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KEMENTERIAN DIKTI DAN RISTEK

PROGRAM STUDI GEOFISIKA JURUSAN FISIKA

FAKULTAS MATEMATIKA DAN ILMU PENGETAHUAN ALAM

UNIVERSITAS GADJAH MADA

PRAKTIKUM METODE SEISMIK I

METODE DELAY TIME (PLUS MINUS)

DISUSUN OLEH :

RAHMI ZAFIRA AMINI

12/334809/PA/15019

DOSEN PENGAMPU :

Dr. EDDY HARTANTYO, S.Si., M.Si.

 YOGYAKARTA

OKTOBER

2015

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I.  DATA

Picking Data Lintasan B Flat Picking Data Lintasan B Flat (Noisy)

Waktu (ms)

Topografi

(m)

Waktu (ms)

Topografi

(m)

Shot 1 2 3 4 Shot 1 2 3 4

Posisi

(m) 5 78 152 225

Posisi

(m) 5 78 152 225

0 15.4 181.8 257.8 350.7 100 0 16.4 177.9 256.3 350 100

10 15.4 163.9 239.9 332.8 100 10 16.6 163.5 239.5 333.3 100

20 46.2 145.9 221.9 314.8 100 20 48.2 146.1 221.2 317 100

30 76.9 129.9 205.9 298.8 100 30 77.7 128.6 207.1 303.5 100

40 107.7 115.6 191.6 284.5 100 40 105.8 118 191.5 286.4 100

50 138.5 87.2 178.8 271.7 100 50 138 87.1 182.3 275.2 100

60 155.4 56.4 165.7 258.6 100 60 154.3 55.3 165.2 254.7 100

70 165.9 25.6 150.4 243.3 100 70 164.9 25.1 155.7 242.2 100

80 174 5.1 133.8 226.7 100 80 175.1 4.8 134 227.4 100

90 180.4 35.9 116.4 209.3 100 90 181.6 34.1 120.4 207.5 100

100 185.8 66.7 99.2 192.2 100 100 185.8 70.5 99.7 190.4 100

110 192.4 80.3 83.5 176.4 100 110 196.5 80.7 84.6 176.8 100

120 201.3 89.2 69.6 162.5 100 120 203.3 89.2 71.5 159.1 100

130 212.6 100.6 58.7 151.6 100 130 211.6 102 61.5 151.6 100

140 229 116.9 35.9 145.9 100 140 227.1 114.3 37.9 147.6 100

150 246 134 5.1 139.6 100 150 246.5 134.2 5.2 142.6 100

160 263.1 151.1 25.6 133.8 100 160 259.9 150.9 26 134.4 100

170 280.1 168.1 56.4 125.6 100 170 283.2 170.6 53.6 125.1 100

180 295.2 183.2 87.2 115.1 100 180 294.6 185 88 116.7 100

190 308.3 196.2 105.2 103.1 100 190 310.1 195.7 104.3 103.3 100

200 319.8 207.7 116.7 76.9 100 200 323.6 206.6 117.7 80.6 100

210 329.4 217.3 126.3 46.2 100 210 329.1 219.5 129 49.4 100

220 338.2 226.2 135.2 15.4 100 220 339.1 226 138.2 16.9 100

230 344.4 232.3 141.4 15.4 100 230 344.1 233.9 141.8 16.3 100

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II. PENGOLAHAN

a.  Pengolahan Data Lintasan B

  SP1 – SP2

Equation V1 (m/s) Source to source time

Direct Forward y = 3.077x - 15.37 V1 F 324.9919 Forward 174.3

Refract Forward y = 1.05x + 92.4 V1 R 332.4468 Reverse 171.005

Direct Reverse y = -3.008x + 236.64 V1 328.7193 Average 172.6525

Refract Reverse y = -1.609x + 179.05

C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

0 15.4 181.8 -166.4 24.5475 328.7193419 752.162467 4.4856723

5 97.65 171.005 -73.355 96.0025 328.7193419 752.162467 17.5429577

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10 102.9 163.9 -61 94.1475 328.7193419 752.162467 17.2039854

20 113.4 145.9 -32.5 86.6475 328.7193419 752.162467 15.8334776

30 123.9 129.9 -6 81.1475 328.7193419 752.162467 14.8284385

40 134.4 114.69 19.71 76.4375 328.7193419 752.162467 13.9677595

50 144.9 98.6 46.3 70.8475 328.7193419 752.162467 12.9462743

60 155.4 82.51 72.89 65.2575 328.7193419 752.162467 11.9247891

70 165.9 66.42 99.48 59.6675 328.7193419 752.162467 10.9033039

78 174.3 53.548 120.752 55.1955 328.7193419 752.162467 10.0861157

 

SP2 –

 SP3

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Equation V1 (m/s) Source to source time

Direct Forward y = 3.08x - 241.3 V1 F 324.6753 Forward 133.922

Refract Forward y = 1.351x - 71.43 V1 R 373.1343 Reverse 135.986

Direct Reverse y = -2.68x + 408.43 V1 348.9048 Average 134.954

Refract Reverse y = -1.613x + 261.8

C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

78 33.948 135.986 -102.038 34.98 348.9048265 674.763833 7.12941780 36.65 133.8 -97.15 35.496 348.9048265 674.763833 7.234585

90 50.16 116.4 -66.24 31.606 348.9048265 674.763833 6.441748

100 63.67 99.2 -35.53 27.916 348.9048265 674.763833 5.689674

110 80.3 83.5 -3.2 28.846 348.9048265 674.763833 5.879221

120 89.2 69.6 19.6 23.846 348.9048265 674.763833 4.860151

130 100.6 52.11 48.49 17.756 348.9048265 674.763833 3.618923

140 116.9 35.98 80.92 17.926 348.9048265 674.763833 3.653571

150 134 19.85 114.15 18.896 348.9048265 674.763833 3.851271

152 133.922 16.624 117.298 15.592 348.9048265 674.763833 3.177869

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  SP3 – SP4

Equation V1 (m/s) Source to source time

Direct Forward y = 3.08x - 467.2 V1 F 324.6753 Forward 140.77

Refract Forward y = 0.996x - 83.33 V1 R 340.3676 Reverse 142.998

Direct Reverse y = -2.938x + 662.69 V1 332.5215 Average 141.884

Refract Reverse y = -1.026x + 298.95

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C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s) T  SD - T 

 S’D 

152 68.062 142.998 -74.936 69.176 332.5214608 989.119683 12.21202

160 76.03 133.8 -57.77 67.946 332.5214608 989.119683 11.99488

170 85.99 125.6 -39.61 69.706 332.5214608 989.119683 12.30558

180 95.95 115.1 -19.15 69.166 332.5214608 989.119683 12.21025

190 105.2 104.01 1.19 67.326 332.5214608 989.119683 11.88542

200 116.7 93.75 22.95 68.566 332.5214608 989.119683 12.10433

210 126.3 83.49 42.81 67.906 332.5214608 989.119683 11.98782

220 135.2 73.23 61.97 66.546 332.5214608 989.119683 11.74773

225 140.77 68.1 72.67 66.986 332.5214608 989.119683 11.8254230 141.4 15.4 126 14.916 332.5214608 989.119683 2.633203

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  SP1 – SP4

Equation V1 (m/s) Source to source time

Direct Forward y = 3.077x - 15.37 V1 F 324.9919 Forward 343.5405

Refract Forward y = 1.2203x + 68.973 V1 R 340.3676 Reverse 326.691

Direct Reverse y = -2.938x + 662.69 V1 332.6797 Average 335.11575

Refract Reverse y = -1.2858x + 333.12

C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

0 15.4 350.7 -335.3 30.98425 332.6797361 795.038957 5.674605

5 75.0745 326.691 -251.6165 66.64975 332.6797361 795.038957 12.20656

10 81.176 332.8 -251.624 78.86025 332.6797361 795.038957 14.44285

20 93.379 314.8 -221.421 73.06325 332.6797361 795.038957 13.38115

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30 105.582 298.8 -193.218 69.26625 332.6797361 795.038957 12.68575

40 117.785 284.5 -166.715 67.16925 332.6797361 795.038957 12.3017

50 129.988 271.7 -141.712 66.57225 332.6797361 795.038957 12.19236

60 155.4 258.6 -103.2 78.88425 332.6797361 795.038957 14.44724

70 165.9 243.3 -77.4 74.08425 332.6797361 795.038957 13.56815

80 174 226.7 -52.7 65.58425 332.6797361 795.038957 12.01141

90 180.4 209.3 -28.9 54.58425 332.6797361 795.038957 9.996822

100 185.8 192.2 -6.4 42.88425 332.6797361 795.038957 7.854028

110 192.4 176.4 16 33.68425 332.6797361 795.038957 6.169095

120 201.3 162.5 38.8 28.68425 332.6797361 795.038957 5.253371

130 212.6 151.6 61 29.08425 332.6797361 795.038957 5.326629

140 229 145.9 83.1 39.78425 332.6797361 795.038957 7.286279

150 246 139.6 106.4 50.48425 332.6797361 795.038957 9.245928

160 263.1 133.8 129.3 61.78425 332.6797361 795.038957 11.31546

170 280.1 125.6 154.5 70.58425 332.6797361 795.038957 12.92714

180 295.2 115.1 180.1 75.18425 332.6797361 795.038957 13.76961

190 308.3 88.818 219.482 62.00225 332.6797361 795.038957 11.35539

200 319.8 75.96 243.84 60.64425 332.6797361 795.038957 11.10668

210 329.4 63.102 266.298 57.38625 332.6797361 795.038957 10.50999

220 338.2 50.244 287.956 53.32825 332.6797361 795.038957 9.766792

225 343.5405 43.815 299.7255 52.23975 332.6797361 795.038957 9.567439

230 344.4 15.4 329 24.68425 332.6797361 795.038957 4.520792

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b.  Pengolahan Data Lintasan B (Noisy)

  SP1 – SP2

Equation V1 (m/s) Source to source time

Direct Forward y = 3.004x - 12.86 V1 F 332.8895 Forward 173.38

Refract Forward y = 1.06x + 90.7 V1 R 322.0612 Reverse 169.85

Direct Reverse y = -3.105x + 242.15 V1 327.4753 Average 171.615

Refract Reverse y = -1.54x + 177.55

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C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

0 16.4 177.9 -161.5 22.685 327.4753362 769.289945 4.104881

5 96 169.85 -73.85 94.235 327.4753362 769.289945 17.05195

10 101.3 163.5 -62.2 93.185 327.4753362 769.289945 16.86195

20 111.9 146.1 -34.2 86.385 327.4753362 769.289945 15.63148

30 122.5 128.6 -6.1 79.485 327.4753362 769.289945 14.38292

40 133.1 115.95 17.15 77.435 327.4753362 769.289945 14.01197

50 143.7 100.55 43.15 72.635 327.4753362 769.289945 13.1434

60 154.3 85.15 69.15 67.835 327.4753362 769.289945 12.27483

70 164.9 69.75 95.15 63.035 327.4753362 769.289945 11.40627

78 173.38 57.43 115.95 59.195 327.4753362 769.289945 10.71141

  SP2 – SP3

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Equation V1 (m/s) Source to source time

Direct Forward y = 3.285x - 259.18 V1 F 304.414 Forward 133.142

Refract Forward y = 1.321x - 67.65 V1 R 355.2398 Reverse 137.416

Direct Reverse y = -2.815x + 428.97 V1 329.8269 Average 135.279

Refract Reverse y = -1.608x + 262.84

C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s) Reverse

T  S’D (s)

T  SD - T  S’D 

78 35.388 137.416 -102.028 37.525 329.826895 682.826903 7.067561

80 38.03 134 -95.97 36.751 329.826895 682.826903 6.921783

90 51.24 120.4 -69.16 36.361 329.826895 682.826903 6.84833

100 64.45 99.7 -35.25 28.871 329.826895 682.826903 5.437643

110 80.7 84.6 -3.9 30.021 329.826895 682.826903 5.654237

120 89.2 71.5 17.7 25.421 329.826895 682.826903 4.78786

130 102 53.8 48.2 20.521 329.826895 682.826903 3.864981

140 114.3 37.72 76.58 16.741 329.826895 682.826903 3.153045

150 134.2 21.64 112.56 20.561 329.826895 682.826903 3.872515

152 133.142 18.424 114.718 16.287 329.826895 682.826903 3.067538

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SP3 – SP4

Equation V1 (m/s) Source to source time

Direct Forward y = 3.1x - 471.13 V1 F 344.3526 Forward 144.9

Refract Forward y = 1.13x - 109.35 V1 R 322.5806 Reverse 143.266

Direct Reverse y = -2.904x + 657.87 V1 333.4666 Average 144.083

Refract Reverse y = -1.017x + 297.85

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C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

152 62.41 143.266 -80.856 61.593 333.4666311 931.532371 10.99847

160 71.45 134.4 -62.95 61.767 333.4666311 931.532371 11.02954

170 82.75 125.1 -42.35 63.767 333.4666311 931.532371 11.38667

180 94.05 116.7 -22.65 66.667 333.4666311 931.532371 11.90451

190 104.3 104.62 -0.32 64.837 333.4666311 931.532371 11.57774

200 117.7 94.45 23.25 68.067 333.4666311 931.532371 12.15451

210 129 84.28 44.72 69.197 333.4666311 931.532371 12.35629

220 138.2 74.11 64.09 68.227 333.4666311 931.532371 12.18308

225 144.9 69.025 75.875 69.842 333.4666311 931.532371 12.47146

230 141.8 16.3 125.5 14.017 333.4666311 931.532371 2.502971

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  SP1 – SP4

Equation V1 (m/s) Source to source time

Direct Forward y = 3.004x - 12.86 V1 F 332.8895 Forward 344.626

Refract Forward y = 1.2266x + 68.641 V1 R 344.3526 Reverse 329.4775

Direct Reverse y = -2.904x + 657.87 V1 338.621 Average 337.05175

Refract Reverse y = -1.3205x + 336.08

C

Travel time T-Minus

T plus V 1  V 2  hD ForwardT  SD (s)

ReverseT  S’D (s)

T  SD - T  S’D 

0 16.4 350 -333.6 29.34825 338.6210489 785.175879 5.507466

5 74.774 329.4775 -254.7035 67.19975 338.6210489 785.175879 12.61064

10 80.907 333.3 -252.393 77.15525 338.6210489 785.175879 14.47888

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20 93.173 317 -223.827 73.12125 338.6210489 785.175879 13.72187

30 105.439 303.5 -198.061 71.88725 338.6210489 785.175879 13.4903

40 117.705 286.4 -168.695 67.05325 338.6210489 785.175879 12.58315

50 129.971 275.2 -145.229 68.11925 338.6210489 785.175879 12.7832

60 154.3 254.7 -100.4 71.94825 338.6210489 785.175879 13.50174

70 164.9 242.2 -77.3 70.04825 338.6210489 785.175879 13.14519

80 175.1 227.4 -52.3 65.44825 338.6210489 785.175879 12.28196

90 181.6 207.5 -25.9 52.04825 338.6210489 785.175879 9.767327

100 185.8 190.4 -4.6 39.14825 338.6210489 785.175879 7.346525

110 196.5 176.8 19.7 36.24825 338.6210489 785.175879 6.802313

120 203.3 159.1 44.2 25.34825 338.6210489 785.175879 4.756829

130 211.6 151.6 60 26.14825 338.6210489 785.175879 4.906957

140 227.1 147.6 79.5 37.64825 338.6210489 785.175879 7.065036

150 246.5 142.6 103.9 52.04825 338.6210489 785.175879 9.767327

160 259.9 134.4 125.5 57.24825 338.6210489 785.175879 10.74315

170 283.2 125.1 158.1 71.24825 338.6210489 785.175879 13.37038

180 294.6 116.7 177.9 74.24825 338.6210489 785.175879 13.93336

190 310.1 85.185 224.915 58.23325 338.6210489 785.175879 10.928

200 323.6 71.98 251.62 58.52825 338.6210489 785.175879 10.98336

210 329.1 58.775 270.325 50.82325 338.6210489 785.175879 9.537444

220 339.1 45.57 293.53 47.61825 338.6210489 785.175879 8.935997

225 344.626 38.9675 305.6585 46.54175 338.6210489 785.175879 8.733982

230 344.1 16.3 327.8 23.34825 338.6210489 785.175879 4.381511

III. PEMBAHASAN

Dalam interpretasi metode plus minus, asumsi awal adalah refraktor memiliki

permukaan yang irregular atau berundulasi sehingga terdapat beda waktu/tambahan waktu

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 Dari hasil pengolahan tersebut, terlihat bahwa meskipun data sedikit noisy, tapi tidak terlalu

mempengaruhi hasil. Trend kemiringan dari model yang dihasilkan sama dengan model hasil

pengolahan data yang tidak noisy. Hanya saja pada model terlihat lebih jelas undulasinya.

IV.KESIMPULAN

 

Metode plus minus dapat digunakan untuk mencari ketebalan lapisan lapuk (weathered

layer). 

  Metode plus minus mengasumsikan bahwa refraktor memiliki permukaan yang

irregular atau berundulasi sehingga terdapat beda waktu/tambahan waktu (delay time) 

penjalaraan gelombang saat mengalami refraksi jika dibandingkan dengan saat

gelombang melalui refraktor yang miring tanpa berundulasi.

  Nilai beda waktu (delay time) berbanding lurus dengan kedalaman refraktor, sehingga

 jika nilainya semakin besar maka lapisan akan semakin dalam.

V.  REFERENSI

Hartantyo Eddy. 2002. Modul Praktikum Seismik Refraksi (Bias) Beserta Analisis

Komputasi Numeriknya. Yogyakarta: Laboratorium Geofisika FMIPA UGM.