which have been "quiet") Strain monitors and ground deformation ```

How is Ottawa/Gatineau area similar to the area of Kathmandu, Nepal

We live on a deposition of very fine grain unconsolidated material = weak