ENDOGENIC PROCESSEARTHQUA

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VIDEO CLIP

Movements on the Earth’s SurfaceTypes of Faults

Active & Inactive Faults

FAULTS ANDEARTHQUAKES

What is FAULT?•It is a fracture or break in the Earth’s crust where earthquakes are most likely to occur repeatedly.•It forms when the rocks of the crust are compressed or stretched by plate movement.

What is FAULT?

SAN ANDREAS FAULT LINE

CEBU FAULT LINE

FAULTS

What is a Fault?•The break/crack along which rocks move•Movements along a fault can be up, down, or sideways•Earthquakes often occur along faults in the earth’s crust.

Parts of a FaultFoot Wall•Block of rocks below a faultHanging Wall•Block of rocks above a fault

Parts of a Fault

Types of Fault• Dip-Slip Fault – where

the crack is slanted or at an angle

2 Types of Dip-Slip Fault

A. Normal dip-slip faultB. Reverse dip-slip fault

TYPES OF FAULTS

ANIMATION

NORMAL FAULT STRUCTURE

•The hanging wall moves down relative to the foot wall•Also known as Tensional Fault

NORMAL DIP SLIP

REVERSEDIP SLIP

• In a Reverse Fault, the foot wall moves down relative to the hanging wall.

• Known as Compressional Fault

Reverse faults• These are formed when rocks are compressed.

•The hanging wall moves up with respect to the footwall, causing the length of the rock body to shorten.

ANIMATION

REVERSE FAULT STRUCTURE

REVERSE FAULT STRUCTURE

Types of Fault• Strike Slip Fault• Oblique Slip Fault

•Shearing will cause the blocks of rock to slide horizontally past each other.

STRIKE SLIP FAULT

ANIMATION

TYPES OF FAULTS

OBLIQUE SLIP FAULT• combination of strike-slip and dip-

slip motion.

ANIMATION

TYPE OF FAULT TYPE OF STRESSNORMAL TENSION

REVERSE COMPRESSION

STRIKE-SLIP SHEARING

OBLIQUE Tension, Compression and Shearing

FAULT MOVEMENTS• Tension stress is when rocks are stretched away from each other.•Compression stress is when rocks are pushed toward each other.•Shear stress is when rocks slide along each other.

Stress Types

ACTIVE & INACTIVE FAULTS•Active Faults are known to have recently generated earthquakes within the last 10,000 years, and may still continue to generate earthquakes.• Inactive Faults do not show signs of ever having generated an earthquake in the last 10,000 years but may possibly still generate an earthquake in the future.

MAJOR FAULTS IN THE PHILIPPINE SETTING

Philippine Fault Zone• The most extensive fault system and cuts through

the entire Philippine Archipelago.

• About 1, 200 km long and is composed of many faults and their branches that traverse the Philippines through Luzon, cutting across Bicol and the Visayas, all the way to the northern portion of Mindanao.

MAJOR FAULTS IN THE PHILIPPINE SETTING

MAJOR FAULTS IN THE PHILIPPINE SETTING

Valley Fault System• Consists of two northeast-trending right-

lateral strike slip faults that begin in San Mateo, Rizal, continue through parts of eastern Metro Manila, and extends southwards through the cities of Paranaque, Muntinlupa, Santa Rosa and possibly Tagaytay Ridge.

MAJOR FAULTS IN THE PHILIPPINE SETTINGLubang Fault•Found offshore between Batangas and Mindoro Island. It is a left-lateral strike-slip fault along the Verde Island passage, but becomes an oblique-slip as it runs closer towards the Manila Trench.

•Central Mindoro Fault•Marked by a break in slope between mountains of

western Mindoro and the flatlands of eastern Mindoro, and is easily seen in topographic maps. It is mostly a right-lateral strike-slip fault, but in some portions also shows normal dip-slip movement.

• Responsible for the 1994 magnitude 7.1 earthquake in northeastern Mindoro, it ruptured the northern segment fault known as Aglubang River Fault.

MAJOR FAULTS IN THE PHILIPPINE SETTING

Seismic Waves in the Earth

VIDEO CLIP

Seismic Waves

LOCATING EARTHQUAKES

1. Earthquakes generate waves that travel through the earth

1. Earthquakes generate waves that travel through the earth

LOCATING EARTHQUAKES

1. Earthquakes generate waves that travel through the earth

LOCATING EARTHQUAKES

LOCATING EARTHQUAKESDEPTH

ELASTIC REBOUND

ANIMATION

EPICENTER AND FOCUSFOCUS•Location within the earth where fault rupture actually occurs

EPICENTER•Location on the surface above the focus

MAGNITUDE AND INTENSITY INTENSITY•How strong earthquake feels to observer.

MAGNITUDE•Related to energy release •Determined from seismic records•Rough correlation between the two for shallow earthquakes

INTENSITYHow Strong Earthquake Feels to Observer

Depends On: •Distance to Quake •Type of Building •Observer •Varies from Place to Place•Mercalli Scale- 1 to 12

Determined from seismic records

Richter Scale:•Related to Energy Release •Exponential •No Upper or Lower Bounds •Largest Quakes about 8.7

MAGNITUDE

How Seismographs Work

SEISMOGRAPH measures ground motion at one instant but –•A really great earthquake lasts minutes •Releases energy over hundreds of kilometers •Need to sum energy of entire record •Modifies Richter Scale, doesn't replace it •Adds about 1 mag. to 8+ quakes

MAGNITUDE AND ENERGY

MAGNITUDE ENERGY EXPLOSIVE POWER EXAMPLE

9 U.S. Energy Use for a month Alaska 1964Indonesia 2004

8 U.S. Energy Use for a day San Francisco, 1906

7 One Megaton World Series Earthquake, 1989

6 U.S. Energy Use for a minute Large Thunderstorm

5 One Kiloton

4

3 One ton of explosives World Trade Center Collapse

MAGNITUDE ENERGY EXPLOSIVE POWER

EXAMPLE

3 One ton of Explosives World Trade Center Collapse

2

1 Topple 50-meter tree One kilogram of explosives

Head-on colision at 60 mph

0 Drop a car 10 meters Half stick of dynamite Very bad day skydiving

-1 Impact of bullet One gram of explosives

-2 Hammer blow

-3 Dribbling a basketball

MAGNITUDE AND ENERGY

1. Earthquakes generate waves that travel through the earth

2. Earthquakes occur when rocks slip along faults

3. Faults are classified by the kinds of movement that occur along them

4. Earthquakes don’t kill people, buildings kill people

5. Magnitude and Intensity6. Seismic waves are used to map the earth’s

interior7. Predicting earthquakes is not yet possible