PEMODELAN KECEPATAN GELOMBANG GESER (Vs) HVSR MULTI 1D UNTUK IDENTIFIKASI KEMENERUSAN SESAR KENDENG DI WILAYAH SURABAYA TIMUR

Wahjudhi, Syarfa Monita (2020) PEMODELAN KECEPATAN GELOMBANG GESER (Vs) HVSR MULTI 1D UNTUK IDENTIFIKASI KEMENERUSAN SESAR KENDENG DI WILAYAH SURABAYA TIMUR. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Secara geografis letak Surabaya berada pada patahan yang diperkirakan masih aktif dan besar kemungkinan bisa menimbulkan gempa bumi dengan kekuatan besar. Sumber gempa tersebut berasal dari Sesar Kendeng. Sesar Kendeng melintas dan membelah Surabaya menjadi dua bagian yaitu utara dan selatan dengan perkiraan magnitudo maksimum mencapai 6,5. Selain itu, strain rate sepanjang segmen timur menunjukkan adanya kompresi sebesar 37.231 ns/tahun ± 20.267 ns/tahun. Mekanisme yang terjadi pada ekstensi Sesar Kendeng ini menunjukkan adanya potensi sumber gempa baru di sekitar Selat Madura. Maka dari itu dilakukan survei geofisika dengan menggunakan metode mikrotremor yang bertujuan untuk menyelidiki posisi dan arah kemenerusan Sesar Kendeng di wilayah Surabaya Timur. Metode mikrotremor cocok digunakan untuk menggambarkan karakteristik dinamis tanah akibat aktivitas seismik melalui kecepatan gelombang geser (Vs) karena mempunyai kelebihan mudah dan tidak perlu sumber buatan. Data mikrotremor kemudian dianalisis menggunakan pendekatan Horizontal to Vertical Spectral Ratio (HVSR) dengan melalui dua tahapan, yaitu analisis kurva HVSR dan inversi. Berdasarkan nilai f0, wilayah Surabaya Timur mempunyai frekuensi natural rendah < 2,5 Hz. Hasil inversi dari kurva HVSR memperlihatkan sebaran nilai Vs bawah permukaan berkisar 80 – 1500 m/s. Berdasarkan sebaran nilai Vs tersebut, wilayah Surabaya Timur teridentifikasi adanya patahan naik yang berasosiasi dengan lipatan. Dugaan tersebut terletak di stasiun SBA06 – SBA04, tepatnya di kecamatan Gubeng dan Sukolilo. ================================================================================================================== Geographically, Surabaya is located on a fault that is thought to be still active and is likely to cause an earthquake with a large force. The source of the earthquake came from the Kendeng Fault. The Kendeng Fault crosses and divides Surabaya into two parts namely north and south with an estimated maximum magnitude of 6.5. In addition, strain rates throughout the eastern segment showed a compression of 37,231 ns/year ± 20,267 ns/year. The mechanism that occurs in the Kendeng Fault extension shows the potential for new earthquake sources around the Madura Strait. Therefore a geophysical survey was carried out using the microtremor method which aims to investigate the position and direction of the Kendeng Fault in East Surabaya. The microtremor method is suitable for describing the dynamic characteristics of soil due to seismic activity through shear wave velocity (Vs) because it has an easy advantage and does not need an artificial source. The microtremor data is then analyzed using the Horizontal to Vertical Spectral Ratio (HVSR) approach through two stages, namely the analysis of the HVSR curve and inversion. Based on the value of f0, the East Surabaya region has a low natural frequency <2.5 Hz. The inversion results from the HVSR curve show the distribution of subsurface Vs values ranging from 80 - 1500 m / s. Based on the distribution of the value of Vs, the Eastern Region of Surabaya was identified by a thrust fault associated with the fold. The allegations are located at SBA06 - SBA04 stations, precisely in the sub-districts of Gubeng and Sukolilo

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: Analisis HVSR, Gelombang Geser, Mikrotremor, Sesar Kendeng HVSR Analysis, Share Wave Velocity, Microtremor, Kendeng Fault
Subjects: Q Science > QE Geology > QE539.2.S4 Seismic models
Divisions: Faculty of Civil Engineering and Planning > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User: Syarfa Monita Wahjudhi
Date Deposited: 12 Aug 2020 02:59
Last Modified: 12 Aug 2020 03:00
URI: http://repository.its.ac.id/id/eprint/77389

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