Mikrozonasi Bahaya Guncangan Gempabumi Berdasarkan Analisis Horizontal-To-Vertical Spectral Ratio (HVSR) di Kecamatan Kalasan, Kabupaten Sleman, Provinsi Daerah Istimewa Yogyakarta dan Kecamatan Prambanan, Kabupaten Klaten, Provinsi Jawa Tengah

KADEK ALITYA A, Dr. Budi Eka Nurcahya, M.Si.

2020 | Skripsi | S1 GEOFISIKA

Gempa Jogja 27 Mei 2006 bermagnitudo 6,3 Mw menyebabkan kerusakan di beberapa tempat. Pusat gempa terletak di kedalaman 12,5 km pada koordinat 7,961 LS dan 110,446 BT. Bahkan, Candi Prambanan yang terletak sekitar 15 km dari episenter juga mengalami kerusakan yang parah. Penelitian mikrotremor dilakukan di sekitar Kecamatan Kalasan dan Kecamatan Prambanan, DIY - Kalasan Jawa Tengah untuk memetakan daerah rentan guncangan akibat gempabumi. Data mikrotemor dianalisis menggunakan metode HVSR untuk mendapatkan nilai frekuensi dominan (f0) dan faktor amplifikasi (A0). Data tersebut diolah hingga didapatkan nilai periode dominan (T0), ketebalan lapisan sedimen lunak (H), dan indeks kerentanan seismik (Kg). Pada penelitian ini didapatkan nilai f0 antara 0,64-19,03 Hz, nilai A0 antara 1,57-9,55 kali, nilai T0 antara 0,06-1,56 s, nilai H antara 3,60-101,39 m, dan nilai Kg antara 0,34-116,83. Pemetaan didasarkan pada amplifikasi hingga didapatkan 4 zona, yaitu Zona Rentan Guncangan Gempabumi I dengan amplifikasi sangat tinggi (> 9 kali), Zona Rentan Guncangan Gempabumi II dengan amplifikasi tinggi (6-9 kali), Zona Rentan Guncangan Gempabumi III dengan amplifikasi sedang (3-6 kali), dan Zona Rentan Guncangan Gempabumi IV dengan amplifikasi rendah (0-3 kali). Zona I mencakup Desa Cucukan. Zona II mencakup Desa Cucukan, Sengon, Madurejo, Sumberharjo, Jogotirto, dan Tirtomartani. Zona III mencakup Desa Cucukan, Sengon, Madurejo, Sumberharjo, Jogotirto, dan Tirtomartani. Zona IV mencakup Desa Joho, Randusari, Brajan, Kemudo, Bugisan, Tlogo, Taji, Kokosan, Kebondalem Lor, Bokoharjo, Sambirejo, Sumberharjo, Madurejo, Wukirharjo, Selomartani, Tirtomartani, Tamanmartani, Tirtomartani, Purwomartani, dan Bimomartani. Secara umum, lokasi penelitian didominasi oleh Zona III dan IV.

The Yogyakarta earthquake on 27 May 2006 with a magnitude of 6.3 MW caused damage in several places. The epicenter was located at a depth of 12.5 km at the coordinates of 7.961 S and 110.446 E. In fact, Prambanan Temple, which is located about 15 km from the epicenter, also suffered severe damage. Microtremor research was carried out in the vicinity of Kalasan and Prambanan, DIY - Central Java to map areas prone to shocks due to earthquakes. Microtremor data were analyzed using the HVSR method to obtain the dominant frequency (f0) and amplification factor (A0). Then the data is processed to obtain the value of the dominant period (T0), the thickness of the sediment layer (H), and the seismic susceptibility index (Kg). The research area has an f0 value between 0.64-19.03 Hz, an A0 value between 1.57-9.55 times, a T0 value between 0.06-1.56 s, an H value between 3.60-101.39 m, and the Kg value is between 0.34-116.83. Mapping is based on amplification until 4 zones are obtained, namely the Earthquake Vulnerability Zone I with very high amplification (> 9 times), the Earthquake Vulnerability Zone II with high amplification (6-9 times), the Earthquake Vulnerability Zone III with moderate amplification (3-6 times), and the Earthquake Vulnerability Zone IV with low amplification (0-3 times). Zone I includes Cucukan Village. Zone II includes the villages of Cucukan, Sengon, Madurejo, Sumberharjo, Jogotirto, and Tirtomartani. Zone III includes the villages of Cucukan, Sengon, Madurejo, Sumberharjo, Jogotirto, and Tirtomartani. Zone IV includes Joho, Randusari, Brajan, Kemudo, Bugisan, Tlogo, Taji, Kokosan, Kebondalem Lor, Bokoharjo, Sambirejo, Sumberharjo, Madurejo, Wukirharjo, Selomartani, Tirtomartani, Tamanmartani, Tirtomartani, Purwomartani and Bimomartani villages. In general, the research locations are dominated by Zones III and IV.

Kata Kunci : Mikrotremor, HVSR, Prambanan, Mikrozonasi, Amplifikasi