EARTHQUAKES & FAULTS
More
than 1 MILLION EARTHQUAKES occur every year Earthquake erve a ev!"ence that Earth# $rut ! cont!nua%%y un"ero!n chane
How do earthquakes occur and how are they detected? • How can people be prepared for earthquakes?
ACTIVE and INACTIVE FA!T" • EA#TH C#"T
The surface$outer%ost layer of the Earth
Earth&s Crust Two "ect'ons Cont'nental Crust )akes up Earth&s land%asses (cean'c Crust Found 'n the ocean floor and usually th'nner than cont'nental crust
*hy are so%e parts of the crust th'cker than other? How does the crust chan+e 'ts shape o,er t'%e?
• Some force is at work pushing and pulling on the crust causing changes on the surface and often well beneath the surface • Th's push-pull 's called stress • As rocks under+o stress. they slowly chan+e shape and ,olu%e/ ,olu%e /
*hat can stress do to rocks? • A rock to beco%e %ore % ore co%pressed or squee0ed s quee0ed
• 1eco%es s%aller 'n ,olu%e • A rock to stretch stretch out o,er a lar+e area/ • The ,olu%e 'ncreases • The rock to tw'st or tear apart/ • Causes the for%at'on of fault
*hat 's a fault? • Fault
Fracture 'n rocks alon+ wh'ch %o,e%ent occured/ "o%e faults %ay cause the +round to crack. r'se or lower/
Two blocks of a faulted rock • Han+'n+ *all • The block of rock abo,e the fault • Foot *all • The block of rock below the fault
2'nds of fault • Nor%al Fault$Nor%al 3'p-sl'p Fault • If a stress pulls the rocks apart due to tens'on. the han+'n+ wall w'll %o,e down relat',e to the foot wall/
2'nds of fault • #e,e #e,ers rse e 3'p3'p-sl sl'p 'p Fau Fault lt$$ Thr Thrus ustt Faul Faultt • If stress squee0ed the rocks due to co%press'on. the han+'n+ wall w'll %o,e up relat',e to the foot wall/
2'nds of Fault • "tr'ke 4 sl'p Fault$*rench Fault • The blocks %o,e by sl'd'n+ and sl'pp'n+ alon+ each other hor'0ontally but 'n oppos'te d'rect'ons/
Act',e faults • are structure where there 's a d'splace%ent/ • sually produce a shallow earthquake • (ne that has %o,ed 'n the past and e5pected to %o,e a+a'n/
Inact',e Faults • are structures that can be 'dent'f'ed but wh'ch do not cause earthquakes/ • If a fault has been 'nact',e for %'ll'on years. 't 's safe to call 't 'nact',e/
• The %ot'on alon+ the faults can be e5pla'ned by the 6!ATE TECT(NIC THE(#7
• !ar+e slabs of Earth&s !'thosphere are cont'nuously %o,'n+ slowly/ These plates 'nteract w'th other plates defor%'n+ the nearby rocks/
6HIV(!C" • 6h'l'pp'ne Inst'tute of Volcanolo+y Volcanolo+y and "e's%olo+y
• 6h'l'pp'nes has se,eral fault l'nes • Faults and trenches are trenches are found 'n the ent're country • Trenches are Trenches are the deepest part of the oceans and are usually V"haped/
Faults 8 Trenches • Are found close to the cont'nents cont'nents • Near str'n+s of 'slands/ • Near these T#ENCHE"9 4 The crust 's act',e caus'n+ stress and creat'n+ faults/
About trenches: • "c'ent'st bel'e,e that the ocean floor 's be'n+ pushed down deep 'nto Earth alon+ the trenches • *hen these rocks are pushed deep enou+h. they are %elted by the heat of Earth/ • "o%e of the %olten rocks w'll r'se up throu+h the crust and produce ,olcanoes but %ost of 't w'll beco%e part of the Earth&s )antle/
EA#TH;A2E Focus and Ep'center • Earthquake: • "hak'n+ and tre%bl'n+ of earth that results fro% the sudden %o,e%ent of Earth&s crust • Fault'n+: • The %ost co%%on cause of earthquake
• 3ur'n+ Fault'n+: • Ener+y 's released as the rocks break and %o,e/ • As they %o,e. they cause the nearby rocks to %o,e also/ • The rocks cont'nue to %o,e th's way unt'l the ener+y 's used up/
Tsuna%': • <'ant ocean wa,e cause by Earthquake that occur on the ocean floor/ • These wa,es can tra,el at speed of =>> 4 >>k%$h/ • Can be as h'+h as @> 4 > %eters Bas they approach the coast/ • The effects are de,astat'n+ • (ne of the world&s world&s worst natural d'saster
• Focus • The po'nt$re+'on where an earthquake ruptures and the rocks break • hypocenter • nder+round po'nt of or'+'n of an Earthquake/
• Ep'center • The po'nt on Earth&s surface d'rectly abo,e the focus • Th's where the %ost ,'olent shak'n+ of the +round occurs/
• Focal 3epth • The d'stance between the focus and the ep'center
Earthquake *a,es: • "e's%'c *a,es • Are the wa,es wa,es of ener+y caused by the sudden break'n+ of rock w'th'n the Earth or an e5plos'on/ • They are the ener+y that tra,els throu+h Earth and 's recorded on seismographs.
Three %a'n types of "e's%'c *a,es • 6r'%ary *a,es *a,es B6 *a,es • The fastest of the se's%'c wa,e • The f'rst to arr',e at a se's%'c stat'on before any other type of se's%'c wa,e • Can %o,e throu+h the sol'd rocks and flu'ds (like water and liquid layers of Earth)
Three %a'n types of "e's%'c *a,es • Can %o,e throu+h the sol'd rocks and flu'ds (like water and liquid layers of Earth)
Three %a'n types of "e's%'c *a,es • "econdar "econdary y *a,e B" *a,e • The second wa,e you feel 'n an earthquake • S wave 's slower than a P wave and can only %o,e throu+h sol'd not throu+h l'qu'd or +ases
• *hat happens to " *AVE" when they reach the l'qu'd part of the earth?
• " wa,es %o,e rock part'cles up and down. or s'de 4 to 4 s'de perpend'cular to the d'rect'on the wa,e 's tra,el'n+ 'n/
Three %a'n types of "e's%'c *a,es • "urface *a,e B! *a,e 4 Tra,el Tra,el fro% focus focus d'rectly d'rectly upward to the ep'centre/ 4 Earth&s surface %o,es up and down w'th each ! wa,e that passes 4 Cause %ost of the da%a+e dur'n+ the earthquake because they bend and tw'st Earth&s surface/
"e's%o+raph: • An 'nstru%ent that that detects and %easures %easures wa,es/
"e's%o+ra%s: • "e's%o+raph&s record of the wa,es/
#'chter "cale: • )easures how %uch ener+y an earthquake releases by ass'+n'n+ the earthquake nu%ber fro% @ to @>/ • The %ore ener+y the earthquake releases. the stron+er the earthquake 's/
Earthquake )a+n'tude and 'ts Effects R!chter Man!tu"e
E''ect Near E(!center
/> and below
/> 4 /D
6otent'ally percept'ble
/> 4 /D
Felt by so%e
/> 4 /D
Felt by %ost
G/> 4 G/D
3a%a+'n+ "hocks
/> 4 /D
3estruct',e 'n populous re+'ons
=/> 4 =/D
)aor earthquakeJ 'nfl'ct ser'ous da%a+e
)od'f'ed )ercall' Intes'ty "cale • New Kealand . n'ted "tates and Canada C anada are countr'es us'n+ %ercall' scale 'n %easur'n+ the 'ntens'ty of an earthquake • Th's 's a descr'pt',e scale fro% @-@ based on // 4 how people feel an earthquake 4 The da%a+e to bu'ld'n+s and the'r contents 4 How the natural en,'ron%ent responds/ r esponds/