## 23.1.8 FOCMEC AUTO

Output FOCMEC has no error estimates. If an average solution is used, the RMS angular difference between the average normal vectors and the individual normal vectors are calculated for each plane. These values give some idea of the spread of the solutions used for the average, an example F-line is given below:

    227.9      56.5     145.7  32.  31.                     3  0 BER FOCMEC  aF


Example with only polarities In this example only polarities are used and the user has selected relative weight. For each test, a line is printed with the result of the test: number of polarities errors accepted, number of ratio errors accepted, the error limit used for ratios. If solutions are found (sol >0), the average solutions is given together with the rms deviation. Finally at the end of the line, the grid size is shown.

#    3 09 May 2019 02:51 52  LQ 59.397   5.447 31.0    .50  1.5LBER  34  ? fa

**** now locating with hyp as a preparation ***

09-0251-24L.S201905
#        0  2019  5 9 0251 51.3 LQ 59.416   5.456 36.9  BER 34 0.4 1.5LBER

Number of polarities:           15
Amplitude types:   Manual:       0   Automatic:   33   Spectral:    33
Automatic amplitude selected
Use amplitudes, (y/n=enter)

Total number of polarities and amplitude ratios =  15  gap in az = 111.0  gap in ain =  30.0
0.0 out of  15 pol, 999 out of  0 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
1.0 out of  15 pol, 999 out of  0 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol, 999 out of  0 amp, err=0.2, # sol= 172, rms dev 10 21, str dip rak  74  29 110, deg 2
2.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 172, rms dev 10 21, str dip rak  74  29 110, deg 2
Use relative polarity error (y/n=enter)
y
0.2 out of  15 pol,   0 out of  0 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
0.4 out of  15 pol,   0 out of  0 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
0.6 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 391, rms dev  7  7, str dip rak 335  64 -82, deg 2

Stop                     (Q)
Plot saved solution(s)   (1)
Plot new solutions       (2)
Plot selected solution   (3)
Find new solutions       (4)
-1, -2, -3 also plot station
2


Example with amplitudes and polarities

#    3 09 May 2019 02:51 52  LQ 59.397   5.447 31.0    .50  1.5LBER  34  ? fa

**** now locating with hyp as a preparation ***

09-0251-24L.S201905
#        0  2019  5 9 0251 51.3 LQ 59.416   5.456 36.9  BER 34 0.4 1.5LBER

Number of polarities:           15
Amplitude types:   Manual:       0   Automatic:   33   Spectral:    33
Automatic amplitude selected
Use amplitudes, (y/n=enter)
y

Q: Local: Qp= 470.0**0.70  Qs= 470.0** 0.7   Global: t*(P)=1.10  t*(S)=4.20

STAT  C PH       AMP    PER TRTIME   QCOR ANGINC ANGEMG Fcor   AZ  DIST
KMY   Z PG        19   0.30    7.0    1.1    143     32  1.6  208    25
KMY   T SG       231   0.28   12.1    1.1    143     32  2.0  208    25
STAV  Z PG        12   0.24   10.4    1.1    120     50  1.2  165    55
STAV  T SG       342   0.32   17.9    1.2    120     50  2.0  165    55
BLS5  Z PG        21   0.30   10.6    1.1    119     51  1.2   89    56
BLS5  T SG       547   0.32   18.3    1.2    119     51  2.0   89    56
BAS21 Z PG        87   0.28   11.1    1.1    117     52  1.2   33    60
BAS21 T SG       197   0.32   19.0    1.2    117     52  2.0   33    60
BAS22 Z PG       101   0.32   11.3    1.1    116     53  1.2   43    62
BAS22 T SG       254   0.28   19.5    1.2    116     53  2.0   43    62
BAS20 Z PG        71   0.30   11.8    1.1    115     54  1.1   22    66
BAS20 T SG       521   0.32   20.3    1.2    115     54  2.0   22    66
BAS19 Z PG        14   0.34   11.9    1.1    114     54  1.1   16    66
BAS19 T SG       221   0.28   20.5    1.2    114     54  2.0   16    66
BAS23 Z PG        40   0.30   12.6    1.1    113     55  1.1   36    71
BAS23 T SG       204   0.26   21.7    1.2    113     55  2.0   36    71
BAS18 Z PG        12   0.30   12.8    1.1    112     55  1.1    6    73
BAS18 T SG       218   0.30   22.0    1.2    112     55  2.0    6    73
BAS17 Z PG         8   0.26   14.5    1.2    108     57  1.0  357    85
BAS17 T SG       436   0.30   25.0    1.3    108     57  2.0  357    85
ODD1  Z PG        11   0.34   14.6    1.1    108     58  1.0   50    86
ODD1  T SG       108   0.30   25.1    1.3    108     58  2.0   50    86
BAS14 Z PG      2222   0.34   15.1    1.1    107     58  1.0   58    89
BAS14 T SG    158000   0.32   26.0    1.3    107     58  2.0   58    89
BAS11 Z PG        24   0.24   15.2    1.2    107     58  1.0   39    90
BAS11 T SG       658   0.28   26.1    1.3    107     58  2.0   39    90
BAS10 Z PG         9   0.26   15.4    1.2    107     58  1.0   28    92
BAS10 T SG       117   0.30   26.5    1.3    107     58  2.0   28    92
BAS16 Z PG         9   0.28   15.4    1.2    107     58  1.0  350    92
BAS16 T SG        66   0.32   26.6    1.3    107     58  2.0  350    92
BAS09 Z PG        13   0.28   15.8    1.2    106     59  1.0   18    94
BAS09 T SG       228   0.32   27.1    1.3    106     59  2.0   18    94
BAS12 Z PG        13   0.24   15.8    1.2    106     59  1.0   49    94
BAS12 T SG       130   0.32   27.2    1.3    106     59  2.0   49    94

STAT  Ratio type  T     Amp 1    Amp 2  Fcor LogRat
KMY   SH(T)/P(Z)  H       231       19   0.8   1.01
STAV  SH(T)/P(Z)  H       342       12   0.6   1.24
BLS5  SH(T)/P(Z)  H       547       21   0.6   1.21
BAS21 SH(T)/P(Z)  H       197       87   0.6   0.15
BAS22 SH(T)/P(Z)  H       254      101   0.6   0.20
BAS20 SH(T)/P(Z)  H       521       71   0.6   0.65
BAS19 SH(T)/P(Z)  H       221       14   0.6   0.98
BAS23 SH(T)/P(Z)  H       204       40   0.6   0.49
BAS18 SH(T)/P(Z)  H       218       12   0.5   1.04
BAS17 SH(T)/P(Z)  H       436        8   0.5   1.47
ODD1  SH(T)/P(Z)  H       108       11   0.5   0.72
BAS14 SH(T)/P(Z)  H    158000     2222   0.5   1.61
BAS11 SH(T)/P(Z)  H       658       24   0.5   1.17
BAS10 SH(T)/P(Z)  H       117        9   0.5   0.83
BAS16 SH(T)/P(Z)  H        66        9   0.5   0.59
BAS09 SH(T)/P(Z)  H       228       13   0.5   0.98
BAS12 SH(T)/P(Z)  H       130       13   0.5   0.75

Total number of polarities and amplitude ratios =  32  gap in az = 111.0  gap in ain =  30.0
0.0 out of  15 pol, 999 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
1.0 out of  15 pol, 999 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol, 999 out of 17 amp, err=0.2, # sol= 132, rms dev 10 23, str dip rak  72  30 108, deg 2
2.0 out of  15 pol,   0 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   1 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   2 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   3 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   4 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   5 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   6 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   7 out of 17 amp, err=0.2, # sol=   0, rms dev      , str dip rak            , deg 2
2.0 out of  15 pol,   8 out of 17 amp, err=0.2, # sol=   9, rms dev  8 26, str dip rak  76  29 120, deg 2
Use relative polarity error (y/n=enter)

Stop                     (Q)
Plot saved solution(s)   (1)
Plot new solutions       (2)
Plot selected solution   (3)
Find new solutions       (4)
-1, -2, -3 also plot station


Example with polarities only and increasing grid size

#    4 17 May 2019 01:22 59  LQ 59.769   5.380 12.1  N .40  1.6LBER  38  ? fa

**** now locating with hyp as a preparation ***

17-0122-11L.S201905
#        0  2019  517 0122 58.6 LQ 59.771   5.404 18.5  BER 38 0.2 1.6LBER
Note: The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG IEEE_DENORMAL

Number of polarities:           15
No amplitude data available

Total number of polarities and amplitude ratios =  15  gap in az = 187.0  gap in ain =  42.0
0.0 out of  15 pol, 999 out of  0 amp, err=0.2, # sol= 500, rms dev 10 12, str dip rak 291  35 -53, deg 2
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 500, rms dev 10 12, str dip rak 291  35 -53, deg 2
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 500, rms dev 17 23, str dip rak 300  40 -49, deg 3
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 500, rms dev 32 35, str dip rak 304  44 -48, deg 4
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 500, rms dev 42 38, str dip rak 307  48 -49, deg 5
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 500, rms dev 36 33, str dip rak 320  60 -27, deg 6
0.0 out of  15 pol,   0 out of  0 amp, err=0.2, # sol= 388, rms dev 32 29, str dip rak 325  68 -19, deg 7

Stop                     (Q)
Plot saved solution(s)   (1)
Plot new solutions       (2)
Plot selected solution   (3)
Find new solutions       (4)
-1, -2, -3 also plot station


In this case, 388 solutions are found due to a bad distribution of polarities and grid size has to be increased in order to find less than 500 solutions. The limit of max 500 could have been decreased to get fewer solutions but then grid size would have been increased. The solution found is the most likely. The other fault plane programs in SEISAN also finds the most likely solution with the given data, see Figure xx for the solution given by HASH, PINV and FPFIT.

It is seen that the 4 programs give very similar solutions so despite the many solutions obtained, the average seem the represent the most likely solution. The solutions are also what we would be expected for the area.

Using multiple models with FOCMEC It is well known that the model can be very critical for the fault plane solutions since different models will give different angle of incidence. If a model change will change an arrival from direct to refracted, the azimuth will change 180 degrees so it is particularly the hypocentral depth that is a critical parameter. In order to check the sensitivity to the model, FOCMEC has an option to make automatic solutions for any number of models in order to compare the solutions and possibly select one solution or more likely an average of the different model solutions. The original HASH program has a similar option, but it has not been implemented in SEISAN. The different models are defined in different STATIONx.HYP files where x indicates the different files. In the test example we will use 5 models defined as a,b,c,d,e. The definition line in FOCMEC.DEF is then:

MODELS   For multi model, one char      abcde


The models are

  a    b    c    d    e    depth
6.65 6.10 6.72 6.40 6.20  0.0
6.75 6.53 6.81 6.50 6.60 12.0
6.88 7.41 6.92 7.11 7.10 23.0
8.39 7.56 8.66 7.32 8.05 31.0
8.49 7.76 9.04 8.54 8.25 50.0


where a-e are the P-velocities (km/s) and depth is depth to interface (km). The multi model can only be used in eev. The command in EEV is FAAA. If multi models are defined in FOCMEC.DEF, the event will be located with each model and the automatic FOCMEC used to get a solution. Each solution is written into the S-file:

    338.1      44.9     -14.8   2.   2.      11.0           0H10 BER FOCMECe aF
343.0      35.4      -3.7   1.   1.      11.4           0H10 BER FOCMECd aF
313.7       6.7      -0.0   1.   1.       6.8           0H12 BER FOCMECc aF
287.6      36.0     -91.7   2.   3.      12.1           0H 9 BER FOCMECb aF
279.0       1.2     -32.5   3.   3.       7.9           0H12 BER FOCMECa aF


The free field 63 has an H to indicate that the hypocentral depth is given in field 51-55 which is not used by FOCMEC. The H then indicates a multi model solution. The model indicator is given in column 76. The 5 average solutions can then be plotted by FOCMEC in EEV, command FO:

Although the models are quite different, the solution are not very different so in this case the solution is no very model dependent. Both P-polarities and amplitudes were used.

After quitting FOCMEC, the user will have option to save the average solution, see example below:

     319.2      23.6     -21.4  20.  28.                          BER FOCMEC  AF


where the A at end of line indicated that this is an average of the multi model solutions. If any of the individual solutions are wanted, the user must edit the S-file.