EPS C20 FINAL REVIEW

Name the two classes of seismic waves.

Body waves and surface waves

Name the four types of seismic waves.

P-waves, S-waves(up and down motion, particles move up and down) , Rayleigh waves, and Love waves

Which type of seismic wave has the same mechanism as an acoustic wave in the air?

P-wave

Name the two major scales by which we measure how big an earthquake is and explain their differences.

Intensity: Determines damage and detailed observation of effects. Magnitude: Determines the energy released by an EQ

Does an earthquake of magnitude 6 have the intensity "6?"

No

How much larger is a magnitude 5 earthquake compared to a magnitude 4 in terms of amplitude?

10 times

What is this factor when you compare a magnitude 4 to a magnitude 7? (think logarithms)

4-7 \= factor 1000 (10^3)

Are the different magnitude scales linear or logarithmic?

logarithmic

On average, how often do earthquakes of magnitude greater than 8 occur per year?

0-1

Approximately, how long was the rupture length of the Sumatra earthquake of 26 December 2004?

1200 km

Seismic Risk is defined as the product of

Seismic Hazard * Vulnerability

Can we change the Seismic Hazard in a given area?

No

Name processes that are a part of the calculation of Seismic Hazard.

Speed of tectonic movement and faults, locked or creeping

Name the factors we take into account when calculating seismic risk.

Injuries and lives lost, magnitude, economic loss, and damage to infrastructure (lifelines)

What is the average speed of a tsunami in the open ocean?

the speed of a jet plane

Did the tsunami generated by the Tohoku EQ in Japan on March 11,2011 reach the San Francisco Bay Area?

Yes

Name two causes other than EQ which can generate a tsunami.

Landslides and volcanoes.

Have seismologist found any measurable parameters which consistently occur prior to EQ?

No!

Can we predict EQ from observing animals behavior?

No!

We can't predict EQ because...

we don't know all the processes

Which country was the first to operate a successful EQ Early Warning System?

Mexico

Name two potential applications for EQ Early Warning in California.

Slowing and stopping automated vehicles such as Bart. Getting people to safer zones and providing them with the resources needed.

Seismic methods are the most important technology for monitoring underground nuclear weapon tests because ...

underground explosions generate seismic waves.

Tsunamis are generated by what kind of EQ?

Megathrust EQ in the ocean

In California, can you build a private residence right on an EQ fault?

No, because it is forbidden by the Aquist-Priolo Act.

Name two of the largest earthquakes ever recorded? Were their magnitudes above or below 9?

Alaska and Chile with magnitudes above 9

What is the minimum number of seismic stations to locate a local or regional earthquake?

3

What do we need to ensure precisely of seismic stations to locate a local or regional EQ?

The time difference between the arrival of the P-wave and the arrival of the S-wave.

They hayward fault is...

a hybrid fault because it is locked and creeping.

As tectonic stress accumulates, how does it get released?

Coseismic slips and creeping

Rank the seismic waves from faster to slowest

P-waves, S-waves, Love waves, Rayleigh Waves

What caused the major damage during the 1906 Great San Francisco EQ?

Fire

In a seismic wave, do the particles move long distances with the wave from source to receiver or do they perform a swinging motion locally.

They perform a swinging motion locally.

What is the average speed with which the Pacific Plate and the North American Plate move relative to one another?

approximately the speed with which a fingernail grows

In modeling a future EQ on the hayward fault did the ground acceleration on some places exceed the gravitational acceleration on the Earth?

No

Name two ways EQs can be generated not only by tectonic forces,but by other natural forces as well.

glacial unloading and movement of magma

Name three major faults in the bay area. What type of faults are they?

Hayward fault, San Andreas, Calaveras, Rogers Creek, all are right lateral strike slip faults

Name the EQ fault closest to campus. How long ago did the last major EQ occur on the fault?

The Hayward fault and 1868

Approximately, how deep is the deepest borehole ever drilled and how does its depth compare to the diameter of the Earth?

12 km and 1/1000 of the Earth's diameter

Name the four major structural elements that make up the interior of the Earth.

Crust, Mantle, Outer core, and inner core

Name the theory that describes why the surface of the earth is not fixed and static, but moves around horizontally?

Plate Tectonics

Name the tree angles which describe an earthquake fault.

Rake, Dip, Strike

Strike

horizontal

Dip

up or down

Rake

angle along which a fault slips

Name the four type of faults

strike slip, reverse, normal, oblique

Strike slip

when plates move along the fault, either left or right, like the San Andreas fault

Reverse

The hanging wall moves up, normally create mountains

Normal

Hanging wall is sliding down while the foot wall is stable.

Oblique

both strike slip and dip slip

Which US State has seen a more than hundredfold increase in seismicity in recent years?

Oklahoma

What is the cause for the increase of Oklahoma's seismicity ?

water injection/fracking

Which area of the US has the largest earthquakes hazard?

Cascadia

What is the seismically most active region in California?

Mendocino Triple Junction

Earthquake Intensity describes...

the effects of an EQ on people, nature and man made structures

Definition of an EQ: Common answer:

when the ground under me is shaking,

Definition of an EQ: Scientific answer:

when the ground breaks along the fault

What is the probability that there will be a 6 and above EQ in the 30 years in the Hayward Fault?

27%

Subduction zone

One plate gets pushed under the other and went it breaks due to a lot of pressure it may create a tsunami

Two tectonic plates separate (move away from each other) - Forms volcanoes and new crust Ex: Iceland and mid-Atlantic ridge. As two plates move apart the magma rises up, hits water (cools down), then makes new crust.

Divergent fault

Two tectonic plate slide past each other horizontally, - Plates are not smooth, they will jerk as they slide causing EQs. Example: San Andreas Fault (Pacific Plate and the North American plate slide.

Transform fault

When two plates collide (move towards each other )

Convergent fault

When two tectonic plates with continental crust collide, they buckle and thicken - pushing the crust upward making mountain ranges and EQs. For example: Himalayan Mountains

Continental/Continental collision

When a continental and oceanic plate collide, the oceanic plate slides under the continental plate

Continental/Oceanic collision

When two oceanic plates collide, one of the plates is subjected, or sinks, under the other. - creates trenches - creates volcanoes

Oceanic/Oceanic Collision

Magma pushed through ocean floor, cooled, formed solid rock but over time grew big enough to make islands that popped above sea level, Example: Hawaiian Islands

Hot spot

Why doesn't Alaska have the highest risk?

Although Alaska has a large amount of earthquakes occurring it is not very populated to the vulnerability is not so high.

Who has a higher risk than Alaska?

Cascadia has more vulnerability than Alaska therefore, a higher risk. A large EQ will have a larger affect to the population and economy.

Has the risk changed in the Bay area since the 1868 EQ?

Yes, there are now major bridges, Bart and higher population density increasing the vulnerability therefore increasing the risk!

What is Peak Ground Acceleration?

1g \= gravitational acceleration towards center of the earth. Everything \> 1g \= weightlessness

Can we predict earthquakes?

No

If we can't predict an earthquake, what can we do?

Forecast

How does the Early Earthquake Warning System work?

Several stations use the p-waves to make an assessment of where the EQ is and the size. It gives seconds to a minute warning before an EQ. This helps shut down or slow equipment down like the Bart.

Is the Bay area at risk of being destroyed by a tsunami?

No, the Golden Gate would help dissipate the water because there would not be much space for all the water to go through, therefore decreasing the amount of water entering.

What is the San Andreas fault?

The San Andreas Fault is the line between the Pacific Plate (which is oceanic) and the North American Plate (which is a land or continental plate), and it's a transform boundary.

In case of an earthquake what should one do?

Drop, cover, and hold on

Where do EQs occur?

Around the world in a distinct pattern (similar to volcanoes)

What are the Wadati-Benioff Zones?

subduction zones

Who was Immanuel Kant?

After the Libson earthquake and tsunami Kant attempted to explain the natural disaster as a result of massive gaseous changes below the Earth's surfaces.

What did the Lawson Report contain?

-Cataloged descriptions of earthquake effects -Identified the San Andreas Fault -Maps of the fault location and ground shaking distribution -Elastic rebound theory

Why is 1963 significant?

They discovered magnetic strips on the ocean floor.

How long has tectonic stress been accumulating in the Hayward Fault?

148 years

Earthquakes occur along major ocean feature like \_____ and \_____.

Ridges and Trenches

What evidence is there for plate tectonics?

Shapes of continents, Fossils, A ridge in the centers of most oceans Surprisingly small amount of sediment on the sea floor

There are 15 major plates... Can you name them?

North American, Eurasian, Pacific, Antarctic, South American, African Australian

Most earthquakes occur along \_______.

Plate boundaries

What happens when you constantly push or pull on a rock?

Option 1: It gets folded or contorted. Option 2: it breaks, or fractures

Normal and Reserve Faults are ....

Dip-Slip faults

Oblique is a ....

Mixed dip-slip and strike-slip fault

What is a fault?

A boundary line between two plates that accumulates mechanical stress from tectonic movement. Releases stress in the form of an earthquake.

Hypocenter:

actual location of the earthquake at depth

Epicenter:

location on the surface of the Earth above the hypocenter

Risk \=

Hazard * Vulnerability

Seismic Hazard

What nature presents to us

Vulnerability

What we put in nature's way

Shake Maps

Combine info on EQ source with observations to make one of these maps, Emergency response units can use these maps. Generated about 5 min after EQ.

How do we quantify seismic hazard?

PGA

UC Berkeley spent...

$1.2 billion

Intensity Scale

Mercalli scale 1 (least) - 12 (most)

Parkfield: town in Southern California

1922, 1934 ,1966 suggested there would be an EQ towards end of 1988 due to sequence but it happened on 2004 with no precursors