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Analisis Resiko Kebencanaan Gempa Bumi Data Mikrotremor Di Desa Fulolo Kecamatan Alasa Kabupaten Nias Utara

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INTISARI

Pengukuran mikrotremor telah dilakukan di Desa Fulolo Kecamatan Alasa Kabupaten Nias Utara. Penelitian ini bertujuan untuk menentukan parameter HVSR berupa nilai frekuensi dominan (f0) dan faktor amplifikasi (A0) serta menentukan parameter ketebalan sedimen lunak (H), indeks kerentanan seismik (Kg), peak ground accelaration / PGA (α) dan ground shear strain (γ) serta menganalisis resiko kebencanaan gempa bumi di Desa Fulolo Kecamatan Alasa Kabupaten Nias Utara. Pengukuran mikrotremor dilakukan pada 5 titik pengukuran dan data mikrotremor dianalisis menggunakan metode Horizontal to Vertical Spectral Ratio. Analisis HVSR berupa nilai frekuensi dominan (f0) dan amplifikasi (A0). Kemudian menghitung ketebalan sedimen lunak, nilai peak ground acceleration/PGA (α), indeks kerentanan seismik (Kg) dan ground shear strain (γ). Hasil penelitian menunjukkan bahwa Desa Fulolo memiliki sebaran nilai frekuensi dominan (f0) berkisar 0,954 Hz hingga 7,149 Hz, nilai amplifikasi (A0) berkisar 0,546 hingga 7,505, ketebalan sedimen lunak (H) berkisar 8,945 meter hingga 112,21 meter, nilai peak ground acceleration (α) berkisar 71,78 gal hingga 194,11 gal, indeks kerentanan seismik (Kg) berkisar 2,06 x 10-07 (1/cm s2) hingga 1,86 x 10-05 (1/cm s2), ground shear strain (γ) berkisar 1,031 x 10-04 hingga 1,338 x 10-03. Daerah yang memiliki resiko tinggi mengalami kerusakan akibat gempa bumi adalah Fulolo 3, Fulolo 4 dan Fulolo 5 yang berada Formasi Gunung Sitoli (QTg) dikarenakan memiliki lapisan sedimen lunak yang tebal sehingga ketiga daerah tersebut memiliki frekuensi dominan rendah (f0) rendah dan mengakibatkan faktor amplifikasi (A0) yang tinggi serta beresiko untuk mengalami deformasi bebatuan dan pergeseran lapisan permukaan akibat penjalaran gelombang gempa bumi.
Kata Kunci: Mikrotremor, HVSR, Frekuensi Dominan, Amplifikasi, Peak Ground Acceleration, Indeks Kerentanan Seismik dan Ground Shear Strain.

ABSTRACT

Measurement of the microtremor have been conducted in the Village of Fulolo, Alasa Subdistrict, North Nias District. This study aims to determine the parameters of HVSR in the form of the dominant frequency value (f0) and amplification factor (A0) and determine the parameters of soft sediment thickness (H), seismik vulnerability index (Kg), peak ground acceleration/PGA (α) and ground shear strain (γ) as well as analyzing the earth quake disaster risk in the Village of Fulolo, Alasa District, North Nias District. Microtremor measurements done on 5 points measurement and microtremor’s data were analyzed using Horizontal to Vertical Spectral Ratio’s method. The HVSR analysis is in the dominant frequency (f0) value and amplification (A0) value. Then calculate the thickness of soft sedimentary , the value of peak ground acceleration/PGA(α), the value of seismic vulnerability index (Kg) and the value of ground shear strain (γ).The results showed that the village of Fulolo have dominant frequency (f0) distribution grade range up 0,954 Hz to 7,149 Hz, the value of amplification (A0) ranges up 0,546 to 7,505, the value of the thickness of soft sedimentary (H) ranges up 8,945 meters t 112,21 meters, the value of peak ground acceleration (α) ranges up 71,78 gal to 194,11 gal, the seismic vulnerability index (Kg) ranges up 2,06 x 10-07 (1/cm s2) to 1,86 x 10-05 (1/cm s2) and the value of ground shear strain (γ) range up 1,031 x 10-04 to 1,338 x 10-03. Area that are high risk of experiencing the ravages of earthquakes are Fulolo 3rd, Fulolo 4th, Fulolo 5th on the Gunung Sitoli Formations (QTg) because of those have a thick layer of soft sediments so that third of the area have a dominant low frequency (f0) and resulting low amplification factor (A0) are high as well as at risk for experiencing shifting rock and deformation of surface layer due to the propagation of earthquake waves.

Keywords: Microtremor, HVSR, Dominant Frequency, Amplification, Peak Ground Acceleration, Seismic Vulnerability Index and Ground Shear Strain.

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Ketersediaan

1184D17IV

551,22 ASR a

Perpustakaan FSM Undip (Referensi)

Tersedia

Informasi Detail

Judul Seri

FISIKA

No. Panggil

551,22 ASR a

Penerbit

: ., 2017

Deskripsi Fisik

-

Bahasa

Indonesia

ISBN/ISSN

-

Klasifikasi

1814

Tipe Isi

-

Tipe Media

-

Tipe Pembawa

-

Edisi

-

Subjek

-

Info Detail Spesifik

-

Pernyataan Tanggungjawab

Asronj Bakkit Simanjutak

Versi lain/terkait

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