Papers by Abraham Arimuko
Pure and Applied Geophysics
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On 18 November 2022, a strong earthquake occurred in the near-trench of Sunda Arc southwest of so... more On 18 November 2022, a strong earthquake occurred in the near-trench of Sunda Arc southwest of southern Sumatra, generating a small tsunami recorded at four tide gauge stations (KRUI, BINT, SBLT, and SIKA). Four seismological agencies (BMKG, GCMT, GFZ, and USGS) obtained nearly similar earthquake parameters and focal mechanisms from a seismic approach. It is situated near two major historical earthquakes that generated destructive tsunamis. One of those historical tsunamis, the 2010 Mentawai tsunami, was produced by a rare shallow and slow rupture earthquake with a higher tsunami impact than predicted from the seismic moment. It is related to the low rock rigidity of the source location. This study aims to understand the source characteristics of the 2022 event, which were probably influenced by the depth-varying rigidity. We examined those four source models using numerical tsunami modeling. We tested five distinct rigidity values, such as 10, 12.5, 15, 17.5, and 20 GPa, for each s...
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Geotechnical and Geological Engineering, Nov 23, 2022
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<p>On December 14, 2021, the Mw 7.3 Flores Sea earthquake occurred approxim... more <p>On December 14, 2021, the Mw 7.3 Flores Sea earthquake occurred approximately 100 km to the north of Flores Island, one of the most complex tectonic settings in Indonesia. The existence of the causative fault that generated this earthquake was not been previously known, therefore making further analysis crucial for assessing future seismic hazard in the region. In this study, we relocated the hypocenter of the mainshock and aftershocks using a double-difference method, determine focal mechanisms using waveform inversion, and then analyse stress changes to estimate the fault type and stress transfer caused by this earthquake. Our relocated hypocenters show that this earthquake sequence ruptured on at least three segments: the source mechanism of the mainshock exhibits dextral strike-slip motion (strike N288<sup>o</sup>W and dip 78<sup>o</sup>) that occurred on a West-East trending fault which we call the Kalaotoa Fault, while rupture of the other two segments located to the west and east of the mainshock (WSW-ESE directions, respectively) may have been triggered by this earthquake. The Coulomb stress change of the mainshock shows that areas to the northwest and southeast experienced an increase in stress, which is consistent with the observed aftershock pattern.</p>
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Journal of Physics: Conference Series, 2021
On February 17, 1996, at 05:59:30 UTC there was an Mw 8.1 earthquake. Besides, it caused a tsunam... more On February 17, 1996, at 05:59:30 UTC there was an Mw 8.1 earthquake. Besides, it caused a tsunami. This event occurred in the northern part of the Cendrawasih Bay, where the New Guinea Thrust segment had a relatively low average slip velocity. To obtain a finite fault, waveforms from a tele-station located 30-90 degrees are used. The far-field body wave equation is used and inverted by the Kikuchi-Kanamori algorithm. In addition to obtaining source parameters, this study also aims to determine the value of the rupture velocity that occurs during coseismic events. From this research was found that the rupture velocity (vr) was 2.5 km/s, which occurred at a depth of 13.7 km. The largest value of vector slip is 2.31 m, with an average slip value of 0.922 m. The dimension area of the fault has a size of 272 km × 110 km. The seismic moment obtained is 1.5 × 1021 Nm, which is equivalent to Mw 8.1. This study also found a variance of 0.2844 in the use of the P and SH wave components, whic...
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The Seismic Record
We reveal the existence of a previously unknown fault that generated the Mw 7.3 Flores Sea earthq... more We reveal the existence of a previously unknown fault that generated the Mw 7.3 Flores Sea earthquake, which occurred on 14 December 2021, approximately 100 km to the north of Flores Island, in one of the most complex tectonic settings in Indonesia. We use a double-difference method to relocate the hypocenters of the mainshock and aftershocks, determine focal mechanisms using waveform inversion, and then analyze stress changes to estimate the fault type and stress transfer. Our relocated hypocenters show that this earthquake sequence ruptured on at least three segments: the source mechanism of the mainshock exhibits dextral strike-slip motion (strike N72°W and dip 78° NE) on a west–east-trending fault that we call the Kalaotoa fault, whereas rupture of the other two segments located to the west and east of the mainshock (striking west-northwest and southeast, respectively) may have been triggered by this earthquake. The Coulomb stress change imparted by the rupture of these segments...
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<p>On December 14, 2021, the Mw 7.3 Flores Sea earthquake occurred approxim... more <p>On December 14, 2021, the Mw 7.3 Flores Sea earthquake occurred approximately 100 km to the north of Flores Island, one of the most complex tectonic settings in Indonesia. The existence of the causative fault that generated this earthquake was not been previously known, therefore making further analysis crucial for assessing future seismic hazard in the region. In this study, we relocated the hypocenter of the mainshock and aftershocks using a double-difference method, determine focal mechanisms using waveform inversion, and then analyse stress changes to estimate the fault type and stress transfer caused by this earthquake. Our relocated hypocenters show that this earthquake sequence ruptured on at least three segments: the source mechanism of the mainshock exhibits dextral strike-slip motion (strike N288<sup>o</sup>W and dip 78<sup>o</sup>) that occurred on a West-East trending fault which we call the Kalaotoa Fault, while rupture of the other two segments located to the west and east of the mainshock (WSW-ESE directions, respectively) may have been triggered by this earthquake. The Coulomb stress change of the mainshock shows that areas to the northwest and southeast experienced an increase in stress, which is consistent with the observed aftershock pattern.</p>
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DIFFRACTION, 2019
Penentuan lokasi hiposentrum gempa Bumi penting untuk dilakukan dengan cepat dan tepat. Hal terse... more Penentuan lokasi hiposentrum gempa Bumi penting untuk dilakukan dengan cepat dan tepat. Hal tersebut bertujuan untuk mengetahui penyebab terjadinya gempa Bumi tersebut. Penelitian ini menggunakan input parameter hiposentrum awal, serta waktu penjalaran gelombang P. Data ini diperoleh dari BMKG Earthquakes Repository. Kejadian gempa Bumi yang digunakan adalah kejadian gempa Bumi pada 9 Februari 2017 dengan magnitudo gempa Bumi (MLv) 4,6 dan 4,2 pada kedalaman 10 km. Posisi stasiun pencatat gempa juga digunakan dalam proses perhitungan. Data tersebut diinversi untuk mendapatkan posisi hiposentrum baru sebagai hasil dari perhitungannya. Selain itu, hasil dari perhitungan ini adalah lama pemrosesan yang akan dianalisis dalam penelitian ini. Hasil yang didapatkan dalam penelitian ini yaitu metode grid search membutuhkan waktu yang lebih lama dalam pemrosesan data dibandingkan metode Geiger karena iterasi Geiger cepat mendapatkan hasil optimum.
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Summary a-Value and b-Value can be used to basic calculation to get seismicity index, repeated pe... more Summary a-Value and b-Value can be used to basic calculation to get seismicity index, repeated period, and vulnerability of earthquakes in a region. Yogyakarta is a region of Indonesia that often earthquakes are happened, caused by an active fault it has, Opak fault. And also because it is flanked by Java Megathrust and an active volcano. Earthquake phenomenon is very detrimental to life and many casualties if there is no preparedness to deal with it. This research aims to get the calculation results from seismicity index, repeated period, and vulnerability of earthquakes to indicate areas prone of earthquakes in Yogyakarta. The method used is a matrix inverse calculation, Gutenberg-Richter’s (1956) least square equation, to obtain a-value and b-value. This research uses USGS and BMKG earthquake catalog data and classifies it based on the region of Yogyakarta in geodetic coordinates ie 7.493°-11.523°S and 109.841°-110.940°E. The results of this research is got a-value and b-value ca...
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Journal of Physics: Conference Series, 2020
This study aims to investigate site conditions based on the dominant period and elliptical curve ... more This study aims to investigate site conditions based on the dominant period and elliptical curve inversion of Horizontal-to-Vertical Spectral Ratio (HVSR). The data were taken using a seismometer portable short period in the minimum time span of data retrieval for 30 minutes. The Nakamura method as known as Horizontal-to-Vertical Spectral Ratio (HVSR) is used to obtain the value of the dominant frequency and amplification factor. The dominant frequency is changed to the dominant period which can indicate the type of soil. HVSR processing use Geopsy software with a guide from the SESAME Project. The results of processing show that the dominant frequency and the amplification factor. In Geopsy there are several modules and packages. This processing uses TFA Module and Max2curve Package and Dinver Package. Waveform can be inversed based on the elliptical curve of HVSR model to produce a shear wave velocity model (Vs) uses that modules and packages. From the velocity model, we can know ...
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Journal of Physics: Conference Series, 2020
Observation of nuclear tests carried out by CTBTO utilizes seismic method. Seismic methods can be... more Observation of nuclear tests carried out by CTBTO utilizes seismic method. Seismic methods can be used to estimate the strength of seismic sources and seismic radiation energy emitted by seismic sources. Seismic waves originating from explosions can be found in the amount of radioactive material using atomic fission equation. From 2006 to 2017, seismic monitoring noted that North Korea conducted a nuclear test six times, namely on 9 October 2006 (mb 4.3), 25 May 2009 (mb 4.7), 12 February 2013 (mb 5.1), 6 January 2016 (mb 5.1), September 9, 2016 (mb 5.3), and September 3, 2017 (mb 6.3). The purpose of this study is to find a comparative value between seismic radiation energy and the energy of radioactive material Plutonium-240. This study used earthquakes originating from the September 3, 2017 nuclear explosion in North Korea. The waveforms used from INCN Station (Incheon, South Korea) were downloaded from IRIS. The processing of earthquake waveforms used Seismic Analysis Code (SAC) utilizing seismic radiation energy of primary wave approximately 30 seconds after the origin time. The results obtained include get moment magnitude (Mw) 6.4, seismic moment (Mo) = 6 × 1018 N.m, and seismic radiation energy (Es) = 3 × 1014 Joule. If energy Q = 4.18 × 106 Joules is energy that can be produced by 1 kg of TNT then the energy released by 72 kt TNT is equal to 72 times the energy released by a nuclear explosion on spontaneous fission of Plutonium-240.
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Jurnal Meteorologi Klimatologi dan Geofisika, 2019
Gunung Sinabung merupakan gunung yang aktif kembali setelah tidak beraktifitas (dorman) selama le... more Gunung Sinabung merupakan gunung yang aktif kembali setelah tidak beraktifitas (dorman) selama lebih dari 400 tahun. Gunung Sinabung sampai saat ini melakukan aktivitas vulkanik. Hal itu membuat masyarakat di sekitar lereng Gunung Sinabung berwaspada. Salah satu aktivitas vulakanik tersebut adalah gempa vulkanik. Penelitian ini bertujuan merelokasi hiposenter untuk mendapatkan model kecepatan 1-D gelombang P dan gelombang S di Gunung Sinabung yang dapat digunakan sebagai data acuan kondisi bawah permukaan. Penelitian ini menggunakan input data magnitudo, parameter hiposenter, serta waktu jalar gelombang P dan gelombang S. Data ini diperoleh dari BMKG EQ (Earthquakes) Repository. Kejadian gempa bumi yang digunakan pada rentang waktu 1 Januari 2017 sampai 28 Februari 2017 dan pada koordinat 3,0931 LU-3,3543 LU dan 98,2928 BT-98,6202 BT. Pada pengolahan ini juga menggunakan parameter letak stasiun (sensor). Data tersebut direlokasi menggunakan software VELEST 3.3 dengan model kecepatan...
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The determination of the subsurface structure can be done using a passive seismic method. This re... more The determination of the subsurface structure can be done using a passive seismic method. This research makes use of earthquakes recorded on seismographs. The velocity profile from the relocation of the earthquake hypocenter shows the subsurface layers. The relocation method used is Joint Hypocenter Determination (JHD). As initial velocity parameters using global velocity models (IASPE91 & AK135) and local speed models in the Indonesian region from Koulakov and Madlazim. This study aims to determine the subsurface layer in an area that is experiencing tectonic earthquakes, volcanic earthquakes, and earthquake swarms. The relocated earthquake had a magnitude of MLv 3.0 to Mw 7.0 for the tectonic earthquake in Nusa Tenggara. Mount Sinabung magma moving in the main crater pipe caused a volcanic earthquake with a magnitude of MLv <5.5. Meanwhile, we used earthquake swarm data for the September 2017 period for the Jailolo region, North Maluku. From the results obtained, there is a hig...
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EarthDoc Publication, 2018
a-Value and b-Value can be used to basic calculation to get seismicity index, repeated period, an... more a-Value and b-Value can be used to basic calculation to get seismicity index, repeated period, and vulnerability of earthquakes in a region. Yogyakarta is a region of Indonesia that often earthquakes are happened, caused by an active fault it has, Opak fault. And also because it is flanked by Java Megathrust and an active volcano. Earthquake phenomenon is very detrimental to life and many casualties if there is no preparedness to deal with it. This research aims to get the calculation results from seismicity index, repeated period, and vulnerability of earthquakes to indicate areas prone of earthquakes in Yogyakarta. The method used is a matrix inverse calculation, Gutenberg-Richter's (1942) least square equation, to obtain a-value and b-value. This research uses USGS and BMKG earthquake catalog data and classifies it based on the region of Yogyakarta in geodetic coordinates ie 7.493°-11.523°S and 109.841°-110.940°E. The results of this research is got a-value and b-value calcul...
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Arabian Journal of Geosciences
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Buletin Meteorologi Klimatologi dan Geofisika Vol. 1 No. 11, 2020
Penelitian ini bertujuan untuk mengetahui persebaran kejadian gempabumi di sepanjang Sesar Paluko... more Penelitian ini bertujuan untuk mengetahui persebaran kejadian gempabumi di sepanjang Sesar Palukoro dan mengidentifikasi jenis patahan Sesar Palukoro melalui perbandingan hasil pengolahan dari program Isolated Asperities dan Kinematic Waveform Inversion dari data kejadian gempabumi tanggal 28 September 2018 hingga 28 Oktober 2018. Telah dilakukan relokasi sebanyak 1.271 kejadian gempabumi dan hasil relokasi tersebut menunjukkan bahwa di sepanjang Sesar Palukoro didominasi gempabumi dengan kedalaman dangkal. Hasil pengolahan dari Isolated Asperities dan Kinematic Waveform Inversion menunjukkan bahwa Sesar Palukoro didominasi gempabumi dengan jenis penyesaran campuran (oblique) dengan kecenderungan bergeser ke kiri (left-lateral strike-slip). Pengolahan menggunakan program Isolated Asperities dan Kinematic Waveform Inversion menunjukkan hasil yang hampir sama, namun waktu pengolahan yang diperlukan oleh program Isolated Asperities jauh lebih lama karena perhitungan fungsi Green dilakukan secara individual untuk tiap kejadian gempabumi.
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Prosideng SENBA ISBN : 978-602-51685-7-4, 2019
Penelitian ini bertujuan untuk menginvestigasi kondisi wilayah berdasarkan periode dominan dan in... more Penelitian ini bertujuan untuk menginvestigasi kondisi wilayah berdasarkan periode dominan dan inversi kurva eliptikal dari Horizontal-to-Vertical Spectral Ratio (HVSR). Data yang digunakan sebanyak 20 titik pengukuran, diambil menggunakan seismometer portable short period dalam rentang waktu minimal pegambilan data selama 50 menit di wilayah Sleman, Yogyakarta. Metode Nakamura (Nakamura Y. 1989) atau lebih dikenal dengan Horizontal-to-Vertical Spectral Ratio (HVSR) diguanakan untuk mendapatkan nilai frekuensi dominan dan faktor amplifikasi. Nilai frekuensi dominan dirubah menjadi nilai periode dominan yang dapat menunjukan jenis tanah. Pengolahan HVSR menggunakan software Geopsy dengan panduan dari SESAME Project. Hasil pengolahan 20 titik pengukuran menunjukan frekuensi dominan memiliki rentang 0.629 Hz sampai 15.298 Hz. Sedangkan faktor amplifikasi memiliki rentang 0.015 sampai 6.613. Selain itu, rekaman mikrotremor dapat diinversi berdasarkan kurva eliptikal dari model HVSR untuk menghasilkan model kecepatan gelombang geser (Vs). Dari model kecepatan tersebut, kita dapat mengetahui Vs30 untuk menentukan jenis tanah juga. Dari menginversi 20 titik pengukuran, Vs30 yang didapatkan memiliki rentang 87.2093 m/s sampai 605.2402 m/s. Model kecepatan gelombang geser yang didapatkan dapat menunjukan estimasi ketebalan sedimen di wilayah yang diteliti.
Kata kunci: mikrotremor, Tdom, HVSR, Vs30, jenis tanah
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Prodi Manajemen Bencana, Fakultas Keamanan Nasional Universitas Pertahanan © UNHAN Press ISBN : 978-602-5808-44-9, 2019
From the occurrence of the earthquake December 22, 2018 took learning for us about signal process... more From the occurrence of the earthquake December 22, 2018 took learning for us about signal processing. The earthquake caused by the eruption of Anak Krakatau Volcano which caused the tsunami was not defined as a large magnitude earthquake, only MLv 3.4. After further processing with the bandpass filter process at a frequency of 0.01 Hz - 0.1 Hz different magnitude values are obtained. In this study, we need a moment that wants to know seismic moments and seismic radiation energy. The data used comes from webDC3 BMKG using 3 stations namely CGJI, SBJI, and BLSI. This processing process uses the help of the Seismic Analysis Code. Signal Processing Guide obtained from the International Institute of Seismology and Earthquake Engineering. Seismic moment values obtained from CGJI 1.7 x 1017 N.m, SBJI 1.1 x 1017 N.m, and BLSI 1.05 x 1017 N.m. The moment magnitude of this third station is Mw 5.3. The tsunami that occurred in the Sunda Strait was generated by an avalanche of volcanic material, which is falling into the caldera formed by the eruption of Krakatau in 1883.
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Prosiding SENBA 2018 ISBN : 978-602-51685-3-6, 2018
Gunung Sinabung merupakan gunung yang aktif kembali setelah tidak beraktifitas (dorman) selama le... more Gunung Sinabung merupakan gunung yang aktif kembali setelah tidak beraktifitas (dorman) selama lebih dari 400 tahun. Gunung Sinabung sampai saat ini melakukan aktivitas vulkanik. Hal itu membuat masyarakat di sekitar lereng Gunung Sinabung berwaspada. Salah satu aktivitas vulakanik tersebut adalah gempa vulkanik. Penelitian ini bertujuan merelokasi hiposenter untuk mendapatkan model kecepatan 1-D gelombang P dan gelombang S di Gunung Sinabung yang dapat digunakan sebagai data acuan kondisi bawah permukaan. Penelitian ini menggunakan input data magnitudo, parameter hiposenter, serta waktu jalar gelombang P dan gelombang S. Data ini diperoleh dari BMKG EQ (Earthquakes) Repository. Kejadian gempa bumi yang digunakan pada rentang waktu 1 Januari 2017 sampai 28 Februari 2017 dan pada koordinat 3,0931° LU-3,3543° LU dan 98,2928° BT-98,6202° BT. Pada pengolahan ini juga menggunakan parameter letak stasiun (sensor). Data tersebut direlokasi menggunakan software VELEST 3.3 dengan model kecepatan global IASP91 sebagai model kecepatan awal. Hasil dari relokasi tersebut adalah koreksi letak stasiun (sensor), parameter hiposenter akhir, waktu jalar gelombang seismik, dan model kecepatan 1-D gelombang P dan gelombang S. Hasil yang didapatkan untuk model kecepatan 1-D gelombang P pada kedalaman 0 km sebesar 5.58 km/s dan untuk kedalaman 210 km, lapisan terdalam pada pengolahan data ini, sebesar 8.30 km/s.
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Papers by Abraham Arimuko
Kata kunci: mikrotremor, Tdom, HVSR, Vs30, jenis tanah
Kata kunci: mikrotremor, Tdom, HVSR, Vs30, jenis tanah