Identifikasi Potensi Tanah Longsor Menggunakan Metode Mikrotremor Di Dusun Tegalsari Desa Ngargosari Kecamatan Samigaluh Kabupaten Kulon Progo

Abstract

Tanah longsor adalah bencana alam yang sering terjadi di Indonesia. Banyak faktor yang menyebab tanah longsor terjadi antara lain curah hujan yang tinggi, topografi yang curam, lapisan sedimen yang tebal dan pergerakan tanah. Salah satu daerah yang sering mengalami tanah longsor adalah Kecamatan Samigaluh. Oleh karena itu, pengambilan data mikrotremor dilakukan di Dusun Tegalsaari Desa Ngargosari Kecamatan Samigaluh Kabupaten Kulon Progo Daerah Istimewa Yogyakarta untuk mengetahui nilai frekuensi dominan dan amplifikasi di daerah tersebut yang diperoleh dari metode Horizontal to Vertical Spectral Ratio (HVSR). Selanjutnya, nilai frekuensi dominan dan amplifikasi diolah untuk mengetahui indeks kerentanan seismik, ketebalan lapisan sedimen, peak ground acceleration dan ground shear strain yang digunakan untuk mengetahui daerah yang berpotensi mengalami tanah longsor. Berdasarkan hasil analisis data mikrotremor diperoleh nilai frekuensi dominan antara 2,1 Hz – 18,7 Hz, nilai amplifikasi berkisar antara 1,4 sampai 8,1, indeks kerentanan seismik antara 0,27 – 26,04 s2/cm, nilai PGA berkisar antara 81,36 – 245,42 gal, ground shear strain antara 2,39 x 10-5 – 2,30 x 10-3 dan ketebalan sedimen berkisar antara 9,06 – 89, 55 meter. Daerah dengan potensi tanah longsor yang tinggi ditentukan dengan menganalisis persebaran nilai amplifikasi, indeks kerentanan seismik, ketebalan lapisan sedimen, peak ground acceleration, dan ground shear strain sehingga diperoleh daerah yang memiliki potensi tanah longsor tinggi berada di area 16, 46, 92, 100, 101, 103, 104, 105, 113, dan 114.

MICROZONATION ANALYSIS IN MANNA CITY & PASAR MANNA SUBDISTRICTS UTILIZING MICROTREMOR DATA, SOUTH BENGKULU REGENCY

“…The higher the value of the amplification factor (A0), the greater the vibration intensity and the resulting hazard. Conversely, if the value of the amplification factor (A0) is low, the intensity of the vibration and the risk will also be smaller [7]. The sediment layer thickness (h) value reveals that the research region exhibits a range of sediment thickness that ranges from 3.77 to 47.48 meters.…”

“…The greater the thickness of the sediment layer in an area, the more significant the impact of the earthquake will be [6]. This is because sites with a thick layer of sediment have rock characteristics that are not solid, so they are easily deformed in a big earthquake [7]. Figure 2 shows an example of the aftermath of an earthquake in the Special Region of Yogyakarta in 2006, which caused more than 100,000 houses to be severely damaged [8].…”

Lithological modelling based on shear wave velocity using horizontal to vertical spectral ratio (HVSR) inversion of ellipticity curve method to mitigate landslide hazards at the main road Of Samigaluh District, Kulon Progo Regency, Yogyakarta

“…So it is important to know the potential for landslides because the main road in Samigaluh District is a vital infrastructure to support transportation, economic development and ease of community mobility, goods and services. Research conducted by [6][7] shows the dominant frequency and amplification values in Samigaluh District. While research [8] shows the value of shear wave velocity and lithology located in Samigaluh District.…”

Determination of Sand Mining Prospective Zones Based on Sediment Thickness Analysis Using HVSR Microtremor and Gravity Methods: A Case Study in Cangkringan, Sleman, Daerah Istimewa Yogyakarta

“…If the strain is high, it can lead to surface deformation and collapse. Ground shear strain is related to the dynamic properties of the soil, such that when ground shear strain is low, the resulting deformation is small, and if the value is high, the deformation will be more significant (Syahputri, 2020).…”