Earthquake Intro & Injection Wells

Question 1

What is an earthquake?

Answer 1

a sudden release of energy that has slowly accumulated in crustal rock

Question 2

An earthquake is a sudden release of _____ that has slowly accumulated in crustal rock

Answer 2

energy

Question 3

Where does the energy powering an earthquake accumulate?

Answer 3

in crustal rock

Question 4

Where do most earthquakes occur?

Answer 4

at tectonic plate boundaries

Question 5

The largest and most powerful earthquakes occur at ______ zones

Answer 5

subduction

Question 6

What happens along plate boundaries?

Answer 6

along plate boundaries there are two plates that are slowly sliding past one another

Question 7

The rocks in plate boundaries lock together and stick due to ______ between the rocks

Answer 7

friction

Question 8

although the plates are locked together, as they continue to move what happens?

Answer 8

the rocks along the boundary start to deform like a plastic like of being deformation.

Question 9

AS the plates continue to move the stored ______ overcomes the force of _______ and the plates slip past one another releasing energy in the form of an earthquake

Answer 9

energy, friction

Question 10

What is the process of an earthquake?

Answer 10

1. The rocks in plate boundaries lock and stick due to friction 2. the rocks start to deform because of there constant contact, friction, and tension/pressure/stress 3. the stored energy overcomes the force of friction and the plates slip past one another releasing energy

Question 11

Major earthquakes occur when there has been a lot of ______ built up along a boundary that has been released

Answer 11

pressure

Question 12

why do some plate boundaries produce frequent, small earthquakes?

Answer 12

they move incrementally throughout time and release small amounts of energy in frequent, small displacements

Question 13

What can elastic rebound theory help us understand?

Answer 13

energy release in an earthquake

Question 14

elastic rebound theory posits that continuing ____ along the fault results in a build up of ______ which is released in an earthquake

Answer 14

stress, energy

Question 15

When rocks are ________ they can become somewhat elastic

Answer 15

pressurized

Question 16

what does elastic mean in the context of rocks and earthquakes?

Answer 16

rocks can bend and snap back to their original state

Question 17

What does elastic deformation do?

Answer 17

it stores energy in the form of potential energy

Question 18

What happens when the energy build up in rocks caused from pressurization is released?

Answer 18

it causes vibrations in rock that travel through the Earth in seismic waves

Question 19

What are injection wells?

Answer 19

the type of wells that are used to hydraulically fracture the Marcella shale can be used to inject waste under the ground can be used to inject carbon dioxide under the ground

Question 20

What happens when hydraulic fracturing occurs?

Answer 20

It cracks the rocks under the Earth, and creates artificial permeability

Question 21

Most earthquakes resulting from injection wells are too ____ to be noticed

Answer 21

weak

Question 22

how can injection cause an earthquake or ground shaking?

Answer 22

1. weakens faults in already unstable areas 2. expansion or contraction of rocks, which will cause the ground to shake 3. cause saturation or very wet conditions in rocks that then leads to subsidence or shrinking of rock units 4. they can cause minerals to precipitate along faults which would cause the faults to expand a bit

Question 23

anything that causes _______ or _______ underground is going to cause ground shaking

Answer 23

expansion, contraction