Analisis Sebaran Hiposenter Gempa Vulkanik Gunung Marapi Menggunakan Metode Geiger’s with Adaptive Damping (GAD)

Abstract

Penelitian tentang klasifikasi gempa dan sebaran hiposenter gempa Gunung Marapi telah dilakukan. Distribusi hiposenter dilakukan menggunakan Geiger's method with Adaptive Damping (GAD). Penelitian menggunakan data rekaman seismogram dari Januari sampai dengan Mei 2019. Dalam periode ini terdapat 82 kejadian gempa vulkanik, terdiri dari 69 vulkanik dalam (VA) dan 13 gempa vulkanik dangkal (VB). Dari jumlah ini, hanya 16 event gempa yang dapat dianalisis dan semuanya merupakan gempa vulkanik dalam (VA), karena hanya gempa ini yang terekam mnimal oleh tiga stasiun. Gempa dominan terjadi pada bulan Mei yang menandai kenaikan aktivitas dari Gunung Marapi. Hiposenter tersebar pada kedalaman 2600 -4700 m. Episenter tersebar mengelilingi puncak Gunung Marapi dimana jarak antar episenternya mengelilingi puncak kawah dengan jarak episenter 1 -7 km dari puncak kawah. Hiposenter dan episenter memiliki sebaran yang tidak beraturan dan magma bergerak dari Barat Laut ke Tenggara. Sebaran hiposenter ini cukup dekat dari kawah Gunung yang menandai kemungkinan untuk terjadi erupsi. Dengan demikian, terjadi lonjakan aktivitas Gunung Marapi tetapi tidak disertai kenaikan level aktivitas gunung. Kata kunci: gempa gunung marapi hiposenter Keywords: eartquake marapi mountain hypocenterResearch on earthquake classification and the distribution of the earthquake hypocenter of Mount Marapi has been carried out. The hypocenter distribution was investigated using Geiger's method with Adaptive Damping (GAD). The study used seismogram data recorded data from January to May 2019. During this period, there were 82 volcanic earthquakes, including 69 deep volcanic (VA) and 13 shallow volcanic earthquakes (VB). Of this number, only 16 earthquake events could be analyzed, and all of them were deep volcanic earthquakes (VA) because at least three stations recorded only these earthquakes. The dominant earthquake occurred in May, indicating increased activity from Mount Marapi. The hypocenter is spread out at a depth of 2600 -4700 m. The epicenters are distributed around the peak of Mount Marapi, where the distance of the epicenters encircles the top of the crater from the top of the crater, being 1-7 km. The hypocenter and epicenter have an irregular distribution, and magma moves from Northwest to Southeast. The distribution of this hypocenter is close enough to the volcano's crater to indicate the possibility of an eruption. While there was a spike in the activity of Mount Marapi but an increase in mountain activity level did not accompany it. .

Hypocenter Distribution Analysis of Sinabung Volcano Eruption in 2021 Using Geiger's With Adaptive Damping (Gad) Method

“…Where 𝑉 𝑝 is the propagation speed of the P wave, 𝑉 𝑠 is the speed of propagation of S waves, 𝐷 is the distance from the hypocenter (earthquake source) and (𝑆 − 𝑃) is the difference in arrival time of S and P waves. In determining the hypocenter, many methods are often used, one of which is the Geiger method [6] [7]. In addition, some parameters become references in determining the hypocenter, including location parameters and earthquake events consisting of longitude, latitude, depth, and time of earthquake occurrence.…”

“…Aiming to find out the depth of volcanic earthquakes, it is necessary to analyse the hypocenter. In this study, hypocenter analysis was carried out using Geiger's Methods with Adaptive Damping (GAD) [7]. The Geiger method was chosen in this study because it has a smaller RMS error, and its use is faster than the two methods above (Grid Search and Random Search).…”