MIKROZONASI KAWASAN RAWAN BENCANA GEMPABUMI DENGAN STUDI PEAK GROUND ACCELERATION MENGGUNAKAN METODE BOORE ATKINSON DAN DATA MIKROTREMOR DI DAERAH KUPANG
DOI:
https://doi.org/10.20956/geocelebes.v1i1.1774Abstract
Abstrak
Letak geografis Indonesia yang berada pada pertemuan tiga lempeng tektonik utama; Lempeng Indo-Australia, Lempeng Eurasia dan Lempeng Pasifik, menjadikan Indonesia sebagai kawasan rawan gempabumi. Berdasarkan data yang dirilis oleh Direktorat Vulkanologi dan Mitigasi Bencana Geologi (DVMBG) terdapat 28 wilayah rawan gempa dan tsunami termasuk Kupang. Kupang terletak di zona busur sangat aktif dan tepian benua aktif. Kegiatan tektonik yang berlangsung saat ini dicirikan dengan kejadian gempa tektonik yang melanda daerah pedalaman, akibat dari aktifnya sesar-sesar yang terdapat di perbukitan sekitar Kota Kupang. Salah satu upaya mitigasi yang dilakukan adalah pengukuran mikrotremor menggunakan metode HVSR (Horizontal to Vertical Spectral Ratio) untuk mengetahui nilai frekuensi dominan yang akan menjadi penentu tingkat kerawanan bencana gempabumi. Nilai frekuensi dominan akan menghitung nilai kecepatan gelombang S hingga kedalaman 30 meter (Vs30) yang selanjtnya digunakan untuk menentukan nilai PGA dan amplifikasi. Hasil analisis data menunjukkan bahwa nilai periode dominan berada pada rentang 0.1-0.97 sekon, nilai PGA antara 92.87-142.84 gal dan nilai amplifikasi adalah 0.99-4.38 dan 2.12-9.43 kali. Maka dapat disimpulkan bahwa daerah penelitian termasuk kategori rawan bencana gempabumi terutama pada bagian tenggara.
Kata Kunci : Amplifikasi, Mikrotremor, Periode Dominan, PGA
Abstract
Geographically, Indonesia located at the meeting of three major tectonic plates; Indo-Australian Plate, Eurasian Plate, and Pacific Plate, that make Indonesia as earthquake-prone area. Based on data released by the Directorate of Volcanology and Geological Hazard Mitigation (DVMBG), there are 28 earthquake and tsunami prone areas including Kupang that the area located in the very active arc zone and the edge of the active continent. The tectonic activity that is currently taking place is characterized by the tectonic earthquake that attacks to countryside areas, resulting from the active fault-faults found in the hills around the area. One of the mitigation efforts is microtremor measurement using HVSR (Horizontal to Vertical Spectral Ratio) method to find out the dominant frequency for determination of the magnitude of the earthquake. The predominant frequency value will determine the Shear wave velocity up to 30 meters (Vs30) which are further used for the PGA and amplification values. The result of data analysis shows that the dominant period value is in the range 0.1-0.97 second, PGA value between 92.87-142.84 gal and the amplification value is 0.99-4.38 and 2.12-9.43 times. The conclusion, the area is categorized as earthquake-prone, especially in the southeast region.
Keywords: Amplification, Microtremor, Dominant Period, PGA
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