1. Shear Wave Velocity- and Geology-BasedShear Wave Velocity and Geology Based
Seismic Site Classification of Port-au-Prince
Brady R. Cox, Ph.D., P.E.Brady R. Cox, Ph.D., P.E.
The University of Arkansas
Department of Civil Engineering
Geotechnical Earthquake Engineering for Seismic Design Workshop,
Department of Civil Engineering
Port-au-Prince, Haiti, November 18-19, 2010

2. Seismic Site Classification
Required by Seismic Provisions in Building CodesRequired by Seismic Provisions in Building Codes
IBC (2009) ASCE 7-05

3. IBC & ASCE Codes – Seismic Site Classification
Vs N SuSite Class: A - F
> 1 500 m/s> 1,500 m/s
760 – 1,500 m/s
360 – 760 m/s
180 360 /180 – 360 m/s
< 180 m/s
V i f d b it i di tl l t d t th
ASCE 7-05
Vs is preferred because it is directly related to the
shear stiffness of the soil deposit (G = Vs
2)

4. Vs Measurement Locations in Port-au-Prince
MASW used to determine Vs profiles at 36 locations
across Port-au-Prince in April, 2010
Vs (Vs30) values calculated from the Vs profiles at
each test location
Show testing pictures
Show site locations in Google Earth with Vs values
and associated Seismic Site Classification
Sit Cl BSite Class B
Site Class C
Site Class D/ESite Class D/E

5. MASW Surveys in Port-au-Prince
For Seismic Site Classification A - E

15. Demo Locations, Vs Profiles, Vs Values
Shear Wave Velocity (m/s)
0 0
4003002001000
Shear Wave Velocity (m/s)
20
10
5
60
40
Depth(ft)
15
Depth(m)
80
25
20
100 30
Vs = Vs30 = 250 m/s
160012008004000
Shear Wave Velocity (ft/sec)
Site Class D

16. Locations Relative to Geology

17. Vs – Geology Correlations
Shear Wave Velocity (m/s)Shear Wave Velocity (m/s)
150010005000
Shear Wave Velocity (m/s)
Median profile
with +/- 1 sigma
0
150010005000
Shear Wave Velocity (m/s)
TL# 8
TL# 9
TL#10
20
TL#10
TL# 11
TL# 13
TL# 15
TL# 17
TL# 32
40
epth(ft)
Vs profile comparison for
geologic unit Qpf
80
60
De
100
80
6000400020000
Shear Wave Velocity (ft/sec)
6000400020000
Shear Wave Velocity (ft/sec)

18. Median Vs Profiles for all Geologic Units

19. Geology – Site Classification Correlations
Geology
Number of
Profiles
Median Vs,30m
(m/s)
NEHRP Site
Class( )
Af 3 278 D
Qham 3 335 D
Qh 2 1 346 DQht2 1 346 D
Qphf 2 480 C
Qpf 8 499 CQp
Ppf 1 504 C
Pf 7 564 C
b 3 CMpb 3 513 C
Lmst 1 1014 B

20. Seismic Site Classification Map of Port-au-Prince

21. Some Potential Refinements?
Shear Wave Velocity (m/s)
0 0
4003002001000
Shear Wave Velocity (m/s)
20
10
5
S ft
60
40
Depth(ft)
15
Depth(m)
Soft
Clay???
80
25
20
Site
100 30
Vs = Vs30 = 250 m/s
Class D
Site Class D or E?
160012008004000
Shear Wave Velocity (ft/sec)

22. IBC & ASCE Codes – Seismic Site Classification
Vs N SuSite Class: A - F
> 1 500 m/s> 1,500 m/s
760 – 1,500 m/s
360 – 760 m/s
180 360 /180 – 360 m/s
< 180 m/s
ASCE 7-05

23. Questions?Questions?