Development of a Seismic Microzoning Map for Lima City andCallao, Peru

Paper:Development of a Seismic Microzoning Map for
Lima City and Callao, Peru
Diana Calderon∗ , Zenon Aguilar∗ , Fernando Lazares∗ ,Silvia Alarcon∗ , and Selene Quispe∗∗∗ Japan Peru Center for Earthquake Engineering and Disaster Mitigation (CISMID),

Faculty of Civil Engineering, National University of Engineering
Av. Tupac Amaru No 1150, Lima 25, Peru
E-mail: dcalderon@uni.edu.pe∗∗
Department of Environmental Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan[Received September 4, 2014; accepted October 10, 2014]

The location of Lima city and El Callao in the Pacific coast and the long history of seismic activity
were the main reasons to develop a seismic microzoning map. The microzoning study was based onlarge numbers of geotechnical and geophysical exploration points distributed around the study area. The
geotechnical exploration consisted of borehole tests
and pits, from which soil samples were taken to thelaboratory to determine the soil mechanical characteristics. The geophysical exploration consisted of onepoint microtremor measurements and various methods to estimate the S-wave velocity profile. The results of both, the geotechnical and geophysical exploration were combined to develop a seismic microzoning map for Lima city and El Callao. This map shows
five zones, where the zone with the best soil mechanicaland dynamic characteristics covers most of the study
area.
Keywords: borehole tests, microtremor, S-wave velocity
profiles, microzoning map

1. Introduction
Lima city and Callao, the capital and the Constitutional
Province of Peru respectively, are constantly exposed toearthquakes due to their location in the circum-Pacificseismic belt. The last large seismic event in the city occurred in 1974, when an earthquake of magnitude Mw 8.0
hit the coast of Lima and Callao, causing severe damage
in the buildings of Callao, Chorrillos, La Punta and La
Molina districts. The damage was related to amplificationof incident seismic waves by the local surface-soil conditions and the depth of the water table.
By the time of the earthquake, few districts were populated; as a result, the seismic response of the nonpopulated areas remained unknown.
During the last three to four decades, the city started toexperience a large urbanization process, which took placein an informal way. In consequence, a large number ofJournal of Disaster Research Vol.9 No.6, 2014

houses were built in non-suitable soils from the engineering point of view.
This problem was regarded to informality, to the indecision of local authorities, and to the lack of a detailed
seismic microzoning studies.
The first seismic microzoning study in the area dates
from 1991, when Huaman developed a map for La Punta
and El Callao districts. This study consisted of geotechnical exploration by borehole tests and single point microtremor measurements.
From 2003 to 2005, CISMID was in charge of developing a microzoning study in forty-two districts of Lima andCallao. New technology and data processing techniques
were introduced by that time, such as velocity sensors,
specially designed to measure microtremors. The result
was a seismic microzoning map of almost all the area of
Lima city and Callao.
The resulting map divided the area of study into fivezones that describe the geotechnical and dynamic characteristics of soils.
From 2010, an effort to update the microzoning mapof Lima and Callao was carried out in the framework of
the SATREPS (Enhancement of Earthquake and Tsunami
Disaster Mitigation Technology in Peru) Project.
The update of the microzoning map was possible not
only by increasing the number of exploration points, butalso by introducing various surface wave exploration techniques in order to estimate the S-wave velocity profiles up
to the basement rock.

2. Seismicity of the Study Area
Lima city and Callao are the target area of this study.
The first one is the capital of Peru, and is located in thecentral coast of the country; it is also, where approximately one third of the country’s population lives. Callao,
is the Constitutional Province of Peru, and is located justnext to Lima bordering the Pacific Ocean.
Currently, Lima city and Callao together are divided
in forty nine districts; the majority of which belong to939

Calderon, D. et al.

Lima. By this moment, forty three districts out of forty
nine districts were studied for microzoning purposes.
The most notable earthquakes that affected Lima andCallao from 1523 to 1974 are listed in a technical report [1]. From the list mentioned before, strong groundmotion with short and long duration, different intensities,
and different frequency content were reported. According
to this list, the maximum intensity observed in Lima was
X MMI; and the predominant period for central Lima was
about 0.1 seconds. Damage was observed in Callao, La
Molina and Chorrillos district mainly.
It is important to notice that the last strong earthquake
reported in Lima was the October 3, 1974; and that sincethen, more than thirty years have passed, increasing theprobability of a seismic event occurrence. According to
Pulido et al. [2] a Mw 8.9 earthquake is expected to occur
in central coast of Peru that will hit directly to Lima City.

3. Geology and Geomorphology
The geology of the Lima region reflects the subductionof the Nazca Plate under the South American Plate, andthe consequent uplift and volcanic activity [3].
Sedimentary and intrusive rocks, as well as, unconsolidated deposits are part of the geologic units of Lima.
Rocks of sedimentary-volcanic origin, placed during
the Late Jurassic to Cretaceous periods, are found mainlyin the northern part of the city. To the East, parallel to thecoast, intrusive rocks that belong to the coastal batholith
spread as pulsations forming individual bodies of magmatic mass.
The unconsolidated deposits are from the quaternary
period, and consist of alluvial, colluvial, marine and eolian deposits. Fig. 1 shows that the majority of themetropolitan area is built on the alluvial deposit that was
originated by the Chillon and Rimac rivers, that eroded,transported and deposited the sediments in their path. The
alluvial deposits consist of gravel, with boulders of 20 cm
in the center of the city and of up to 60 cm in the east. The
sand as well as the silt-clay material creates lenses within
the gravels. Occasionally, isolated areas of organic soil ofmore than two meters depth appears. Along the coastal
cliffs the poor horizontal stratification of the debris can beobserved through the effects of erosion.
The depth of the alluvial deposits can be expected to befrom 400 to 600 m for the area of the alluvial cone of theChillon River; and the depth of the alluvial deposit fromthe Rimac River is about 200 m.
Besides the alluvial deposits, there are also marine deposits. These are relatively new-sand deposits, createdthrough the erosive action of the ocean’s waves and currents. Furthermore, the more recent eolian deposits are
generally found in the areas of the alluvial cones of the
Rimac and Chillon rivers [6].

940Fig. 1. Geology of Lima [4] and [5].

4. Geotechnical Aspects
In order to evaluate the geotechnical characteristics ofthe foundation soil at Lima city, exploration campaigns
were carried out. The campaigns consisted of direct exploration through borehole tests.
Soil samples were taken during the exploration and sent
to a geotechnical laboratory where various tests were conducted. The results allowed describing soil profiles thatdefine the conditions of specific areas.

4.1. Soil Exploration Campaigns
Information regarding the soil profile of Lima city
was collected from different sources. The main sourceswere engineering consulting companies that developed
geotechnical studies in the districts. The National Waterand Sewer Company was another source.
In addition to the gathered information, exploration
campaigns were performed. The campaigns were carriedout by districts, and the type of exploration was decided
based on the soil conditions of the site.
In the majority of the districts, pits were enough to explore the subsurface (Fig. 2). The average depth reachedby conducting these pits was 3 m.
In the districts with surficial loose sand, borehole tests
were conducted. The maximum depth was not higher than
10 m.
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Development of a Seismic Microzoning Map for Lima City andCallao, Peru

Fig. 2. Borehole at the independencia district.

4.2. Laboratory Tests
The soil samples obtained from the soil exploration
were tested in a geotechnical laboratory. Standard andspecial tests were carried out with the samples; the type oftest was chosen according to the soil characteristics foundin the visual inspection during the soil exploration. Standard tests were applied to disturbed samples following theUnified Soil Classification System (USCS).
4.3. Material Types
Based on the information obtained from previous collected studies, field exploration, and from the results ofthe soil tests, the area of Lima city and Callao was divided
according to the soil types with similar geotechnical characteristics.
The material types considered for the division are rock,gravel, sand, silt and clays, and debris and landfill, as canbe seen in the soil distribution map of Fig. 3.
From the map of Fig. 3 some comments can be maderegarding the soil distribution at Lima and Callao.
For example, an alluvial gravel deposit which is composed of a medium to dense coarse gravel with a sandy
matrix covers most of the area of Lima. Boulders andpebbles are also part of the deposit. These materials aremostly from the alluvial fan of the Rimac River; except in
the districts of Ventanilla, Carabayllo, Comas, Los Olivos,
and the northern area of the El Callao and San Martin dePorres districts, where the materials forming the soil deposits are from the Chillon River.
Besides the gravel deposits, there are silty sand deposits
situated mainly in the northern districts of Puente Piedra,
Comas and Carabayllo; and in the eastern districts of La
Molina and Ate Vitarte. This deposit was reported until
four meters depth in Puente Piedra (which was the maximum exploration depth), and until around three meters
depth in Ate Vitarte, in both sites the deposit overlays agravel deposit.
Clayey and organic soil deposits were found in a large
extension of El Callao district, with a maximum depth of
fifteen meters. Swampy soil deposits were identified in
Chorrillos and Ventanilla district.
Journal of Disaster Research Vol.9 No.6, 2014

Fig. 3. Soil distribution map [6].

Finally, another important deposit is the eolian sand deposit which covers most of Villa El Salvador and a large
area of Ventanilla district. The difference between thesand deposits in Villa El Salvador and Ventanilla is the
topography, while in the first district the sands were deposited mainly in a mild slope area, in Ventanilla the sands
were deposited over the hills of the Pachacutec locality.
The fact of being over the hills suggests that the thickness of this sand deposit is smaller than in Villa El Salvador, where the sands were found until the maximum
exploration depth of 8 meters.
It is worthy to point out that there are some landfill andwaste fill areas with depths from 2 to 20 meters in the
districts of Surquillo, Rimac, San Juan de Lurigancho,
Central Lima (Rimac River borders, Alfonso Ugarte Av.
among other places), and San Juan de Miraflores. These
landfills were also found in the cliffs of La Perla, San
Miguel, Magdalena del Mar, San Isidro, and Miraflores
districts.
The landfills originated from old ground removal madewith the purpose of construction materials extraction or
waste disposal. Although the size of these fills is limited,their presence involves serious problems to the structures
founded on it.
The rock basement is found at depths from 100 to 400
meters [6].

941Calderon, D. et al.

4.4. Geotechnical Microzoning Map
The area of Lima city was divided in zones according
to the geotechnical characteristics of the soils. The purpose of this grouping is to develop a map that allows to
identify the most convenient and inconvenient zones forsoil foundation of common structures.
The allowable bearing capacity was estimated at eachzone. This parameter was calculated for a typical building with a strip foundation of 0.60 m width and with aminimum foundation depth of 0.80 m. The bearing capacity theory proposed by Terzaghi was applied with thebearing capacity factors proposed by Vesic.
In all the zones, foundations must rest over the naturalsoil deposits and not over landfills.

5. Dynamic Characteristics

Fig. 4. Microtremor measurement.

The dynamic analysis of the soils is a fundamental toolin the microzoning study because it allows determining
the seismic soil response.

5.1. Calculation of the Fundamental Period of Vibration
The period of vibration is a dynamic parameter that defines the seismic soil response.
Researchers agree that the fundamental period of vibration of the soils can be determined by microtremor measurements. Microtremors are defined as ambient or noise
vibration [7] and [8]. These vibrations contain Rayleighand Love waves that are affected by the geological structure of the site where they are measured [9].
In 1989, Nakamura [10] developed a method to calculate the fundamental period of vibration of soils frommicrotremor records. The method, often called the H/Vspectrum method, consists of the division of the horizontal Fourier component with the vertical Fourier component. The fundamental period is the period correspondent
to the maximum value of the H/V spectrum.
5.1.1. One-Point Microtremor Measurement Campaigns
The first attempts to measure microtremors in the study
area started in 1991, when Huaman conducted surveys in
El Callao district [11].
From 2003 to 2005 CISMID carried out microtremors
measurement campaigns massively in the study as part ofthe microzoning project APESEG.
Finally, from 2010 up to now, in the framework of the
SATREPS Project, a more detailed measurement campaign was carried out by CISMID; the campaign consisted
in increasing the number of measurement points in the
study area.
The equipment used in the measurement campaigns isa velocity sensor CR 4.5-1S, which natural period is one
second, with the data acquisition system GEODAS 15HS
manufactured by Anet Co., Ltd. (Fig. 4).
942

Fig. 5. Distribution of one-point microtremor measurements.

The measurements are performed over the soil surface,
using high sensitive sensors. Velocities of microtremors
are recorded and then stored digitally for data processing.
Currently, around one thousand four hundreds of onepoint microtremors were measured in the city. The fundamental period in the study area ranges from less than
0.1 to 1.2 s. Fig. 5 shows the distribution of the one-point
microtremor measurements.
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Development of a Seismic Microzoning Map for Lima City andCallao, Peru

Fig. 6. Microtremor array test in the Ventanilla district.

5.2. Estimation of the S-Wave Velocity Profile
In addition to the predominant period of vibration, theS-wave velocity profile defines the seismic response of thesoil structure in the study area.
There are many techniques to estimate the S-wave velocity profile. In this study, we had used the MASW, themicrotremor array, and the P-S logging test.
These methods are based on observing the wave propagation through the soil structure. For the MASW andthe microtremor array test, surface waves are measured,
while for the P-S wave logging test the P and S-waves aremeasured directly.
The analysis followed in the MASW and microtremor
array tests consists on computing a dispersion curve ofRayleigh waves, which is then inverted in order to obtain
the S-wave velocity structure.
The analysis for the P-S wave logging test is different, it consists of identifying the first arrival time of the
P and S waves, so that the velocity can be computed ateach depth where the sensor is placed.
Small and large microtremor array measurements wereconducted in places like Central Lima, Callao, Puente
Piedra, Villa El Salvador, La Molina, Ventanilla district
among others [12]. Fig. 6 shows an array measurement in
Ventanilla district.
In Central Lima, high velocity values were found atshallow depths, meaning that soils have a rigid dynamic
behavior. On the contrary, in Callao and Villa El Salvador,
thick layers with medium velocity values were identified.
These layers are associated with the long periods observed
there.

6. Seismic Microzoning Map
Based on the geotechnical and the dynamic characteristics of the soils, the area of study was divided into fivezones. The map showing the zones is called the seismic
Journal of Disaster Research Vol.9 No.6, 2014

Fig. 7. Seismic microzoning map.

microzoning map (Fig. 7). The description of each zone
is mentioned below.
Zone 1This zone includes the rock formations with different
fracturing degree that form the hills. The dense to very
dense gravel and sand deposits are also considered in thiszone; as well as, the hard and very hard silt and clay deposits.
The different types of materials described in this zone
show the best geotechnical characteristics for building
foundation.
The allowable bearing capacity in this zone, for a
strip foundation of 0.60 m width varies between 196 and392 kPa, if it lies over the gravel at a minimum depthof 0.80 m; and it is more than 491 kPa if the foundation
lies over a slightly fractured rock at a minimum depth of
0.40 m. If the foundation rests on the sand, silt or clay
deposit, it is suggested to take values around 196 kPa.
The period of vibration in this zone is less than 0.3 s.
Zone 2This zone includes the medium dense to dense sand deposits, and, the medium stiff silt and clay deposits.
Additionally, the areas with medium geologic hazard
that are found in the hillside and in the small hills of Los
Olivos district, where potential landfill instability is probably to occur in a seismic event, are included.
The types of soils described in this zone show good
geotechnical characteristics for foundation purposes.
943

Calderon, D. et al.

The allowable bearing capacity in this zone, for a strip
foundation of 0.60 m width and at a minimum depth of
0.80 m, varies between 98 and 294 kPa, if it lies over thesand and it varies between 69 and 98 kPa if the foundation
lies over the silt or clay deposits.
The period of vibration in this zone is less than 0.4 s.

d) The most flexible soils are located in El Callao, andVilla El Salvador district, where long period of vibrations were observed.

Zone 3This zone includes the loose to medium dense sand deposits, and the soft to firm clay and silt deposits.
The type of soils described in this zone show bad
geotechnical characteristics for building foundation.
The allowable bearing capacity in this zone for a spreadfoundation of 0.60 m width and between 1.0 and 1.5 m
deep varies between 49 and 98 kPa. The natural period ofvibration in this zone is longer than 0.4 s.

f) Zone 1 covers most of the area of study and shows
the best geotechnical and dynamic characteristics.
g) Zone 2 shows good geotechnical characteristics.
However, areas with potential landfill instability during a seismic event were identified in this zone.

Zone 4This zone includes marine and eolian deposits thatcomprise loose to very loose sands that are prone to liquefaction, and swampy soil deposits with long periods ofvibration.
Steep slope hills prone to suffer external geodynamic
phenomena such as rock block falling are also consideredin this zone.

i) Zone 4 includes areas covered by problematic soils.
Therefore, according to the Peruvian National Standard E-050 Soil and Foundations [1997] any construction project must have a specific geotechnicalstudy.

Zone 5This zone includes the debris and waste materials identified at isolated points of the city, and old mining excavations.
According to the Peruvian National Standard E-050
Soil and Foundations (1997), in this zone, building construction is not allowed since the material shows a badseismic response, and it is not possible to estimate thebearing capacity on landfills.
Historical cases have demonstrated that buildings constructed over this kind of soils suffer large settlements andsevere damage. If these areas are required for urban development uses, it is suggested the removal of the debris andlandfill, and the replacement with suitable materials. The
urban development will be possible only if the results ofthe soil mechanics studies support this decision. Sanitary
landfill cannot be considered for urban development.

7. Conclusionsa) At Lima, the alluvial gravel, composed of a medium
to dense coarse gravel with a sandy matrix covers
most of the area of the city. This soil shows highallowable bearing capacity for foundation purposes.
b) At Callao, on the other hand, clayey, organic, andsandy deposits predominate. These deposits were
found until the maximum exploration depth of fifteen meters.
c) The S-wave velocity profile obtained at Central Lima
city shows that the soil is rigid below few meters
depth. The short values of the fundamental periodof vibration support this rigid characteristic.
944e) The area of study was divided into five zones according to their geotechnical and dynamic characteristics.

h) Zone 3 is made up of soils with large periods of vibration, which is associated with bad geotechnicalcharacteristics.

j) Zone 5 is identified at specific places, and building construction in this zone will be possible only
if landfill is removed and technical studies support
this decision.
Acknowledgements
The authors want to express their deep gratitude to Armando Sifuentes, Carlos Gonzales and Rocio Uriarte, as well as to others research assistants of CISMID who at different periods of the
project collaborated with dedication to fulfill the outlined objectives.

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Development of a Seismic Microzoning Map for Lima City andCallao, Peru[10] Y. Nakamura, “A method for dynamic characteristics estimationof subsurface using microtremors on the ground surface,” Quarterly Report Railway Technology Research Institute, Vol.30, No.3,
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Name:
Diana Calderon

Affiliation:
Assistant Professor, National University of Engineering

Address:
Tupac Amaru Av., Rimac, Lima, Peru

Brief Career:2012 Ph.D. Eng., Chiba University
2012- Assistant Professor, National University of Engineering

Selected Publications:• “Study of the Amplification and Noise from Microtremor Arrays andSeismic Records in Lima Peru,” Journal of JAEE, Vol.12, No.2, pp. 1-12,
2012.

Academic Societies & Scientific Organizations:• Peru-Japan Center for Seismic Research and Disaster Mitigation, Peru

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