PRAMUJI, BRAM (2015) PENGOLAHAN DATA SITE EFFECT DI KABUPATEN BANTUL BERDASARKAN PENGUKURAN MIKROTREMOR DENGAN STUDI KASUS GEMPA YOGYAKARTA 27 MEI 2006. Masters thesis, UPN ''VETERAN'' YOGYAKARTA.
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Abstract
Gempa tektonik berkekuatan 6,3 SR, hari sabtu pagi pukul 05.53 WIB yang terjadi pada tanggal 27 Mei 2006, telah meluluhlantahkan daerah-daerah di wilayah Yogyakarta dan sebagian wilayah Jawa Tengah (Kabupaten Klaten). Gempa tersebut berpusat di koordinat 8° Garis Lintang Selatan dan 110° Garis Bujur Timur atau sekitar 25 km ke arah barat daya dari Kota Yogyakarta. Penyebab gempa ini adalah adanya pergeseran sesar Opak yang membentang dari pesisir pantai Bantul hingga ke Prambanan sepanjang 40 km dengan arah 30°NE (Northeast-Timur Laut). Gempa ini juga tergolong “perusak” karena termasuk jenis gempa dangkal, yaitu hanya berkedalaman 17 km di bawah permukaan tanah. Selain itu, kondisi tanah di daerah Yogyakarta dan sekitarnya merupakan endapan fluvio vulkanik yang rapuh sehingga gempa di Yogyakarta ini mengakibatkan banyak kerusakan. Di Graben Bantul, nilai frekuensi resonansi rendah kurang dari 3,0 Hz terdapat pada dataran fluvio vulkanik yang mempunyai sifat unconsolidated material. Karakteristik kurva H/V pada kondisi geomorfologi ini memiliki puncak spektral relatif tinggi pada frekuensi resonansinya. Frekuensi resonansi tinggi antara 3,0 hingga 3,9 Hz terdapat pada geomorfologi perbukitan struktural dan lerengkaki koluvial perbukitan struktural. Semakin dalam batuan dasar maka semakin kecil frekuensi resonansinya, sebaliknya makin dangkal batuan dasar fekuensi resonansi makin tinggi. Kebanyakan rumah yang roboh terjadi pada daerah yang memiliki frekuensi rendah (3 Hz<). Ada potensi getaran gempa bumi periode panjang di Graben Bantul yang membahayakan gedung-gedung bertingkat tinggi daerah Bantul pada masa mendatang. Penelitian site effect dilakukan dengan mikrozonasi bencana geologi di Kabupaten Bantul melalui pengolahan data site effect, dengan pengukuran mikrotremor menggunakan studi kasus gempa Yogyakarta 27 Mei 2006, serta menggunakan metoda Horisontal to Vertikal Spectral Rasio (HVSR) melalui pendataan parameter percepatan pergerakan tanah serta pengaruhnya terhadap kerusakan struktur bangunan. Metode HVSR mampu memprediksi persebaran kerusakan gempa bumi masa lampau dan masa yang akan datang. Kata Kunci : Site Effect, Unconsolidated Material, HVSR, Mikrotremor, Mikrozonasi. Tectonic earthquake measuring 6.3 magnitude, Saturday morning at 5:53 am that occurred on May 27, 2006, has been slammed areas in Yogyakarta and parts of Central Java (Klaten). The quake was centered at coordinates 8° South latitude and 110° East longitude, or about 25 km to the southwest of the city of Yogyakarta. The cause of this earthquake is a shift Opak fault that stretches from the coast up to the Prambanan Bantul along 40 km in the direction of 30° NE (Northeast-Northeast). This earthquake also classified as "destroyer" as including the type of shallow earthquake, which is only 17 km depth below the ground surface. In addition, the soil conditions in the area of Yogyakarta and surrounding areas fluvio volcanic deposition is fragile so the earthquake in Yogyakarta This resulted in a lot of damage . In Bantul Graben, low resonance frequency value is less than 3.0 Hz contained in fluvio volcanic plains that have unconsolidated nature of the material. Characteristic curve H/V on geomorphological conditions have relatively high spectral peak at the resonance frequency. High resonance frequency between 3,0 to 3,9 Hz contained in the hills structural geomorphology and structural lerengkaki koluvial hills. The deeper bedrock, the smaller the resonant frequency, whereas the more shallow bedrock fekuensi higher resonance. Most of the houses that collapsed occur in areas that have a low frequency (3 Hz <). There is potential for long periods of vibration earthquake in Bantul Graben dangerous high-rise buildings in Bantul area in the future. Research conducted by the site effect microzonation geological disasters in Bantul through data processing site effects, with mikrotremor measurement using case studies Yogyakarta earthquake May 27, 2006, as well as using the method of Horizontal to Vertical Spectral Ratio (HVSR) through data collection acceleration of ground motion parameters and their influence on the damage building structure. HVSR method is able to predict the distribution of earthquake damage of the past and future. Keywods : Site Effect, Unconsolidated Material, HVSR, Mikrotremor, Microzonation.
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) |
| Divisions: | Faculty of Engineering, Science and Mathematics > School of Engineering Sciences |
| Depositing User: | Erny Azyanti |
| Date Deposited: | 19 May 2016 01:36 |
| Last Modified: | 19 May 2016 01:36 |
| URI: | http://eprints.upnyk.ac.id/id/eprint/1592 |
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