lecture 7

Question 1

subduction zone earthquakes

Answer 1

crustal earthquakes within forearc
megathrust events along shallow plate interface
outer rise normal faults from plate flexure
intermediate depth intraslab events
deep earthquakes within subducting slab
seismicity associate with arc volcanism

Question 2

megathrust earthquake cycle

Answer 2

earthquake cycle on subduction zone megathrust faults involves vertical and horizontal motions

Question 3

interseismic period of megathrust

Answer 3

lower plate slowly subducts and is locked

at the trench upper plate is dragged downwards but at the coast it contracts and bulges upwards

Question 4

coseismic phase of megathrust

Answer 4

motions are reversed, megathrust slips upper plate rebounds and sea-floor trench suddenly uplifted and the coastline subsides

Question 5

japan trench

Answer 5

earthquake ruptured the japan trench megathrust where pacific plate subducts westward beneath the Japan arc
- range of frictional behaviors that control earthquake depths

Question 6

conditionally stable

Answer 6

originally thought megathrust was aseismic but it was conditionally stable
- allowed rupture all the way to the trench

Question 7

continental plate boundary zone

Answer 7

involve upper crustal earthquakes only

• seismogenic zone is like 15km thick
• continental collision zones, shear zones, rifts

Question 8

arabia eurasia collision

Answer 8

africa arabia and india continental plates are each moving north
results in broad zone of mountain building called alpine himalayan belt

Question 9

arabia eurasia collision

Answer 9

earthquakes occur along the edges of mountain ranges

- mountains are being raised along thrust faults in response to the collision

Question 10

bam earthquake

Answer 10

Mw 6.6 - desert city with the largest mud brick building in the world
one of the first mapped using InSAR

Question 11

InSAR

Answer 11

used to map earthquakes - large antenna stimulated by combining multiple images along track (Synthetic Aperture Radar)
measures amplitude + phase of back scattered energy

Question 12

bam0baravat ridge

Answer 12

earthquake rupture runs along
- ridge-bounding fault is impermeable so water table dams against it
tunnels called “qanats” tap into this water source

Question 13

arid regions

Answer 13

active faults act as a water source in arid tectonic landscapes
- many cities situated next to active faults
ex. Tehran
abundance of highly destructive earthquakes within the alpine himalayan belt

Question 14

intraplate earthquakes

Answer 14

occur far from plate boundaries (unusual)
plates arent rigid and can slowly deform internally
- pose a hazard to central and eastern canada

Question 15

postglacial earthquakes

Answer 15

postglacial rebound following melting of ice sheets causes crust to flex and triggers postglacial earthquakes

Question 16

induced earthquakes

Answer 16

manmade stresses associated with injection of fluids into the subsurface and changes in pore fluid pressure
ex. colorado, texas