Microtremor measurements
and seismic zonation in Peru
H. Yamanaka, K. Chimoto, K. Araki(Tokyo Inst. Tech)
S. Matsuzaki, D. Calderon, S. Nakai, T. Sekiguchi(Chiba Univ)
S. Quispe, Z. Aguilar, F. Lazares A. Balvin, J. Flores,
and A. Sifuentes(CISMID, UNI)

Contents
Microtremor observation in PiscoStatus for a year after installation ofnew strong motion sensors in Lima
Application of seismic interferometry tocontinuous recording dataResults of analysis for earthquake datain Lima by Selene Quispe andmicrotremor data by Diana Calderon

Microtremor exploration in Pisco
Jan 18-19, 2012 Triangular arrayswith 4 sensors

21354

Microtremors obs in Pisco

Site Length (m)1 3,10,30
2 3,8,20,50
3 3,8,16
4 3,10,20
5 3,8,20

2Results of analysisof array data

14350PISCO

600

0.6Phase velocity (m/s)

site1
site2
site3
site4
site5

0.8

0.4
0.2
0.005

1015
Freq. [Hz]146OBS
INV

500

8400

100 200 400 600 800
Vs (m/s)

300200
1000220site 1
4 6 810
Freq (Hz)30 50S-wave velocity profiles
Site AVs30 AVs10
1345
191
2455
225
345309
439
228

164
208
160

2143

50PISCO5
Depth (m)Phase Velocity [km/s]

1.0Depth (m)21015201234525
300 200 400 600 8001000
Vs (m/s)Site amplifications
PISCO JAN2012

21
4

Amplification

Dominant periods are similar
at all sites. The site 5 may beslightly difference.

312
3
4
510

5

1
0.01

0.1
Period (s)1Strong motion sites

10 strong motion instruments areprepared in the projectTemperature of theinstruments is very highunder strong sunshine

New strong motion instruments
Acc. Sensors withrecording unit
(2GB CF mem)

GPSContinuousdata stored inCF (60MB/day)PC①transfer realtime data
②event trigger data (5min)sensor

HDD-less PC for
factory use
Backup compressed
continuous data oncea day

UPS battery

SSD 128GB

Internet access

5-6 hours

USB mem 32GB
Change memory to retrieve data

Spectra at different levels
Continuous data provide records before and during event(M4.8, h54km), its aftershock and ambient noises arecompared.

2011121900.VES2

10ambient (-200s)
P&S-waves
Coda1(100s)
Coda2(200s)
coda3(300s)

2

Fourier spectra (cm/s *s)

Ambient noises are enough larger than instrumental
noise levels to use the records as microtremor data1010

coda3(300s)
coda2(200s)
coda1

aftershock(100s)

10

P&S-waves-1

10

ambient(-200s)

-2

10

0.1

1
Period (s)10Seismic interferometric analysis ofcontinuous recording in Limasources

×× Cor×× ×××× relation A
B× A B××××××××G (τ)   A t  τ B t  dt
×××××× ×Contribution from sources in yellow zone
remain with constructive interferences

Every one hour data

AB

Example in Tokyo
showing surface wave propagation

Correlation between all station pairs Lima
BEV - VES
32days

T = 2 – 10s

T = 2– 10s

Analysis of ground motion data for site
amplifications by S. Quispe (CISMID)
Spectral separation technique was applied to theexisting strong motion data before the project.
30 records at 5 sites during 11 earthquakes wereavailable for Lima area.
Only onerecord at CSM

CDLCIP as reference site

Source, Path and Site effects reference Vs800m/s
CSM station
10.0

10.0

10.0

Site amplification factor

Site amplification factor

MOL station

Site amplification factor

CAL station

1.0

1.0

Gj (f)

0.1

1.0

Gj (f)

0.1
0.1

1.0

10.0

0.1
0.1

1.0

10.0

Frequency (Hz)Frequency (Hz)
1.E+22

1.E+03

0.1

1.0

10.0

Frequency (Hz)20050725 (ML=4.0)
20061211 (ML=4.2)
20060525 (ML=4.5)
20080607 (ML=5.0)
20080329 (ML=5.3)
20050302 (ML=5.7)

Seismic momet density function
Mi(f)Qs-value (This study)
1.E+21

Qs(f) = 80.4f0.63
R² = 0.7974

Gj (f)

Qs value

1.E+201.E+19

1.E+02

1.E+18Q-value
1.E+01

1.E+17

Source1.E+160.1

1.0Frequency (Hz)

10.0

0.1

1.0

Frequency (Hz)

10.0

7

From PhD Thesis by D. Calderon
at Chiba Univ

Amplifications from microtremor array measurements
Transfer Functions forshallow and deep soils

16Information available for empirical equation
AVS10=F(soil type, dominant freq, elevation)
Amplification (freq=1-20Hz) =G(AVS10)

Amplification
4.Period (T)orSoiltype Dominant
PeriodElevation
3.Soil Type
5. Elevation (Z)Frequency (f)SOILTYPE

17Conclusions
 Vs-profiles were estimated at 5 sites in Pisco.
Amplifications are the similar.
 Continuous records from strong motion
observation were accumulated. Small troubles
must be resolved for stable observation.
 Preliminary analysis using seismic interferometryshows difficulty to retrieve surface waves in Lima.
 Preliminary analysis of strong ground motion dataaround Lima was conducted to know source, pathand site effects.
 Site amplification map was successfully
constructed in entire Lima area.
 Strong motion simulation was conducted for
scenario earthquake in Lima