Analisis SBA (Simple Bouguer Anomaly) Sebelum Gempa Padang Panjang 6 Maret 2007 Sebagai Prekursor Gempa Bumi
DOI:
https://doi.org/10.25077/jfu.10.3.310-316.2021Abstract
Telah dilakukan penelitian mengenai analisis SBA (Simple Bouguer Anomaly) sebelum gempa Padang Panjang 6 Maret 2007 yang bertujuan untuk melihat adanya korelasi antara perubahan anomali gravitasi dengan kejadian gempa bumi. Data gravitasi yang digunakan adalah data dari satelit GRACE (Gravity Recovery And Climate Experiment). Metode yang digunakan adalah metode time-lapse microgravity. Hasil kontur anomali selisih SBA menunjukkan adanya polarisasi anomali gravitasi yang terjadi di sekitar episenter gempa pada 35 hari sebelum gempa. Terdapat zona anomali tinggi di bagian tenggara dan zona anomali rendah di bagian barat daerah penelitian. Berdasarkan hasil sayatan melintang pada kontur harian SBA, diperoleh nilai harian SBA dan grafik harian SBA yang menunjukkan penurunan secara perlahan dari 35 hari hingga 20 hari sebelum gempa. Penurunan maksimum terjadi pada tanggal 12 Februari 2007. Lalu diikuti kenaikan secara terus menerus dari 20 hari hingga 15 hari sebelum gempa. Berdasarkan grafik selisih harian SBA, pada 35 hari sebelum gempa muncul anomali medan gravitasi tanggal 28 Januari 2007 dengan perubahan anomali gravitasi maksimum dari tanggal 22 – 23 Februari 2007 sebesar 0,490763281 µgal pada titik episenter gempa magnitudo 6,4 dan sebesar 0,49639576 µgal pada titik episenter gempa magnitudo 6,3. Sehingga anomali yang muncul tersebut dapat dijadikan pertanda awal (prekursor) gempa bumi.
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Kata kunci : anomali bouguer, gempa bumi, GRACE, gravitasi, polarisasiReferences
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