chapter 3: Earthquakes

Lisbon Earthquake

• 9 Am

• caused fires, tsunamis

• 1775

• 60,000 died

Seismicity

earthquake activity

sesimic waves

vibrations generated by earthquakes

joint

crack from weakness

fault

creak with shearing

hanging wall

rock wall above the fault plate

footwall

rock below fault plate 

normal fault

Reverse fault 

thrust fault

very mild “incline”

left lateral displacement

slip-strike; looking across, movement to the left

right lateral displacement

slip-strike; looking at, displacement to the right

focus/hypocenter 

location inside of earth where seismic activity occurs 

• shallow about 70km 

• med, 70-300 

• deep 300+

epicenter

point on earth surface above the focus

foreshock

minishocks before

mainshock

the big one

aftershocks

minishocks after

body waves

waves that go through the interior of earth

P-waves 

“in” interior (Slinky), type of body wave

• primary, faster 

S-waves

tyep of body wave, up and down (secodary, slower)

Surface waves 

you are a literate creature 

L-waves

type of surface wave, “snake” (back and forth)

R-waves

type of surface waves, up and down

Attentuation

waves weaken as they get farther away

amplification

waves slow as they get farther away

S-P time

time between S and P waves, used to determine epicenter/focus

Modified Mercalli Scale (MMI)

OG scale, quantities based on perception of shocking (1-7)

Magnitude/Richter scale

measures energy released by earthquake 

• each Magnitude 10x more energy than that below

• today is moment magnitude scale

Seismic belts

areas with frequent earthquakes

Convergent boundary

area where 2 plates touch/collide

Mid-ocean divergent boundry

cause smaller earthquakes, might cause transform faults 

transform boundry

aobve ground, dangerous for population zomes

interplate seismic activity

not on tectonic fault lines

Resonance

period of time a building sways for

resonance disasters

building sway matches up with ground sway=jenga