Perbandingan Seismik Interferometri Cross Correlation Dan Cross Coherence Pada Data Seismik Pasif Untuk Perhitungan Kecepatan Gelombang P

Terakahfi, Almarsa Iman (2020) Perbandingan Seismik Interferometri Cross Correlation Dan Cross Coherence Pada Data Seismik Pasif Untuk Perhitungan Kecepatan Gelombang P. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Akuisisi data seismik dibedakan menjadi dua variasi berdasarkan sumbernya yaitu seismik aktif dan seismik pasif. Seismik pasif menggunakan sumber dari ambient noise (sumber yang tidak diketahui letak pastinya) yang kemudian direkam untuk mengkarakterisasi batuan dibawah permukaan tanah. Rekaman seismik pasif tersebut diberlakukan proses seismik interferometri untuk mendapatkan virtual source pada masing masing receiver terhadap receiver lainnya. Dalam pembuatannya, terdapat beberapa metode yang dapat dipakai, diantaranya adalah cross correlation dan cross coherence. Pada penelitian ini dibuat perbandingan proses pembuatan dan hasil virtual source antara cross correlation dan cross coherence. Akuisisi data dilakukan pada 8 titik stasiun di sekitar Surabaya. Data hasil akuisisi kemudian dilakukan pre-processing yang meliputi linear detrending, polynomial detrending, normalisasi rata – rata, normalisasi amplitudo, EMD filter, dan bandpass filter. Data yang telah dikondisikan lalu dilakukan perhitungan cross correlation dan cross coherence untuk membuat virtual source. Virtual source lalu dilakukan stacking dengan hari pengukuran lainnya. Hasil stacking lalu dilakukan picking pada peak amplitudo per trace untuk mendapatkan nilai waktu tempuh antar stasiun, kemudian dibuat permodelan cepat rambat gelombang dari nilai waktu tempuh tersebut dengan refraction tomography. Hasil dari kedua metode pembuatan virtual source memiliki beberapa perbedaan. Cross correlation menghasilkan noise yang lebih rendah, sedangkan cross coherence memiliki bandwidth yang lebih lebar (0.02 – 0.3 Hz) sehingga menghasilkan noise yang lebih tinggi dan memiliki peak amplitudo yang lebih tinggi (0.7). Hasil dari refraksi tomografi menghasilkan 3 rentang Vp, 300 – 400 m/s, 400 – 600 m/s, dan +880 m/s. ==================================================================================================================== Seismic data acquisition is divided into two variations based on the source, namely active seismic and passive seismic. Seismic data is useful for knowing subsurface characters with fairly high accuracy. Passive seismic uses a source of ambient noise (a source whose exact location is unknown) which is then recorded to characterize subsurface rocks. Passive seismic recording is implemented by the interferometry seismic process to obtain a virtual source on each receiver against the other receivers. To obtain the virtual source, there are several methods that can be used, including cross correlation and cross coherence. In this study a comparison is made between the process and the results of virtual sources with cross correlation and cross coherence methods. Data acquisition was carried out at 8 station points around Surabaya. Data acquisition results are pre-processed which includes linear detrending, polynomial detrending, mean normalization, amplitude normalization, EMD filter, and bandpass filter. Virtual source creation then conducted with the cross correlation and cross coherence method with the pre-processed data as the basis. The virtual source then stacked with other measurement in another days. The results of the stacking are then picked at the peak amplitude per trace to get the value of travel time between stations, then velocity modeling of the travel time is conducted using refraction tomography. The results of the two virtual source creation methods have several differences. Cross correlation results is lower in noise, whereas cross coherence has wider bandwidth (0.02 – 0.3 Hz) resulting in higher noise and have higher peak amplitude (0.7). Refraction tomography result indicates 3 range of Vp, 300 – 400 m/s, 400 – 600 m/s, and +880 m/s.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: seismik interferometri, cross – correlation, cross coherence, seismik pasif. seismic interferometry, cross correlation, cross coherence, passive seismic.
Subjects: Q Science > QE Geology > QE538.5 Seismic waves. Elastic waves
Q Science > QE Geology > QE538.8 Earthquakes. Seismology
Q Science > QE Geology > QE539.2 Seismic traveltime inversion
Q Science > QE Geology > QE539.2.S4 Seismic models
Divisions: Faculty of Civil Engineering and Planning > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User: Almarsa Iman Terakahfi
Date Deposited: 24 Aug 2020 03:58
Last Modified: 24 Aug 2020 03:58
URI: http://repository.its.ac.id/id/eprint/78820

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