Pemetaan Potensi Kerentanan Gempabumi Pada Kota Bengkulu Menggunakan Data Mikrotremor dan Metode Analytical Hierarchy Process

Arif Ismul Hadi; Muchammad Farid; Refrizon Refrizon; Budi Harlianto; Nurul Hudayat; Malik Krisbudianto

doi:10.20527/flux.v18i2.9479

Pemetaan Potensi Kerentanan Gempabumi Pada Kota Bengkulu Menggunakan Data Mikrotremor dan Metode Analytical Hierarchy Process

Arif Ismul Hadi, Muchammad Farid, Refrizon Refrizon, Budi Harlianto, Nurul Hudayat, Malik Krisbudianto

Abstract

ABSTRAK- Kota Bengkulu merupakan daerah yang sangat rawan terhadap ancaman gempabumi. Salah satu upaya mengurangi dampak bencana gempabumi adalah melakukan analisis potensi tersebut berdasarkan data mikrotremor dan metode pembobotan statistik. Penelitian ini bertujuan memetakan dan menganalisis daerah-daerah yang rentan mengalami ancaman bahaya gempabumi. Penelitian ini dilakukan menggunakan data sekunder dan survei lapangan. Data sekunder bersumber dari penelitian-penelitian terkait, sedangkan data survei lapangan berupa data mikrotremor menggunakan metode Horizontal to Vertical Spectral Ratio (HVSR). Alat yang digunakan untuk survei lapangan berupa broadband seismometer PASI Gemini-2 triaxial geophone dengan natural freq. 2 Hz ± 10%, berat 2 kg (s.n.: 12/004). Akusisi data lapangan dilakukan selama 30 menit (360.000 samples) per titik pengukuran dengan sampling rate 5 ms (200 Hz). Selanjutnya, tumpangsusun hasil pengolahan data sekunder dan lapangan menggunakan metode pembobotan statistik Analytical Hierarchy Process (AHP), sehingga diperoleh peta potensi kerentanan gempabumi di wilayah studi. Berdasarkan hasil analisis yang ditunjukkan dalam peta kerentanan gempabumi di daerah Kota Bengkulu dalam penelitian ini, Kecamatan Gading Cempaka, Kecamatan Singaranpati, Kecamatan Selebar, sebagian kecil Kecamatan Ratu Agung, dan Kecamatan Muara Bangkahulu adalah daerah yang mempunyai potensi kegempaan tinggi, sedangkan Kecamatan Selebar adalah daerah yang mempunyai potensi kegempaan rendah. Oleh karena itu untuk daerah berisiko tinggi perlu lebih diwaspadai dan perlu perencanaan pembangunan yang mengacu kepada standar risiko bencana.

ABSTRACT− Bengkulu City is an area that is very prone to earthquake threats. One of the method to reduce the impact of an earthquake disaster is to conduct a potential analysis based on microtremor data and statistical weighting methods. This study aims to map and analyze the areas have the vulnerability to experience an earthquake hazard. This study was conducted using secondary data and field surveys. Secondary data comes from related studies, while field survey data is in the form of microtremor data using the Horizontal to Vertical Spectral Ratio (HVSR) method. The instrument used for the field survey was a broadband seismometer PASI Gemini-2 triaxial geophone with natural freq. is 2 Hz ± 10%, weight is 2 kg (s.n .: 12/004). Field data acquisition was carried out for 30 minutes (360,000 samples) per observation point with a sampling rate of 5 ms (200 Hz). Furthermore, the overlay of the results of secondary and field data processing uses the statistical weighting method of Analytical Hierarchy Process (AHP), in order to obtain a map of potential the seismic vulnerability in the study area. Based on the results of the analysis shown in the seismic vulnerability map in the Bengkulu City area in this study, Gading Cempaka Sub-district, Singaranpati Sub-district, Selebar Sub-district, a small part of Ratu Agung Sub-district, and Muara Bangkahulu Sub-district were areas that had a high seismic vulnerability, while Selebar Sub-district were areas that had low seismic vulnerability. Therefore, high-risk areas need to be more vigilant and need development planning that refers to disaster risk standards.

Keywords

kerentanan; mikrotremor; AHP; HVSR; Kota Bengkulu.

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References

Allen, T.I. & Wald, D.J. (2007). Topographic slope as a proxy for global seismic site conditions ( ) and amplification around the globe. Reston, Va.: U.S. Geological Survey. http:// purl.access.gpo.gov/GPO/LPS89104.

Anderson, J.G., Bodin, P., Brune, J.N., Prince, J., Singh, S.K., Quaas, R., & Onate, M. (1986). Strong ground motion from the michoacan, mexico, earthquake. Science, 233(4768), 1043-1049. https://doi. org/10.1126/science.233.4768.1043.

BMKG. (2010). Katalog gempa 2005-2009. Bengkulu: Badan Meteorologi Klimatologi dan Geofisika.

BNPB. (2012). Peraturan kepala badan nasional penanggulangan bencana nomor 02 tahun 2012 tentang pedoman umum pengkajian risiko bencana, badan nasional penanggulangan bencana. Jakarta: BNPB. https://bnpb.go.id//uploads/migration/pubs/30.pdf.

BPS. (2018). Kota Bengkulu dalam angka. Bengkulu: Badan Pusat Statistik Kota Bengkulu.

Daryono. (2011). Indeks Kerentanan Seismik Berdasarkan Mikrotremor pada Setiap Satuan Bentuklahan di Zona Graben Bantul Daerah Istimewa Yogyakarta. Disertasi. Universitas Gadjah Mada.

Dewi, C. (2017). Analisis sebaran kerawanan longsor dan arahan mitigasi dengan metode analitycal hierarchy process (AHP) di Desa Kelapa Dua dan Desa Kunyi di Kecamatan Anreapi Kabupaten Polewali Mandar, Provinsi Sulawesi Barat. Tesis. Universitas Gadjah Mada.

Gafoer, S., Amin, T.C., & Pardede. (2007). Geological map of Bengkulu Quadrangle, Sumatra, scale 1:250,000. Bandung: Department of Mines and Energy, Directorate General of Geology and Mineral Resources, Geological Research and Development Centre.

Gafoer, S., Amin, T.C., & Pardede. (2012). Geology of the Bengkulu Quadrangle, Sumatra. Bandung: Department of Mines and Energy, Directorate General of Geology and Mineral Resources, Geological Research and Development Centre.

Hadi, A.I. & Brotopuspito, K.S. (2015). Pemetaan percepatan getaran tanah maksimum dengan menggunakan pendekatan probabilistic seismic hazard analysis (PSHA) di Kabupaten Kepahiang Provinsi Bengkulu. J. Berkala Fisika, 18(3), 101-112.

Hadi, A.I. (2019). Studi Potensi Longsor Daerah Kabupaten Kepahiang, Provinsi Bengkulu Terutama Akibat Gempabumi Menggunakan Pendekatan Parameter Elastis. Disertasi. Universitas Gadjah Mada.

Hadi, A.I., Farid, M., & Fauzi, Y. (2012). Pemetaan percepatan getaran tanah maksimum dan kerentanan seismik akibat gempa bumi untuk mendukung rencana tata ruang dan wilayah (RTRW) Kota Bengkulu. J. Simetri (Jurnal Ilmu Fisika Indonesia), 1(2(D)), 1217-81- 1217-86.

Hadi, A.I., Refrizon, Halauddin, Lidiawati, L., & Edo, P. (2021). Interpretasi tingkat kekerasan batuan bawah permukaan di daerah rawan gempa bumi Kota Bengkulu. Indonesian Journal of Applied Physics, 11(1), 11-24.

Hadi, A.I., Suhendra, & Efriyadi. (2010). Studi analisis parameter gempa bengkulu berdasarkan data single-station dan multi-station serta pola sebarannya. Berkala Fisika, 13(4), 105-112.

Hadi, A.I., Suhendra, & Manik, O.O. (2013). Pemetaan gempabumi berdasarkan tingkat keaktifan gempa di Provinsi Bengkulu periode 1971-2011. Prosiding Semirata BKS PTN Barat. Universitas Lampung, 269-272.

Irsyam, M., Sengara, W., Aldiamar, F., Widiyantoro, S., Triyoso, W., Hilman, D., Kertapati, E., Meilano, I., Suhardjono, Asrurifak, M., & Ridwan, M. (2010). Ringkasan hasil studi tim revisi peta gempa Indonesia 2010. Bandung: Kementerian Pekerjaan Umum.

Ishihara, K. (1996). Soil behaviour in earthquake geotechnics. NY, USA: Oxford University Press.

Konno, K., & Ohmachi, T. (1998). Ground-motion characteristics estimated from spectral ration between horizontal and vertical component of microtremor. Bulletin of the Seismological Society of America, 88(1), 228-241.

Kusumadewi, S., Hartati, S., Harjoko, A., & Wardoyo, R. (2006). Fuzzy multi-atribute decision making (fuzzy MADM). Edisi Pertama. Yogyakarta: Graha Ilmu. ISBN-10: 979-756-125-x.

Megawati, K., Pan, T-C., & Koketsu, K. (2005). Response spectral attenuation relationships for Sumatran-Subduction earthquakes and the seismic hazard implications to Singapore and Kuala lumpur. Soil Dynamics and Earthquake Engineering, 25(1), 11-25. https://doi.org/ 10.1016/j.soildyn.2004.08.003.

Murjaya, J. (2011). Zonasi energi tektonik daerah subduksi berdasarkan bentuk kerutan (buckling) searah busur (studi kasus: wilayah Sumatra). Disertasi. Universitas Gadjah Mada.

Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using mictrotremor on the ground ground surface. Quarterly Report of Railway Technical Research Institute, 30(1), 25-33.

Nakamura, Y. (2000). Clear identification of fundamental idea of nakamura’s technique and its application. The 12th Word Conference on Earthquake Engineering. Auckland, New Zealand.

Nakamura, Y. (2008). On the H/V spectrum. The 14th World Conference on Earthquake Engineering. Beijing, China.

Nakamura,Y., Saita, J., & Sato, T. (2003). Development of vulnerability assessment models using microtremor/strong motion. Prepared for 6th EQTAP Workshop in Kashikojima, Japan.

Natawidjaya, D.H. & Triyoso, W. (2007). The Sumatran Fault Zone: From Source to Hazard. J. of Earthquake and Tsunami, 1(1), 21-47. https://doi.org/10.1142/S1793431107 000031.

Nepop, R.K. & Agatova, A.R. (2008). Estimating magnitudes of prehistoric earthquakes from landslide data: first experience in Southern Altai. Russian Geology and Geophysics, 49(2008), 144-151.

Oliveira, C.S., Roca, A., & Goula, X. (2008). Assessing and managing earthquake risk (geo-scientific and engineering knowledge for earthquake risk mitigation: developments, tools, techniques). The Netherlands: Springer.

PASI. (2013). HVSR data acquisition unit GEMINI-2 user manual. Torino, Italy: PASI.

Petersen, M.D., Dewey, J., Hartzel, S., Mueller, C., Harmsen, S., Frankel, A.D., & Rukstales, K. (2004). Probabilistic seismic hazard analysis for Sumatra, Indonesia and across the Southern Malaysian Peninsula. Tectonophysics, 390(1-4), 141-158. https://doi.org/10.1016/j.tecto.2004.03. 026.

PUSGEN. (2017). Peta sumber dan bahaya gempa Indonesia tahun 2017. Bandung: Pusat Studi Gempa Nasional, Pusat Litbang Perumahan dan Permukiman, Badan Penelitian dan Pengembangan, Kementerian Pekerjaan Umum dan Perumahan Rakyat.

Russo, R. de F.S. & Camanho, R. (2015). Criteria in AHP: a systematic review of literature. Procedia Computer Science, 55(2015), 1123- 1132. DOI: 10.1016/j.procs.2015.07.081.

SESAME. (2004). Guidelines for the Implementation of the H/V spectral ratio technique on ambient vibrations: measurements, processing and interpretation. Brussels, Belgium: European Commi-ssion-Research General Directorate, Project No. EVG1-CT-2000-00026 SESA-ME. ftp://ftp.geo.uib.no/pub/seismo/SO-FTWARE/SESAME/USERGUIDELINES/ SESAME-HV-User-Guidelines.pdf.

Sieh, K. & Natawidjaja, D.H. (2000). Neotectonics of the Sumatran fault, Indonesia. Journal of Geophysical Research, 105(B12), 28,295-28,326. https://doi.org/10. 1029/2000JB900120.

SNI. (2019). Tata cara perencanaan ketahanan gempa untuk struktur bangunan gedung dan non gedung, badan standardisasi nasional (SNI 1726:2019) sebagai revisi dari SNI 1726:2012. Jakarta: Badan Standardisasi Nasional.

Steiguer, J.E. de., Duberstein, J., & Lopes, V. (2003). The analytic hierarchy process as a means for integrated watershed management. Tucson: School of Renewable Natural Resources, University of Arizona.

UBC. (1997). Structural design requirements, uniform building code, volume 1. Whittier, California: International Conference of Building Officials.

USGS. (2012). Search earthquake archives. USA: U.S. Geological Survey. http://earthquake. usgs.gov/earthquakes/search/.

Wald, D.J., Quitoriano, V., Heaton, T.H., & Kanamori, H. (1999). Relationships between peak ground acceleration, peak ground velocity, and modified mercalli intensity in California. J. Earthquake Spectra, 15(3), 557-564. https://doi.org/10. 1193/1.1586058.

Wangsadinata, W. (2006). Perencanaan bangunan tahan gempa berdasarkan SNI 1726-2002. Jakarta: Short course HAKI.

Wood, N. & Ratliff, J. (2011). Population and business exposure to twenty scenario earthquakes in the State of Washington. USA: U.S. Geological Survey. https://doi.org/10. 3133/ofr20111016.

DOI: http://dx.doi.org/10.20527/flux.v18i2.9479