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Uji Resolusi Tomografi Seismik Waktu Tempuh Lokal Menggunakan Dua Input Model Sintetik Mohamad Ramdhan; Said Kristyawan; Andry Syaly Sembiring; Daryono; Priyobudi
Limits: Journal of Mathematics and Its Applications Vol. 16 No. 2 (2019): Limits: Journal of Mathematics and Its Applications Volume 16 Nomor 2 Edisi De
Publisher : Pusat Publikasi Ilmiah LPPM Institut Teknologi Sepuluh Nopember

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Abstract

Uji resolusi dalam tomografi seismik telah diterapkan secara luas pada berbagai skala. Uji tersebut digunakan untuk mengetahui kehandalan data seismik yang digunakan pada suatu area penelitian. Checkerboard resolution test (CRT) merupakan salah satu teknik uji resolusi yang diterapkan secara luas pada data tomografi seismik. Uji resolusi dilakukan untuk mengetahui secara spasial area mana saja yang bisa diinterpretasi dari suatu tomogram seismik. Pada penelitian ini akan menguji resolusi dengan input model CRT dan Non-CRT. Area yang memiliki kemiripan pola antara input model dan hasil inversinya menunjukkan area tersebut bisa diinterpretasi baik secara geologi maupun dari properti fisika batuannya. Pada uji resolusi model Non-CRT juga ditambahkan random noise untuk mengetahui sejauh mana pengaruh noise terhadap data seismik. Hasil uji resolusi pada kedua input model tersebut menunjukan konsistensi pada area-area yang bisa diinterpretasi ataupun tidak. Hal ini menunjukkan data seismik yang digunakan pada penelitian ini memiliki kualitas yang cukup baik sehingga hasil studi tomografinya bisa menjelaskan kondisi geologi di bawah permukaannya
Seismisitas di Wilayah Jawa Tengah dan Sekitarnya Berdasarkan Hasil Relokasi Hiposenter dari Empat Jaringan Seismik Menggunakan Model Kecepatan 3-D Ramdhan, Mohamad; Priyobudi; Kristyawan, Said; Sembiring, Andry Syaly
EKSPLORIUM Vol. 41 No. 1 (2020): MEI 2020
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2020.41.1.5828

Abstract

Hypocenter relocation is a method used to get precise earthquake parameters. They will be useful for an advanced tectonic study like seismic hazard assessment in an area. The hypocenter relocation using a 3-D velocity model will theoretically obtain better results than a 1-D velocity model because the earth subsurface model is closed with a 3-D model. Some 767 earthquakes recorded by DOMERAPI, MERAMEX, BMKG, and BPPTKG networks used in this research. They were relocated by using a 3-D velocity model and analyzed for seismotectonic study in Central Java area and its surroundings. The result of hypocenter relocation using a 3-D velocity model is successfully detecting some tectonic features more clearly like columnar structure related to the backthrust structure at the south of Kebumen. The west-east vertical cross-section crossing the Opak fault indicates the dip of the fault plane is directing to the east. This study could not identify the double seismic zone, which was detected by the previous research. Some volcano-tectonic (VT) earthquakes related to the shallow magma activity of Mount Merapi also are detected clearly in this study.
Indikasi Sesar Naik di Plampang, Pulau Sumbawa Berdasarkan Analisis Gempa Bumi 13 Juni 2020 Priyobudi; Ramdhan, Mohamad
EKSPLORIUM Vol. 42 No. 2 (2021): NOVEMBER 2021
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2021.42.2.6273

Abstract

The existence of an active fault with a reverse fault mechanism in the Plampang area is successfully delineated from the distribution of the relocated hypocenter, the moment tensor inversion, and the Coulomb stress changes. This study also reveals the source of the earthquake in the active fault with a relatively shallow depth which can be a threat on Sumbawa Island if the maximum magnitude is released in the future. Seismicity from hypocenter relocation shows the distribution of the epicenter with a southwest–northeast direction. It is also supported by the moment tensor inversion result which shows the fault plane trending southwest–northeast (N2240E) with a steep dip (490). The vertical section of seismicity in the dip direction shows that the slope of the plane has a lower angle with increasing depth. The lower angle of a fault plane shows a decollement structure at a depth of 10–15 km and gradually becomes steep as a splay fault structure at a depth of 0–10 km. It is consistent with the result of moment tensor inversion which shows the mechanism of a reverse fault that occurred at a depth of 7 km. The Coulomb stress changes show the stress increasing outside the fault plane area, which triggers aftershocks. The distribution of aftershocks shows a hypothetical fault plane of 19 km long and 12 km wide. A fault of this size has the potential to generate an earthquake with a magnitude maximum of Mw 6.4. The Sumbawa earthquake on June 13, 2020, having M 5.3 was caused by a small part of the activity from the fault.