Struktur Kecepatan Gelombang Geser (Vs) di Daerah Rawan Gerakan Tanah (Longsor) Jalan Lintas Kabupaten Bengkulu Tengah-Kepahiang

Nanang Sugianto, Refrizon Refrizon

Abstract

Shear wave velocity (Vs) structure at along of Central Bengkulu-Kepahiang crossline has been mapped. This research aims to identify the subsurface structure and to estimate the constituent material type of rock in landslide-prone areas (Central Bengkulu-Kepahiang crossline). Shear wave velocity structure on each site is obtained by the HVSR-inversion of 146 microtremor data (ambient noise recording of seismometer). Vs structure at the line mapped from the surface until to 30 meters of the depth. Groups of Vs are identified in class E (Vs <180), Class D (180≤ Vs <360), Class C (360≤ Vs <760), and Class B (760≤ Vs <1500). The subsurface structure at the depth of 0 to 10 meters are dominated by stiff soil, very dense soil, and soft rock which has highly fractured and weathered rock properties. At the depth of 15 meters to 30 meters, the subsurface structure is dominated by hard rock but it is high potential or easy to fracturing and weathering like the properties of the rocks in areas that have landslides in the past. Based on Vs value, rock constituent materials are deposition of sand, clay, gravel and alluvium ranging from soft to relatively hard structures at the depth.

Keywords

landslides; micro-tremor; shear wave velocity; subsurface structure.

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References

  1. BNPB. 2019. Trend Kejadian Bencana 10 Tahun Terakhir. Diakses melalui http://dibi.bnpb.go.id pada 14 Februari 2019.
  2. BNPB. 2010. Peta Indeks Resiko Bencana Gerakan Tanah Provinsi Bengkulu. Diakses melalui http://geospasial.bnpb.go.id/2010/06/22/peta-indeks-risiko-bencanagerakan-tanah-provinsi-bengkulu/ pada 28 Februari 2019.
  3. Suhendra, Bahrum, Z. dan Sugianto, N. 2018. Geological Condition at Landslides Potential Area Based on Microtremor Survey. ARPN Journal of Engineering and Applied Sciences, 13.
  4. Nandi. Longsor. Jurusan Pendidikan Geografi. Bandung: FPIPS-UPI. 2007.
  5. Wuryanta, A. 2004. Identifikasi Tanah Longsor dan Upaya Penanggulangan Studi Kasus di Kulon Progo, Purworejo dan Kebumen. Prosiding Ekspose BP2TPDAS-IBB: Surakarta.
  6. Motamed, R., Ghalandarzadeh, A., Tawhata, I. & Tabatabei, S. H. 2007. Seismic Microzonation and Damage Assessment of Bam City. Southern Iran: Journal of Earthquake Engineering, 11 (1), 110-132.
  7. Nakamura, Y. 2000. Clear Identification of Fundamental Idea of Nakamura’s Technique and Its Application. The 12th World Conference of Earthquake Engineering, Auckland, New Zealand, 30 Jan-4 Feb.
  8. Arai, H and Tokimatsu H. 2004. S-Wave Velocity Profiling by Microtremor H/V Spectrum. Amerika: Bulletin of the Seismological of America, 94 (1).
  9. Herak, M. 2008. Model HVSR: A Matlab Tool to Model Horizontal-to-Vertical Spectral Ratio of Ambient Noise. Computers and Geosciences, 34, 1514–1526.
  10. Mufida, A., Santosa. B.J., Warnana, D.D. 2013. Profiling kecepatan gelombang geser (Vs) Surabaya berdasarkan pengolahan data mikrotremor. Jurnal sains dan seni pomits, 2 (2), B_76-B_81.
  11. Bignardi, S., Mantovani, A., Abu Zeid, M., 2016. OpenHVSR: Imaging the Surface 2D/3D Elastic Properties Through Multiple HVSR Modeling and Inversion. Computer and Geosciences, 93 (1), 103-113.
  12. Garcia-Jerez, A., Pina-Flores, F., Sanchez-Sesma, F.J., Luzon, F., and Perton, M. 2016. A Computer Code for Forward Computation and Inversion of the H/V spectral Ratio Under the Diffuse Field Assumption. Computers & Geosciences, 97(1), 67-78.
  13. Anbalagan, R. 1992. Landslide Hazard Evaluation and Zonation mapping in Mountain Terrain. Engineering Geology, 32: 269-277.
  14. National Earthquake Hazards Reduction Program (NEHRP). 1997. Recommended provisions for seismic regulation for new buildings and other structures, edition, Part 1 – provisions, Part 2 – commentary, International Building Code, 198, FEMA 302, No.12.
  15. Milsom, J and Eriksen. 2011. Field Geophysics Fourth Edition, PP.216. Cambridge: University Press, London.
  16. Nakamura, Y. 1997. Seismic Vulnerability Indices for Ground and Structures using Microtremor. World Congress on Railway Research: Florence.
  17. Nausil. S, Efendi. R, dan Sandra. 2015. Penentuan Struktur Batuan Daerah Rawan Longsor Menggunakan Metode Seismik Mikrotremor di Desa Enu Kecamatan Sindue Kabupaten Dongala. Gravitasi, 14 (1), 83-89.
  18. Wibowo, B. A., Ngadmanto D., Listyaningrum Z., dan Putra, Y. M. K. 2015. Identifikasi Lapisan Rawan Longsor menggunakan Metode Seismik Refraksi Studi Kasus: Kampus Lapangan LIPI Karangsambung. Prosiding Seminar Nasional Fisika SNF2015, 4, 19-24.
  19. Refrizon, Irkhos. & Suhendra, Yenny, S.M. 2015. Studi Site Effect Dengan Indikator Percepatan Getaran Tanah Maksimum, Indeks Kerentanan Seismik, Ground Shear Strain Dan Ketebalan Lapisan Sedimen Di Kecamatan Muara Bangkahulu Kota Bengkulu. Jurnal Gradien, 11 (2).

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