~ Useful Links ~




"We learn geology the morning after an earthquake."

~ Ralph Waldo Emerson

~ Seismology ~

PBS Quakes

About Earthquakes

Earthquakes in History

Earthquakes / More Quakes

Recent Equakes / Latest Equakes

The Science of Earthquakes / Fun Facts

What Causes Earthquakes: An Interactive World Map

Animations of Plate Boundaries / Annenburg Interactive Plate Boundaries

~ The Three Types of Stress ~

Types of stress that cause rock to fold and fracture:

Tension & Compression & Shearing

~ Folding ~

Folding is due to the slow force of compression acting upon rock.

Over millions of years, solid rock can slowly

bend, stretch, break, tilt, fold, and slide.

Anticline (upward arch) and Syncline (downward arch):


Faulting and Folding


What about the other 10%? (Answer: Faults)

~ The Three Types of Plate Boundaries ~

A. Divergent ( moves apart / separates / extensional )

B. Convergent ( moves together / collides / compressional )

C. Transform ( moves in opposite directions, horizontally / sliding )

Below: Map Showing the Three Types of Tectonic Plate Boundaries

Convergent (compressional) & Divergent (extensional) & Transform (sliding)


Below: Map of U.S. Earthquake Hazard Zones

~ Earthquake Faults ~

Fault: A crack in the crust along which movement occurs.

Hanging Wall: The Rock Block ABOVE the Fault

Foot Wall: The Rock Block BELOW the Fault

Normal Fault
Reverse Fault
Strike-Slip Fault

Earthquake Fault Animations

Test your knowledge:

Identify the Hanging Wall and Foot Wall.

What kind of faults are shown above and below?



Transform (Lateral) Fault

( Stress: Shearing )



Normal Fault

( Stress: Tension )



Reverse (Thrust) Fault

( Stress: Compression )

Left: Normal Fault ..............................Right: Reverse Fault

~ Focus and Epicenter ~

Focus and Epicenter

FOCUS: Underground location along a fault where displacement (movement) occurs.

EPICENTER: Point on the surface directly above the focus (greatest shaking occurs here).

TRIANGULATION: Locating the Epicenter

Triangulation Technique

~ Seismic Waves ~

Primary Waves: arrive first / travel the fastest / can go through both solids and liquids / are gentle

Secondary Waves: arrive second / travel through solids (not liquids) / cause much damage

Surface Waves: travel the slowest / make the ground roll like ocean waves / are the most destructive

P-waves compress and expand like an accordian or like slinky coils that are held and then released.
S-waves travel up and down & side to side like a rope that is flicked.

Left: P-waves / Right: S-waves

Click here: Green Dot Demo / P and S Blue Dot Animations

Primary (P) Secondary (S) Surface (L/R)

Below: Surface Waves (Love Waves and Rayleigh Waves)

Below: Surface Wave Damage to an Athletic Track (Japan)

How do scientists rate the severity of an Earthquake?

Charles Richter
Guiseppe Mercalli

Click here: The Richter, Mercalli, and Moment Magnitude Seismic Scales

~ Earthquakes of New England ~

Our New England Earthquakes / Equake Map / History

Mass Earthquake Resource Guide / The Weston Earthquake Observatory

The Clinton-Newbury Fault

The Lake Char-Bloody Bluff Fault

Above: Exposed Fault at the Bloody Bluff, Concord, MA

Above: Earthquake Proof Home on Virginia Road in Concord, MA

Earthquake-Proof Geodesic Dome Homes in California


"You fish on your side; we fish on our side; nobody fishes in the middle"

Lake Chargoggogga...whatever...

Click here: The Lake Char Sing-along Song / Ethel Mermon / Let's Go Canoeing


The 1755 Cape Ann, Massachusetts Earthquake

on the Lake Char-Bloody Bluff Fault

Cape Ann Earthquake of 1755 / More Info / Verses

Richter Magnitude Estimate: 6.5 - 7.0

~ Earthquake Safety ~

Earthquake Safety Regulations / Damage Photos

Disaster Plan / Hazards

Drop, Cover, Hold On Song: Caribbean Style

Earthquake Rumble Song / Earthquake Safety Turtle Song

Remember to:

DROP, COVER and HOLD during an earthquake!

Rather than: PANIC, CRY and DIE!

What to Do After the Quake

Above: Rescue Dog

Post-Earthquake Danger: Bridge/Bridge/Bridge / Freeway / Building Collapse / Photos

Post-Earthquake Danger: Seismic Sea Wave-Tsunami (See Below)

Post-Earthquake Danger: Gas Pipe Breakage and Fire

Post-Earthquake Danger: (Fore) & Aftershocks

Post-Earthquake Danger: Liquefaction

Earthquake-Proof Your Home / Easy Steps / Build / Prepare

Above: Epic Fail

~ Liquifaction ~

Mexico City, Mexico, 1985

Above: Damage to structural foundations due to Liquefaction

Liquifaction (Quicksand Soil) = Water-Saturated Loose Sediment that Flows like a Liquid.

Mini "Sand Blow Craters" form as a result of Liquefaction:

Water from the "saturated zone" perculates up to the surface:

Above: Aquifer and Water Table

Above: Note the tighter packing of sediment grains after an earthquake

(Less pore space = Less room for groundwater)

Learn About Liquefaction / Video Clips

Above: Liquefaction Zone after the Sendai, Japan earthquake of 2011

~ Tsunami ~

Click here: Tsunami Information Page