Strong motion estimation and seismic
microzoningii iin major
j cities
iti iin P
Peru
S. Nakai, and T. Sekiguchi (Chiba Univ.),
H A
H.
Araii (BRI)(BRI),
N. Pulido (NIED),
H. Yamanaka (Tokyo Inst. Tech.),j ((BRI)) and,Y. Fujii
Y. Yagi (Tukuba Univ.)
JUNE 10, 20091

Large earthquakes in subduction zone
1960 01 13 Arequipa
Arequipa, Peru M7M7.5
5
1966 10 17 Near the Coast of Peru M8.1
1970 05 31 Chimbote, Peru M7.9
1974 10 03 Near the Coast of Central Peru M8.1
2001 06 23 Near the Coast of Peru M8.4
2007 08 15 Near the Coast of Central Peru M8.02Ground motion&existing microzoning map(EERI 2007)(EERI,2007)

Rimac

Aug,g 17, 2007

CallaoLa Molina
San Isidro

Rimac, San Isidro: ggravel
La Molina: shallow soils (<100m)
Callao:soft soils
3

Researches in ground motion team
 Fault models for large
g scenario earthquakes
qalongg thesubducting plate with cooperation of Tsunami group.
 Installation of strong motion instruments on ground or BF
off buildingsb ildi(3 areas off LiLima, Pi
Pisco, anddAArequipa)i ) Geophysical and geotechnical surveys for shallow anddeep S-wave structure including borehole loggings
 Analysis of earthquake data from small events topand site amplificationpcharacterize source,, path
 Calculation of site amplifications for microzonation map
p failure from g
geotechnical surveysy Estimation of slope
 Strong motion simulation based on hybrid approach oftheoretical and empirical methods
4Source model
Gathering
g of information on
historical seismicity, geology,
focal mechanisms andavailable
il bl studies
t di on seismoitectonics.
Gathering of strong motion
records of earthquakes.
Elaboration of several
scenario earthquakes fromthe subduction of the Nazca
plate
l t thatth t could
ld likely
lik l affect
ff tLima, Pisco and Arequipa
citiescities.

2007/8/15
Acc in Lima

5

Strong motion simulation
Simulation of broadband strong
gmotion on engineering bedrock fromdifferent scenario earthquakes inLima, Pisco and Arequipa areasusing a hybrid approach.
3D FDM iin llong-period
i d range, andd
stochastic method using 1D modelin short-period range)Calculation of surface motion
considering 1D amplification insurface layers due to input motion
gg bedrockon engineering

surface
Surfacelayers
Eng. bedrock
VS0.4km/s
0 4km/s
Seismic bedrock
VS3.0km/s
3 0km/s

ShortLong

6

Strong motion observation
Existing strong motion stations
Lima: 14 stations (4 by CISMID)
Arequipa: 4 stations
Pisco: ?
In our study, two plans are proposed;
1) Modern strong motion instruments
Lima, Pisco, Arequipa(e.g.,3sites/area)
2) Temporary earthquake observations
using small-aperture array in Lima

Lima stations

We will discuss with members of other groups and Peru for thefinal plan (1 or 2 or 1&2) considering plans of the other projects
7

Analysis of small earthquake data
 Estimation of source characteristics of small events, Qf t forfactorf theth crustt andd mantle,
tl siteit amplification
lifi ti Estimation of envelope function of small events for use ofstochastic Green’s
Green s function in strong motion calculation
 Exploration of deep S-wave velocity profiles using
earthquake datadata, such as receiver function
function, phase velocity
and Rayleigh wave ellipticity
 Validation of geological models from geophysical andgeotechnical surveys using 1D site amplification or 3D
simulation of moderate events
 Examination of applicability of existing attenuation
equations8Geophysical & Geotechnical surveys
Soil Investigation
BoringLaboratory Test

Surface Wave Method(Short Period Range)

Microtremor measurement
Seismic Observation(Long Period Range)

Geological map
S il Structure
SoilSt tModelM d l
1D, 2D, 3D

Source model

Strong motion simulation

Model validation withearthquake data
Seismic Micro Zoning
Ground Motion
Liquefaction

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Surface Wave Method
 To estimate the shallow soil profiles and the soil
amplification characteristics,
surface wave method including microtremor
measurement will be conducted.
 Microtremor measurement with one three
three-component
component
sensor and linear array measurement with several verticalsensors will be conducted.

Sensor

Surface Wave
excited by
Artificial Vibration

Linear Array
Observation Equipment
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Seismic Risk of Slopes (1) In Lima, there are many steep
slopes where houses are denselyb iltbuilt.
 Ground motion tends to becomelarge
g due to groundg
irregularity
gy(slopes), which may cause failure orlandslide during an earthquake.

Densely built houses in Lima

Slope failure during EQ
11Seismic Risk of Slopes (2) The research plan includes:
 Select a few target sites in Lima, where houses aredensely built.
 Collect soil investigation data, if any.
 Conduct soil investigation,investigation if possiblepossible.
 Conduct a series of microtremor measurements.
 Construct soil models
and perform finite
element analyses.
 Evaluate seismic risksof the area with slopes
based on these data
alonglwith
ith ththe results
ltfrom other groups inthis project.
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