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Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December, 1968 LARGE SCALE PROCESSING OF SEISMIC DATA IN SEARCH OF REGIONAL AND GLOBAL STRESS PATTERNS BY A. BnN-MENAHEM, H. JAROSCH Am) M. ROSnN~AN ABSTRACT A composite computer program has been devised for a fast reduction of multi- station seismic data in the period range 50-500 sec for mantle surface waves and 20-100 sec for body waves. The analysis aims at the reconstruction of the seismic source from the spectrum of its far radiation field and the correlation of its parameters with its depth, size and regional environment. The capability of the computational procedure has been demonstrated in two studies of WWNSS records: one includes a spectral analysis of surface waves from a shallow shock in the Kurile Islands; the other includes a spectral analysis of P waves from 9 shocks in the depth range 550-700 km at Fiji, Mariana, Java, Japan, Peru and Brazil. Other applications of the proposed data processing routine are foreseen; a tsunami warning system and focal depth determination from spectral modal ratios. It is believed that a persistent search for stress patterns, based on the processing of a sufficiently large sample of seismic events, is essential to any future program of earthquake prediction. INTRODUCTION A major problem in seismology is the development of dependable numerical pro- cedures for the extraction of source information from the various seismic signals. Chief among them is the spectral equalization method. (SatS, 1955; Tukey, 1959; Aki, 1960; Brune, 1961; Ben-Menahem and ToksSz, 1963; Kasahara, 1963; Toks6z, Ben-Menahem and Harkrider, 1964). According to this method one isolates on the seismogram certain wave forms which correspond to seismic rays or modes. These wave forms are separated from the records, transformed into digital form and then subjected to a Fourier analysis. The spectrums are then compensated for whatever "happened" to them on their routes from the source to the stations. Effects such as dispersion, attenuation and instrumental distortion are taken into account. Finally, one compares the amplitude and phase residuals with theoretical source models in order to determine the physical parameters of the source. (Ben-Menahem, 1961; Haskell, 1963; Ben-Menahem and Harkrider, 1964; Brune, 1964; Ben-5.[enahem, Smith and Teng, 1965; and Aki, 1966). This equalization procedure is applicable to the entire spectrM range from body waves of 20 second period to periods of the order of one hour. (Alsop and Brahe, 1965; Teng and Ben-Menahem, 1965). Recent studies in this particular field have furnished us with an incomplete picture of the seismic source. Most of these previous studies were based on data from a single seismic event. Since the establishment of a world-wide network of standard stations by the USCGS, studies have been made of single events around a network of stations. However, in order to obtain a fuller understanding of the nature of the seismic source, it would be extremely helpful to study many earthquakes from many regions, achier- 1899

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Page 1: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December, 1968

LARGE SCALE PROCESSING OF SEISMIC DATA IN SEARCH OF

REGIONAL AND GLOBAL STRESS PATTERNS

BY A. BnN-MENAHEM, H. JAROSCH Am) M. ROSnN~AN

ABSTRACT

A composite computer program has been devised for a fast reduction of multi- station seismic data in the period range 5 0 - 5 0 0 sec for mantle surface waves and 2 0 - 1 0 0 sec for body waves.

The analysis aims at the reconstruction of the seismic source from the spectrum of its far radiation field and the correlation of its parameters with its depth, size and regional environment.

The capability of the computational procedure has been demonstrated in two studies of WWNSS records: one includes a spectral analysis of surface waves from a shallow shock in the Kurile Islands; the other includes a spectral analysis of P waves from 9 shocks in the depth range 550 -700 km at Fiji, Mariana, Java, Japan, Peru and Brazil.

Other applications of the proposed data processing routine are foreseen; a tsunami warning system and focal depth determination from spectral modal ratios.

It is believed that a persistent search for stress patterns, based on the processing of a sufficiently large sample of seismic events, is essential to any future program of earthquake prediction.

INTRODUCTION

A major problem in seismology is the development of dependable numerical pro- cedures for the extraction of source information from the various seismic signals.

Chief among them is the spectral equalization method. (SatS, 1955; Tukey, 1959; Aki, 1960; Brune, 1961; Ben-Menahem and ToksSz, 1963; Kasahara, 1963; Toks6z, Ben-Menahem and Harkrider, 1964). According to this method one isolates on the seismogram certain wave forms which correspond to seismic rays or modes. These wave forms are separated from the records, transformed into digital form and then subjected to a Fourier analysis. The spectrums are then compensated for whatever "happened" to them on their routes from the source to the stations. Effects such as dispersion, attenuation and instrumental distortion are taken into account. Finally, one compares the amplitude and phase residuals with theoretical source models in order to determine the physical parameters of the source. (Ben-Menahem, 1961; Haskell, 1963; Ben-Menahem and Harkrider, 1964; Brune, 1964; Ben-5.[enahem, Smith and Teng, 1965; and Aki, 1966).

This equalization procedure is applicable to the entire spectrM range from body waves of 20 second period to periods of the order of one hour. (Alsop and Brahe, 1965; Teng and Ben-Menahem, 1965).

Recent studies in this particular field have furnished us with an incomplete picture of the seismic source. Most of these previous studies were based on data from a single seismic event. Since the establishment of a world-wide network of standard stations by the USCGS, studies have been made of single events around a network of stations. However, in order to obtain a fuller understanding of the nature of the seismic source, it would be extremely helpful to study many earthquakes from many regions, achier-

1899

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1900 BULLETIN OF TI-IE SEISMOLOGICAL SOCIETY OF AMERICA

ing through the resulting distribution of events a much firmer basis for the drawing of more general conclusions regarding the mechanism of earthquake sources.

We shall now turn to a detailed description of the computational procedure,

ANALYSIS OF SURFACE WAVES

With the aid of modern ultra long-period seismographs it now becomes possible to record mantle Rayleigh and Love waves from shocks with a Richter magnitude that is as low as 5½ (Figure 1). Had the WWNSS been equipped with seismographs of this kind, the present suitable data for source studies would have increased by a factor of at least ten. With the recordings of the WWNSS, however, we must restrict ourselves to magnitudes higher than 7. For lower magnitudes it is difficult to obtain a good azimuthal coverage for most source locations.

PASADENA, Z

DISPLACEMENT SEISMOGRAPH

Tg =85 sec Ts =60 sec T=50

05 5 0 0 0 RI 06 O0 O0

06 50 O0 07 O0 O0 R2

08 50 O0 ,~D 5 09 O0 O0

At =-17.4 sec

SOUTH SANDWICH ISLAND REGION FEB 9, 1966

56.7S 25.7W to=O4 40 28.4 M : 5 { - - 6 ½ , H:27km.

FIG. 1. Displacement seismograms of mantle ~ayleigh waves from an earthquake in the inter- mediate magnitude range. (By courtesy of Mr. l~alph Gilman and Dr. Stewart W. Smith, Cali- fornia Institute of Technology, Pasadena, California.)

Let us therefore assume the availability of a readable set of long-period seismograms with a fair azimuthal coverage. Assume also that the origin time, the source coordinates and the source depth are known, and that the relevant Rayleigh and Love signals have been separated from the records and digitized. To speed up the identification and separation of the various signals from the records, we found it quite useful to prepare a routine which prints for each station "arrivals" and "departures" of Love and Ray- leigh waves, corresponding to a few chosen group velocity windows.

Figure 2 summarizes the chain of operations relevant to the first stage of the data analysis. Let a time-interval on the seismogram be represented by the function If(t) ./(to, tl)} where I = i for to < t < ti, and I = 0 for tl < t and t < to. Its Fourier transform (the trace spectrum) was defined by us as

ft tl F ( ~ ) = f ( t ) e - i~ ' dr. 0

(i)

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REGIONAL AND GLOBAL STRESS PATTERNS 1901

Using the modified trapezoid rule to evaluate the integral the program then prints amplitudes, phases, normalized amplitudes and log (amplitudes) for any specified set of frequencies. The program was designed with multi-station input data in mind, namely, with the object of minimizing the visual and manual labor of the research staff by letting the computer do most of the routine work, including simple decisions.

The output of the first stage is obtained simultaneously in two forms: (1) as corn-

SURFACE WAVE ANALYSIS PROGRAM PT.I-FOURIER OR POWER SPECTRUM ANALYSIS

AT FRG

N

N R

PRINT T

N

r

~ANS ER

CO~PUF~WlNL<

b J Q

FIG. 2.

Q P I

q

N

N

Y

Flow diagram for a routine Fourier analysis of multi-station seismic data. Y = YES, N = NO. Connections (1) and (2) lead to Figures 3 and 14.

purer sheets on which the trimmed, detrended, filtered and tapered (if so required) Signals are plotted nnd their Fourier spectrums tabulated and plotted, and (2) as tape or card output carrying the same information.

This output serves as the input to the second stage, which is summarized in Figure 3. The reader should keep this scheme in mind while we explain its details in the sub- sequent figures.

The theoretical background of the equalization method is as follows:

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1902 ] ~ U L L E T I N O F T H E S E I S M O L O G I C A L S O C I E T Y O F A M E R I C A

The source is assumed to be specified as a product of three factors: (1) the spatial factor, which depends upon the equivalent force system; (2) the temporal factor, which is the Fourier transform of the source time function; (3) the finiteness factor, which arises from the hypothesis that the rupture along

the fault moved horizontally with a uniform speed over a finite distance. The spatial factor, like the other two factors, is complex; it is determined by the

orientation of the source, its depth, and the structure of the layered medium through which the signal propagates. As the signal spreads out on its way to the recording station, its spectrum is modified by:

SURFACE WAVE ANALYSIS PROGRAM PART I I - SOURCE MECHANISM

<

OF SN. ~ , SN. i VELOCITY I [pRINT

OBSERVED COMPUTE PHASE COMPUTE SEARCH FOR BEST RAYLEIGH AN D VELOCIT(ES FROM FIT OF FAULT LENGTH LOVE RADIATION PHASE SPECTRA INITIAL PHASE AND RUPTURE pATTERN

AMPLITUDE OBSERVED AND FIT OF DIP AND CALCULATED

SPECTRUM DIRECTIVITY SUP ANGLES

COEFFICIENTS FROM CALCULATED I AMPLiTUOE SPECTRA [RAOIATION RATTERNj

C OFLF:C!C, 2 'NM E

FIG. 3. Flow diagram for quasi-automatic derivation of source parameters from multi-station surface wave data.

(i) attenuation due to the inelasticity of the upper mantle; (2) dispersion, geometrical spread, and polar phase shift over a spherical Earth; and (3) the filtering and directional effects of the recording instrument. The compensation for these distorting agents is known as the amplitude and phase equalization of the signal's spectrum.

In the case of earthquakes which exhibit multiple arrivals of both even and odd orders, the "directivity method" can be used to determine the fault length and the rupture speed (if any) from records of a single station. A ratio of spectra of even and odd arrivals is fitted to theoretical curves for various combinations of fault length and rupture speed. This ratio, known as the directivity, can perhaps be better visualized if one imagines the radiation field of a moving antenna of finite length. The spectral

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R E G I O N A L AND G L O B A L S T R E S S P A T T E R N S 1903

ratio of the forward to the backward fields is diagnostic of the radiator's length and speed.

Once the source parameters have been determined from the direetivity, an immediate comparison is made with the extent of the aftershoek zone. Previous results indicate that there is some relationship between the "direetivity fault length" and the after- shock extent.

The phase equalization method can be used only if the phase velocities over the

P~IGIN a - I LATITUDE= L1~0~0~ t ONCI TUD[ - I~5.1CO

STATION L&T|TUDL Lf]N~ITUnE bZIWUTH yNV.AZINUTH D[STIDEG) OISTIKM| CIRCLE

A-I 1%650 145.1cO 0 C u 0 ~OOo9.15 GUA~ 1 3 . 5 ~ 8 1 ~ 4 . q12 1 ~ 1 . 7 6 1 . 7 0 5 . q ~ ~,65,~L, ~ C O o g . 2 1 MAT" 36°542 138. Z19 341.71 15fl°44 17.q3 Iqq4°47 40015°17 SHKb 34.530 132.678 325.98 140.~9 18.51 2C5~.85 ~OOLS.ZJ &NPl 25.183 121.517 2~5,61 9%5& 72.49 25C2*2t 4bOOS.34 DAV~ 7.08~ 125,575 239,38 54.B3 22.67 2523.47 40053*~0 MAN" ] ~ ° 6 6 7 121.0P3 2 ~ 1 . 6 8 74*55 23.46 2610.79 ~b067*79 ~aG~ 16°411 12O.~0 ?~b.20 75.5b 23.5~ ;O18.35 4bUOe*Sb SEO~ 37.567 12~ .qb7 322.35 133.55 23,88 2656,59 ~0U31*75 RAB$ - 4 . 1 9 3 152.171 152.88 343.84 24*&4 2743*22 4001~.2b PNG~ -9 .40g 147.154 175.80 355.qq ?fl. QC 3216.53 40609.47 HKC~ 22.30~ I14.172 280.81 59.57 28,98 3225.14 40067.15 HN5* -0 ,432 15q.947 151,80 333.16 32.34 36C0,30 4bU27,3~ OAR - 1 2 ° 3 ~ 3 13U,8~3 2~4*qg 24°0& 3 ~ . 7 q 3Rb7,97 ~UUI�*73 NMA$ 1 2 . 2 1 0 i09,212 263.43 7 3 * ~ 35.?~ 3g?I,2~ 4 0 & b 8 . 2 0 CTA$ -ZO*OBH 14b*254 17B.29 358.29 3g,46 43qz,og aOU~9.~l CHG" 18,790 98 .g77 276.92 PI.C,B 43,46 483&.66 4U0b~*~5 ADA 51.863 -176.655 ~3.63 237.34 ,3 .~8 ~ 7 9 . ~ 9 4bU~7.55 SNG* 7 ,173 lO0 .&20 2~C.20 6g .~7 #4, R~ 4 q g 2 * ~ 40007*31 LEM" - 6 . 8 3 3 107*~17 238.23 53°8Z 45 ,2q 5041.~7 4U052.29 BIND -b,�OO IC7.650 238.13 53.75 4~.31 5043.25 40052.ZO NOU - 2 Z * 3 1 0 16b*~51 152*35 331.B0 ~6.5g 5185*33 4 0 u ~ * 9 6 SHL m 25 .567 g l , ~ 3 2~7,23 85*54 4g .23 5477.b3 ~O~bJ*B7 HOW ~2.~17 M~.3~g 2E3°b8 ~I .8b 5~°53 5577*g& 4006b.75 KIP ~ 21*623 -158,C15 77,53 278. q0 53*06 5906.01 4006b.31 RIV~ - 3 3 ° 5 2 9 151*15~ 173,72 352. Be 5~*44 ~ 4 7 . 7 7 4~009.8b &FI * -13.909 - 1 7 1 . 7 7 7 124*81 307.14 53.q5 b004*53 ~0049.39 ~DE~ - 3 4 , q67 13~.7;~9 1P6.4~ 7 .40 54.~C 6076*82 40U~g.�u MUN* - 3 1 , g 7 5 116.227 2(8 .P7 32,35 5B°28 64Bb°~3 40083°03 P ~ 7~*1~3 --156mg~0 ~8*3~ 245°63 6 | * ~ q bB3Z.43 4bO~5.Ub NDI$ 28. b83 77 .p17 2o2,66 81 .q5 61.q~ 6885,64 4C0b0.18 TAU* -~Z, gIO I~7*320 178.1~ 357*63 62,23 6924.66 40u¢9.21 COt~ b4.900 -147.7°3 26.23 2~7.60 67.74 &972°59 4UOZU*84 ~AHO 31.550 74*333 2~6*2~ 8Z. 1~ &3.g7 7116.3b 40USl*~b KOD 1b*733 7 7 . ~ 7 272*&1 73.10 65.67 7308.65 4U068.94 WFL* - 4 1 . 7 8 7 174.767 156.01 32g,4z 66*54 7404.0~ 4UOIg*Uu ~000 1 ~ , 5 3 3 7 ~ , 8 5 0 2~2.32 7 6 . 1 7 66*57 7440.~7 4u066.34 R~R~ - 2 1 . 2 1 7 -150.773 124.54 303.14 67 .4~ 7511.2b 4005u.18 O U ~ 30°IA8 6~ .q5~ 2qb ,g~ 78*25 70.4& 78~7*'7g 4Cb57*57 PPT - 1 7 * 5 3 3 -1~q*5~3 I15*59 796.9~ 73.99 8235.89 ~b05?*81 ~5H* 36.311 5 q , 5 8 ~ 3 6 3 ° 5 9 76.49 7 5 * 1 6 5358.24 4OUSU.bB CMC* b 7 , 8 3 3 - I15*0~3 22.7( 2~6.50 75.67 ~407.35 ~OUI~.O5 ~OR~ 44.55b -123°313 47°~0 Z55,23 77,61 562~*91 46O41*14 L~N • 46 .750 - l ~ l . 8 1 0 ~4*5~ 285.79 7 5 * ~ ~676.O6 ~ 0 0 ~ . ~ 1 N~R~ 51 ,~00 - 1 ~ . ~ 3 357.31 17.50 7q.57 8727*39 4UOug. Z8 RKS~ 37*877 - 1 2 ~ * ~ 5 53.3~ 287.15 5&,26 ~ 4 . e 4 40U4 / ,b~ KE~O 69*757 27*~15 3~ I .R~ 57*39 M~.~( ~g87.44 ~0Ol4*92 RIG* 70.a17 2 1 . ~ 3 3~3.43 52*89 81.94 9 1 C 2 . 1 ~ 40UI4.Ui CCG • 77 .167 - b l . l ~ 3 5.72 3~5*13 87*1 ~ 912~*47 ~OOuq.?5 SH|$ 29. b44 52.526 2~8.74 71.72 52.69 9197.39 40u55.iO T A ~ 35 .675 46*3P7 3¢~,00 69.3~ P4,55 9401.21 4OO45.2b P~S 3~.148 - I 1 8 . I~7 75.53 ~8g.~6 8~*57 q406.34 ~OO50.Ib 80Z* 45*600 - l l l . b ~ 3 ~3°3G Zq2*q3 ~5,0 o 9458°89 40067°2~ G$C~ 35 ,302 - l i b . @ C 5 54.35 290.~1 85.23 9477.Za 4004~.b5 PLNO 3~*353 -11E*8~2 56.1g 2qO*t~ 85*E6 g54~*84 4U05b.45 DUGm 40o195 - 1 1 2 . 6 1 3 ~ * b 3 Z92*S2 86*38 g6c3.74 4 0 ~ 4 ~ . 8 ]

Fro. 4. A computer output o~ a distance-azimuth subroutine for a network of WWNSS.

great circle path from the source to the station are known. If the path is mostly continental or purely oceanic, appropriate phase velocities must be employed. The essence of this method is basically a careful "bookkeeping" of the phase history of the signal. The thumb rule is, that all phase advances due to propagation, sphericity, source to station geometry and instrumental distortion, must be subtracted, and all phase retardations (such as the initial phase due to time dependence and finiteness) must be added to the phases of the Fourier analysis. The algebraic signs of the Fourier phases depend upon whether the Fourier transform has been performed with

ioJt e-i~,t e o r

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190~t : B U L L E T I N O F T H E S E I S M O L O G I C A L S O C I E T Y O F A M E R I C A

Once the phases have been stripped of everythh~g which "happened to the signal on its way to the station", interpretation in terms of source elements begins. Theo- retically, for the horizontal component of displacement due to a point source, the sum of the spatial phases of two opposite-going signals must (for a shear fault) be exactly equal to ~/2. If the source is of the propagating rupture type, the sum will be equal to ~/2 - ,f, where f is the frequency and r is the time of rupture.

Next, the remaining phases are explained in terms of the orientation angles of a displacement vector at the source. This is done with the aid of an inversion program which calculates theoretical phase spectrums for various orientations and depths in a multilayered flat earth model.

Figure 4 shows a typical output sheet which gives the necessary geometrical dis- tances and angles from the source to the recording station network.

Figure 5 shows a sample of the amplitude equalization procedure. The second and

CflROESTED &MP[ITUDF SPECTOUM I ~ I I | PERIOD AMPINI, I ) ATT AIN$ CnRRAMP 1 5,0OOOF -3 2,0030F 2 5,646BE 3 2.901BE - I 4o?D26F ? 6.6225F I 2 5,2000F -3 1,92~IE ? 5.g~OPF 3 2.6~P3E - I ~.O431E ~ 4,~Sg~F 1 3 5,~OOOE -~ I.851~E 2 5.qgl2F 3 ?o3807F - I 5.104oE Z 4,°132F l

%@000[ -5 1,7q57F ? 5m6R74L 3 2,2657E - I ~°5~7~F ~ 4°4@~2E I 5 5.~OOCF -~ 1 , 7 ~ I E ~ 5~37~PF ~ 2,C522F -1 6oO~g~ ~ 4o2~73F 1 6 5.O000r -~ 1.6067E ? ~,3742F 3 l , q ~ 3 1 E - I 6.613BE ~ ~.155~F 1 7 5, SDDOF -3 1.612qF 2 <,751FE 3 l . eS@BF - I 7,15e3F 2 4.~lqTF [

b,~OOOF -3 1,5675F ~ 6.26gCF 3 I,~B36E - 1 7 ° 7 0 7 ~ 2 ~ , ~ O F I q b, bOOOF -3 Io5"152t ? 6.615~F ~ 1.6023F - I 8,?BIDF 2 6.97736 1

| 0 5 , 8 0 0 0 F -3 1,47G~E ) 5.6283~ 3 I,~@~2F - ] B.@703~ ? 5 ° 4 0 0 8 E I 11 7,0030f -3 1,4286E ~ ~.381~F ~ I.IOC7F - 1 q.474~F 2 5 . 6 ~ 7 4 F 1 12 ?.2000F -a 1.3~89E P b.O~6IE 3 l°lqOTF - I l .COqS~ 3 5°0~95E 1 13 7 , ~ 0 3 0 E - 3 1 , ~ 5 1 4 E ~ 5 , 7 3 ~ 5 F ~ 1 . l q C T F - 1 l ° n 7 2 3 E 3 4o4@~OE l I* ?,SOOOF -3 1,3158E ? 5,2484F 3 I.I~32F -I 1.1366E 3 4.~b80~ I I~ 7,803~ r - 3 1 , 2 8 7 1 E ? 4°505~F ~ 9 . 7 6 ~ 3 E - 2 I.2O?~F ~ 3 , 8 3 0 6 F I I~ @.OO30E -.3 1.250~E ? 3.616~F 3 I.C264F - I I°26~5E 3 ~o7734E 1 17 8.20DOE -3 1.21O5F P 2.5~07F 3 I,C138~ - I 1.335o~ 3 ~,IOI4E 1 18 B.4OOOE -3 1.1905E ~ 2.5042F ~ I.O013F - 1 1.40~1~ 3 1.77@1E 1 lq 8,6030E -3 1.1628F 2 Z.6346F a °,B@OgF -2 1,47~IE ~ 1.8C53E I 23 8.8900E -~ 1 . 1 ~ 5 4 E ? ~.9384~ 3 9.76~3F -2 I.~42~E ~ l.q~64F 1 ?1 9. OODOE - 3 l . l l l l f ? 3 . 1 1 2 3 ~ 3 0 . ~ 1 2 4 F -2 1 , ~ 1 3 1 ~ 3 ? .G~ &3F l 22 9, SDDOE -3 I.O87DE 2 3,10o4 c 3 o ° o ~ -? I . ~ 'xt; ~ ?.0375E 1 23 9,4DOOF -3 1,5638E ? 3,ObBR~ ~ P,73eq ~ - ) 1.7~5~F ~ 1,9~72F I 2~ %6000F -3 1,04lTE ? 3oOEO~F ~ ~.47' 5F -? l .~27:E ~ l,qSbOF l 25 9 . 8 0 0 0 ~ - ~ | ° O ? 3 A E ;' 3 . 0 6 8 ¢ F 3 7 , R I l l c - 2 1 ,COROt ~ 2 . 0 6 3 4 r 1 25 I.DO30F - ] I,OOODE :" 3.1503F 3 7 ,2 '~P7r -? I . °712 c 3 2.1O~OF I

FIG. 5. A computer output for amplitude equalization of surface wave signals from a network of WWNSS. The particLflar result shown here is for a Rayleigh wave R8 recorded at Aquila, Italy from the Kurile Islands aftershock of October 20, 1963.

third columns from the left list the frequencies and the periods, respectively. The fourth column lists the Fourier amplitude spectrum over the given frequency range. Next is the physical attenuation factor e -~c~)A where -~(~) is the frequency dependent attenuation factor, and A is the central angle in radians from station to epicenter.

The column AINS lists the amplitude response of a critically damped and zero- coupled WWNSS seismograph system:

AINS (~) = MJ/(~02 + J)(~g2 + J ) where M is a constant pertinent to the magnification at the recording station. Ex- plicitly M ~--- M#0 where M0 takes one of the values: 6000, 3000, 1500, 750, 375. For a general reference see tIagiwara (1958).

Finally

C0R RAMP -- (AMP) (INV.AZC~I%) ~ A. (ATT) (AINS)

Letting INV.AZ be the inverse azimuth at the station, measured clockwise from

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REGIONAL AND GLOBAL STRESS PATTERNS 1905

north, then

INV.AZCOR = 1 for U, (vertical displacement) at all angles.

1 sin (INV.AZ)

1 cos (INV.AZ)

for N S Love waves and E W Rayleigh waves

for E W Love Waves and N S Rayleigh waves

The corrected amplitudes are given in units of ram-see.

I - 7 , O0 !

32 33 34 35 36 37 38 39 4.o ','1 . 2 *,3

45 4.6 ~7

4q '50 51 "SZ

53 5*. 55 56 57 58 ~9 60 6 ! 62 63

~5

67 68 69 70 71.

7~ 7 ,

?b ?? 78 79

81

FI 3 1 0 Z * * O l C - 7 q 6 5 . 0 ) F I l l T i l l C ( I ) A ( ] ) F ~ I J R I I I P H | N ~ I I ) F I N I I I I i P H J ~ F l l )

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FIG. 6. A c o m p u t e r o u t p u t for phase equa l iza t ion of sur face wave s ignals f rom a n e t w o r k of WWNSS. T h e pa r t i cu la r resu l t s h o w n here is for a Ray le igh wave R2 recorded a t S t u t t g a r t , G e r m a n y , f r o m the Kur i l e I s l ands a f t e r shock of October 20, 1963.

An example of a phase equalization is given in Figure 6. The wave R2 had traveled a distance of 31024.0 kin. along the major arc from the Kurile Is. to Stuttgart. The time difference between the origin-time and the onset of the filtered time series was 7965.0 sec. The appropriate phase velocities (in kin/see) for that path are listed in colunm four. The spatial initial phase of the far-field vertical component of R2 is generally given by

PHASE(I) = A ( I ) - FRP(I ) -- Pt I INS(I) -1- I F IN(I ) [ + ]STEP[ -- POLAR

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Page 9: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 10: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 13: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 15: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 18: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 19: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 20: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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Page 27: Bulletin of the Seismological Society of America. Vol. 58, No. 6~ … · 2017-02-27 · Bulletin of the Seismological Society of America. Vol. 58, No. 6~ pp. 1899-1932. December,

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• snao 3 aqc~ c~s £qdsa~odol out.aamqns oq# qlpa saa~amsasd oaanos otmstos oq:~ 3o UOl.~Sut.qmoa OlqSaOAS 3 amos £q pouaoao$ st. ilouomouoqd oqqt c~sqc l q~aodxo Ol olqsuossoa s~. c~,. 'pooc~saapun ilo~a c~ou s.t s!msunsc~ 3o mst.usqaam uot.~saauoS aql qSnoql -[V "aut.aSc~ oq~ 3o soaoqs oqc~ no stmsuns I ~llt.Tg�~ssAo p poanpoad ~ioq a�N%I-mnaa p aqcr m. poaanaao qa.N.~ s~aoqs ao[sm aq~ 3o ~so~ "~. oaoqs mmpom p~.ntt oqc~ pus aOOlJ usaao poqanwIp aqc~ uaa~ac~oq ~ut.idnoa S~aaua oqc~ m. a[oa c~uslaodmt, us £Nd Sam cmaaa aqc~ 3o uot~sanp IISaoAo aq~ pus 'uoDaun 3 om~ 3 s,aaanos OR1 'ao~aoa luomaas[ds~.p aq~ 3o uOt.lSCma!ao oqc~ 'oaanos oqcr jo ozI.s aql Isqc~ st.soqcrodgq us ol eraoddns spuoI so'4snbqlasO ,to~sm amos £q st.mvuns~ 3o uoDsaauo~ lua[.a~o oq& "uta~fi~ ~uzuotm~ .~u~vuns~ V (I)

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dnoa~ #sag oqqt qtvq~ oanc~voj ~utyoaoc~ut. aqc~ o~o N 'suo~.c~om int.c~t.u.t pun sapn}t.idms oa~,x jo stsnq oq~ no papanas~.p ss~a qa~.qat uoi.~nlos q~ctaaoSjt.p s £q pot.usdmoaos ssa~ uloqq~

~o ouo qana "suo!c~nloa Saq~acuuaSs snotaoad oqc~ moa~ snoDqo st ss 'vc~vp oq# ~o suot.a -~#aadaoc~m. o[qt.ggod oe,~a o# puodso.taoa ~ou op guot.}nlog oA~4 osoq,L "(t-a '0t-V '9-g 'g-V '~e-V 'IW) ~InvJ ~utddt.p og~e s uo uot.c~oua dt.is-dt.p s pun (~-g 'I-~¢ 'g-V 'g-V 'g-V) qqn~t isat.aaoa s uo uotq~om dt.is-dt.p ¥ :s~iaoqs doap oq~ ao t asoddn suot.cmIOS ~o sod£# o~a&

• m.oaoqc~ ~mavodds suo~.c~aun t at.ac~ocuouo~m aq# jo ssouonbmn-uou oq# moa~ s~Insoa #t. pun '(0I) o# (g) suot.#vnbo to oauonbosuoo ~ooa~.p s s~. ~t.q& "soa~±a d a°t uao#c~d uot.#m.psa omss oq# aa!$ iiFa qatqa~ ~atvd ~utpuodsoaaoa oaom ao ouo oq Snm oaoqc~ (y '{?) uoDnios qaso ao~ '[naauo~ u I

• snoDqo st (L) su°13vnb° oc~ £c~Vs .l.Xtu!s aq, L "sooa~op m. possoadxo oar SOlSUV ii s

'0 = (x)v + (0~t + x)v

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'(St) o# (8) suot.#snbo cuoaj pug oA~ 'X pus , sc~uamolO q~D~ oaanos #uomaaNdst.p n moat v., oa~,oSaacuo to o[Suv q~Fa sooaSap 0 to q:mln./zn us ~n popaoaaa Oanax d s to opn3t.iduls isa#aods oq# (0 "¢ '~) V ~q ~m.c~ouo(i "soas.~a d a°J suaac~:~sd uo!~st.psa aq~ ~to suot.:~sioa Sac~omcu~s oq# m. poc~aOl~ -oa st. s/.q& "onbNn clou oas suot.~nlos oq~ 'utsSs oaai_ I "(g961) aunaa puv dosig to ~qc~ qc~t.~ sooaSs #In~oa ano ~'-V to osva oq~ u I "guo!#nIos iva#aods pus uot.c~om-ist.~t.m " uoom -aq pom.~qo sww c~uamooa~v iinj s sassa osolt9 ~ iis u I "ao~.iaso poqt.aosop mna$oad om.qasm ocgsodtuoa ano Sutsn 'sn £q pomyNo oao~a 'm21 00L-00g oSu~z q#dop oq~ m. s:,iaoqs 6 ~m.pnlam. 'osoqc~ jo nOaOla "poq#oua uo!~om im.~N~, aq# £q poutyNo uo.tqmlos isuo~y.ppn u~ pus poq#om [~a~aods oq# Sq pom.s#qo suo~.anios ou~id-c~ins ~ gI s#uosoad I o[qs,L

• oSvaoAoa isonmt.zs #uot.a!ttns v qc~D~ 3.t punoas suo~.c~nc~s 0I ~o aSnaoas us jo smna#oods aq~ moat pat.pn#s uooq svq #uoao qan~ "it.zvaa pu~ nao d 'usdsf ,sAsr 'sust.asiA ~ 't.!~.~ I #s s:,[aoqs 6 1 o Spn#s oqc~ papnlauOa oAsqo~a '£pn~s st.q~ ao~ popuo~m. S~UOAO gf JO IV#O~ V jo #n O "L-9 o~uva apn#~.u~m 900 oqc~ ut. ~iooqs doop £aOa 10 £pms o~t.~asdmoa s ao~ posn oao.~ ~N3A3A oq# lo n#n(i

• inJ~m.usom oaom puv aot~o q#oq sl. uot.~vzt.inuot~oa oq# 'oaaq~ ~vq~ oaotlo q oa~ oam.s s~iaoqs doop q~I.~ po#av~s oaw[ oak "UOI~Oa llOAI~ S O~ r gJ0#0LlI~a~gd 10 Clr0g S tO #llOllIU~t.gsn 01.[q r 'gI. ~q~qc~ 'so!pn#s oaanos isuo~.~aa .lO t st. tu~a:~oad ano jo uot.gvo.qdds snot.Aqo #sore aq~ L "ga/ao,/~ daap fo @n~e ~)qolD (~)

~ "~O pus

oq# moaeI "ao#s I anoq u~ ~o~:ut~ ~/to os~qd-Xat.V aq~i, "a.m aof~m aq~ ~uois ov.i_ I t[a~a:t oc~ sanoq {g puods [it.~ ~/jo ossqd-Xa W oq# 'ao~o~ao H "~ocmm.m 0~ cmoq~ ut. oau~c~!p s~.q# sao~oa ~/ "sanoq L ~noqs s~. oou~#s.~p ~nq# ao~ om~.~ [oasa~ ~.msuns# ~m.puodsoa -aoa oR& "009 ~noqs st. Xaoqd~.aod s,usoao oR# moa~ oi! H o~ oausc~st.p o~aaas oqc~ :#ao[oad oqc~ o# c~usaolOa oar ~oas~a oasjans o[~mam pus soas~a .tmsun~# 1o saint.# io~sa# o~t.#SlO H

• oaanos l.msuns# oq# jo sao#omsasd o O 1o smao~ ut. po~adao~ut uoqa pus punoj oq IV.At s~uomo[a ~invj pus suot.#aun~ om n 'sot~t.M~aaa~.p 'suao##sd uot.#s/.psa a~.oq& "uoI.3sc~ Isa~uoa oqc~ c~ poz~.[snbo pu~ poz£i~u~ oq IID~ soAma~

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: ~mami[oj aqc~ sc~aoddns uosDa £q pac~uasaad s~sp aqa ~sqc~ aao~oaot D papniauoa s.~ c~ I • £[aaF~aodsoa ~uaa aad g6 pus ~noa aod g8 jo so~3t.asiod oc~ spuods

-oaaoa s~.q& "snao 5 oassans s aoj 03 ~noqs pus m:, I 0.e9 jo ~Ddop ISaOj s ao 5 L sI ~nba c~I • { I - a["~P]g } £q uoa!~ s! d ismaa}xo aq& "o06 jo o[~us d~.Is s pus o.e~ 5o oI~us d~.p ~ o~ s£s~aIs spuodsaaaoa £~.aslod [suioa~xo aq& "6[ °an~.<I ui. u~tsoqs oas salnsoa oq& "soi~uv di[g pus dip jo p,.a$ oa~.c~vc~uasaadaa s ao 5 pa:mduioa uooq s~q (y '~)d uoDaun5 oq&

(9[) "(Y'9)J = ('~ + OgI'9)d = ('( -- 0gI'~)d = (~('9 -- 08[)d

aam.s o08[ ~ '~ ~ 0 '006 ~ ~ -~ 0 osooqa ocl c~ua~.a~ns s.~ ~I (t796I aoP~.a~asIt pun uioqsual/V-ua~t)

u.~s y ms 'I ,~ ~us~ + ~2 ~us~ a N (~I) ~ ~ui.s ,~ ~ui.s i/,x" = ,~ usc~ - - ~N - ('~ '~)J -- ap T ,

'd a~uaoaod £~.as[od oq~ ao~ a~.aa~ pu~ o N < qN ~q~ ouinss~ Xsm o~ 'ousid oous~s!p papua~xo oq~ uo Xdnoao £aq~ qo.N~ ~oa~ aq~ o~ isuo!~aodoad aq o~ (suo~.ssaadtuoo ao) suoD~Ni.p ~o aoquinu oq~ ~ui)is~ pu~ s~aa~ a~.aq~ ~o runs at D ocl oA*.q~sIoa soloa~.a o~c~ oW~ ~o ~oa~ uouiuioa o1I, 1 ~m3ooi~a±~ "£[oA~.c~aodsoa 'ouNd £a~a~[~.xn~ aqc~ pun ausld-cqns 5 aqcl 5o saI~V dip ag~ oas ,~ pun ~ aaoql~ ,~ u~c~ { = ~/sn.,psa jo aoq~o aq~ pras ~ us~ { = .t sm.psa jo ouo 'saiaa~.a isuo~o~I~aO oa~ 5o ~s.ts*IOO ad£~ aaoqs oq~ 5o aaanos aapao puoaos s moa 5 saavl,a d a°J sam.[ lspou aq~ c~sqc~ uatou~i-iioea s~. ~. 'aattc~an d

• ausld aausc~st.p popua:~xa s,Xlaa~; a uo Lg'~ > t P [ > 96"I aauaH • sq~dop oaaz c~s o~9I = v.z o:~ q~dop Isoo5 auioa~xo cls age[ = v.~ uioaj £asa og0I = V aoJ soi~us jjo-a.,tm (8e6i) suios~.l t oc~ ~ui.paoaag "£sa aAs,~ d oqc~ 5o ai~us jjo-a:,is ~ aqc~ s~. (V)> = v? oaaq.,a v.~ ~oa = p sm.psa ~o aIaa~.a s m.tI,~.~ts o~.i IV..~ s~m.od poAaosqo aqc~ I[v c~sq~ oai.~ou a~a 'o90I usqc~ ssa I aas qa!tpa saauscls~.p isac~uoa~.do aoj slsu$~.s oasis- d oc~ SOA[asano ~ui.~a*.ac~solI "~asqa aaus:~s~.p popua~xo X[aoX a s no pocno[d uooq oasq c~uaao uaa~$ s UlOa 5 suo~/lom-asa 9 paaaasqo oqcl asqa ~xou ouinss v .~ OlSt, s d~.p s pus ',~ aiSus &.i s s £q pam.m -aoc~op s~. qa~.qax jo rJot.c~s~uo~.ao oq~ '~[ns 5 asusid s no uo~.~SOOlS.~ p :~**auiaaNds~ p s £laulsn 'aapao puoaos o~tc ~ 5o aaqc~sa cmq aopao oaoz lo ~ou s, oaanos aqc~ qsqc~ 's~.soqcmdAq s,.qq o~ £asac~uoo 'ouinsss sn cla~ I "s:,iaoqs auios ao 5 aaanos aqc~ c~s odsqs 50 aSusqa s 5o £c~.p.q -tssod s soanpoa~m, raos~.a~t 'soaanos ,,aa~.so[duq-i[%, ao ,,oa~.soidxo-i[s,, uioa~ soamasdop u.tsldxo O,L "g96I-g_e6[ po~.aad oq} u.~ s:,iaoqs g9 jo so~.a~.aNod uoF~om ~sag jo noF~nq~.ac~s~.p oq~ uo ~saa sc~r.Iotun~as st.H "oa,.soidtui " ao oa~.soldxa £Dusm.uiop ss poD~.sssia aq oc~ c~q~no sosi~nbqc~aso c~sqc~ pasodoad ssq aq 'sc~sp 5o soidmss u!sc~aaa ~u!u!uisx~ -tuns a!aq~ 5o oSsquaazod s ss passaadxo saoqmnu am aqc~ jo aa~saa~ atlc~ ss £c~.asiod ottc~ pou~ap pus c~uoao noa~ s 5o (~N) suotssasduioa 5o aoqmnra oq~ pus (PN) su°~.~s:~Slt.P 5 ° aoqmnu oq~ pa~unoa ssq oi_ I "£aooqc~ uo.~w~u-asag u., ctdoauoa injosn v paonpoac~m. (L96I) u°sDEt

• s~sp £~!aNod uo.~oui-~sag jo uot.~sc~oadaac~m.aa

uioa 5 samoa 006 = Y 'ogt~ = ~ uoF~nIos oq:~ jo oansu.vJ~op aqc~ ao 5 c~aoddns isuoD!ppv '@96[ ) suias'~.II 5 ° s~ui.pug aa,.iasa q~.~ c~uauiaaaSs

u.~ s.~ oiduiss ~uasoad aqc~ ui. s~[ooqs doap ao 5 uoDoui d~.Is-d~.p oqc~ 5o aausm.mop oq& • SIOliSasd o~ asaqc~ uaa.~c~

-oq uoI$os is,ao~snba oqc~ oc~ pauguoa oas dnoa$ puoaas aqc~ jo ~.aoj oq~ oi.N~a naoa~.ads 9 5o a!doa& aq~ 5o q~nos oq~ o~ pun aoaus D jo a~.doaz aq~ 5o q~aou aqc~ oc~ .,ao 5 s~,. ssq

L~6[ gNH~Vd ~gXH~g 'IV~OqD (INV ~IVi~OIDN~[

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s~aaj~a asaq~. 5o amo S "uo~.~Ouovo pu~ _~auonbaa~ 'q~dap s,oaanos aq~ uo spuadap q~dap u.~ sa~u~qa o~ suaa~d oq~ ~o _,~.AD.~suas aq~ ~sq~ pu~ q~dap s,oaanos aq~ jo aDsou~s!p st saAs~ q~.ai_~_ [ pu~ aAoq q~oq jo uaa~d uot.~s~.psa oq~ ~q~ puno~ oA~q (1e96I) aopw, Ia~ H pu~ maq~ua~-ua~ "~o}Tw, 7~Taad~ 7~pou~ ,uo~f uo.~Tvu.~u~,~aTap ~tTda o ( ~)

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jo sapom aoq$!q jo smnac~aads pacmdmoa (L96[) aopt.,~IaSH "sq~dap aaanos am[[sqs ~qs Iopom qla~a pla!qs ~ ao/006 = '( oel~ = ~ uo.~qscmolao ogc~ jo ~ql moa/oiqsqs!n~m.c~s!pm " st. c~qsq~ uaocF~qsd uoTc~t.p~a s s~q 006 = ~ 'o08 = ~ jo raoDqsc~uoTao ms qID~ aaanos z~ags s !-sql- u~aoqs oasq (~7) uot.c~vnbo uo pos~q suot.~[nais 0 "SlV~laas oava~- duo pos~q '~oDvu -~.maolop qc~dop ~DOgfl oqc~ scar 3 osis qot.q~,a 'm~ I .eg jo q~dop s aoAvj suoTqmAaosqo 'aao H • so~u~qa qc~dop-oaanos oc~ snaa~c~d uo!l~.p~a oqc~ ~o £c~.aT~.~suos oqc~ £ia~Ol a aaq~sa ol~a~s

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suapssv d '£~OlOUqao & jo o~n.aNsu I ~.uaop.Is O 'u0~ -vc~aoss~.G I~ao~ao(I '~apg~R paL*w) u~a?s'ac~ a*/~ u.z uo.,~fi~do~d aa~ca aa~f~n~ "(g96D "~ '~ 'a°pu~xaIv

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• sotu~.~ [oava:~ oav~a-Xpoq ot D jo ~m.mmva~oad oqcl ttcO.m sn podDq o~n~t:~su I nu~mz!oA~ ati1 jo ~.uoqsmvt ~ iosqa!iA~ "a(i "UoDvaHqnd jo aausApv u~. salnsoa s~q sno¢ su!~sa*unu~ -moa aoj 'pmais I opolpd 'X~.saoAV*fl ~aoalt jo aopla:~a~ H "O P~.A~G aosso~oad ~lU~q~ 0% qs~.~ o?A

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sm~va~vo~a~ao,vxa v

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o~'~- ouoz ist.aoc~nbo oq% jo i~at.d£~ st. oAt.~uao~i~ puooos o~[# ~q# so, solOns £IOAD -vC~llO% Oldm~s ~uosoad an 0 • (ogtr = ~ '006 = Y) "og~r ~v Sut.ddt.p c~in~ ~ ~ uo d~.is-d~.p s pu~ (°06 = e '006 = X) ~Inv~ Isa~3a eA s no dt.is-d~.p ~ :%u~ra.mlop oa~ suot.c~qm~uot.ao oa~/L "(I oIqS/L) "s:'Iaoq s doop poz£Ivuv c~som o~ uommoa s~. uot3s~uo~.ao d~.is-dt.p V (1~)

• (gI oan~.¢I) anaao Xoqc~ qa~.gea ut uot~oa oq~ lo oan~lsu~t.s v £aava OSlV Lyre s)iaoqs daap jo suot 3 -ounj am~.& "c~uouodmoa uo~.c~aun~-sc~io p v uty~toa £sm s~Iaoqs daap jo c~vq/L "uot~ -aunj dec~S4lUn v jo ~[~ q~t.~ spaoaav s>iaot[s ~OliSqs ~o aa~avavtia i~aodmoc~ 9q& (g) • q~dap s,oaanos oq~ no spuadap uo~3vaois!p aq~ jo az~.s aq/L "uo~.~vao[s!p av~qs ac~t.u~

jo cmqc~ oq oc~ stuoas sttc~do p ~o o~usa opD~ s c~s soaanos jo a~avavqa isBsds oR& (g) "mo~sLs

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• sgmt.c~ [aAvac~ oa~-Xpoq jo ash oqc~ q~noaq} poAt.aep q~dop oq~ qc~,.~ ~uoc~s~.suoo st. qa,.qa~ mN Og q: m~I 001r jo q:ldgp IVaOj v no aoaSv sassa qc~oa "o*0 - 006 = 0 jo q~nmt.z~ uv q~t?a o0 = '~ 'oel~ = ~ uoDvc~not.ao oqc~ jo c0aqc~ o3 ua~c~vd ~UOlSat.nbo us aonpoad ilPa 'o*0 = 0 qcmmtzv us qc~t.A~ oglg = "{ '006 = ~ suo~.}vc~not.ao oR% cmqc~ (L uot~nbo) aot.iavo poat.c~on oBA "suaoc~ -~d uot~m.p~a poAaosqo oqc~ o~ c~g c~saq v oAs~ oglg = X '006 = 9 ~o~.~nlos oq~ ~vqc~ uoqa punol s~a ~I 'S~NA~3A 9qc~ no pewoooa saA~l d jo sapnc~!idm~ I~a~aads moal (~96I) moq~uel?~-uaIt pus ~uoK dq pamtuaa:~gp u~oq s~ t ~iaoqs ~o S ~pus~[ o N jo mst.u~qaom oaanos oq& • ~//~/jo ot.c~sa isa}aads s moaj q~dop s,oaanos oqc~ aaaoaaa oc~ pasn aa~ :,[aoqs doop ~ moaj s[suSt.s oAs~ oaS~ans po,.aad-Suo I eaoq~a 'gg puv [g soanS~I m. u~otis st. oldm~xo u V "q3d~p [saoj oq~ jo uot.c~smy, iaa~gp aqc~ ao~ ioo% inpsn s ss aaaos ~sm soa~ea oao~ I pus q~tolgs E ~o sopom aoq~tq ~o suo~.#mqqmoa snou~A Jo Sot3~a Isa~oods "qL pl_tv .sL soan$~.~I m. poc~uosaad aa~ suo.v~slnalva st.q uo passq sc~insoa OUlO~ "[opom q~a~o aa~ds-jiv q paaoAvi,.~inm v m. suoD~aOOlS~.p-avoqs c~m.od moq saava~ aaoq pns q~DiAv~

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"~L-8~ '6. e "gfiydoaD "ddv pus a~n d 'suoDnIos ouvId ~In~J oiq~!ioa omo9 @96I) "~I V '~mos%r~ '0I-I '~e ua~u.~lapWoWa A '~ohw~pofi( 1 "~u I .~,~ldoa D pus

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DVIS~rA "a°~d 's°~Im~bq~avo ~o[[~qs I[~ms ao~ uot~oa ooanos OLI~ Jo suo.isLtom.i(i (~96I) "¢[ 'ssoacI 9[g-60~ '[~' "~suI "~a~t

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"oo S "Ms.*as" "lln~I 'q~an~ aq~ 3o sopom Ivmaou p~v SaA~A £poq 'somI.~ IoaVa/L '(~96[) "N "f 'ouna~[ "L2g-L~g ' I'd "~uV "oos" "Ms}as" "lln,ff

'oaoqd~ ~ uo SOAV3A ~anjan~ Jo a3.tqs os~qd an[Oc[ oq: L "([96[) dos[v '~ "~I pu~ ojn K "~[ "K 'f '°unaa • (ssoad m.) '£aooq& i~a.mdltdooo o0 suoD~a.qddn

sa! pus spnd(I s,uooa O jo suo.Isundx~ ao~aoauo~.I a '(L96I) q~ut~ cgf naan S pun "g 'txloqnnoJ/V-uoa "2g}-I0> 'I~ "v~V "aos' "*us}as'

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