Description of the program S Y N F A N Program SYNFAN is designed for the computation of ray synthetic seismograms at a system of receivers situated along the Earth's surface, an internal interface or vertical profile. Short description of the program SYNFAN Program SYNFAN is a modification of the program SYNT from program package BEAM87 written by V.Cerveny. The seismograms are computed from the frequency responses stored in the file LU8, generated in the program FRESAN. Program SYNFAN generates file LU9 containing tables of synthetic seismograms which can be plotted in the form of seismograms in the program BPLOT or in the form of particle motion diagrams in the program POLARPLOT. Both programs are included in the program package ANRAY. The fast Fourier transform algorithm is used to compute the synthetic seismograms corresponding to individual components of the displacement vector (vertical, radial, transverse) from frequency responses. Various source-time functions (input signals) can be optionally used in the program SYNFAN: Gabor signal, Ricker signal, Berlage signal, Muller signal,etc. Any other signal may be easily introduced in a discrete form by a table of points. The input signal may be filtered in various ways to introduce some required frequency domain effects (recording instruments, etc.). Moreover, filterring should be applied to exclude very low frequencies from the source-time functions, since the ray method is a high-frequency method and does not yield sufficiently accurate results for very low frequencies. Such filtration can be suitably performed by the double cosine filter, see input data No.11. The application of the double cosine filter is also suitable to select only the frequency range of interest and to increase the numerical efficiency and speed of computations. Positive polarity of pulses in seismograms is to the left of vertical time axis. Some plotting possibilities are available in the program SYNFAN. For each receiver under consideration the computed synthetic seismogram may be optionally plotted in a single frame. Moreover, it is also possible to plot optionally the modulus of the frequency response and/or the amplitude spectrum of the synthetic seismograms. All these curves are plotted individually, one curve in one frame. Such figures may serve for a detailed investigation of the wave field at selected receiver positions. Several figures may be also plotted to investigate in detail the properties of the source-time function: the input signal, its amplitude spectrum, the amplitude spectrum after filtering, and the input signal after filtering. The last figure is very important since it enables to see the actual shape of the input signal used to construct synthetic seismograms. The program SYNFAN also offers a possibility to investigate systematically the properties of various input signals and the effects of frequency filtration of these signals on their shape, without computation of synthetic seismograms. Note that the program SYNFAN does not depend on the way in which the frequency response was obtained. Thus any frequency response stored in the prescribed way can be used for computing synthetic seismograms. As the program synt uses the fast Fourier transform algorithm, attention should be paid to possible aliasing effects. Description of input and output data Input data consist partially of the data generated by the program FRESAN, stored in the formatted form in the file LU8, and partially of the additional input data prepared by the user and stored in the file LIN. Output data describing the computations are stored in the file LOU. Output data for plotting synthetic seismograms are stored in the file LU9. Specification of the files LIN, LOU, LU8 and LU9 can be made through the routine SERV, which is part of this program package. If the routine SERV is not used (put 'C' in front of 'CALL SERV' in the beginning of the main program), the files LIN and LOU are automatically specified LIN=5, LOU=6, the file with plot has number 7 and the number LU8 is read from the file LIN, see below. For plotting purposes, the CALCOMP routines PLOTS, PLOT, SYMBOL and NUMBER are used in the program SYNFAN. These routines are not included in the package, but must be linked with FRESAN. The data stored in LU8 The data are stored in LU8 in a formatted form. For details see the description of the content of the file LU8 in program FRESAN. 1) MPRINT FORMAT(A) 2) IPRINT FORMAT(A) 3) XSOUR,YSOUR,ZSOUR,TSOUR,RSTEP,FL,FD FORMAT(5F10.5,2E15.7) 4) NDST,NFS,ILS,MCOMP,ILOC FORMAT(26I3) 5) DST,AA FORMAT(F10.3,E12.5) 6) (IS(I),I=1,2*NFS) FORMAT(12I6) The additional input data These data are specified by the user. The data control the computation of synthetic seismiograms. The places, where the data from LU8 are read in are denoted by **LU8/1, **LU8/2, etc. 1) Arbitrary alphanumeric text describing the data set. TITLE FORMAT(A) 2) Switches controlling the output of results into the output file LOU and specifying the input and output files LU2 and LU8. IPR1,IPR2,LU8,LU9 FORMAT(16I5) IPR1... controls the storage of a general information. IPR1=0... input data are stored. IPR1=1... tables of input signal, its amplitude spectrum, filtered amplitude spectrum, and filtered input signal are stored. IPR2... controls storage of synthetic frequency responses, spectrum of synthetic seismograms and synthetic seismograms. IPR2=0... no data are stored. IPR2=1... synthetic seismograms are stored. IPR2=2... synthetic seismograms and frequency responses are stored. IPR2=3... synthetic seismograms,frequency responses and spectra of synthetic seismograms are stored. Warning: The above tables for IPR.NE.0 are stored for all epicentral distances. Print is heavy, particullarly for IPR1=1 or IPR2=3. LU8... the number of the file generated in FRESAN,in which the data for constructing synthetic seismograms are stored. LU9... the number of the file in which tables of synthetic seismograms computed in SYNFAN are stored. 3) Various switches controlling the computations. NSIG,NPTS,NT,NWIN,NFILT,NPLOT,NSTOP,NSH,NDER,NINT FORMAT(16I5) NSIG... controls the input of the source-time function. NSIG=0... analytical signal. NSIG.GT.0... source-time function introduced by a table, see input data No.10. NPTS... number of points in the definition of the signal. Use NPTS.LE.2048. NT... number of points in the FFT. Use 2048,1024,512,256 or 128. Default value, NT=1024. NWIN... controls the filtration of the input signal. NWIN=0... no filtration. NWIN=1... Fuchs' double cosine filter, see additional input data No.11. NFILT... controls an additional filtering in the routine FILTER. NFILT=0... no filtration. NFILT=1... filtration. NPLOT... controls the plotting of results. NPLOT=0... no plotting. NPLOT.GT.0... plotting required. NSTOP... NSTOP=0... standard computation of synthetic seismograms. NSTOP=1... investigation and plotting of input signal, its amplitude spectrum, filtered spectrum and filtered input signal. No computation of synthetic seismograms. NSH... shift between individual figures, in cm. Default value NSH=5. NDER... derivative of the input signal. NINT... integral of the input signal. 4) Specifies the receivers for which plots of frequency response, amplitude spectrum and synthetic seismogram are to be performed. Specified only for NPLOT.NE.0. NNPLOT,(NDIS(I),I=1,NNPLOT) FORMAT(16I5) NNPLOT... number of receivers for which plots are to be made. NDIS(I)... successive number of the receiver, for which plots are to be made. **LU8/1 **LU8/2 **LU8/3 **LU8/4 5) Data for plots of frequency responses. Under the frequency response, the modulus of the frequency response is understood here. The phase of the frequency response is not plotted. ARESP(1)-ARESP(6),JRESP(1)-JRESP(4) FORMAT(6F10.5,4I5) ARESP(1)... horizontal (frequency) axis: minimum frequency, in Hz. ARESP(2)... horizontal (frequency) axis: maximum frequency, in Hz.. ARESP(3)... length of the horizontal axis, in cm. ARESP(4)... vertical (frequency response) axis: minimum value. ARESP(5)... vertical (frequency response) axis: maximum value. ARESP(6)... length of the vertical axis, in cm. JRESP(1)... number of intervals along the horizontal axis. JRESP(2)... number of intervals along the vertical axis. JRESP(3),JRESP(4)... control the precision of numbers describing the coordinate axes in the plots. JRESP(3) corresponds to the horizontal axis, JRESP(4) to the vertical axis. JRESP.GT.0... the number of digits to the right of the decimal point. JRESP=0... only integer portions of the numbers with decimal points. JRESP.LT.0... integers. 6) Data for plots of amplitude spectra of input signal and/or synthetic seismograms. Phase spectra are not plotted. ASPECT(1)-ASPECT(6),JSPECT(1)-JSPECT(4) FORMAT(6F10.5,4I5) The meaning of the parameters is analogous to the parameters specified in additional input data No.5, horizontal axis corresponds to frequency, vertical axis to spectral values. 7) Data for plots of synthetic seismograms and/or input signals. ASYNT(1)-ASYNT(6),JSYNT(1)-JSYNT(4) FORMAT(6F10.5,4I5) The meaning of the parameters is analogous to the parameters specified in additional input data No.5, horizontal axis corresponds to time, vertical axis to values in which seismogram (impulse) is measured. 8) Controls the plotting of the input signal (source-time function) and related functions. NPL1,NPL2,NPL3,NPL4 FORMAT(16I5) NPL1... controls input signal (source-time function). NPL2... amplitude spectrum of the input signal. NPL3... amplitude spectrum of the filtered and/or windowed input signal. NPL4... filtered and/or windowed input signal. NPL=0... no plot. NPL=1... reduced plot, with unit maximum. NPL=2... non-reduced plot. 9) Data for input signal given analytically. Included only for NSIG=0. The computations are performed in the routine SFUN. The user is free to add to the routine SFUN its own analytical signals. IAUX(1)-IAUX(4),AUX(1)-AUX(4),TO FORMAT(4I5,5F10.5) IAUX(1)... specifies the type of the input signal. IAUX(1)=1... Gabor signal: F(T)=EXP(-(2*PI*FM*(T-TI)/GAMMA)**2) *COS(2*PI*FM*(T-TI)+VNI) IAUX(2)-IAUX(4)... no meaning. AUX(1)=FM (prevailing frequency) AUX(2)=GAMMA AUX(3)=VNI AUX(4)=TI IAUX(1)=2... Berlage signal: F(T)=EXP(-BETA*(T-TI))*SIN(2*PI*FM*(T-TI))* *(T-TI)**VNI IAUX(2)-IAUX(4)... no meaning. AUX(1)=FM AUX(2)=BETA AUX(3)=VNI AUX(4)=TI IAUX(1)=3... Muller signal: F(T)=SIN(N*PI*T/TP)-(N/(N+2))*SIN((N+2)*PI*T/TP) for 0.LE.T.LE.TP, F(T)=0 for T.LT.0 AND FOR T.GT.TP IAUX(2)=N IAUX(3),IAUX(4)... no meaning. AUX(1)=TP IAUX(1)=4... Ricker signal: F(T)=(1-2*((T-TI)*BETA)**2)*EXP(-(BETA*(T-TI))**2) F(T) is the normalized second time derivative of the Gaussian signal EXP(-(BETA*(T-TI))**2) IAUX(2)-IAUX(4)... no meaning. AUX(1)=BETA AUX(2)=TI IAUX(1)=5... Box-car signal: F(T)=0 for T.LT.AUX(1) and T.GT.AUX(2) F(T)=AUX(3) for AUX(1).LE.T.LE.AUX(2) IAUX(1)=6... Ramp function: F(T)=0 for T.LE.AUX(1) and T.GT.AUX(3) F(T)=AUX(4) for AUX(2).LE.T.LE.AUX(3) F(T) is linear between AUX(1) and AUX(2) IAUX(1)=7... Triagonal function: F(T)=0 for T.LE.AUX(1) and T.GE.AUX(3) F(T)=AUX(4) for T=AUX(2) F(T) is linear between AUX(1) and AUX(2) and between AUX(2) and AUX(3). IAUX(1)=8... One sample function: F(I)=AUX(1) for I=IAUX(2) F(I)=0 for I.NE.IAUX(2). TO... initial time in the plot. The last four signals serve only for special purposes. Please, do not use them without a suitably chosen frequency window. 10) Data for input signal given discretly by a table. Included only for NSIG.GT.0 IS(I),I=1,NPTS FORMAT(16I5) IS(I)... I-th sample of the discretly specified source-time function (input signal). The actual signal is given by the relation: F(I)=IS(I)*10**(-NSIG), where F(I) corresponds to the time T=T0+DT*FLOAT(I-1). 11) Data for the frequency filter (double cosine Fuchs filter). Included only if NWIN=1. FLO,FLEFT,FRIGHT,FRO,FEXP FORMAT(8F10.5) FLO,FLEFT,FRIGHT,FRO,FEXP... parameters of the filter. FLO.LE.FLEFT.LE.FRIGHT.LE.FRO. Outside the interval , the filter is zero. Inside the interval , the filter is equal one. Within the intervals and , cosine smoothing with the exponent FEXP is applied. For example, for FLO.LT.F.LT.FLEFT: W(F)=(0.5+0.5*COS(PI*(F-FLO))/(FLEFT-FLO))**FEXP, with PI=3.14159. Choose FLO.GE.FL and FRO.LE.FR, where FL and FR are lower and upper limit of frequency range in which frequency response was computed. **LU8/5 **LU8/6 Data LU8/6 and LU8/7 are successively read in from LU8 for all receivers (NDST times). 12) Data for plots of frequency responses, synthetic seismograms, etc., for individual receivers. NPR1,NPR2,NPR3 FORMAT(16I5) NPR1... index controlling frequency response (modulus). NPR2... index controlling amplitude spectrum of the synthetic seismogram. NPR3... index controlling synthetic seismogram. NPR=0... no plot. NPR=1... reduced plot,maximum=1. NPR=2... non-reduced plot. The input data sub 12 are repeated NNPLOT times, see input data sub 4 for NNPLOT, for each receiver for which plots are re- quired. The selection of receivers is performed as follows: The data LU8/7 are read successively for all receivers. For each reading, it is checked whether DST from LU8/7 corresponds to some NDIS(I). If yes, input data sub 12 are read in and plotting is performed. Thus, the order of readings 12 must correspond to the order of receivers NDIS(I). OUTPUT TABLES Output to the file LOU (information about computations) All the input data are automatically stored in the file LOU. In addition the data LU8/1-LU8/5 are also automatically stored. C C THE ADDITIONAL PRINT IS CONTROLLED BY THE INPUT PA- C RAMETERS IPR1 AND IPR2. C C IF IPR1.NE.0, FOUR TABLES RELEVANT TO THE INPUT SIGNAL C ARE PRINTED, WITH THE FOLLOWING HEADINGS AND QUANTITIES: C A) INPUT SIGNAL,TO,DT,AREDUC,NPTS C B) AMPLITUDE SPECTRUM OF THE INPUT SIGNAL,DF,AREDUC,IRS C C) AMPLITUDE SPECTRUM OF THE INPUT SIGNAL, WINDOW APPLI- C ED,DF,AREDUC,IRS C D) INPUT SIGNAL,FREQUENCY WINDOW APPLIED,TO DT,AREDUC,NPTS C C IF IPR2.NE.0, ONE OR TWO OR THREE TABLES ARE PRINTED C FOR EACH RECEIVER POSITION. C A) FOR IPR2=1, SYNTHETIC SEISMOGRAMS ARE PRINTED.THE HEA- C DING SHOWS THE QUANTITIES DST,TO,DT,AREDUC,NT C B) FOR IPR2=2, MODULUS OF THE FREQUENCY RESPONSE IS PRIN- C TED IN ADDITION TO THE TABLE OF SYNTHETIC SEISMOGRAMS. C HEADING SHOWS DST,DF,AREDUC,IRSS. C C) FOR IPR2=3, AMPLITUDE SPECTRUM OF THE SYNTHETIC SEISMO- C GRAMS ARE PRINTED, IN ADDITION TO A AND B. C HEADING ALSO SHOWS THE QUANTITIES DST,DF,AREDUC,IRSS. C C C OUTPUT ON THE FILE LUO C ********************** C C TO PLOT THE SYNTHETIC SEISMOGRAM SECTION IN THE PROGRAM C BPLOT AND/OR THE PARTICLE MOTION DIAGRAMS IN THE PROGRAM C PMPLOT, THE SYNTHETIC SEISMOGRAMS CALCULATED IN THE PROGRAM C SYNT ARE STORED ON THE FILE LUO, TOGETHER WITH SOME OTHER C NECESSARY OR INFORMATIVE DATA. C THE DATA ON LUO ARE STORED IN THE FOLLOWING SUCCESION: C C 1) RTTEXT FORMAT(20A4) C ALPHANUMERIC TEXT, DESCRIBING THE INPUT DATA FILE FROM C THE PROGRAM RT C C 2) GBTEXT FORMAT(20A4) C ALPHANUMERIC TEXT, DESCRIBING THE INPUT DATA FILE FROM C THE PROGRAM GB C C 3) STEXT FORMAT(20A4) C ALPHANUMERIC TEXT, DESCRIBING THE INPUT DATA FILE FROM C THE PROGRAM SYNT C C 4) XSOUR,ZSOUR,TSOUR,RSTEP,DT,DF FORMAT(4F10.5,2E15.7) C XSOUR,ZSOUR... COORDINATES OF THE SOURCE C TSOUR... INITIAL TIME C RSTEP... THE DISTANCE BETWEEN RECIEVERS FOR A REGU- C LARLY DISTRIBUTED SYSTEM OF RECEIVERS. C THE AVERAGE DISTANCE BETWEEN RECIEVERS FOR C AN IRREGULARLY DISTRIBUTED SYSTEM OF RECE- C IVERS. C DT... TIME STEP C DF... FREQUENCY STEP C C 5) NDST,NT,MBEAM,MCOMP FORMAT(14I5) C NDST... NUMBER OF RECEIVERS C NT... NUMBER OF POINTS IN THE FAST FOURIER TRANS- C FORM ALGORITHM (2048,1024,512... ). C MBEAM... SPECIFIES THE CHOICE OF PARAMETERS OF GAUSSI- C AN BEAMS USED IN THE SUMMATION PROCEDURE C THE CHOICE MBEAM=0 CORRESPONDS TO THE RAY METHOD C MCOMP... MCOMP=0... VERTICAL COMPONENT C MCOMP=1... RADIAL COMPONENT C MCOMP=1... TRANSVERSE COMPONENT C C 6) SH1,SH2,SH3 FORMAT(3E10.8) C THESE QUANTITIES HAVE BEEN USED IN THE SELECTION OF PARA- C METERS OF GAUSSIAN BEAMS USED IN THE SUMMATION C C 7) DIST,DEPTH,TO,AREDUC,NT FORMAT(3F10.3,1E12.5,I5) C DST... X-COORDINATE OF THE RECEIVER C DEPTH... Z-COORDINATE OF THE RECEIVER C TO... INITIAL TIME CORRESPONDING TO THE FIRST POINT C OF SYNTHETIC SEISMOGRAM C AREDUC... MAXIMUM AMPLITUDE IN THE SYNTHETIC SEISMO- C GRAMS CORRESPONDS TO NT GIVEN IN LUO/5. C NT... NUMBER OF POINTS OF THE SYNTHETIC SEISMOGRAMS C C 8) IS(I),I=1,NT FORMAT(20I4) C SYNTHETIC SEISMOGRAM CORRESPONDING TO THE RECIEVER SITU- C ATED AT THE X-COORDINATE GIVEN BY DST, IN A REDUCED FORM. C C NOTE THAT THE QUANTITIES RTTEXT, GBTEXT, STEXT,XSOUR,ZSOUR, C TSOUR,MBEAM,SH1,SH2,SH3 AND DEPTH HAVE ONLY AN INFOR- C MATIVE MEANING AND ARE NOT USED IN THE COMPUTATIONS IN THE C PROGRAMS BPLOT AND PMPLOT. C C C GRAPHICAL OUTPUT C **************** C C THE GRAPHICAL OUTPUT HAS MANY OPTIONS WHICH ARE WELL DES- C CRIBED IN THIS DOCUMENTATION, SEE ABOVE.IN FACT, MOST OF C COMPUTED QUANTITIES CAN BE PLOTTED.FOR EACH RECEIVER POSITION C THREE PICTURES CAN BE OPTIONALLY PLOTTED.THUS THE MAXIMUM C NUMBER OF GENERATED FIGURES IS 3*NDST+4.IN PLOTTING SYNTHETIC C SEISMOGRAMS, PAY ATTENTION MAINLY TO A CORRECT CHOICE OF TMM C IN THE INPUT RECORD 12.FOR INCORRECTLY CHOSEN TMM, ONLY A NUME- C RICAL NOISE WITHOUT ANY ACTUAL SIGNAL MAY BE OBTAINED.THIS C MISTAKE MAY BE EASILY RECOGNIZED FROM THE REDUCTION FACTOR, C PRINTED IN ALL CASES ABOVE THE RIGHT HAND CORNER OF THE FRAME. C C **************************************************************** C