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Abstract

This paper presents the study of the seismic response and liquefaction potential of the coastal area of Bengkulu City during the September 2007 Sumatra earthquake. The study is conducted by collecting site investigation data (standard penetration test) and applying input motion to observe soil response. Synthetic ground motion is generated by considering the important aspects of earthquakes, including focal depth, epicenter, earthquake source, and site classification. The synthetized ground motion is then used as the input motion in the seismic response analysis. The results of this analysis are spectral acceleration and peak ground acceleration at each depth. The resulting spectral acceleration is compared with that specified in the seismic design code of Indonesia (SNI 03-1726-2012). Liquefaction potential analysis is performed on the basis of the results of the seismic response analysis. Results show that spectral acceleration depends on soil type. A high soil density equates to a low spectral response. The designed spectral acceleration may still be considered for each borehole, especially for T (period) < 1. However, for T > 1, spectral acceleration should be prioritized, especially for high-rise building construction. The liquefaction analysis reveals that a shallow depth is vulnerable to liquefaction. In general, this study could give a better understanding on the implementation of seismic ground response for liquefaction potential analysis.

Bahasa Abstract

Potensi Likuifaksi Berdasarkan Response Tanah Nonlinear pada Area Pesisir Kota Bengkulu, Indonesia. Naskah ini menyajikan studi respon seismic dan potensi likuifaksi pada area pesisir Kota Bengkulu akibat Gempa Sumatra September 2007. Studi ini dilakukan dengan mengumpulkan data investigasi lapangan berupa data penetrasi standard dan menerapkan perambatan gelombang untuk mengamati bagaimana respon tanah. Gelombang sintetis dihasilkan dengan mempertimbangan aspek penting kegempaaan, seperti kedalaman, jarak episenter, sumber gempa, dan klasifikasi kelas situs. Gelombang sintetis selanjutnya digunakan sebagai input pada analisis respon seismik. Hasil analisis ini adalah percepatan spektra dan percepatan gelombang gempa pada setiap kedalaman. Percepatan spektra hasil perambatan gelombang seismik selanjutnya dibandingkan dengan SNI 03-1726-2012. Analisis potensi likuifaksi juga dilakukan berdasarkan hasil analisis respon seismik. Hasil penelitian ini menunjukkan bahwa percepatan spektra bergantung pada jenis tanah. Semakin tinggi kepadatan tanah maka percepatan spektra semakin rendah. Spektra desain masih dapat diterapkan untuk setiap lokasi yang di studi, khususnya untuk perioda (T) kurang dari satu. Meskipun demikian untuk T > 1 detik, percepatan spektra harus diutamakan, khususnya untuk bangunan berlantai tinggi. Analisis likuifaksi juga menjelaskan bahwa likuifaksi dapat terjadi pada kedalaman dangkal. Secara umum, hasil penelitian ini dapat memberikan pemahaman yang lebih baik mengenai implementasi respon gelombang seismik untuk analisis potensi likuifaksi.

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