MIKROZONASI INDEKS KERENTANAN SEISMIK DI KAWASAN JALUR SESAR OPAK BERDASARKAN PENGUKURAN MIKROTREMOR MICROZONATION OF SEISMIC VULNERABILITY INDEX IN OPAK FAULT LINES AREA BASED ON MICROTREMOR MEASUREMENT (Jurnal Ilmu Fisika dan Terapannya (JIFTA), 2017)
AbstrakPenelitian ini bertujuan untuk mengetahui nilai indeks kerentanan seismik di kawasan jalur sesar Opak dan mikrozonasinya. Pengambilan data mikrotremor dilakukan di jalur sesar Opak dari kecamatan Bambanglipuro, Kabupaten Bantul sampai dengan Kecamatan Prambanan, Kabupaten Sleman sebanyak 35 titik penelitian. Data mikrotremor diolah menggunakan metode Horizontal to Vertical Spectral Ratio (HVSR) untuk mendapatkan kurva H/V yang menghasilkan nilai frekuensi predominan (fg) dan faktor amplifikasi (Ag) di setiap titik penelitian. Nilai frekuensi predominan (fg), faktor amplifikasi (Ag) dan kecepatan pergeseran gelombang di batuan dasar (Vb) digunakan untuk menentukan nilai indeks kerentanan seismik (Kg). Mikrozonasi indeks kerentanan seismik dilakukan dengan menggunakan software Surfer 12. Hasil penelitian ini menunjukkan bahwa nilai indeks kerentanan seismik di kawasan jalur sesar Opak berkisar 0,20 10-6 s2/cm sampai 25,14  10-6 s2/cm yang memiliki kategori rendah hingga tinggi. Hasil mikrozonasi indeks kerentanan seismik (Kg) terendah berada di bagian barat daya dan barat laut jalur sesar Opak pada Kecamatan Prambanan. Hasil mikrozonasi indeks kerentanan seismik (Kg) tertinggi berada di bagian timur jalur sesar Opak menyebari pada Kecamatan Banguntapan. Kata kunci:     Horizontal to Vertikal Spectral Ratio, Indeks Kerentanan Seismik, Mikrotremor, Sesar Opak AbstractThe aim of this study was to determine the value of seismic vulnerability index and its microzonation at Opak fault line area. The area of this study was in Opak fault lines of  Bambanglipuro District, Bantul Regency until Prambanan District, Sleman Regency by taking the microtremor data of 35 locations. The microtremor data were then processed using Horizontal to Vertical Spectral Ratio (HVSR) method to get H/V curve which generates predominant frequency (fg)  value and amplification factor (Ag) at every observation point. Predominant frequency (fg)  value, amplification factor (Ag), and S-wave velocity of basement ground (Vb) was used to determine the value of seismic vulnerability index (Kg). Seismic vulnerability index microzonation was generated using Surfer12 software. The results showed that the value of seismic vulnerability index in the Opak fault line area is between 0,20 10-6 s2/cm to 5,55 10-6 s2/cm which is categorized as low to high. The lowest results of seismic vulnerability index (Kg) microzonation located in the southwestern and northwestern part of Opak fault line area and spread in the Prambanan District. The highest results of seismic vulnerability index (Kg) microzonation located in the eastern part of Opak fault line area and spread in the Banguntapan District. Keywords:     Opak Fault, Horizontal to Vertical Spectral Ratio, Microtremor,  Seismic Vulnerability Index