raid/vol6/convert/1020186/0000150272 -101 report documentation page 1. reportnsfjra-761696no. 4....
TRANSCRIPT
, )
PB 301164
) Prepared for theNational Science Foundation
under Grant GI 44056
UCLA-ENG-7653JUNE 1976
R.T. EGUCHIK.W. CAMPBELL
C.M. DUKEA.W.CHOW
J. PATERNINAREPRODUCED BY
NATIONAL TECHNICALINFORMATION SERVICE
u. S; DEPARTMENT OF COMMERCE_ SPRINGFIELD, VA. 22161 _
PRINCIPAL INVESTIGATOR: C. M. DUKE
SHEAR VELOCITIES AND NEAR-SURFACE GEOLOGIES ATACCELEROGRAPH SITES THAT RECORDED THESAN FERNANDO EARTHQUAKE
,}
ASRA INFORMATION RESOURCESNATIONAL SCIENCE FOUNDATION
UCLA • SCHOOL OF ENGINEERING AND APPLIED SCIENCE
50272 -101
REPORT DOCUMENTATIONPAGE
1. REPORT NO.
NSFjRA-761696,
4. Title and Subtitle
Shear Velocities and Near-Surface Geologies at AccelerographSites That Recorded the San Fernando Earthquake
7. Author(s)
__~~~.__Eguchi~ __K W. Carnpb~ll, c. r~. Duke, et al9. Performing Organization Name and Address
University of CaliforniaSchool of Engineering and Applied ScienceEarthquake LaboratoryLos Angeles, California 90024
5. Report Date
June, 19766.
8. Performing Organization Rept. No.
UCLA-ENG-765310. Project/Task/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G) GI44056f----------------- -. --.
12. Sponsoring Organization Name and Address
Engineering and Applied ScienceNational Science Foundation1800 G Street, N.W.Washington, D.C. 20550
15. Supplementary Notes
16. Abstract (Limit: 200 words)
(EAS)13. Type of Report & Period Covered
14.
This study seeks accurate near-surface shear-wave velocity data at several sitesin the Los Angeles area. These data currently are being used to correlate bothseismic velocity and strong-motion indices with local near-surface site conditions.Included is a compilation of refraction seismic survey and geotechnical data on thirtythree sites selected within the Los Angeles, California area. The sites were chosenon the basis of two criteria: (1) their relative closeness to strong motion accelerographs that recorded the 1971 San Fernando earthquake; and (2) their geologicrepresentativeness. The main areas of concentration for these surveys were WilshireBoulevard, Downtown Los Angeles, and Pasadena. Using the refraction technique,shear wave velocities and layer thicknesses down to approximately 70 feet weredetermined. Geotechnical data on geology, age, lithology, and depth, from severalsources, were compiled for each site. Also provided is a summary of new fieldtechniques developed and applied during the study. Results for this work phaseare included in Appendix A.
1------------ ----------------~------- --------------- - - ..----~---------------j17. Document Analysis 3. Descriptors
EarthquakesSecondary wavesShear propertiesSeismic surveys
b. Identifiers/Open·Ended Terms
Los Angeles, CaliforniaShear velocitiesSan Fernando Earthquake
c. COSATI Field/Group
18. Availability Statement
NTIS
(See ANSI-Z39.18)
I--------------------"---~11-9-.-Se-c-ur-itY-CI;ss (This Report)
I
120. Se~';rity Class (This Page)
See Instructions on Reverse OPTIONAL FORM 272 (4-77)(Formerly NTIS-35)Oepartment of Commerce
~APITj\;__ S-'(:) 1c.i\'iS (i,\\'_h_'I~1 iNC.6110 EXECUTiVE BOULEVARD
SUITE 250ROCKVILLE, MARYLAND 20852
SHEAR VELOCITIES AND NEAR-SURFACE GEOLOGIES AT
ACCELEROGRAPH SITES THAT RECORDED THE
SAN FERNANDO EARTIIQUAKE
R.T. EguchiK.W. CampbellC.M. DukeA.W. ChowJ. Paternina
PRINCIPAL INVESTIGATOR: C.M, DUKE
The research reported here was supportedby the National Science Foundation, underGrant GI 44056
Any opinions, findings, conclusionsor recommendations expressed in thispublication are those of the author(s)and do not necessarily reflect the viewsof the National Science Foundation.
Earthquake LaboratorySchool of Engineering and Applied Science
University of CaliforniaLos Angeles, California
~ .., I
UCLA-ENG-7653JUNE 1976
Abstract
Thirty-three shallow geophysical surveys were conducted at sites
affected by the San Fernando earthquake of February 9, 1971. These surveys
yielded shear wave velocities and layer thicknesses down to approximately 70
feet. Geotechnical data on geology, age, lithology and depth, from several
sources, were compiled for each site.
Also contained is a summary of new field techniques that were developed
and applied during the course of the study.
PrecetiJ"109 page blank
iii
List of Figures.
List of Tables
Introduction
Procedure.
Analysis
Results.
Site Sheets.
References
Appendix A
Appendix B
Appendix C
Table of Contents
v
Page
vii
ix
1
3
5
7
21
23
25
59
63
Preceding page blank
V\
List of Figures
Page
Fig. lAo Site Locations for Los Angeles and Vicinity. . 8
Fig. lB. Site Locations for Central Los Angeles . 9
Fig. B-l. Time-Distance Curves (Asphalt - Soil). . 61
Fig. B-2. The Effect of Impact Intensity on Wave Amplitude . 62
Preceding page blank
vii
V'li
List of Tables
Table 1. Site Information. •
Table 2. Local Geology . . ••
Table 3. Layer Properties ••
ix
Page
10
13
17
Preceding page blank
x
Introduction
This report contains a compilation of refraction seismic survey and
geotechnical data on 33 sites selected within the Los Angeles, California
area. The sites were chosen on the basis of two criteria; (1) their rela
tive closeness to strong motion accelerographs that recorded the 1971 San
Fernando earthquake, and (2) their geologic representativeness. The main
areas of concentration for these surveys were Wilshire Blvd., Downtown Los
Angeles, and Pasadena.
Using the refraction technique, shear wave velocities and layer
thicknesses down to approximately 70 feet were determined.
The previous report, by Duke et al. (1971) at D.C.L.A., provided seismic
velocity and geologic data for sites, numbered 1 through 30, in the San
Fernando earthquake area. The same basic refraction techniques used in the
previous study for measuring shear-wave velocities were utilized in the pre
sent program conducted in the Summer of 1975. To provide continuity between
the two reports, the sequencing of site numbers in this report begins with
Site 31. Appendix A provides the results of this phase of the work.
The primary purpose of this study is to obtain accurate near-surface
shear-wave velocity data at several sites in the Los Angeles area. These data
are currently being used to correlate both seismic velocity and strong-motion
indices with local near surface site conditions.
1
Procedure
The seismic refraction technique is based upon the principle that
horizontal shear waves traveling through the ground are reflected and refracted
by soil layers of different velocity. Although other methods to determine
velocity exist, such as down-hole and cross-hole surveys, the refraction method
has the advantage of requiring less manpower and less field equipment.
The basic procedure is one that has been used previously at D.C. L.A. to
obtain geophysical site data. It consists of horizontal blows to a heavy
wooden plank from a 25-pound wooden mallet. The plank is laid out so that it
is perpendicular to the geophone line. The front wheels of an automobile
are then placed on the plank to insure maximum ground contact. The energy
pulses from the transverse shots are then picked up by horizontal geophones
which, in turn, are recorded by an oscillograph. For a more complete descrip
tion of the technique References 3 and 4 may be examined.
In the process of conducting the present surveys, two new techniques
were examined and applied:
conducting surveys on asphaltic surfaces
examining the effect of impact intensity on records
The new techniques were examined because (1) their application would make the
surveying of an asphalt-paved site possible, and (2) they would preclude,
in some cases, the need for larger energy sources. Results are given in
Appendix B.
Preceding page blank3
+
Analysis
The records obtained in the field refraction surveys consisted of a
series of 12 traces and a time break from an oscillograph camera. The
camera recorded a time mark for every hundredth of a second.
Since most sites were noisy, it was frequently difficult or impossible
to distinguish a clear onset. As a result, for some records the first
distinguishing wave form of a trace had to be used in place of the onset.
In most cases this peak or trough was very close to the onset, and in all
cases it was as close to onset as possible. Since the frequency content of
a wave form changes with distance from the source, the velocity resulting
from using peaks or troughs will vary somewhat from that resulting from using
true onsets. However, a careful comparative study showed that the error
involved is considerably less than that involved in determining items from
the records or drawing a straight line through the corresponding points when
plotted on a travel time graph.
The points derived from the records in the above manner were plotted
on a time-distance graph. When a series of straight lines was drawn through
the plotted points, the apparent velocities of the resulting layers were
computed as the inverse of the slopes of these lines. It was estimated that
a precision of from 4 to 6 percent was obtained for the velocities. Critical
distances also were read off to the intersections of straight line segments,
with a precision estimated to be about 20 percent.
These graphs contained information from shots at both ends of the shot
line. Thus, both up-dip and down-dip apparent velocities and intercept times
were found. This information and the computerized algorithm of Mooney (1973)
yielded the thickness of each layer at both ends of the shot line and the
true layer velocities. For a more complete descripU (W' J,; « nage \l\at\~YteC8U\t\D "
in seismic surveying, see Reference 6.
5
tiques
Results
The general locations of the sites are presented in Figures lA and lB.
The sites range geographically as far north as the OSO Pumping Plant in
Gorman down to the Long Beach State University in Long Beach. Figure lA
presents a Los Angeles Vicinity map which includes those sites outside the
Downtown and Wilshire areas. Figure IB is an insert to Figure IA and locates
sites in Downtown Los Angeles and along the Wils&ire Blvd corridor. These
figures are meant to serve as general location maps. To obtain the exact
locations, the site maps in Appendix A or the corresponding map and grid
numbers of the Thomas Bros. Maps (Table 1) should be used.
General information about the location of each site is contained in
Table 1. In this table, the sites are given sequence numbers which corres
pond to the numbers in Figures lA and IB and in the site sheets given in
Appendix A. The sequencing of site numbers begins with Site 31. A total of
33 sites were surveyed. In addition, page and grid numbers of the Thomas
Bros. Maps for Los Angeles are given. These can be used to locate the site
with respect to individual streets.
Information about the length and geophone spacing of each survey is
also contained in Table 1. The horizontal lengths range from 100 to 360 feet,
the value depending on the local site conditions. For most of the downtown
and Wilshire sites, the average length was approximately 120 to 130 feet.
Longer spreads could not be obtained because of local noise problems (i.e.,
passing traffic). For sites located away from the metropolitan area, lengths
ranging from approximately 165 feet to 360 feet were attained. In general,
the spacing of the geophones was set at 10 or 15 feet. By using the shorter
spacings, more detailed information was gained about the thinly bedded strata
close to the ground surface.
Preceding page blank7
61
-
54-
-__----40 585"6 SEE ENLARGEMENT
- OF THIS AREA
SCALE INKILOMETERS
SCALE IN MILES
o 2 4 6 810I I I , I I
o 4 8 12161'1 I I! I II !
Figure 1A. Site Locations for Los Angeles and Vicinity.
8
coE
------I-----I----~l----+--'
SCALE IN MILES012I I
012I I I I
SCALEKILOMETERS
Figure 1B. Site Locations for Central Los Angeles.
9
TABLE 1
SITENO. LOCATION
SITE INFORMATION
MAP1
NO. LOCATION
SPREADLENGTH SPACING
ft ft
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
MacArthur Park, L.A.
Ambassador Hotel, L.A.
Nor.mandie Ave. andSixth St., L.A.
Grand Ave. and ThirdPlace, L.A.
First St. and Hope, L.A.
Figueroa St. and ThirdSt., L.A.
Olympic Blvd. andValencia St., L.A.
750 S. Garland, L.A.
Von Kleinsmid Center,U.S.C., L.A.
Loma Vista Ave. and49th St., Vernon
3710 Wilshire Blvd., L.A.
Wilshire Blvd. andSpaulding, L.A.
Wilshire Bl~d. andMcCarthy Vista, L.A.
Wilshire Blvd. and PalmDr., Beverly Hills
435 Oakhurst Dr.,Beverly Hills
Santa Monica Blvd. andLinden Dr., Beverly Hills
Beverly Dr. and SuttonWay, Beverly Hills
44
43
43
44
44
44
44
44
44
53
43
42
42
42
33
42
33
A2
F2
E1
D3
D2
C2
B3
B3
/1.6
C3
E2
F2
F2
Cl
cs
Bl
B4
130
120
120
195
130
200
180
120
270
182
180
130
130
120
120
120
120
10
10
10
15
10
10
10
10
15
14
15
10
10
10
10
10
10
1These numbers and locations correspond to those listed in the Thomas Bros.Maps for Los Angeles and Orange counties.
10
TABLE 1 (Cont'd)
SITE INFORMATION
MAP SPREADSITE LENGTH SPACINGNO. r...0 CAT ION NO. LOCATION ft ft
48 D.C.L.A., Westwood 32 E6 360 30
49 Zonal St. and SanPablo St., L.A. 45 B2 130 10
50 Pomeroy St- and MarkSt., L.A. 45 A2 120 10
51 Cal Tech Athenaeum,Pasadena 27 C5 165 15
52 Cal Tech MillikanLibrary, Pasadena 27 C5 180 15
53 Cal Tech SeismologicalLaboratory, Pasadena 26 E6 100 10
54 Flintridge Riding Club,Pasadena 19 D4 240 15
55 900 S. Fremont, Alhambra 37 A5 180 15
56 Westchester Rec.Center, Westchester 56 A2 240 10
57 Malaga Lane, PalosVerdes Estates 72 D2 120 10
58 Whittier Narrows Dam 47 C6 165 15
59 Legg Lake Rec. Center 47 C5 200 15
60 OSO Pump Plant, Gorman 141 200 20
61 Pearblossom Pump Plant,PearblDssom 185 B7 220 20
62 Ocean Blvd. and CedarAve. , Long Beach 75 C5 120 10
63 Long Beach State Dniv. ,Long Beach 76 C3 130 10
11
Table 2 provides detailed descriptions of the local geology of the
sites. The geology and age were obtained from relevant geologic maps
(References 7,8,9,10,12,13) and soil logs. A description of the geologic maps
is provided in Appendix C. The lithology data were obtained directly off of
soil logs supplied by Le Roy Crandall and Associates, Los Angeles, and the
United States Geological Survey. Also obtained in this way were the thick
nesses of fill or the depths to specified layers. Note that, in most cases,
two sets of numbers are given in Table 2. The numbers in parentheses were
taken from the geophysical surveys while the others were taken from available
soil logs. The purpose of presenting both numbers was to provide a means
of checking geophysical data with geotechnical data. In most cases, as may
be seen, the agreement was quite good.
The layer velocities and thicknesses for each site are given in Table 3.
Due to noise problems, the largest number of layers that could be detected
was four. In some cases, only the thickness of the first layer could be
defined. Note, however, that velocity information for each layer is available
despite a lack of bottom boundary information.
12
TABL
E2
LOCA
LGE
OLOG
Y
SIT
EN
O.
LOCA
TIO
N--
31M
acA
rthu
rP
ark
,L
.A.
GEOL
OGY
Fil
lo
ver
Old
All
uv
ium
ov
erP
uen
teFm
.
AGE
Ho
loce
ne
ov
erP
leis
tocen
e("
\'t'
tn.'
\>'"
TTM
";1"
'\.,.
"_
"_
....
oJ
•..I
....
..._
_~J.~
LITH
OLO
GY
Sil
t,S
and
&C
lay
ov
erS
ilts
ton
e
DEP
THI
(3')
of
Fil
l;2
0'-
30
'(3
6')
...._
n1'
::'_
Lo
U...
.U~1.J.
I..C
,L·i
ll.
32 33
Am
bass
ador
Ho
tel,
L.A
.
Nor
man
die
Ave
.an
dS
ixth
St.
,L
.A.
Old
All
uv
ium
Ple
isto
cen
eo
ver
Pu
ente
Fm.
ov
erU
.M
ioce
ne
Rec
ent
ov
erO
ldH
olo
cen
eo
ver
All
uv
ium
ov
erP
leis
tocen
eo
ver
Pu
ente
Fm.
U.
Mio
cene
Sil
t,S
and
&C
lay
ov
erS
ilts
ton
e
Sil
t,S
and
&C
lay
ov
erS
ilts
ton
e
15
'-2
0'
(15
'-2
0')
toP
uen
teFm
.
(9')
toO
ldA
llu
viu
m;
25
'-3
0'
(27
')to
Pu
ente
Fm.
I-'
W
34G
rand
Ave
.an
dT
hir
dP
lace,
L.A
.O
ldA
llu
viu
mo
ver
Fer
nan
do
FIn.
Ple
isto
cen
eo
ver
Pli
ocen
eS
ilt,
San
d&
Cla
yo
ver
Sil
tsto
ne
(15
')to
Fer
nan
do
Fm.
35F
irst
St,
and
Hop
e,L
.A,
Com
pact
edF
ill
Ho
loce
ne
ov
ero
ver
Pu
ente
Fm.
U.
Mio
cene
Fil
lo
ver
Sil
tsto
ne
(8')
of
Fil
l
36
37 38
Fig
uer
oa
St.
and
Th
ird
St.
,L
.A.
Oly
mpi
cB
lvd
.an
dV
alen
cia
St.
,L
.A.
750
S.
Gar
lan
d,
L.A
.
Com
pact
edF
ill
ov
erO
ldA
llu
vi
umo
ver
Fer
nan
do
FIn.
Fil
lo
ver
Old
All
uv
ium
Old
All
uv
ium
ov
erF
ern
and
o, FIn.
Ho
loce
ne
ov
erP
leis
tocen
eo
ver
Pli
ocen
e
Ho
loce
ne
ov
erP
leis
tocen
e
Ple
isto
cen
eo
ver
Pli
ocen
e
Sil
t,S
and
&C
lay
ov
erS
ilts
ton
e
San
dan
dC
lay
wi
Gra
vel
San
dan
dG
rav
elly
San
do
ver
Sil
tsto
ne
(5'-
10
')o
fF
ill;
20
'-3
0'
(20
'-4
5')
toF
ern
and
oFr
o.
(5')
toO
ldA
llu
viu
m
15
'-3
5'
(15
')to
Gra
vell
yS
and
Lay
er;
55
'to
Fer
nan
do
Fro
.
lNo
te:
Val
ues
rep
rese
nt
thic
kn
ess
of
fil
lo
rd
epth
tosp
ecif
ied
lay
er.
Num
bers
inp
are
nth
ese
sare
tak
enfr
omg
eop
hy
sica
lsu
rvey
s;o
thers
are
tak
enfr
omso
illo
gs.
TABL
E2
(Co
nt'
d)
LOCA
LGE
OLOG
Y
SIT
EN
O.
LOCA
TIO
N
39V
onK
lein
smid
Cen
ter,
U.S
.C.,
L.A
.
GEOL
OGY
Rec
ent
ov
erO
ldA
llu
viu
m
AGE
Ho
loce
ne
ov
erP
leis
tocen
e
LITH
OLO
GY
Sil
t&
San
dwI
Gra
vel
ov
erG
rav
elly
San
d
DEP
TH
10
'-1
5'
(15
')to
Gra
vel
lyS
and
40Lo
ma
Vis
taA
ve.
and
49
thS
t.,
Ver
non
Rec
ent
All
uv
ium
Ho
loce
ne
San
dw
lGra
vel
NA2
l-'
.j:'
-
41 42 43 44 45 46 47
3710
Wil
shir
eB
lvd
.,L
.A.
Wil
shir
eB
lvd
.an
dS
pau
ldin
g,
L.A
.
Wil
shir
eB
lvd
.an
dM
cCar
thy
Vis
ta,
L.A
.
Wil
shir
eB
lvd
.an
dP
alm
Dr.
,B
ever
lyH
ills
435
Oak
hu
rst
Dr.
,B
ever
lyH
ills
San
taH
on
ica
Blv
d.
and
Lin
den
,B
ever
lyH
ills
Bev
erly
Dr.
and
Su
tto
nW
ay,
Bev
erly
Hil
ls
Old
All
uv
ium
Com
pact
edF
ill
ov
erO
ldA
llu
vi
um
Old
All
uv
ium
Rec
ent
ov
erO
ldA
llu
viu
m
Rec
ent
ov
erO
ldA
llu
viu
m
Rec
ent
Old
All
uv
ium
ov
erS
anta
Mon
ica
Sla
te
Ple
isto
cen
e
Ho
loce
ne
ov
erP
leis
tocen
e
Ple
isto
cen
e
Ho
loce
ne
ov
erP
leis
tocen
e
Ho
loce
ne
ov
erP
leis
tocen
e
Ho
loce
ne
Ple
isto
cen
eo
ver
Tri
ass
ic
Sil
t,S
and
&C
lay
Sil
t,C
lay
&S
and
ov
erA
sph
alt
icS
ands
Sil
t,C
lay
&S
and
ov
erA
sph
alt
icS
ands
Cla
yo
ver
Gra
vel
lyS
and
Sil
t,C
lay
&S
and
ov
erG
rav
elly
San
d
Sil
t,C
lay
&S
and
NA
NA (8')
of
Fil
l;2
5'
toA
sph
alti
cS
ands
45
'-5
0'
toA
sph
alti
cS
ands
15
'(1
0')
toG
rav
elly
San
d(V
ery
Den
se
Old
All
uv
ium
?)
10
'-2
0'
(20
')to
Gra
vel
lyS
and
NA (3'-
11
')to
Sla
te
NA2
:N
otav
ail
ab
le.
TABL
E2
(Co
nt'
d)
LOCA
LG
EOLO
GY
SIT
EN
O.
LOCA
TIO
N
48U
.C.L
.A.,
Wes
twoo
d
49Z
on
alS
t.an
dS
anP
ablo
St.
,L
.A.
50P
omer
oyS
t.an
dM
ark
St.
,L
.A.
51C
alT
ech
Ath
enae
um,
Pas
aden
a
52C
alT
ech
Mil
lik
an
Lib
rary
,P
asad
ena
GEOL
OGY
Fil
lo
ver
Rec
ent
All
uv
ium
Dil
uv
ial
So
ilo
ver
Pu
ente
Fm.
Old
All
uv
ium
Old
All
uv
ium
Old
All
uv
ium
AGE
Ho
loce
ne
Ho
loce
ne
ov
erU
.M
ioce
ne
Ple
isto
cen
e
Ple
isto
cen
e
Ple
isto
cen
e
LITH
OLO
GY
Sil
tan
dS
and
Cla
yo
ver
Sil
tst
on
e
NA NA NA
DEP
TH
(10
')o
fF
ill
5'-
15
'(9
'-1
6')
toP
uen
teFm
.
(10
'to
Pu
ente
Fm
.?)
NA NA
I-'
V1
53
Cal
Tec
hS
eism
olo
gic
alL
abo
rato
ry,
Pas
aden
aB
asem
ent
Com
plex
Mes
ozo
icG
ran
ite
NA
54 55 56 57
Fli
ntr
idg
eR
idin
gC
lub
,P
asad
ena
900
S.
Fre
mo
nt,
Alh
ambr
a
Wes
tch
este
rR
ec.
Cen
ter,
Wes
tch
este
r
Mal
aga
Lan
e,P
alo
sV
erd
esE
state
s
Old
All
uv
ium
Old
All
uv
ium
Old
erD
une
San
d
Old
All
uv
ium
ov
erM
on
tere
yF
m.
Ple
isto
cen
e
Ple
isto
cen
e
Ple
isto
cen
e
Ple
isto
cen
eo
ver
Mio
cene
Sil
t&
San
do
ver
Gra
vel
lyS
and
Sil
t&
San
do
ver
Gra
vel
lyS
and
Fin
eto
Med
ium
San
d
San
do
ver
Sh
ale
(14
')to
Gra
vel
lyS
and
5'-
7'
(10
'-1
5')
toG
rav
elly
San
d
(Part
iall
yC
emen
ted
Zon
eN
ear
Su
rfac
e)
(14
')to
Sh
ale
58W
hit
tier
Nar
row
sD
amR
ecen
tA
llu
viu
mH
olo
cen
eG
rav
elly
San
d(S
hal
low
Wat
erT
able
)
J-I '"
TABL
E2
(Co
nt'
d)
LOCA
LGE
OLOG
Y
SIT
EN
O.
LOCA
TIO
NGE
OLOG
YAG
ELI
THO
LOG
YD
EPTH
59L
egg
Lak
eR
ec.
Cen
ter
Rec
ent
Hol
ocen
eS
ilt
and
San
d(L
oose
San
ds)
All
uv
ium
60OS
OPu
mp
Pla
nt,
Gor
man
Rec
ent
Hol
ocen
eNA
NAA
llu
viu
m
61P
earb
loss
om
Pum
pP
lan
t,B
asem
ent
Com
-M
esoz
oic
Gra
nit
eNA
Pea
rblo
sso
mp
lex
62O
cean
Blv
d.
and
Ced
arO
ldA
lluv
ium
Ple
isto
cen
eNA
NAA
ve.
,L
ong
Bea
ch
63L
ong
Bea
chS
tate
Un
iv.,
Fil
lo
ver
Old
Hol
ocen
eo
ver
Sil
tan
dS
and
(3')
of
Fil
lL
ong
Bea
chA
llu
viu
mP
leis
tocen
e
TABL
E3
LAY
ERPR
OPE
RTI
ES
SIT
EN
O.
LOCA
TIO
NFI
RST
LAY
ERSE
CON
DLA
YER
THIR
DLA
YER
FOU
RTH
LAY
ERV
HV
HV
HV
ss
ss
31M
ar.A
rthu
rP
ark
:L
.A.
410
374
09
1280
2426
40
32A
mba
ssad
orH
ote
l,L
.A.
990
1625
00
33N
orm
andi
eA
ve.
and
620
911
6018
2790
Six
thS
t.,
L.A
.
34G
rand
Ave
.an
dT
hir
d88
02
1110
1313
70P
lace,
L.A
.
35F
irst
St.
and
Hop
e,L
.A.
no8
1260
36F
igu
ero
aS
t.an
dT
hir
d59
08
870
2614
20I-
'S
t.,
L.A
.-..
.J
37O
lym
pic
Blv
d.
and
510
510
2012
1530
13
1980
Val
enci
aS
t.,
L.A
.
3875
0S
.G
arla
nd
,L
.A.
1000
1519
80
39V
onK
1ein
smid
Cen
ter,
790
1517
1024
2310
U.S
.C.,
L.A
.
40Lo
rna
Vis
taA
ve.
and
870
1613
9032
2000
49
thS
t.,
Ver
non
4137
10W
ilsh
ire
Blv
d.,
L.A
.10
4012
1250
42W
ilsh
ire
Blv
d.
and
630
810
30S
pau
ldin
g,
L.A
.
43W
ilsh
ire
Blv
d.
and
820
914
80M
cCar
thy
Vis
ta,
L.A
.
TABL
E3
(Co
nt'
d)
LAY
ERPR
OPE
RTI
ES
SIT
EN
O.
LOCA
TIO
NFI
RST
LAY
ERSE
CON
DLA
YER
THIR
DLA
YER
FOUR
THLA
YER
VH
VH
VH
Vs
ss
s
44W
ilsh
ire
Blv
d.an
d10
0010
1610
Pal
mD
r.,B~verly
Hil
ls
4543
5O
akh
urs
tD
r.,
600
878
015
1600
Bev
erly
Hil
ls
46S
anta
Mon
ica
Blv
d.an
d56
013
830
2114
70L
ind
enD
r.,
Bev
erly
Hil
ls
47B
ever
lyD
r.an
dS
utt
on
960
728
60W
ay,
Bev
erly
Hil
ls
48U
.C.L
.A.,
Wes
twoo
d44
010
880
2211
7044
1700
~
49Z
onal
St.
and
San
590
1316
90(X
l
Pab
loS
t.,
L.A
.
50P
omer
oyS
t.an
dM
ark
890
928
60S
t.,
L.A
.
51C
alT
ech
Ath
enae
um,
Pas
aden
a86
09
1200
1113
80
52C
alT
ech
Mil
lik
an98
017
1270
Lib
rary
,P
asad
ena
53C
alT
ech
Sei
smo
log
ical
2670
3442
10L
abo
rato
ry,
Pas
aden
a
54F
lin
trid
ge
Rid
ing
Clu
b,
850
1419
00P
asad
ena
5590
0S
.F
rem
ont,
Alh
ambr
a84
01
116
70
TABL
E3
(Co
nt'
d)
LAY
ERPR
OPE
RTI
ES
SIT
EN
O.
LOCA
TIO
NFI
RST
LAY
ERSE
CON
DLA
YER
THIR
DLA
YER
FOU
RTH
LAY
ERV
HV
HV
HV
ss
ss
56~'!estchester
Rec
,8<
W21
2000
Cen
ter,
Wes
tch
este
r
57M
alag
aL
ane,
Pal
os
1000
1418
50V
erde
sE
state
s
58W
hit
tier
Nar
row
sD
am10
5017
1840
59L
egg
Lak
eR
ec.
Cen
ter
520
867
018
820
60OS
OPu
mp
Pla
nt,
Gor
man
560
1274
034
1190
61P
earb
loss
om
Pum
pP
lan
t,13
809
3930
I-'
Pea
rblo
sso
m'-
0
62O
cean
Blv
d.
and
Ced
ar10
007
1310
Av
e.,
Lon
gB
each
63L
ong
Bea
chS
tate
Un
iv.,
500
310
0012
1980
Lon
gB
each
Site Sheets
The results of the analysis of each site are displayed on site sheets
found in Appendix A. A master sheet is presented at the beginning of the
Appendix which graphically describes and explains the information contained
on each sheet.
Each site sheet contains both a map and a section. The map positions
the shot line with respect to major streets and landmarks in the area. The
section displays the subsurface stratification along the shot line (A-B) as
determined from the surveys. The layer depths at both ends of the section
were determined from the analysis previously described, which assumes straight
line boundaries between layers. The shear-wave velocities are inserted in
the corresponding layers.
There were some sites where the velocity boundary of the next layer was
detected on only one end of the survey line. It was thought that this
information, although partial, would provide useful data and therefore it was
included. From this limited data a horizontal layer boundary could be
estimated. This boundary is represented on the site sheets by dotted line
interfaces.
Preceding page blank21
References
1. Bolt, B.A., W.L. Horn, G.A. MacDonald and R.F. Scott, Geologic Hazards,Springer Verlag, New York (1975).
2. Chase, G.W., and Chapman, R.H., "Black-Box Geology," CaliforniaGeolog~, CDMG, January 1976, pp. 8-12.
3. Duke, C.M., "Techniques for Field Measurement of Shear Wave Velocityin Soils," Proceedings Fourth World Conference on Earthquake Engineering,Santiago, 1969, pp. 39-54.
4. Duke, C.M., Johnson, J.A., Kharraz, Y., Campbell, K.W., and Malpiede,N.A., "Subsurface Site Conditions in the San Fernando Earthquake Area,"San Fernando, California, Earthquake of February 9, 1971, Vol I, Part B,U.S. Dept. of Commerce, 1973, pp. 785-799.
5. Eguchi, R.T., "An Earthquake Risk Hodel that Incorporates Local NearSurface Site Conditions," Mechanics and Structures Dept., University ofCalifornia, Los Angeles, UCLA-ENG-7547, 1975.
6. Heiland, C.A., Geophysical Exploration, Prentice-Hall, Inc., New York,1940, pp. 1013.
7. Jennings, C.W., and Strand, R.B., Map, Los Angeles Sheet, CDMG,Sacramento, 1969.
8. Jennings, a.p., Map, Long Beach Sheet, CDMG, Sacramento, 1962.
9. Jennings, a.p., Map, San Bernardino Sheet, CDMG, Sacramento, 1969.
10. Lamar, D.L., "Geology of the Elysian Park-Repetto Hills Area, Los AngelesCounty, California," Special Report 101, CDMG, Sacramento, 1970.
11. Mooney, Harold M., "Handbook of Engineering Geophysics," Bison Instruments, Inc., Minneapolis, Minn., 1973.
12. Poland, J.F., Garrett, A.A., and Sinnott, A., "Geology, Hydrology, andChemical Character of Ground Waters in the Torrance-Santa Monica Area,California," Geological Survey Water-Supply Paper 1461, USGS, 1959.
13. Poland, J.F., Piper, A.M., and others, "Ground-Water Geology of theCoasta,l Zone Long Beach-Santa Ana Area, California," Geological SurveyWater-Supply Paper 1109, USGS, 1956.
14. Power, J.H., and Real, C.R., "Shear Have Velocity-Progation and Measurement,'1 California Geology, CDHG, Sacramento, February 1976, pp. 27-29.
Preceding page blank23
NO. *
APPENDIX A
MASTER SITE SHEET
SITE: NAME AND GENERAL LOCATION OF SITE
~ 1 1 1_____
SHOTLlNy .A
I I 0 200 FEET
'I'iiiiiiiiiiiil!~~i
IITRUE NORTH
GEOLOGIC SECTION TAKEN FROMTHE SHOT LINE A TO B
A
SECTION
DISTANCE ALONGSHOT LINE IN FEET
o 60 120 180 240 300o r--....,.------rl-..........-----,-I-~_""""TI-..,..---I....---r--r--I...... 0 B
DEPTH INFEET
Vs = - 60
~ • •• • • • • ••••••••••• • ••••• • • • • ••~~~~~I~~·7··..~ 80
80 -
20 ~--~;~~~~=VS::=7-----------j-2040 - VELOCITY ./ - 40INTERFACE-./
60 _ (SH)
SECTIOI\ILETTERS,FOUND ONSHOT LINEABOVE
v =s INTERFACE FORTHOSE LAYERS WHEREONLY ONE sIDeCOULD BE DETECTED
* SITE NUMBER CORRESPONDS TONUMBERS FOUND IN TABLE 1AND ON SITE LOCATION MAPS
DATE: DATE OFFIELD WORK
25Preceding page blank
SITE: MAC ARTHUR PARK, L.A.
B
A
NO. 31
N
~IWILSHIRE BLVD
SECTION
o 200 FEET
740 fns
100 120B
25 ~ 1280 fps -••••••••••••••••••••••••••••••••••••••••••••••••••• 4
50 ......2640 fps
26
-
DATE - JULY 1975
NO. 32
SITE: AMBASSADOR HOTEL, L.A.
,__ILWILSHiRE BOULEVARD
o 200 FEET
Iwwex:Ien«z-l«~(J
Nr---1/8IA
7th STREET
1SECTION
50 100 120I I I B
990 fps
2500 fps -25 .-
oA 0 r--..,..-......---r--.-""-OOOYO---'---'-__"",-"""",,__
50- -
DATE - AUG. 1975
27
NO. 33
SITE: NORMANDIE AVE. AND SIXTH ST., l.A.
L5th St
A B Ww> >« «w wa: C0 z:E «C :iEa: 0::, « 0z
0 200 FEET N
II6th St
II120
A
SECTION
o 50 100O,..--r---r---r----,r-.,..--,--.....,.---r----,r-or---r--w
I I I , 1620 fps I I
1160 fps25 ..
B
50-
2790 fps
-
DATE - AUG. 1975
28
NO. 34
SITE: GRAND AVE.AND 3RD PL., L.A.
o
I
200 FEET
N
SECTION
0 50 100 150 195A 0 B
L 880 f~sI I
1110 fps
25 ~1370 fps -
50 I- -DATE - JULY 1975
29
NO. 35
SITE: 1st. ST. AND HOPE ST., l.A.
N
, go 200 FEET
A
SECTION
o 50 100 130O...---r---w--.....---......--...-~--r"~-....-..-__-....--..
I 1 720 fps I 1 I I I I 1 IB
25 f-
50 '-
1260 fps -
-
DATE - JULY 1975
30
NO. 36
SITE: FIGUEROA ST. AND 3RD St., l.A.
o 200 FEET
N
SECTION
0 50 100 150 200A 0 • I • • ! T 590 f~S • 1 • • I -.- B
r-. 870 fps25 ~ -
1420 fps -50 '- -
DATE - FEB. 1975
31
NO. 37
SITE: OLYMPIC BLVD. AND VALENCIA ST., l.A.
(
o 200 FEET
SECTION
B- N
I I , I I I 510fps ' I I
1020 fps
- 1530 fps -1980 fps
- -
oA 0
25
50
50 100 150 180B
DATE - FEB. 1975
32
SITE: 750 S. GARLAND AVE., L.A.
7th STREET
w::::>zw>«c2: A B«..Ja::«Co:)
N
NO. 38
,
8th STREET0 200 FEET
SECTION
0 50 100 120A 0 I I I I B
1000 fps
:!5 ~1980 fps -
!;O ~
33
-
DATE - AUG. 1975
NO. 39
SITE: VON KlEINSMID CENTER, U.S.C., l.A.
w>«>I-Cf.lII:w>Z:::>
VON KlEINSMID CENTER
A-------B
N
Ao
o
o
50 100 150I I I I I I I I, T T, I
790 fpsI
200 FEET
200 250 270I I I I I I I I B
25 I-
50 ~
1710 fps
2310 fps
34
-
-
DATE - SEPT. 1975
NO. 40
SITE: LOMA ViSTA AVE. A~O 49TH ST•• VER~O~
__-IDISTRICT BOULEVARD
N
\\iiSiiiiiii";;;l.!!!!!!l!! u.i() 200 fEET ~
~ -====4am:fS~;;;;:;-------...A ~ 1r- ..::4~8T~H~..:S~T:!:R~E:!:E~T~=====-
o..J
aI 1~49TH~STREET~
Se.Cl\ON
Ao
o 'T • 'T
50, 1
150 182• 1 ...... .,. B
-1390 fps
2000 ips
5ll "' ..
261-'
DATE.: SEPT .1976
35
NO. 41
SITE: 3710 WILSHIRE BLVD., l.A.
WILSHIRE BLVD.
N
w>«o:2:«a::a:wCI)
3710
w
~oa:ou..Xo
B A,
7th ST. 0 200 FEET
~ I l ISECTION
180B
00 50 100 150.-....,--,....,--'-.'-r--.'--'-.'--I..--....'-'--,-s..--.....-,--,-,--.1040 fps
A
25 r- 1250 fps -
50 ~ -
DATE - AUG. 1975
36
NO. 42
SITE: WILSHIRE BLVD. AND SPAULDING AVE., LA.
fiiiiiiiiiiiii-~~o 200 FEET
WILSHIRE BOULEVARD
A
IB
IN
SECTION
130B
o 50 100o r--..,.I---,I-y---r--...,I----.----r---,.I---.~~l630 fps
A
25 ~1030 fps -
50 L -
DATE - AUG. 1975
37
NO. 43
SITE: WILSHIRE BLVD. AND McCARTHY VISTA, l.A.
WiLSHIRE BOULEVARD
N
7/WARNER DRIVE
o 200 FEET
SECTION
130B
o 50 100O..--_~--.---.,r---r-.....--....,.,.--,r---.,..--.,--r---'II
, 1 820 fps I •A
25 ,.... 1480 fps -
50 ..... -
DATE - AUG. 1975
38
NO. 44
SITE: WILSHIRE BLVD. AND PALM DR., l.A.
WILSHIRE BOULEVARD
w>
w c:>------0a:S-Ar--1-o I I ~
liiiiiiiiiiii~-!!!!!!!!!J :5 I I ~o 200 FEET ~ I I ~
II 0
N
SECTION
120o 50 100A 0 ~__...,.....--r--.-r--I-'--""""'--'----'-"'--I""'-_
1000 fpsB
25 -
50 -
1610 fps-
-
DATE - AUG. 1975
39
NO. 45
SITE: 435 OAKHURST DR.• BEVERLY HILLS
B
A
o 200 FEET
BEVERLY BOULEVARD
N
I ISECTION
0 50 100 120A 0
1600 fps I B
780 fps
25 f-1600 fps
50 l- -
DATE - FEB. 1975
40
ItIN
NO. 46
SITE: SANTA MONICA BLVD AND LINDEN DR., BEVERLY HILLS
o 200 FEET
SECTION
0 50 100 120A 0 B
560 fps
25
501470 fps
DATE - AUG. 1975
41
NO. 47
SITE: BEVERLY DR. AND SUTTON WAY, BEVERLY HillS
B
A
SUTTON WAY
;200 FEET
N
A
SECTION
o 50 100o ..............--.---.-.....-....I--,960-fps' , I '
2860 fps
25 I-
50 .....
42
120B
-
-
DATE - AUG. 1975
NO. 48SITE: U.C.LA. ATHLETiC F!ElD, WESTWOOD
TRACKSTADIUM
B----.......----A
L- ---I -+ _
t+IN
PAULEY
PAVILLION
FOOTBALL Fi ELD
o 200 F~ET
-II
I0 50 100
A 0 • i • I i i 6 I I
25 -
i
50 I75L
10J
SECTION
150 200 250 300I 440'fps l iii Iii i , Iii
880 ips
1170 fps
1700 fps
43
STRATHMORE DRIVE
360
-
-DATE - SEPT. 1975
NO. 49
SITE: ZONAL ST. AND SAN PABLO ST.,l-A.
Iww0:I(J)
o..J00<CQ.
Z<C(J)
A---BN
ZONAL STREET
o 200 FEET
SECTION
120B
o ~ 100o r--'"T.-,.--,-r---r--r
I-,.---r----r---r---"r--.,......."r---1
590 fpsA
25 ~ 1690 fps -
50 '- -
DATE - AUG. 1975
44
NO. 50
SITE: POMEROY ST. AND MARK ST., L.A.
t
N
o 200 FEETSECTION
120B
o 50 100A 0 .r--....--r---.----..,-..--,----.----.,r--..---,...,.--.,
890 fps
25 '-2860 fps -
50 '- -
DATE - AUG. 1975
45
NO. 51
SITE: CALTECH ATHENAEUM, PASADENA
ATHENAEUM
o =
N
200 FEET
oA
B
CALIFORNIA BLVD
SECTION
Ii
o 50 100 150 165o r-""I',-r-,""",-..-,-r,--"..-.....--r-........-.,I..--r,-.....-.TU--,U...--'T1--,u,.....
860 fps
1200 fps
25 /-
50 '-
1380 fps
46
-
-
DATE - AUG. 1975
NO. 52
SiTE: CALTECH MILLIKAN LIBRARY, PASADENA
I Iw>.<3::zoen-l
s:I
NMILLIKANLIBRARY
B A~ ~
6 G!
~0 200 FEET
CALI FORNIA BLVD
I ISECTION
0 50 100 150 180A 0 I I I • B
980 fps
25 ~ -1270 fps
50 '- -
DATE - AUG. 1975
47
NO. 53
SITE: CALTECH SEISMOLOGICAL LABORATORY, PASADENA
A B(SEIS_ILAB.
N
,0 200 FEET
SECTION
0 50 100A 0 I I I I I I I I I B
2670 fps25 I- -
50 ...... 4210 fps -
DATE - AUG. 1975
48
NO. 54
SITE: FLINTRIDGE RIDING CLUB, PASADENA
N
JETPROPULSIONLABORATORY
200 FEETo
~•••••••••••••• ••••••••••••••••••••••••••••••••••••• 8 ••••••••••• a=
c 0«~ B A ~o 0~ g> FLINTRIDGE ~
RIDING CLUB d
SECTION
240B
20015010050oA 0 r-r--r"""T"""--r-T--r"""T"""--r-T--r"""T"""T""'1r-T-"-"""T"""--T"""T-"-~
850 fps
25 1900 fps
50
DATE - AUG. 1975
49
NO. 55
SITE: 900 S. FREMONT AVE., ALHAMBRA
900
w
~IZo~wa:u.
A-----B
ORANGE
N
,0 200 FEET
SECTION
0 50 100 150 180A 0 I I I I I I I I I I I I I I B
840 fps
25 -. 1610 fps -
50 ....
50
-
DATE - AUG.1915
NO. 56
SITE: WESTCHESTER RECREATION CENTER, WESTCHESTER
MANCHESTER AVE
A
B
N,0 200 FEET
SECTION
0 50 100 150 200 240A 0 . . I I . I . I B
890 fps
25 -2000 fps
50 -- -
DATE - AUG. 1975
51
NO. 57
SITE: MALAGA LANE, PALOS VERDES ESTATES
--J%\L-T-E-JO-N---------
v,~ %0 l-:=J8 LANE ---------
_MA~Gl r----/;:-B
N
o 200 FEET
SECTION
o 50 100 120o r--"-r,-,r--'T""""",...,--r--t~""T"""--r--,r--~I"TI---'
1000 fps
25 I-
50 I-
52
1850 fps -
-
DATE - SEPT. 1975
NO. 58
SITE: WHITTIER NARROWS DAM
o
SECTION
0 50 100 150 165A 0 ,
I,
I I B
1050 fps
25 1840 fps -
50 I- -
200 FEET
DATE - SEPT. 1975
53
NO. 59
SITE: LEGG LAKE REC. CENTER
LEGG LAKEREC. CENTER
B""A
N•0 200 FEET
SECTION
0 50 100 150 2000 I • • 520'fps' I • I ,
670 fps25 I- -
820 fps
50 ..... -
DATE - SEPT. 1975
54
NO. 60
SITE: osa PUMPING PLANT, GORMAN
N
//
//
//
//
//
//
/
SECTiON
A
/B
o 500 FEET
o 50 100 150 200A 0 r--"-,.--r-r---.,-r---"-..,--r-,.-,.,--,...--r----.-1r---,.-...,...-,...--.-. ......., B
560 fps
25 r-740 fps -
50 ~ •••••••••••••••••••••••••••••••• ;;.~~.~~;••••••••••••••••••••••••••••••••••~
DATE - SEPT. 1975
55
NO. 61
SITE: PEAR BLOSSOM PUMPING PLANT, PEARBLOSSOM
PEARBLOSSOM HIGHWAY
N
\ ,, I\ ,, I\ I\ \\ );> I\g,\~\\ ~\'-q\ \\ \\ \
PUMPINGPLANT --M-li
:~-=rJ'
o 500 FEET
SECTION
220B
o 50 100 150 200o .--.....-...,'.--.....-........-...-1........--.-.......,•.--..,...........1-................--.---.,--,...-1...,•.--..,............-,...-.....,-,...-.,·
1380 fpsA
25 --3930 fps
-
50 '- -DATE - SEPT. 1975
56
NO. 62
SITE : OCEAN BLVD. AND CEDAR AVE., LONG BEACH
LBROADWAY
w>«I::lZl(/)w:I:U
'W>«a:«CiwUB",
A
lrN
OCEAN BLVD
I I I
0 200 FEET
SECTION
0 50 100 120A 0 B
1000 fps1310 fps25
50
DATE - AUG. 1975
57
NO. 63
SITE: LONG BEACH STATE UNIV.
~I '--
ATHERTON STREET
IIIII w
>
tI ~I i w
I I 0I I a::
I I w0 A I I >
t3 0I I I ..Jco !!-1 I.. -" «a::. "
Q..
UJ ---,.. \~ I \..J i Nu....J i..JUJ I r---co
I ~ \" - ---, 'I I II I I ,I I
iI I 0 1200 FEETI II
~7TH STREET
~
SECTION
0 50 100 130A 0 B
L 500 fps 1000 fps
25 /- 1980 fps -
50 ~ -DATE - AUG. 1915
58
APPENDIX B
NEW TECHNIQUES IN FIELD MEASUREMENT
The conducting of refraction surveys has been largely restricted to
those sites where ample space and bare ground were available. However, many
sites exist where the space is available, but where a survey could not be
conducted due to the existence of some type of asphaltic surface. To deter
mine the feasibility of performing a refraction survey on a paved site, a
comparative study was performed on the U.C.L.A. campus. Two sets of geophone
lines were set up, one on asphalt and the other on soil. These lines were
parallel to each other and had a separation of fifty feet between them. For
the paved site, the geophones were simply placed on the pavement. For the
soil site, the geophones were spiked into the ground.
Two sets of records were then obtained and time-distance curves plotted
to represent them, Figure B-1. The arrival times were identical beyond the
first three geophones. However, there existed some difficulty in interpreting
the first three arrivals for the paved site. This was apparently due to the
occurrence of two direct waves. The first direct wave, possessed a
velocity much too high for the underlying soil (the soil logs were examined).
It is believed that this first velocity was the shear-wave traveling through
asphalt. This is conceivable since the shear wave velocity is larger for
asphalt than for soil. The second direct wave for the first 3 geophones on
the paved site, however, had a slope equal to that of the adjacent soil site
and consequently had the same shear-wave velocity. This can be seen in Figure
B-l.
Therefore, with careful interpretation, supplemented with available geo
technical data, surveys at six other sites were conducted on asphalt: Sites
41, 51, 53, 55, 57, and 61.
59
.25
.20
- -- ASPHALT--- SOIL
IUCLA ATHLETIC FIELD I .25
.20
.05DIRECT WAVE TRAVELINGTHROUGH ASPHALT
.05
u .15 .15 uw w~ ~w w~ ~
I- .10 .10 I-
oll::::::::::...-----l..-----....L.-----L-----==:::ilIIoo 45 90 135 180
DISTANCE (FT)
Figure B-1. Time-Distance Curves (Asphalt - Soil).
60
To examine the effect of impact intensity on the shape and amplitude of
a record, a series of hits was made with the 25 lb. hammer using varying
intensities. These intensities ranged from soft golf type putts to hard
baseball type swings. Although the study was not conducted quantitatively,
the results generally showed that beyond a certain threshold intensity, a harder
hit provided no increase in amplitude, Figure B-2. A possible reason for this
is that the additional energy produced by a harder hit was lost in the slippage
of the plank. Experience showed that a hard hit displaced the plank by as
much as an inch. Although this is not a desirable quality in general, in
many cases it is not a hindrance. One such case would be a site where the
rock is encountered at a relatively shallow depth. Here, a larger energy
source will not, in general, provide any additional information beyond the
direct wave velocity.
However, for most sites, the loss in energy will often hinder the
acquisition of much needed information. By devising a method to eliminate
this loss, one could obtain records with clearer onsets resulting in less
ambiguity in interpretation. A possible procedure to eliminate this loss
would be to line the bottom of the plank with a corrugated surface. This
would provide additional friction to resist board movement while assuring
that the amplification of P-waves remains TIlinima1. A heavier weight on the
plank might also help. More study is needed, however, before this procedure
can be implemented.
61
w>I<!I-...l<!:::lowCl:::lI-..J0...:?E<!wUic::(c::I-
• •
• •
HAMMER INTENSITY (NOT TO SCALE)
Figure 8.-2. The Effect of Impact Intensity on Wave Amplitude.
62
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