GEOLOGICAS ACTIVE FAULT IN PERU INGLES.docx

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GEOLOGICAS ACTIVE FAULT IN PERU

INTRODUCTION

In Peru, the Neotectonics has advanced to the point you have

identifed, mapped and recognized the eatures o the major active

aults in the country. However, this inormation as such is not directly

applicable or useul in seismic hazard assessments. Necessary goes

to the net step o the !parameter!. "t this stage it is by

palaeoseismological !method o determining the magnitudes o the

earth#ua$es that each ault is capable o generating, their return

periods. %hese are the minimum data that can be processed with

programs currently available. &ther typical inormation as brea$ing

length, displacement $inematics, direction o propagation o the

deormation over time and others added accuracy evaluations.

'onsidering that seismic hazard assessments should not be an

eercise in style or a report in the fle o a project, the best result

obtained with the inclusion o the inormation specifed shall be

immediately useul or project engineering l as well as or land use

plans and the design o prevention and mitigation plans in the regions

involved.



GOALS:

Y. DEVELOPMENT:

(eological tectonic aults, ractures are ormed in the earth)s crust are

ound in sedimentary roc$s, intrusive, metamorphic and volcanic

product o tectonic deormations.

&ne o the terrain that can be seen more easily are the aults or

brea$s o a olding, especially i the ground is sefmentario type.

*ailures are a type o deormation o the earth)s crust ending rupture,

leading to a variety o geological structures.

+hen this brea$down occurs abruptly, an earth#ua$e occurs.

ometimes the ault line allows, at certain points, to surace the

magma rom the lower layers and a volcano is ormed.

1. CONCEPT:

In geology it called a brea$ ailure o a roc$ layer due to an e-ort

where a shit can be observed. I no movement we say that there is a

rit which i not cross the roc$ say it is a fssure. I the movement has

not bro$en strata but there is a signifcant and sharp accentuation o

the dip o the strata, stretched and thinned, called e.



%he ailure is caused when the geological material shows great

strength or plasticity is overcome by the intensity o the tectonic

orce. %he aw may be ormed by compression, to pass on the yield

stress o the materials, or straining, by relaing the e-ort to racture

not recover the previous state appears. In distinguish ailure/ ault

plane, ault or lip bloc$, ault line, jump or escarpment, a sense o

ailure.

2. PARTIES OF FAILURE:

In the morphological level, ailures can have a prominent role in the

feld.

It is called the ault plane to brea$ the surace o the layers move. I

the ault plane is polished and striated say it is a mirror o ailure. In

this case you can give phenomena o dynamic metamorphism.

It)s called lip ails, or bloc$ members separated by the ault plane

ragments. +e distinguish between high bloc$, which amounts, and

sun$ bloc$, which descends.

%his ault line is called the line o contact between the lower lip and

the ault plane.



It is called jump ails or escarpment, to the total height vertically

measured displacement. I the tear occurs horizontally, in the same

plane 0without jumping ault1 we say that it is a tear.

3. CHARACTERISTICS OF FAILURE:

%he ollowing eatures allow us to describe aults/

2 "ddress/ the angle between a horizontal line contained in the ault

plane with the north3south ais.

2 4ip/ the angle between the ault plane with the horizontal.

2 jump ails/ 4istance between a given one o the bloc$s 0eg one

surace o a layer..1 "nd the corresponding point in the other, ta$en

along the ault plane.

2 5scarpe/ 4istance between suraces o the two lips, ta$en vertically.

2 ailure mirror/ the at surace although decline, which occurs along

the ault scarp

2 triangular acets are mirrors showing cutting ailures occurred in a

mountainous row when the ailure occurs perpendicular to the



direction o this mountainous row. 6oth the sun$en part o the mirror

itsel as ailure have triangular appearance, hence the name.

4. TYPES OF FAILURES GEOLOGICAS:

CLASSIFICATION OF FAILURE TO YOUR MOVE:

%he aults are classifed into three types based on the e-orts that

originate and relative movements o the bloc$s/

2 reverse ault. %his type o ailure is generated by compression 0*ig.

"1. %he movement is preerably horizontal and the ault plane

typically has an angle o 78 degrees to the horizontal. %he ceiling

bloc$ is on the ootwall. +hen thrust aults have less than 9: ;anteo,

these happen to ta$e the name o thrust.

2 normal ault. uch ailures are generated by traction 0*ig. 61. %he

motion is predominantly vertical to the plane o ailure, which

typically has an angle o <8 degrees to the horizontal. %he bloc$ slides

down is called the hanging wall, while rising is called bloc$ oor.

"nother way to identiy these aults is as ollows. 'onsidering bloc$

fed to the oor 0one that is above the ault plane1 gives the

impression that the roo bloc$ alls on this. ets o normal aults can

lead to the ormation o horst and grabens.

2 stri$e3slip ault, direction, or transcurrent. In this type the vertical

component o the jump is negligible and the predominant movement

is horizontal 0*ig. '1. . 4etral and sinistral %wo types o stri$e3slip

aults are distinguished. =eaching the observer at any o the bloc$s



and where travels acing the other, are detral those where the

relative movement o the bloc$s is cloc$wise, while the sinistral, the

opposite occurs.

hould not be conused with transorm aults, which are associated

with the concept transorming edge o the theory o plate tectonics,

or with transverse aults, which are those that allow acomododar

di-erential movements o bloc$s along a ault plane.

2 =otational or scissors *alla. It is the one originated by a tilting

motion o the bloc$s rotate around a fed point, as the two parts o

scissors.

2 *ailure obli#ue. ;ovement is one that has a vertical component and

a horizontal component.

*ailures can occur associated in a number o structures/

2 staggered *ailures/ set o normal aults parallel planes.

2 tectonic scales/ reverse aults set o parallel planes.

2 horst/ a set o normal aults that orm a conve structure.

2 overriding chain/ set o thrust aults that orm a conve structure.



2 =it >alley 0recorded1/ a set o normal aults that orm a concave

structure.

2 tectonic ;assi 0horst1/ pillars and association tectonic grabens,

alternately.

2 ;antle 6leed/ recumbent old in which it has reached a ailure occur

between the upper edge and the lower, so that rolls over it.

5. ACTIVE AND INACTIVE FAULT:

" ault is active when deormed ?uaternary sediments, that is when it

shows evidence o movement during the last @.A million years. ome

active aults oten have associated earth#ua$es which shows that

continue to operate. %he slip can be sudden jumps shaped leading to

earth#ua$es and a process is that two aults collide occurs, and

earth#ua$es occur when hitting ollowed downtime. %he larger

earth#ua$es have been caused by brea$s A3@B m. %he slip can also

occur slowly and continuously, perceptible only with instruments such

as (P stations ater several years o observations.

%he frst type are seismic aults while the latter are aseismic or

crawling. However, when considering large time intervals on the order

o thousands o years, both moving at average speeds o a ew

millimeters to a ew centimeters per year.



&ne eample is the large aults distributed in the interior o the

continent, such as system ailures %ambomachay 0'uzco1, 'ordillera

6lanca 0"ncash1, Huaytapallana 0Huancayo1, ?uinche 0'ajamarca1

and =ioja 3;oyobamba 0an ;artin1 etc.

%here are also inactive old aults created in previous eras and survive

as ossil structures to this day. %hese do not represent any danger to

nearby towns.

"ctiva ails pecifcally/

%here is no type o study the type o data available is general

agreement about when a ault should be considered !active! and

most o the defnitions put orth are based on the tectonic structure,

and and C or the perception o the author problem. ;oreover, the

geological ?uaternary deormation scenarios vary the limits o active



pla#ues in virtually stable cratonic areas, where the instrumental

seismicity in general has little correspondence with morphotectonic

eatures. In areas where the structures have the time intervals o

recurrence rates and slow slip aults in the shortest time since the last

brea$ 0the most !active! consideration1 might not be the most

dangerous in terms o seismogenic capacity. %hus, the term well3

established !active ault! is not considered ade#uate, and may even

be misleading as to the legends o objective and consistent and

accurate broadcast assignment.

'onse#uently, the characterization o the deormation unction o

time since the last ault slip3recorded 0ie, aults late ?uaternary

displacement Holocene or historical1 is considered more appropriate

characterization as an active, capable, potentially active, inactive

aults, and so on. %his time3based classifcation allows some eibility

in reporting between di-erent tectonic environments or countries due

to the compleity or di-erent levels o research and s$ills prehistoric

date ault events.

6. MAIN ACTIVE FAULTS IN PERU:

%he chain o the "ndes stretches over D,888 $m along the Pacifc

active margin o outh "merica, resulting rom the subduction o the

Nazca plate beneath the outh "merican plate. %he width o the

"ndes varies greatly, more than :88 $m in the central part o 6olivia

and southern Peru until just

@:8 $m at its ends in 5cuador and southern 'hile.



%he type o "ndean subduction is characterized by a subducting

oceanic plate at a low angle and with a predominantly compressive

tectonic regime. In the case o the "ndean subduction geometry o

the oceanic plate it has two types o segments, each sin$ing at an

angle o ca. 78 E 0'olombia35cuador, Peru36olivia3outh North 'hile,

'hile and 'entral and outh1 and other low3angle or at subduction

0Fordan et al. @DA71.

%he "ndes are divided into three main segments, rom the 'aribbean

ea 0@8 E N1 to %ierra del *uego 0:: E 1 0see oler @DD@ Grreiztieta

@DD<, (erman and =amos B888, Faillard et al. B888, =amos

B8881. %he northern "ndes 0@8 E N3: E 1 are developed in a comple

cinematic contet due to the interaction o the 'aribbean, 'ocos,

northern part o the Nazca plate and the outh "merican plate plates.

%he central "ndes 0: E 39< E 1 are located along the western margin

o outh "merica where the Nazca, "ntarctic and outh "merican

plates interact. outh, or the outhern Patagonian "ndes 09< E 3:: E

1 resulting rom the interaction o "ntarctic plates, "merican and

cotia. %he convergence vector is obli#ue in relation to the contact

area o the plates. %hus obli#ue accommodation is complicated,

particularly in regard to the relationship between the deormation and

the overriding plate subduction. "lso, the geometry o the coast also

a-ects the distribution o deormation and resulting morphology.

"lthough the main structures o the "ndes developed during the

;iocene, its e-ects are now visible.



;ain characteristics and

geotectonic setting neotectonics

the continent o outh "merica

and around. @. Northern "ndes,

B. 'entral "ndes B". Peru at

slab B6. Normal subduction

segment, B'. Pampeana plane

o the slab.

%he "ndes have traditionally been divided into three main sectors,

namely the northern "ndes, the 'entral "ndes and the southern

"ndes.

%he present *ault ystem in Peru, are the result o the ongoing

process o deormation o the continental crust. %hese systems are

present in greater numbers, rom north to south, on the oot

ubandino the eastern edge o the "ndes, a-ecting the major olds o

the 6razilian shield 0ault systems

;oyobamba, atipo, ;other o (od, etc.1. %he number o these ault

systems is lower on the High 'ordillera and the "ltiplano 0ault system

o the 'ordillera 6lanca, Huaytapallana and %ambomachay1. In

general, the largest number o aults are o reverse type evidencing

shortening the corte.



4istribution o the main morpho3tectonic structures o the "ndes

between @ and N

9< E . ocation o areas o study/ 5cuador, 6olivia, 'hile.



<.@. ;ajor ault systems/

In general, these systems are reverse type on ubandino at the oot

o the main olds ormed by the subsidence o the 6razilian shield in

the 5astern 'ordillera 0ailure o ;oyobamba, atipo, ;other o (od1.

+hile in the High 'ordillera and the "ltiplano, the number o these

systems is lower and are mainly located at the oot o some major

glaciers, and owe their origin to etensive processes 0ailure o the



'ordillera 6lanca and %ambomachay1 and compressive

0 Huaytapallana system ailures1.

%hen the most important characteristics o major ault systems will be

described according to their location in each o the units described

above moroestructurales

In the 'oastal Jone, north o : E outh ailure Huaypira 0HP1 is located

with a N53+ and 5+ orientation between @9 E and @< E outh, the

presence o the ailure o ;arcona 0;"1 acing the N+35 ault

aPlanchada 0P1 and the height o @<.: E , stands out with N+35 is

observed. %hese ailures have lengths o about D8 $m on average and

are o normal type.

%he process o deormation o the continental crust, ollowing the

liting o the "ndes, has given rise to the ormation o di-erent aults

on distribution systems throughout Peru. In general, these systems

are reverse type on ubandino at the oot o the main olds ormed by

the subsidence o the 6razilian shield in the 5astern 'ordillera 0ailure

o ;oyobamba, atipo, ;other o (od1. +hile in the High 'ordillera

and the "ltiplano, the number o these systems is lower and are

mainly located at the oot o some major glaciers, and owe their origin

to etensive processes 0ailure o the 'ordillera 6lanca

%ambomachay1 and compressive 0Huaytapallana system ailures1.

%hen the most important characteristics o major ault systems will be

described according to their location in each o the units described



above moroestructurales 0*igure71. In the 'oastal Jone, north o : E

outh ailure Huaypira 0HP1 is located with a N53+ and 5+

orientation between @9 E and @< E outh, the presence o the ailure

o ;arcona 0;"1 with N+35 ault o the Planchada 0P1 and the

height o @<.: E , stands out with N+35 is observed. %hese ailures

have lengths o about D8 $m on average and are o normal type. In

the +estern 'ordillera the presence o the ailure o the 'ordillera

6lanca 0'61, this being normal rate dipping to + and the most

etensive in the world 0B88 $m1 is important. North o the ault branch

called ?uiches ailure. "t the height o latitude @< Pampacolca ailure

0P'1 appears E outh with a length o 78 $m, this being normal type

with its main plane dipping towards +. Ichupampa ailure 0IP1 is

between @K E and @A.: E south over a length o about BB8 $m. %his

ailure is normal rate dipping to the + and as 'hile nozzle etends

westward. In the high mountains, on the latitude o @B.: E , stands

the reverse ault system type Huaytapallana 0HG1 with a length o B:

$m N+35 direction and dipping to the N5.

"t the latitude o @7.: E , stands the ault system "yacucho 0"L1. In

the "ltiplano and 5astern 'ordillera, between @7 E 3@9.: E , the ault

system o %ambomachay 0%;1 is located, virtually the same across the

southern tip o the department o 'uzco. %his system also considers a

signifcant number o normal aults that are distributed along di-erent

directions, with the longest >iscachani ailures, "lto >ilcanota,

Pomacanchi and angui3ayo, all with a ocus on 5ast3+est.



In ubandino systems include reverse aults "lto ;ayo 0";1 located

between latitudes 9 E to A E outh, system ailures atipo3"mauta

0"1 between D and @B E outh and the system ailures ;other o (od

0;41 between @B E and @9 E outh. "ll these systems have aws o

di-erent lengths 0between 7883:88 $m1 and in general, are oriented

parallel to the "ndean 'ordillera dipping to the +.

"ll ault systems, described above, have led or supported in the past,

long reactivations due to the occurrence o earth#ua$es o high

magnitude, the same as in some cases, have highlighted on the cli-s

ailure surace uneven, on ground level o the order o B to 9 meters

0*ailure Huaytapallana and ?uiches1. *or eample, in the ubandino

earth#ua$es o @DD8 and @DD@ they reactivated the system ailures

"lto ;ayo in the 5astern 'ordillera, %ambomachay ailure was

reactivated with the earth#ua$e o @DA< in the +estern 'ordillera,

?uichMs ailure originated with the earth#ua$e o @D9< and the ailure

o Huaytapallana, two earth#ua$es occurred in @D<D in the high

mountains, the ailure o "yacucho was reactivated with the

earth#ua$es in @DA@ and @DDD.

6.1.1. PERUVIAN FLAT-SLAB (4 S - 14 S!

%his sector has a temporary migration o deormation toward the

oreland 0east1 as a result o the subduction o the at slab geometry

during the past : ;a 0Mbrier and oler @DD@ Mbrier et al. @DAA

(utscher et al. B8881 . =aised marine terraces are among the ew

deormed eatures as described on the ground, which emphasize the



vertical component o subduction3related response and the elastic

crust along the plane o the slab Peru sector 0;achare and &rtlieb,

@DDB1.

%he resulting movement o the earth)s crust led to the raising

'ordillera 6lanca, which has some o the highest elevations in the

"ndes and in the ?uaternary normal aults associated with recent

surace aults 0@DA9 6onnot, 6onnot et al. @DAA, chwartz @DAA ,

;achare et al. B8871. It is also important to note that the surace

seismicity that characterizes the 5astern 'ordillera and the sub3

"ndean region 0uarez et al. @DA7, 4orbath et al. @DD@1, where the

active deormation is dominated by the olds o related ailures, as the

system hitari aults and other structures unnamed 0;achare et al.

B8871.

FONT:

I. 6ernal and H. %avera

National (eophysical 4ata 'enter C (eophysical Institute o Peru.

6.1.2. GEOLOGICAL MAP OF ACTIVE FAULTS IN PERU:

&utline main ?uaternary deormation along the 'entral "ndes,

including the Peruvian at slab segment 09 E 3@9 E 1 and normal

subduction segment 0@9 E 3BK E 1. 4ual systems and lac$ respect in

the tet are/ @. hitari, 'ha#uilbamba B., 7. ?uinche, 9. 'ordillera

6lanca, Huaytapallana :., <. 'uzco, K. Incapu#uio A. 5scoma3

"chacachi3Peas3Oen$o D. 6eni, @8. ;ande3Lapecua @@. omas de

&lmedo, @B. "tacama @7.%rench.



FAILURES IN PERU :

2 %H5 (=5"% PI% P5=G3'HI5

2 *"IG=5 'H"?GI6";6"

2 *"IG=5 5scoma3"'H"'"'HI3=&'O3O5NO&

2 *"IG=5 &* 65NI

2 *"IG=5 Huaytapallana 0Funin1

2 *"IG=5 ?uinche 0"ncash1

2 *"IG=5 %";6&;"'H"L 0'uzco1

2 *"IG=5 Huambo and '"6"N"'&N45 0"re#uipa1



2 *"IG=5 &* %H5 +HI%5 ;&GN%"IN 0"ncash1

2 *"IG=5 Pomacanchi 0'uzco1

2 *"IG=5 "%IP&.

2 *"IG=5 &* ;&%H5= &* (&4.

2 *"IG=5 ;"='&N".

2 *"IG=5 ironed

2 *"IG=5 Pampacolca.

2 *"IG=5 Ichupampa.

'ompiling deormation regimes during the ?uaternary in the "ndes



North and 'entral.

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