Strong Motion Estimation andSeismic Microzoningin Major Cities in Peru
Research Plan of G1 Groupp(Seismic Motion and Geotechnical / SMGT Group)Japanese members:
S. Nakai, T. Sekiguchi, D. Calderon (Chiba Univ.),
H. Yamanaka (Titech),
H. Arai, S. Koyama (BRI),
N Pulido (NIED)N.
Peruvian members:
Z. Aguilar, F. Lazares, D. Luna, L. Chang, P. Peri, R.
Piedra (CISMID),
H. Tavera, I. Bernal, L. Ocola, J. Gomez (IGP)
March 15, 2010
1Overall Flow Chart of the Project2Strong Motion Prediction

Fault Model → Deep Soil Structure → Surface Soil Structure
3Research Topics of G1 (SMGT) Group4

Strong Motion Records and Historical
Seismicity
1960 01 13 Arequipa, Peru M7.5
1966 10 17 Barranca M8.1
1970 05 31 Chimbote, Peru M7.9
1974 10 03 Lima M8.1
2001 06 23 Atico M8.4
2007 08 15 Pisco M8.0
2010 02 27 Offshore Maule, Chile M8.8

5Strong Motion Observation

6

Source Model and Strong Motion Simulation

Construction ofSource Model

Strong Motion Simulation
by 3D Finite Difference Method
7

Surface Soil Investigation (1)New index has to be introduced.

Lima, Peru

Chiba, Japan8

Surface Soil Investigation (2) Borehole and PS logging will be conducted at several
sites to examine the soil profiles and the soil
properties of the surface soil.

BoreholePS Logging

Surface Wave Method
 In order to estimate the shallow soil profiles, thesurface wave method will be conducted, in addition to
single point / array microtremor measurements.
S-Wave Velocity ProfileSensor

Linear Array

Surface Wave
excited by
Artificial Vibration

Array Measurement of Microtremors
 Array measurements ofmicrotremors areconducted in severalllocations
tiiin orderd tto
estimate the deep soil
profile of the target site in
1D, 2D or 3D.

Array of sensors

Strong Motion Prediction

Fault Model → Deep Soil Structure → Surface Soil Structure→ Strong Motion Prediction Analysis based on Wave Prop. Theory
12

Prediction of Ground Motions

13

Prediction of Response of Buildings

14

Prediction of Tsunami Run-up

15

Seismic Risk of Slopes
 In Lima, there are many steep slopes
where houses are densely built.
 Ground motion tends to become large
ground irregularitygy ((slopes),p ),due to gwhich may cause failure or landslide
during an earthquake.

Densely built houses in Lima

Slope failure during EQ

Seismic Microzoning

17

Summary: Research Plans of G1 Group Construction of fault models for large scenario earthquakes along
the subducting plate.
 Survey of historical seismic activities.
 Strong motion observations by installing seismometers.
 Construction of deep and shallow soil models.
 Geophysical and geotechnical surveys including boreholeand PS loggings.
 Surface wave and microtremor measurements.
 Analysis of earthquake data from small events.
 Construction of microzonation maps.
 Strong motion simulation based on fault models anddeep/shallow soil models.
 Estimation of amplification due to surface soils.
 Estimation of slope failure.

18

19

Strong Motion Simulation
Simulation of broadband strong
motion on engineering bedrockfrom different scenario
earthquakes in Lima, Pisco andArequipa areas using a hybrid
approach.
3D FDM in long-period range, andstochastic method using 1D modelin short-period range).
Calculation of surface motion
considering 1D amplification insurface layers due to input motion
on engineering bedrock.

surface
SurfacelayersEng. bedrock
VS0.4km/s
Seismic bedrock
VS3.0km/s

ShortLong20

Seismic Observation
 Seismic observation is also carried out to examine theeffect of surface soils by using the array of sensors in
Lima city.
Mountain

LimaObservation
Point
Seismometer

Pacific Ocean
10km

Use of Converted
Wave for Vs-profiling

PsS

Many later phases
can beb seen b
betweeninitial P- and S-waves.
P waveS waveSurface

Interface dPpPds PpSds Pp PsPSp

StationInitial P-wave generates
P- and S-waves at each
V 3 0(k / ) interface.
Vp=3.0(km/s)
ifTheTh PP anddS
SVs=1.5(km/s) waves at surface appear
ρ=2.0(g/cm3) in vertical and radialcomponents. These data
H =2.0(km)are used to obtain deep
Vp=4.6(km/s) Vs profile.
Vs=3.0(km/s)
ρ=2.5(g/cm3)

Research Plans of SM/GT Group Fault models for large scenario earthquakes along thesubducting plate with cooperation of Tsunami group.
 Installation of strong motion instruments on ground or BFof buildings (5 locations in Lima at first)
 Geophysical and geotechnical surveys for shallow anddeep S-wave structure including borehole loggings
 Analysis of earthquake data from small events tocharacterize source, path and site amplification
 Calculation of site amplifications for microzonation map
 Estimation of slope failure from geotechnical surveys
 Strong motion simulation based on hybrid approach oftheoretical and empirical methods
23Analysis of Small Earthquake Data
 Estimation of source characteristics of small events, Qfactor for the crust and mantle, site amplification
 Estimation of envelope function of small events for use ofstochastic Green’s function
 Exploration of deep S-wave velocity profiles using
earthquake data, such as receiver function, phase velocity
and Rayleigh wave ellipticity
 Validation of geological models from geophysical andgeotechnical surveys
gy using
g 1D site amplification
por 3D
simulation of moderate events
 Examination of applicability of existing attenuation
equationsEstimation of Empirical Site Amplification fromfrom Earthquake Data
Case for Tokyo areaby Yamanaka (2009)

Site amplification

103
INVRegression

1Qs

Amplification

10TKYH13
TKYH12
TKY2080
TKYH110.1

1210

Qs=101f0.67
110Freq (Hz)10Q-value for propagation path incrust and mantle

Freq (Hz)Inversion of Rayleigh Wave Phase Velocity
for Exploration of Deep Vs Profile
0Parameterization 3

Find a model that fit observation!

NGT

Phase veloocity (km/s)

-2.5

L4-1

L3
L2
S3-0.5

S7
S2

13

L5-1.522

L6

L7-2NS(kmm)

Depth (km)

1OBS
INV

S40NGTS5

S6S1(L1)0.52NGT
40123Vs (km/s)

4

Estimation of
amplification withnumerical simulation

00123Period (s)

41.5

10.5
EW (km)50-0.5-1

2
Phase Velocity(km/s)

Joint Inversion of
Phase Velocity andReceiver Function(Kurose and Yamanaka, 2006)

2100

214
6
Period(s)680

1 2 3Vs(km)

48
Obs.
Inv.

4
Abs. Amp..

Depth(km)

0Obs.
Inv.

05
0.5

0-0.5

0246Time(s)8Geophysical & Geotechnical surveys
Soil Investigation
BoringLaboratory TestSurface Wave Method(Short Period Range)

Microtremor measurement
Seismic Observation(Long Period Range)

Geological map
Soil Structure Model
1D, 2D, 3D

Source model

Strongg motion simulation

ModelMd l validation
lid ti withithearthquake data
Seismic Micro Zoning
Ground Motion
Liquefaction

28

10

Seismic Micro Zoning Seismic Micro Zoning will be
improved based on various
in-depth surveys.
 2 or 3-Dimensional soil
structure model will be
constructed.

2-Dimensional Soil Structure Model

Seismic Hazard Map in Lima(CISMID)

Seismic Risk of Slopes (2)2100Acc. (cm/s )200Foot0-200
20200

Shoulder

0-200

Fourier Spectrum

2Acc. (cm/s ) It is known that the response due to an earthquake tends tobecome large at the shoulder of a slope.

3040

5070 (s)

60

20

30

40

50

101Ratio = Shoulder / FootShoulder
Foot0.102

4681012 (Hz)6070 (s)Seismic Risk of Slopes (3) One of the reasons is believed that the surface soil of a slope is“weakened” due to weathering.
 The existence of this weakened soil has a negative influence topthe seismic risk from various aspects.

H/V Spectral Ratio
 This is another example of the effect of a slope. The results ofmicrotremor measurement are also affected by the slope.

24.2HzHorizontal-to-V
Vertical
Amplitude RRatio

Horizontal-to-V
Vertical
Amplitude R
Ratio

210036912Frequency [Hz]1510036912Frequency [Hz]15

Research Plan for Evaluation of Risk of Slopes The research plan includes:
 Select a few target sites in Lima, where houses are denselybuilt.
 Collect soil investigation data, if any.
 Conduct soil investigation, if possible.
 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
along with the resultsfrom other groups inthis project.