Geography Hazards Lecture 7 Earthquakes

What are the 2 scales for earthquakes?

Richter Scale (100km from epicentre) (old), Magnitude Scale (M) : logorithmic (base 10) scale (new)

What is the difference between an MA8 and MA5 earthquake?

1000 (10×10×10)

What is the strongest earthquake recorded ever?

M9.5 Chile, and M8.1 in Canada BC

Modified Mercalli Intensity Scale

A qualitiative scale (descriptive and categorical, damage to property)

Strike-slip faults (horizontal), Dip-slip faults (vertical)

What are the 2 types of faults?

Tectonic Creep

Fault creep, extremely slow movement of rock along fracture caused by stress. AKA Fault Creep. Damages roads, building foundations…

P Waves

Primary / Compressional waves, relatively fast, push-pull motion. Travels through solids and liquids

S Waves

Secondary / Shear waves, relatively slow, up/down motion, only travels through solids

The difference between P waves and S waves

Determines distance to epicenter

Triangulation

The epicenter is where the 3 seismic station circle intersect

In _____ NA you feel more shaking than in ______ NA

eastern, western. Due to underlying homogenons and bedrock more in the west.

Allucial

Sediment deposited by water

San Francisco

Which city has enhanced damage due to Amplification?

What is the aftershocks formula?

Aftershocks on first day after / given day.

29

If 200 aftershock 1st day, 7 days later how many aftershock?

Anchorage, Vancouver, Victoria, Seattle, Portland, San Francisco, Los Angeles, Mexico City

What are some NA cities at risk of earthquakes?

Strike-slip earthquake

Plates slide horizontally. Common in California on San Andreas Fault.

Thrust earthquakes. AKA Subduction earthquakes

Separate converging plates. Strongest.

Normal fault earthquakes

Divergent plates. Under Oceans.

Primary VS Secondary effects of earthquakes

Primary : Ground shaking, surface rupture. Secondary : liequfaction, land-level change, landslides, fire, tsunamis.

What are some natural services of functions of Earthquakes?

Faults provide pathways for the downward flow of surface water. Can channel groundwater to surface discharge points (springs.). New mineral resources can be exposed. Scenic landscapes (hills, valleys)

What human activities contribute to earthquakes?

Weight from water reservoirs can create new faults. Injecting liquid waste increases pressure and cause slippage along fractures. Testing nuclear weapons cause explosions that increase strain.

Can earthquakes or volcanoes be predicted?

NO!! They can only be *forecasted*

An oil pipeline was bult to withstand an earthquake in…

Devali, which withstood 2002 Alaska earthquake.

How much in advance can we warn an earthquake?

15-30 seconds, after it has already happened