FORMULA EMPIRIS PENENTUAN MAGNITUDO MENGGUNAKAN TIGA DETIK PERTAMA GELOMBANG P (STUDI KASUS STASIUN CISI, GARUT – JAWA BARAT)
Keywords:
magnitudo, filter, cut-off, tiga detikAbstract
Indonesia merupakan negara yang rawan terjadi bencana gempabumi. Salah satu wilayah yang cukup rawan adalah Jawa Barat. Wilayah ini tercatat beberapa kali diguncang gempabumi yang cukup besar. Penentuan magnitudo dengan menggunakan fase awal gelombang diperlukan untuk membangun Earthquake Early Warning System (EEWS) di Indonesia. Studi ini menganalisis waveform gempa yang tercatat di stasiun Cisomped (CISI). Waveform kecepatan difilter dengan variasi cut-off yang nilainya 0,05; 0,075; 0,1; 0,5; dan 1 Hz, dan diintegrasi untuk mendapat sinyal displacement. Magnitudo dihitung dengan menggunakan amplitudo maksimum tiga detik pertama (MPd). Studi ini menghasilkan rumusan formula penghitungan MPd untuk tiap-tiap cut-off. Untuk gempa besar, dengan menggunakan variasi cut-off tersebut dihasilkan nilai MPd yang mendekati magnitudo (MCat) yang dikeluarkan GFZ untuk cut-off 0,05; 0,075; dan 0,1 Hz. Untuk cut- off 0,5 dan 1 Hz menghasilkan nilai yang jauh berbeda dengan selisih mencapai 0,9. Sedangkan untuk gempa kecil menghasilkan nilai MPd yang bervariasi.
Kata kunci : magnitudo, filter, cut-off, tiga detik
References
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