CONST

E ¹⁵

(.)

_J •

a. 10

Cf)

-

0 <! 5

w a..

§ x

0<.D

r-!- -

^Cl)^<.D

-OoNO

ro

----l.1.. -

<!><!>(!)

:c

z

x

lO~ <.D~OI"- 0

0 0 ()) C\.l Cl) Cl) C\.l

C\JC\.l---0 (\j

OOZ:C~l.1..

a.

())

z

o E-W COMPONENT

x N- S COMPONENT

-31-

It is seen from Figure 2. 2 that the peak displacement data are more scattered than peak velocities, which, in turn, are more

scattered than peak accelerations. This is in contrast to the data of Esteva and Rosenblueth (1963) in which peak accelerations were more scattered than peak velocities. Since their data had been normalized with respect to magnitude, this may be due to a closer

relationship between magnitude and peak velocity than between magnitude and peak acceleration. However, that exph.ins only the wider scatter seen in Esteva and Rosenblueth¹s peak accelerations, which were obtained from many earthquakes. It does not explain why in Figure 2. 2 the acceleration peaks are less scattered than the velocity peaks, since they are obtained from the same earthquake. Furthermore they were recorded within a narrow range of azimuths, eliminating

source-station direction as a variable. The principal variable remaining is local geology, in this instance referring to the upper 10 to 15 km of the crust. From an examination of the Volume II plots of acceleration, velocity and displacement -in which the peak values are marked-it is seen that acceleration peaks occur early in the accelerograms, peak displacements generally occur

several seconds later, with velocity peaks occurring between the two.

This suggests that the high frequency components contributing to the development of acceleration peaks (frequencies above 5 Hz; Brady and T rifunac, 1975) travel a larger proportion of their propagation paths in basement rock whereas to some extent, the middle range frequencies at which velocity peaks develop, and particularly the low frequency components developing peak displacements travel

considerable distances as surface waves in the low-velocity surface sediments. The relatively low scatter in acceleration peaks may then be attributed to their more uniform, basement-rock travel paths.

On the other hand, the anomalous appearing growth in peak displacement from sites GllO to F086 has been attributed by Hanks (l 974b) to the development of surface waves. At station GllO (The Jet Propulsion Laboratory, Pasadena) which rests on a small depth of alluvium relative to the wavelengths developing displacement peaks, Hanks identified the displacement waveform as predominantly one of body wave arrivals. As the waves move out across the increasing depths of sediment in the San Gabriel Valley and Los Angeles Basin . (see Figure 2. 7), surface waves are seen to develop in the displacement records with increasing amplitudes until site F086, the Vernon CMD Building, is reached. At this point the Basin sediments are 20, 000 feet deep (Yerkes et al., 1965) and should contribute to the formation of Love waves. Beyond Vernon, wave dispersion and geometric

attenuation apparently dominate, and the displacement peaks again decay with increasing epicentral distance. The high amplitude at

station C048, the Holiday Inn, 8244 Orion Boulevard, Los Angeles, can also be explained by the development of surface waves across the deep, sediment-filled San Fernando Valley (Drake and Mal, 1972).

As with the peak displacements, peak velocities increase, rather than decay, with distance from GllO to F086, but the increase is not as marked as that seen in the peak displacements. Since peak velocities are developed by higher frequency components of motion [approximately 0. 3 to 3 Hz (Brady and Trifunac, 1975)] than peak

-33-

displacements, it appears that the influence of surface waves is not as strong in this mid-frequency range as it is at the lower frequencies characterizing peak displacements.

In a homogeneous, isotropic, linearly elastic, unbounded solid, except at small distances, body-wave amplitudes decay by geometric spreading in proportion to the inverse of distance from the earthquake source. Surface-wave amplitudes on a similarly idealized half space decay in proportion to the inverse of the square root of distance (see Bullen, 1963, for example). Energy absorption by the propagation medium furth.er attenuates the amplitudes of waves travelling in real materials. This effect is referred to as material damping or material

attenuation. The curves plotted in Figure 2. 2 enable a comparison to be made between the ob served amplitude decay and that expected in an idealized solid.

Because of the amount of scatter in the peak displacement values, it is difficult to tell whether or not they are better fitted by the curve whose ordinate.s are inversely proportional to epicentral distance or by that with ordinates proportional to the inverse of the

square root of epicentral distance. The general trend in velocity peaks is more clearly proportional to the inverse of epicentral

distance. Peak acceleration data appear to decay at a greater rate than the inverse of epicentral distance. Since peak accelerations are developed by high frequency components (~ 5 Hz, Brady and T rifunac, 1975), this suggests the presence of some frequency-dependent material attenuation. Development of surface waves does not appear to be

reflected in peak acceleration values. The high values in records

Gl 10 and Gl06 are consistent with lower material attenuation expected from crystalline rock propagation paths. No definite explanation has been found for the differences in records Gl07 and Gl08, which were recorded within 1000 feet of each other on the Caltech carnpus. The main differences in amplitude spectra of the two records occur between 3 and 6 Hz, with Millikan Library (Gl 08) spectra being

stronger. A possible, simple explanation is that standing surface waves were formed in the soil between the Library basement and the deep

basements of the adjacent buildings. Distances and wave velocities are consistent with this hypothesis.

The presence of material attenuation apparent in the peak acceleration data of Figure 2. 2, was investigated further using root mean square (r. m. s.) acceleration values from the same group of accelerograrns. The r. m. s. accelerations were obtained from an unpublished study of accelerogram correlation functions begun by H.-Y. Ko and R. F. Scott, and continued by the writer. R. m. s.

accelerations were available from N-S, E- W, and from radial and

transverse components. In order to elim.inate the component orientation with respect to the source-station direction as a variable, transverse

components were chosen for study rather than N-S or E-W components.

The logarithm of r. m. s. acceleration, normalized for the effect of an assumed body-wave geometric spreading (inverse of distance) are plotted against epicentral distance, s, in Figure 2. 3. Although

including considerable scatter, the data again show a well-defined

straight-line falloff with epicentral distance, represented by the equation

C\J

0 x u Ji 400 x SAN FERNANDO EARTHQUAKE, 1971 E u

.... CJ)

x 200

•••••• ~x

..•••••. z 0 ~ .. ,o'% .. ·x ... O==aoo (t-5 x "6" 0 x x · · · · .... ~. Hz) " . x •...•.• 'x Q ...• ' :::10 ' C2S O(f:::5L1

ti 100 w

w u u

.

(/)

. E

•

ct:

Xx

'~)

c 1 e Q '..(;r,

zs~

0 <.0~

-<.O

<.0 '-..'<)

LO ~ - 00

(\JO) Q) '

~o<.O~ om

(j)

l'- 0 - -- -0 - '

(j)(\J Q) --

60 U <.9 <.9<.9 ILL Z

C\J--

-O Z

-1

301 I I I OZI l~LL I I I 0 20 40 60 80 100 120 140 DISTANCE FROM EPICENTER, s, km

Figure 2. 3. R.

m.

s. acceleration, normalized for effect of spherical spreading by multiplying acceleration by epicentral distance. Transverse components only.

I w \JI I

(2. 2)

where (a) is r. m. s. acceleration and c1 and c

2 are constants.

This expression is consistent with body-wave amplitude decay expressions commonly used in seismology, where c

=

Trf

/13

is employed,

13

being shear wave velocity and 1 /Q a dimension- less constant, the specific attenuation (Knopoff, 1964).

Since the r. m. s. acceleration is a frequency-averaged quantity, it would be expected that r. ^p:l.s. accelerations are less

scattered than peak accelerations. Comparing Figures 2. 2 and

2. 3, this is seen to be so. If it is assumed that the average frequency characterized by the r. m. s. acceleration is 5 Hz, and assuming a

shear wave velocity

13

of 3. 0 km

I

sec, the slope of the solid line in Figure 2. 3 corresponds to a value of Q = 400. To show the effect of changes in the value of Q, the dotted line is drawn for a value of Q = 800 and the dashed line for a value of Q = 160 both for an assumed f = 5 Hz. Alternatively, for constant Q = 400, the dotted line corresponds to a frequency of 2. 5 Hz and the dashed line to a frequency of 12. 5 Hz.

-37-

The conclusions of this preliminary investigation may be summed up as follows:

1) Peak ground displacements do not show a regular pattern of attenuation with increasing epicentral distance. Their values are

·influenced by the development of surface waves in deep, relatively soft surficial soil layers, and they show much more scatter than peak velocities and peak ·accelerations: Their mean trend cannot be well described by a geometric spreading term such as the. inverse of either epicentral distance or of its square root.

2) Peak ground velocities are clearly influenced by the development of surface waves but not to the same extent as peak displacement values. Surface waves do not dominate peak velocities, and with considerable scatter, their amplitude decay is proportional to the inverse of epicentral distance.

3) Peak and r. m. s. ground accelerations follow a well-defined pattern of attenuation with distance; the rate of fall-off is greater

than the inverse of distance, and is consistent with an exponential material attenuation term with Q of about 400, in addition to a spherical spreading term proportional to the inverse of epicentral distance.

From this limited set of data it appears that the propagation of low frequency components of strong ground motion is dominated by generation of surface waves depending upon path geology and epicentral distance. The higher frequency components, however, which

contribute to peak velocities and peak s.ccelerations, behave in a

· much more regular manner, decaying steadily with distance and exhibiting less scatter; part of the scatter in these data is caused, but not dominated, by surface waves. These observations suggest that studies of strong ground motion attenuation should deal separately with the low frequency band, where surface waves are an important factor, and with the intermediate and high frequency bands, where a much more regular amplitude decay behavior is observed. The

remainder of this chapter describes an empirical and much more detailed study of the amplitude decay of strong ground motion from the San Fernando earthquake, in the higher frequency band, from 0. 4 to 16 Hz.

-39-

2. 2. Main study: the data set.

Of the 229 strong motion accelerograms from the San Fernando earthquake, 101 were recorded at ground level, mostly in building basements, within a radius of 209 km of the epicenter (Hudson, 1971).

Of these, 95 were included in the set of corrected accelerograms -published by the Earthquake Engineering Research Laboratory; the

remaining six records were of very low amplitude, and were not

processed to the Volume II stage. Fourier amplitudes of the horizontal components of these 95 accelerograms form the data set for this study.

The recording sites, labelled by their Caltech reference numbers, are shown in Figure 2. 4 and are listed in Table 2. 1.

Two separate sets of Fourier amplitude data were derived from the set of accelerograms. One was taken directly from Volume IV which presents Fourier transforms of the corrected

accelerograms given in Volume II. Details of the transform computations using the Fast Fourier Transform algorithm are given by

Trifunac and Udwadia (1972) in Part A of Volume IV.

Since accelerographs are usually oriented so that the accelerogram component directions coincide with the principal axes of the building in which they are located, the horizontal accelerogram

components in the Volume II data are randomly oriented with respect to the earthquake source- station direction, or azimuth. In order to eliminate component orientation as a variable, a set of rotated accelerograms was computed from the Volume II records having radial and transverse components parallel and perpendicular to the

35'N 34°N Figure 2. 4.

+ Santa Paula Port Hueneme 1'222 + ll9°w

Pt. Dune PAClFIC OCEAN

Mohave ~ 118°\V

Etj:to11ed basement rock: Basement rock contours: (feet, relative to sea level}

cY

50 Kilometers SOUTH-EASTERN GROUP (!)02!0 Basement exposure not !3hown in this area. ~'\s-. Stations 0210 and N197 on sediments. ~o . :.p-e-(!)Nl97

"'

-1c, '<'.,_ Accelerograph sites and site groupings used in study.

CALTECH REF NO. C04l C04 R C051 C054 ':'O~b 0057 ')058 0059 0062 0065 '1068 f07l E072 to 7 5 E07B t:U6l rne3 F086 F087 FJ~8 f 089 F092 F095 FQ9q FlOl Fl02 Fl03 Fl04 FlO~ GlOI> GlJ7 GlOB GllJ Gll2 Gll 4 Hll5 1-l l fl STATION STATION COORDINATES DISTANCE~KM)* TIME (SECl AT N E AZIMUTH re h S-ARRIVAL** P~COIMA UAM, ,;,\l. 8244 UklGN dLVu. 1~r ~LJU~r LUS ~NGELESt CAL. 25J E Flk>T 5T~EEI .it51:M!:NT, LUS ANGELt:S, l.AL. 445 ~ !GUtKuA STkdT, SJt>-bASE:MtNT t L J~ ANGlU:Sr l.AL. CASTA!L ULU R!UGt KJUltr CAL. HOLLYwUuU STUKAG!: d>MT. LU, ANGEL!:S, CAL HOLLY~OuJ sru~AGt: P.l. LUI, LU; ANGELES, 'AL. lqo1 AVE. J~ THl sr.; ... s SUtlt>;.~r., LJS Af;GtLt,, CAL. 1640 S. MAFEi'Hd >l. 151 FL., LUS ANU!:LcSr l.AL. J710 •ILSrl!KE ~LVU. BA5~MENT, LUS ANUtLES, CAL. 1oao lilJLLYIWUU ULVU. OA>EME1;T, LU> ANGELES, CAL. WHFEL~~ ,(QG~, ~AL. 4!>80 w!LSH!RE t>LVD., oA>lMt1;f, LU; Ar.GtL!:St CAL. 347'.J ~ILSHlkE i:!LVD., SUllbASEMt:NTr LOS AN;;!:Lb, CAL. ~ATF~ ANO µJ~E:~ t>UILUi~u, l:!AjtM!:Nft LJS ANU!:LESt CAL. !A~TA FELICIA OAM. CAL OUTLET WORKS 3407 6TH STl\EEft &11;EMENT, LJ~ Ao'lUtLESr 1.AL. VFqNJN, GMO dLUC,., l.i.L. ENGINE:ERI'lG dUIL~I~(,, ~Ar.TA ANA, JRANU~ ~JUNTY, CAL. (33 E BROADWAY, HUNIClPAL SFRVf[F~ RLn~A Gl.FNnALF. CAL. ~08 SOUTH OLIVE :>rncET, ~Tl\EET Lei/EL, LU> ANC,E:LE~.

0 1.AL. 2011 lJNAL AVtNUE:r aA~E:MlNT, LUS ANGELES, 1.AL. 12J NO~Trl RU~EATSU~ bLVu., >Ub-dA:)EMtNT, LUS ANGtLc~1 CAL. 646 SOJTrl ULIVE AVENJE, dA>tHENT, LOS ANuE:LtS, l.~L. EOISJN CuMPANY, CULfGN, C~L. Ff• ftJJN, TE JUN, C~L. PUHP!N:> PLANT, PtA.~.>LJ~SJMr ~AL. 050 PUMPING ?LANT, ~L~MAN, CAL. UCLA K~ACTJk LAbuRAluKlt LJ> AN~ELES, LAL. CAL ftCH Si:JjH.JLUU!CAL LAb., PASADcl•Ar CAL. C~LTECH AfHf~AtUM, ~•SAJENA, CAL. CALTECH MILLIKAN Lld~AKYt dAStHENT, PASADtNA, CAL. JET P~OPULSIJN LAb., BASEME:Nl, PAjAOENA, CAL. 611 .;E:>T SIXTH STRtd, bllSEMtNT, LOS AN(,i:LcS, i.AL. PALMt>ALt Fl•\t :>TAT!uf' ... sru".~~c kuOMt l'ALMDALc, ~AL. 1525U l/~NTUM~ dLVU., tiA~tM~NT1 LOS ANGtLtS1 CAL. 863~ LINCOLN AVE., t>AStMENT, LOS ANGiLE:S, CAL.

->'+ 2U Uo :;4 l, 1 b .;4 03 u l ;4 0.:1 U 34 jj 18 34

0,

uu 34 05 00 .H u:; 14 .>4 u, 3b .>4 UJ 4£ 34 Uo 05 .:>5 Ol U5 .:14 UJ '+l. .:i ... U.> 40 .>4 OJ Ull 34 27 41 3 ... UJ <tS 34 00 (,l) .:13 45 uu 34 08 00 3 ... 0£ 01 34 OJ 3b ::I'> u ... jt; :;4 U.: '0 _,,. U.i J ... ,., 5£ U3 ... JU .:HJ 34 48 05 .:>4 (J ... uo _;., us 55 ,4 08 .<U J4 08 l.2 .:>4 l.: Ul. j4 02 !:> 1 _;4 34 'tU ::,., \H J.4 .:>3 57 jb TABLE 2. 1

-118 n .. a -llo ib lb -lib 14 21> -ll8 15 24 -118 39 £4 -llB 20 <JO -Hd LO llll -lit! l.4 58 -118 1£ 4tl -lltl ltl , ... -ll.d 20 31 -lld 59 05 -ll.b 19 Sl -Ho 17 S8 -lld 15 Ou -118 45 02 -ll.8 17 4.:1 -llt1 12 uo -111 52 Ull -118 14 50 -lib 15 l)J -lib 12 lb -llt> 22 5d -118 15 l 4 -l.L 7 18 ... 5 -lld 5 ... U'I -l.ll "' ld -ll8 43 J3 -lld .0 OU -lL8 lll 15 -J.l.8 07 l.7 -ll!! o7 JO -l.18 lU .I.'.> -l.18 l.!:> lb -ll"tl 06 4, -us £7 !>\J -llb 25 07 Listing of accelerograms in study.

159 Ji, 45 199 J5 4<. 15~ 33 U3 161 n a 3U3 5J ... ) l.:.b 4ll .. ... i.i,s 4u 44 18 3 5 7 a 155 34 15 ii,i, 15 3u l.o9 3.:1 45 )l.l. 35 3l. l.b9 l.d 42 lb5 54 32 lt>O .iU 17 279 45 36 lb'.> 21 49 l.57 3£ l.6 l.45 54 30 154 53 42 lbl 20 :> ... l.54 44 _;3 175 27 20 lbl Ob <.l uo 5b 55 31 7 44 .1.1 7i, 11 14 3~5 5o l.O lod li, 3£ J.4.:1 45 .H 139 Lb Ul. l.:>9 '.>9 1 ... U8 02 £.> li,O :>'.! ll :;;, 10 15 193 Ul. 5L 183 >4 L9 9.l 2<..4 .. 2.8 41.9 id.(> J7.l 31. l ;9.S 4L. b 40.0 35.0 db. v _;9.5 <tU. l 4,.5 32. 9 <tO.O 49.4 88.5 34. I 44.0 4j.l 37.4 4£. 7 l07~b 66.;, 4,.4 !:>L. 2 Jo. 7• 3t....l J<;.il 39.8 .il.5 4£.5 32 • .> 29.3 :>0.2

15.9 25.9 44.7 43.9 31.4 39.3 39.3 41.8 44.·8 42.0. 37.3 87.0 41.6 't2o l. 44.5 35. 3 42.l 51.1 89.4 36. 5 45.9 45.0 39.b 44.o lllb.4 o9.7 4 7.£ 53.b 40.8 38.4 41.B 41.8 34. l 44.5 34.8 32.l 51.9

1.7 2.s o.o 1. ti o. ti l.5 l.5 (-0. l)b 4.4 (-0. 3)b

o.oa o.uc 2.6 l.3 l. 3 b (-I. 9) 1. l 1.7 o.o l.. 2 4.o (-0. l)b 2.5 4.9 l.3 o.oc 0.2 o.oc 2.3 L.9 5.0 4.5 l. 8 2.0 l.l 4.1 l.O

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CALTECH· STATION COORDINATES DISTANCE(KMI* TlME(SEC)AT REF NO, STATION N E AZIMUTH re rh S-ARRIVAL** HIZI >CO ;uur~ f"tMJNI AVlNUc1 dAiEMlhT, Alt1AHtlKAt I.Al• J'-OS Ub -lltl <lb Sb l'-1 iJ1 us 1t;.1 1t5.o 6.0 t-124 21,()C rivr .. OJU AVt•ilJc1 oA >t 14t,., I, ~ULLcK rur., C.AL. :;, ,2 J9 -U7 !>.! H hO 51 JO ro.z 11 • .:i tl.8 112~ 4 ~? l~Uo{ TH UAI( H.Jl< >I A~tl•JE1 .lA~tM£:NT, llEVti-LY HILLS, I.Al. J't O't 'tO -118 2) /.b lH 1t2 't9 .H .1 . J9.) s.1 1131 45:J •U-<f,1 •U,\tll.lkY U«IVt, Fl«•' FLOUR, t>cVtKLY HILL~, CAL. .>'t U't U7 -Utl .24 :U. 184 .:b 0.1 .>b." 40.) 6.4 I l34 l~JO CtNlURV p~µ~ tA~J, dASl~cNI IP-;), LO~ AN~E~c~, LAL. .l't .i .. 'tb -118 V 'tZ l 7<t :;o oo 38.9 "l. 0 6.0 113 7 I 59 hl Vi':"' lUkA .ll ~U., llA jl:Mt:.• f, Lu~ ANui: LcS, vAl. .J't U9 Jo -Utl 2t1 'td !'15 52 4d , 9. (J Jl.8 4.9 Jl4l LAKE HUGH£5, A-'~ AY , l .\11\Ji• 11 CAL• .l't 'tU JO -Ut> /.b /.4 J50 "' ... i.'1.6 32.3 . 2. l Jl42 L~KF HUt;tlc51 AKl'."Y ~I ,.1 IUN 't, i..AL • J4 3d .hl -118 211 .. a hl 2b 2t. /.b.d 2 ':1.8 2.0 Jl43 L<\KE HUuHE~. l\kl<AV •l•.Tli..N 'l1 CAL. J4 Jo :;u -118 ,3 'tL :;,:; 11 4':1 ti>. b 29.b o.o Jl44 LAK F. HC!.;rtES 1 A~R"Y ~141 lu"' lL1 (;Al• :;., ,4 ld -H<> H J6 '19 "" 't4 c!.:I. 3 2 IJ. 1 o.a Jl4S l?l01 VA>-IJWh ..) T" ti: 1 , t>AScMt.ll 1 LJS AN~EL E~, (..l,L • J .. ll 4l -11 b 27 42 193 15 05 24. 7 28. 0 1.5 JI 4-3 1· l ~ ; • 'IJkM4~UIE NV~!'.ut, dA~c:Mt:~r t LUS ANijt:Lt:5t C"L. ,., OJ .,; -llb 17

,b

loo uJ lll JC,. 9 'tl..O 5.6 Lio'> 1~18 LA~K~R5rl!M t>lVJ., uASl:Mcl.T. LU~ ANGcLE~, \.."4L • J4 lit> 1!> -l lb 21 j~ 17U :>I O't }ll. 8 JJ.lt 1.a ll 71 S'ltJlH~k·~ l.AL If. bJ!'.)Lil ... , t.\Jl.l~ "" PU., Ek f'LANI, SA1~ l11~uFRb CAL. .,, .:/. OJ -1 !7 J3 17 145 4.> H 1J9.6 140.4 l.4c 1'17o 11 ';0 ~JUTH Hill :, If< 1:t T, )tJtl-tJA51::Mi:o~l 1 L!J) Al'lutlc), I.AL. .14 U/. 4\J -11<> 15 "H lo l 't3 't4 42.-i 44.8 2.5 "(79 TEHA.:HA>'l ~.JMP 11'.t, PLAN{ 1

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j'

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,j

-lld l1 JJ lo7 llt. J; 7;.o 7't.S 1. d OlOb HALL Uf ritC.Ui<O;, ~ >\.i dfi<NAR U I NO, (.AL. '" Oo iu -117 17 O<t 101 5d llb IUt!.2 109.o 6.; r:.207 RE SE<{VOl 1<, FAI °'Mu1,I 1'.cStkVul K, (;AL. J't 42 la -llb i5 J7 35, Qll 14 .>l. ts 3S.J a.Ile 0208 u"1v2~s11Y uf l.Al I fU;,NjA1 oiA·'lTA ~4~tlA~At C.4L. J'> i .. "" -U'1 51 OU 27ll /.o '3 l.H.4 lJlt.O l.1 0210 H')S~ Shl"AGE 1<Jt_;,1, lli:MEI F I ;..i; S T AT ION , HcMCl t C4L. >3 .. , 47 -llo 5tl 4S ll'f ;~ ~I> l:>l.4 152.0 2.2 1>214 4fo7 SlJo"'ISt 1 .lUJlcV>1.<lJ. BASEM~Nr. LUS ANGt:Lt:S, t;"L I FURNIA J4 us , .. -lltl 17 J7 lt>3 31! H Jo • .!. J8.5 1. 0 TABLE 2. 1. Continued.

CALTECH REF NO. STATION P2l7 3345 W!LSHlkE BUULEVtd{lJ, BAStMtNT, LOS ANt;t:LE5, CAL. P220 666 wEST l'I TH >TKEtT, GkUUi'U F LUU!<, CUSTA Mt>A, C.AL. P22 l SA~T~ ANITA Kf;ERVulKt ARC AU I At CAL. P222 PORT HuENE:MC, iMVY LAoO~ATURY, CAL. P223 PUCDli'lGSTUNt Kl:'Stt<VO! Kt SAN DIMAS, CAL. P231 9841 AIRPORT BOULtVA<ll, BASb~cNT, LUS AN.,i:LE5, C.ALo 0233 1472., VE~TUl<A bLlULl:VAkU, !ST FLOUR, LtJS AN.,ELI:>, CAL. 0236 1760 N. J.{:HID AvHUE:. uN) FLLJLJI<, .;uLLYWOUJ, t..AL. 0239 9100 wlL>HlRc oOULtV~KDt oA>tMtl\T, BtVl:kLY tHLL>t CAL. 0241 BOO "• FlKST 5TREtT, i>T FLUJK, LOS ANl.tL t; t l..AL. R244 222 FIGUERUA STREET, 15T rlJOk, LJS ANt;tLt:St CAL, R246 6464 SUNSET BUULEVA~u, dA ~E1'lt:NT, Lll5 ANGcLE5, ~AL. R249 19CO AVENUE )f Tt1t: SI »KS, bASC:MC:NT, LU5 Af'<l>cli:5, CAL. <1251 234 rlGUc~JA STktEf, llA 5b1lN ft LJS ANGt Lt::>, CAL• R253 535 5. f.{EMOIH AvEIMI:, o145EMENT, LOS ANGt:L t>, l..AL • S255 620() ~IL5rHR: ~UULi:VARDt (,~UUNO FLLOK, LOS AN~ELES, CAL. S258 3440 UNI VtK51 TY .:.vENu lt bAStMENT, LUS ANl>i:LESt LAL • S261 1177 tlE\/E~LY OKI Vt, tlA5cMENT, LUS ANGELES, CAL. S265 3411 wlLSHIKE BOULEVARU, 5TH tlASEHE:NT, LOS ANt;ELcS, CAL. S266 3550 wJL!>HIKE oOULt VAkO, llASi:HENT, LilS ANGELtS, LAL. S26 7 5260 CENTUARY BUULEllAKUt !ST FLUU~r LLJS ANt;t:Lt:), LAL. * re is epicentral distance; rh is hypocentral distance. ** From beginning of accelerogram. a Instrument triggered by S-arrival.

STATION COORDINATES DISTANCE(KM)* TIME(SEC)AT N E AZIMUTH re rh S-ARRIVAL"" .:>4 OJ 45 -ll!l 17 43 lo5 21 't9 <tu.o 't2. l l. l c:'3 _;o JS -117 55 _;5 152 36 ~4 95.a 96.7 o.oc 34 11 IJ(J -li!l 01 Ob 1£5 24 H 4.:1.3 45.2 0.6 34 u-, 00 -119 l2 00 24d 45 09 79.3 ao.3 0.5 _;4 05 16 -Ll1 48 4tj 1.:3 LO 46 b5. i) 6b.2 2.5 3.:S !>o '+6 -Lid ,:_; 0'1 llb 3:0 l7 51.7 53.3 o.oc .:>4 09 Lib -l lt:i n 19 l '1 l l<l .. 7 L'l.3 .:S2 .1 4.'1 .>4 06 i.O -110 .:o .:o 168 ~l u.: J4.9 Ji.:; 4.6 .>'t 04 00 -1 ld £J 2L 176 Lu 3<> Jo.4 40.~ ... s .:>4 OJ 2b -llo 15 02 loJ Ob <tL 41." 43.8 6.2 .:>4 UJ .<5 -llll IS 03 lbu 01 51 41.9 4::1.8 s.2 34 U~ !>U ·-lid 19 52 167 51 lO jj.7 J8.0 5.0 .>4 U3 .>5 -lltl 24 5<> lb4 40 lO J9." 41.3 5.0 ;4 u; ,u -llo 15 25 lbU Sl J2 41.o 't.3.8 2.9 .>4 0.:1 u9 -lid 15 211 lbl 2.:1 .:u 4£.U 44.0 5.9 ;,4 U.:> 4 7 -us 21 43 17;; JO 5o 3!l.9 41.0 1. u 34 Ul .!.l. -ll!l lb 59 io:i 14 ;,4 44.0 4o.5 4.8 ::>4 Q; .:1 -118 l3 43 175 21 05 .:19.o 41. 7 o.o ;>4 OJ <t5 -ua 17 57 166 Qj 01 .:19.9 42.0 5.9 ::>4 0.:1 42 -llB 16 06 165 54 1) 40.0 42.l 5.b J3 5b 4£ -11~ 22 19 174 513 07 52.0 53.6 6.2 b Instrument triggered after S-arrival; 0. 0 used in computations. Value given is inferred by comparison of ground displacement waveform with that of nearby record. c EstiJnate uncertain. TABLE 2. 1. Continued,

r ,.p. l._N r

Dalam dokumen A Study of High-Frequency Strong Ground Motion from the San Fernando Earthquake (Halaman 37-52)

E 15