8/12/2019 Seismik Bias Modifikasi 22

1/54

Seismik Bias

8/12/2019 Seismik Bias Modifikasi 22

2/54

Keunggulan Seismik Bias

Pengamatan refraksi membutuhkan cakupan lokasisumber dan penerima yang sempit, sehingga relatifmurah dalam pengambilan datanya.

Prosesing refraksi relatif simpel dilakukan kecualiproses filtering untuk memperkuat sinyalfirst breakyangdibaca.

Karena pengambilan data dan lokasi yang cukup kecil,maka pengembangan model untuk interpretasi tidakterlalu sulit dilakukan seperti metode geofisika lainnya.

8/12/2019 Seismik Bias Modifikasi 22

3/54

Kelemahan Seismik Bias

Dalam pengukuran yang regional , Seismik refraksimembutuhkan offset yang lebih lebar.

Seismik bias hanya bekerja jika kecepatan gelombangmeningkat sebagai fungsi kedalaman.

Seismik bias biasanya diinterpretasikan dalam bentuklapisan-lapisan. Masing-masing lapisan memiliki dip dantopografi.

Seismik bias hanya menggunakanwaktu tibasebagai

fungsi jarak (offset) Model yang dibuat didesain untuk menghasilkan waktu

jalar teramati.

8/12/2019 Seismik Bias Modifikasi 22

4/54

Body waves : Dan Russell

animationsA wave pulse

Animation courtesy of Dr. Dan Russell,Kettering University

http://www.kettering.edu/~drussell/demos.html

http://www.kettering.edu/~drussell/demos.htmlhttp://www.kettering.edu/~drussell/demos.html

8/12/2019 Seismik Bias Modifikasi 22

5/54

Compressional Wave (P-Wave) Animation

Deformation propagates. Particle motion consists of alternating

compression and dilation. Particle motion is parallel to the

direction of propagation (longitudinal). Material returns to itsori inal sha e after wave asses.

8/12/2019 Seismik Bias Modifikasi 22

6/54

Dan Russell animationsTransverse

wave

Animation courtesy of Dr. Dan Russell,Kettering University

http://www.kettering.edu/~drussell/demos.html

http://www.kettering.edu/~drussell/demos.htmlhttp://www.kettering.edu/~drussell/demos.html

8/12/2019 Seismik Bias Modifikasi 22

7/54

Shear Wave (S-Wave) Animation

Deformation propagates. Particle motion consists of alternating transverse motion. Particle motion

is perpendicular to the direction of propagation (transverse). Transverse particle motion shown

here is vertical but can be in any direction. However, Earths layers tend to cause mostly vertical

(SV; in the vertical plane) or horizontal (SH) shear motions. Material returns to its original shapeafter wave passes.

8/12/2019 Seismik Bias Modifikasi 22

8/54

Surface Wave

8/12/2019 Seismik Bias Modifikasi 22

9/54

Rayleigh Wave (R-Wave) Animation

Deformation propagates. Particle motion consists of elliptical motions

(generally retrograde elliptical) in the vertical plane and parallel to the direction

of propagation. Amplitude decreases with depth. Material returns to its

original shape after wave passes.

8/12/2019 Seismik Bias Modifikasi 22

10/54

Love Wave (L-Wave) Animation

Deformation propagates. Particle motion consists of alternating transverse motions. Particle

motion is horizontal and perpendicular to the direction of propagation (transverse). To aid in

seeing that the particle motion is purely horizontal, focus on the Y axis (red line) as the wave

propagates through it. Amplitude decreases with depth. Material returns to its original shape

after wave asses.

8/12/2019 Seismik Bias Modifikasi 22

11/54

Dan Russell animationsRayleigh

wave

Animation courtesy of Dr. Dan Russell,Kettering University

http://www.kettering.edu/~drussell/demos.html

http://www.kettering.edu/~drussell/demos.htmlhttp://www.kettering.edu/~drussell/demos.html

8/12/2019 Seismik Bias Modifikasi 22

12/54

Dan Russell animationsThe

people wave

Animation courtesy of Dr. Dan Russell,Kettering University

http://www.kettering.edu/~drussell/demos.html

http://www.kettering.edu/~drussell/demos.htmlhttp://www.kettering.edu/~drussell/demos.html

8/12/2019 Seismik Bias Modifikasi 22

13/54

Proses Refraksi: Hukum Snell

i

r

21

sinsin

vr

vi

v1

v2

8/12/2019 Seismik Bias Modifikasi 22

14/54

8/12/2019 Seismik Bias Modifikasi 22

15/54

Simple Raypath Horizontal Model

Gelombang langsung

8/12/2019 Seismik Bias Modifikasi 22

16/54

Simple Raypath Horizontal Model

Gelombang

pantul

8/12/2019 Seismik Bias Modifikasi 22

17/54

Gelombang bias

8/12/2019 Seismik Bias Modifikasi 22

18/54

Ilustrasi

Geophone Vertikal

SumberPalu

Rock: Vp2

Soil: Vp1

osiloskop

x1x2x3x4

t1t2

t3t4

Kecepatan Vp1< Vp2

zR

Tentukan kedalamanlapisan rock, zR

8/12/2019 Seismik Bias Modifikasi 22

19/54

Data Sintetis 2 Lapis

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

5

10

15

20

25

30

35

40

45

50

geophone

time(s)

Model Sintetis seismik 50 Geophone

8/12/2019 Seismik Bias Modifikasi 22

20/54

Real Data

8/12/2019 Seismik Bias Modifikasi 22

21/54

Single Shot..only forward (Line-8 Jl. Kaliurang)

8/12/2019 Seismik Bias Modifikasi 22

22/54

Forward Shot (Line-3 Jl. Kaliurang)

8/12/2019 Seismik Bias Modifikasi 22

23/54

Backward Shot (Line-3 Jl. Kaliurang)

8/12/2019 Seismik Bias Modifikasi 22

24/54

Wavefront Model

8/12/2019 Seismik Bias Modifikasi 22

25/54

8/12/2019 Seismik Bias Modifikasi 22

26/54

Skema Wavefront

8/12/2019 Seismik Bias Modifikasi 22

27/54

Waktu

Jarak

Langsung

Pantulan

Biasan atau muka gelombang

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

5

10

15

20

25

30

35

40

45

50

geophone

time(s)

Model Sintetis seismik 50Geophone

8/12/2019 Seismik Bias Modifikasi 22

28/54

First Break

Waktu (mS)

8/12/2019 Seismik Bias Modifikasi 22

29/54

Synthetic Picks

Horizontal Layer

Varying V1

8/12/2019 Seismik Bias Modifikasi 22

30/54

Synthetic Picks

Horizontal Layer

Varying V2

8/12/2019 Seismik Bias Modifikasi 22

31/54

Synthetic Picks

Dipping LayerVarying V2 and Dip

8/12/2019 Seismik Bias Modifikasi 22

32/54

0.000

0.005

0.010

0.015

0.020

TravelTim

e

(secon

ds)

0 10 20 30 40 50

Distance From Source (meters)

Horizontal Soil Layer over Rock

Vp1= 1350m/s

1

Vp2= 4880

m/s

1z x

2 V VV V

cc p2 p1

p2 p1

Kedalaman Rock:

zc= 5.65 m

xc= 15.0 m

Nilai x

Nilait

Plot First Break

Jarak dari Sumber (meter)

W

aktuJalar(detik)

8/12/2019 Seismik Bias Modifikasi 22

33/54

Waktu

Jarak

12

2

1

2

21

2

)(2

VV

VVh

V

xT

Snell

Xco12

21

221

21

)(2

VV

VVh

V

x

V

xCOCO

Tin12

2

1

2

21 )(2

VV

VVhTin

8/12/2019 Seismik Bias Modifikasi 22

34/54

8/12/2019 Seismik Bias Modifikasi 22

35/54

Pickwin Time Travel Pick

8/12/2019 Seismik Bias Modifikasi 22

36/54

Plotrefa processed model

8/12/2019 Seismik Bias Modifikasi 22

37/54

Plotrefa raytracing model

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

38/54

D a n b om G e op hy si csZilker Park Study Austin TX

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

39/54

D a n b om G e op hy si csZilker Park Study Austin TX

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

40/54

D a n b om G e op hy si csZilker Park Study Austin TX

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

41/54

D a n b om G e op hy si csZilker Park Study Austin TX

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

42/54

D a n b om G e op hy si csZilker Park Study Austin TX

Zilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

43/54

D a n b om G e op hy si csZilker Park Study Austin TX

b hZilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

44/54

D a n b om G e op hy si csZilker Park Study Austin TX

D b G h iZilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

45/54

D a n b om G e op hy si csy

D b G h iZilker Park Study Austin TX

8/12/2019 Seismik Bias Modifikasi 22

46/54

D a n b om G e op hy si csZilker Park Study Austin TX

METODE HAGIWARA

8/12/2019 Seismik Bias Modifikasi 22

47/54

METODE HAGIWARA

Dua Lapis

8/12/2019 Seismik Bias Modifikasi 22

48/54

8/12/2019 Seismik Bias Modifikasi 22

49/54

8/12/2019 Seismik Bias Modifikasi 22

50/54

METODE MASHUDA

Tiga Lapis

Banyak Lapis

Metode Kaneko

8/12/2019 Seismik Bias Modifikasi 22

51/54

8/12/2019 Seismik Bias Modifikasi 22

52/54

8/12/2019 Seismik Bias Modifikasi 22

53/54

8/12/2019 Seismik Bias Modifikasi 22

54/54