Observing Volcanic Activity at Mt. Merapi 2018-2023 with An Advanced InSAR Time – Series Method Mudju Silfara Rifu Rinamu, Asep Saepuloh OPHIOLITE : Jurnal Geologi Terapan Vol. 7 No. 3 2026 DOI 10.56099/ophi.v7i3.p133-139