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Pemikiran Eksploratif Tentang Kemungkinan Hubungan Antara Gempabumi Aceh 26 Desember 2004, Perubahan Pola Geoid, Dan Erupsi Gunungapi Sinabung 2010-2017 Brotopuspito, Kirbani Sri
Jurnal Fisika Indonesia Vol 21, No 3 (2017)
Publisher : Department of Physics Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (316.453 KB) | DOI: 10.22146/jfi.42356

Abstract

Aktivitas volkanik Gunungapi Sinabung sejak 27 Agustus 2010 yang menerus sampai dengan 2017 telah menarik banyak perhatian, karena Gunungapi ini sudah tidak aktif dalam kurun waktu yang lama, yaitu lebih dari 400 tahun dari tahun 1600. Melanjutkan penelitian pada tahun 2016, penulis ingin mengkaji apa penyebab Gunungapi Sinabung aktif kembali. Maka dari itu, penelitian ini mengkaji kemungkinan penyebab aktifnya kembali Gunungapi Sinabung, terutama berdasarkan kejadian gempabumi Aceh 2004 dan Nias 2005 yang menyebabkan terjadinya undulasi geoid rendahan di Selat Malaka di sebelah timur Sumatra Utara, dan keberadaan Gunungapi Sinabung yang tidak terlalu jauh dari komplek Kaldera Danau Toba. Pemodelan komplek kantong magma Gunungapi Toba berdasarkan hasil tomografi seismik mengindikasikan adanya zona rasio kecepatan gelombang P dan S (vp/vs) rendah pada bagian yang berdekatan dengan lokasi Gunungapi Sinabung, yang dapat ditafsirkan sebagai batuan dengan material lelehan. Hal ini juga akan dikaji kemungkinan terjadinya aliran material lelehan/magma ke atas di bawah Gunungapi Sinabung, yang mungkin dipicu oleh adanya pembukaan rekahan akibat tarikan gaya gravitasi oleh undulasi geoid rendahan yang terjadi setelah gempabumi Aceh 2004 dan Nias 2005.
ANALISIS SINYAL SEISMIK GUNUNG MERAPI, JAWA TENGAH - INDONESIA MENGGUNAKAN METODE ADAPLET (TAPIS ADAPTIF BERBASIS WAVELET) Putra, Agfianto Eko; Susanto, Adi; Brotopuspito, Kirbani Sri; Istiyanto, Jazi Eko
Seminar Nasional Informatika (SEMNASIF) Vol 1, No 1 (2008): Computational
Publisher : Jurusan Teknik Informatika

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Abstract

Telah dikembangkan suatu metode analisis sinyal non-stasioner, khususnya sinyal seismik Gunung Merapi, Jawa Tengah, Indonesia, melalui proses Tapisan Adaptif  berbasis  Wavelet,  yang  selanjutnya  dinamakan  Adaplet.  Proses  ini  diawali dengan melakukan penundaan pada sinyal asli d(n) untuk  mendapatkan x(n) yang  diumpankan ke  tapis  adaptif  sehingga  menghasilkan  keluaran  y(n).  Kemudian  keluaran  ini  dibandingkan dengan  masukan  sinyal  asli  d(n),  sebagai  sinyal  yang  dikehendaki  (expected  signal) dan selisihnya berupa keluaran  ralat  e(n)  yang  kemudian  digunakan  sebagai  tuner  untuk memperbaiki kerja tapis adaptif tersebut, sedemikian hingga ralat e(n) bisa mendekati 0 (nol).Hasil untuk data-data seismik volkanik yang mewakili 3 jenis event yang berbeda menunjukkan adanya pola-pola tertentu, yang ditunjukkan dari plot hingga 4 koefisien polinomial  3-komponen  (Sn,  Se  dan  Sz)  dan  hubungan antar  koefisien yang dinyatakan dalam persamaan garis linear dalam format bentuk y=ax+b. Serta pengelompokan (klaster) semua koefisien untuk semua tipe memperkuat adanya fitur-fitur khusus pada sinyal yang bersangkutan.
Gliding and Quasi-harmonic Tremor Behaviour of Raung Volcano: November 2014 Crisis Period Case Study Ipmawan, Vico Luthfi; Brotopuspito, Kirbani Sri; Triastuty, Hetty
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3132.834 KB) | DOI: 10.17014/ijog.5.1.13-21

Abstract

DOI: 10.17014/ijog.5.1.13-21The seismic activity of Raung Volcano was raised on 11 November 2014. As many as 1709 tremors were recorded followed by continuous tremors appearing in late November 2014. Quasi-harmonic and gliding tremors appeared in a spectrogram on 12 November 2014. The quasi-harmonic tremors refer to tremors that have no fully harmonic form in spectrum. The gliding harmonic tremors refer to harmonic tremors that have frequency jumps with either positive or negative increment. After signal restitution processing, the Maximum Entropy Spectral Analysis (MESA) method was applied in Raung recordings resulting the spectrum and the spectrogram of tremors. The quasi-harmonic tremors have the monotonic spectrum in its head and centre segment, and the harmonic one in its tails. There are twenty-four spectrums that show frequency changes between the monotonic and harmonic. The similarity between the fundamental frequency range of the monotonic and harmonic ones suggests that both signals are excited from a common resonator. The alternating of monotonic and harmonic respectively over this period is qualitatively similar with Julian’s synthetic time series about the nonlinear oscillator model. It is suggested that Raung Volcano magma pressure is sizeable to make a chaotic vibration. A pressure increasing in Raung magmatic conduit causes the increasing of P-wave velocity and makes a positive gliding frequency.
SITE RESPONSE CHARACTERISTICS OF H/V SPECTRUM BY MICROTREMOR SINGLE STATION OBSERVATIONS AT PALU CITY, INDONESIA Thein, Pyi Soe; Pramumijoyo, Subagyo; Brotopuspito, Kirbani Sri; Wilopo, Wahyu; Kiyono, Junji; Setianto, Agung
Journal of Applied Geology Vol 5, No 1
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1018.266 KB) | DOI: 10.22146/jag.7202

Abstract

In this study, we estimated predominant period of an H/V spectrum in Palu City, Indonesia, by using microtremor single station observations. Sulawesi Island, eastern Indonesia, is located at the junction between the converging Pacific-Philippine, Indo- Australian Plates and the Eurasian Plate. One of the major structures in Central Sulawesi is the Palu- Koro Fault system, which extends NNW-SSE direction and cross-cuts Sulawesi along more than 300 km from the North Sulawesi trench passing southward through Palu Bay then turn to the southeast, connecting to the Matano and Lawanopo Faults and further eastward both faults join to Tolo trench. Several earthquakes have been known along Palu-Koro Fault system such as Gimpu earthquake (1905), Kulawi earthquake (1907), Kantewu earthquake (1934), and offshore Donggala earthquake (1968) which caused tsunami that destroyed 800 houses and killed 200 people at Donggala district. Palu City, located at the northern tip of Palu depression, is a capital of the Central Sulawesi Province. It is located in the active seismic zone of the Palu-Koro fault. Spectral ratios for horizontal and vertical motion (H/V) from single-station microtremor records were used to identify the predominant periods of the ground vi- brations. Understanding the parameters of predominant period[s] and seismichazard is important for mitigation and environmental planning of the Palu region. Keywords: H/V spectrum, predominant period[s], microtremor single station observation
ESTIMATION OF SUBSURFACE STRUCTURE BASED ON MICROTREMOR, BORE HOLE OBSERVATIONS AND STOCHASTIC STRONG GROUND MOTION SIMULATIONS IN PALU CITY, CENTRAL SULAWESI, INDONESIA: A VALIDATION AND SENSITIVITY STUDY ON THE 23 JANUARY 2005 (PALU) EARTHQUAKE Thein, Pyi Soe; Pramumijoyo, Subagyo; Wilopo, Wahyu; Setianto, Agung; Brotopuspito, Kirbani Sri; Kiyono, Junji
Journal of Applied Geology Vol 6, No 2
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.7222

Abstract

In this study, we investigated the subsurface structure and strong ground motion parameters for Palu City. One of the major structures in Central Sulawesi is the Palu-Koro Fault system. Several powerful earthquakes have struck along the Palu-Koro Fault during recent years, one of the largest of which was an M 6.3 event that occurred on January 23, 2005 and caused several casualties. Following the event, we conducted a microtremor survey to estimate the shaking intensity distribution during the earthquake. From this survey we produced a map of the peak ground acceleration, velocity and ground shear strain in Palu City. We performed single observations of microtremors at 151 sites in Palu City. The results enabled us to estimate the site-dependent shaking characteristics of earthquake ground motion. We also conducted 8-site microtremor array investigation to gain a representative determination of the soil condition of subsurface structures in Palu. From the dispersion curve of array observations, the central business district of Palu corresponds to relatively soil condition with Vs ≤ 300 m/s, the predominant periods due to horizontal vertical ratios (HVSRs) are in the range of 0.4 to 1.8 s and the resonant frequency are in the range of 0.7 to 3.3 Hz. Three boreholes were throughout the basin especially in Palu area to evaluate the geotechnical properties of subsurface soil layers. The depths are varying from 1 m to 30 m. Strong ground motions of the Palu area were predicted based on the empirical stochastic green’s function method. Peak ground acceleration and peak ground velocity becomes more than 0.04 g and 30 kine in some areas, which causes severe damage for buildings in high probability. Keywords: Palu-Koro fault, microtremor, bore holes, peak ground acceleration and velocity.
Pemodelan Sebaran Sistem Hidrotermal dan Identifikasi Jenis Batuannya dengan Metode CSAMT (Studi Kasus Gunungapi Ungaran) Hadi, Arif Ismul; Brotopuspito, Kirbani Sri; Wahyudi, Wahyudi
Jurnal Fisika FLUX Vol 6, No 1 (2009): Jurnal Fisika Flux Edisi Februari 2009
Publisher : Lambung Mangkurat University Press

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/flux.v6i1.3048

Abstract

The investigation of the hydrothermal system distribution andidentification of its rock type has been done by CSAMT method at Ungaran Volcano area. The acquisition data has been done around 750 m x 100 m area with 4 lines at N750E direction. Sounding site distanced 250 m, whereas the data was measured by Stratagem model 26716-01 Rev.D. Processing of the data wasstarted by 1-D inversion of Robust method. The 1-D results were then used as the input of MT2D software. The results showed that subsurface resistivity were 8.6 to 46.4 Ωm estimated as hydrothermal system, 55.8 to 102.6 Ωm estimated as aquifer zone or permeable saturated zone, 145.3 to 495.7 Ωm  stimated as pra-caldera rock associated with vapor dominated zone, and 1420.5 to 15.083 Ωm estimated as lava pile associated with basaltic and andesitic rock. The most prospective hydrothermal system area existed at all along line 4 on 30 to 140 m depth.
Gliding and Quasi-harmonic Tremor Behaviour of Raung Volcano: November 2014 Crisis Period Case Study Ipmawan, Vico Luthfi; Brotopuspito, Kirbani Sri; Triastuty, Hetty
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1307.912 KB) | DOI: 10.17014/ijog.5.1.13-21

Abstract

DOI: 10.17014/ijog.5.1.13-21The seismic activity of Raung Volcano was raised on 11 November 2014. As many as 1709 tremors were recorded followed by continuous tremors appearing in late November 2014. Quasi-harmonic and gliding tremors appeared in a spectrogram on 12 November 2014. The quasi-harmonic tremors refer to tremors that have no fully harmonic form in spectrum. The gliding harmonic tremors refer to harmonic tremors that have frequency jumps with either positive or negative increment. After signal restitution processing, the Maximum Entropy Spectral Analysis (MESA) method was applied in Raung recordings resulting the spectrum and the spectrogram of tremors. The quasi-harmonic tremors have the monotonic spectrum in its head and centre segment, and the harmonic one in its tails. There are twenty-four spectrums that show frequency changes between the monotonic and harmonic. The similarity between the fundamental frequency range of the monotonic and harmonic ones suggests that both signals are excited from a common resonator. The alternating of monotonic and harmonic respectively over this period is qualitatively similar with Julian’s synthetic time series about the nonlinear oscillator model. It is suggested that Raung Volcano magma pressure is sizeable to make a chaotic vibration. A pressure increasing in Raung magmatic conduit causes the increasing of P-wave velocity and makes a positive gliding frequency.
Analisis Karakteristik Dinamika Tanah Berdasarkan Data Mikrotremor di Kota Mataram, Nusa Tenggara Barat Azmiyati, Uzlifatul; Brotopuspito, Kirbani Sri; Dibyosaputro, Suprapto
JUPE : Jurnal Pendidikan Mandala Vol 3, No 3 (2018): JUPE : Jurnal Pendidikan Mandala
Publisher : Lembaga Penelitian dan Pendidikan Mandala

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (406.417 KB)

Abstract

Gempabumi diketahui sebagai fenomena alam yang menimbulkan kerugian yang sangat besar baik secara moral maupun material. Berdasarkan beberapa kasus gempabumi merusak di dunia, diketahui bahwa tingkat kerusakan akibat gempabumi tidak hanya dipengaruhi oleh besarnya kekuatan gempabumi dan jarak suatu daerah dari pusat gempabumi tetapi juga dipengaruhi oleh karakteristik dinamika tanah. Kota Mataram sebagai ibukota Provinsi Nusa Tenggara Barat yang padat penduduk (6.741 jiwa/km2) merupakan bagian dari wilayah Indonesia yang rawan terhadap bencana gempabumi menjadi lokasi penelitian ini.Karakteristik dinamika tanah diperoleh berdasarkan analisis data mikrotremor yang ada di Kota Mataram dengan metode Horizontal to Vertical Spectral Ratio (HVSR) yang menghasilkan nilai frekuensi alami tanah (f0) dan faktor amplifikasi tanah (A0). Frekuensi alami dan faktor amplifikasi menjadi input untuk menghitung karakteristik dinamika tanah lainnya yaitu periode dominan (Tg), danindeks kerentaran seismik (Kg).Hasil analisis menunjukkan bahwa pola spektrum mikrotremor Kota Mataram menghasilkan frekuensi alami rendah (0,13–10,96 Hz) dengan faktor amplifikasi tinggi (3,04–6,59), dan nilai periode dominan tinggi (0,02–2,25 detik). Hal tersebut menunjukkan bahwa Kota Mataram memiliki lapisan sedimen yang tebal dan batuan dasar yang dalam. Indeks kerentanan seismik tingggi ditunjukkan di bagian barat Kota Mataram.Hasil analisis dinamika tanah yang telah dilakukan dapat menjadi langkah dalam mitigasi bencana gempabumi di Kota Mataram Nusa Tenggara Barat.
PEMETAAN PERCEPATAN GETARAN TANAH MAKSIMUM MENGGUNAKAN PENDEKATAN PROBABILISTIC SEISMIC HAZARD ANALYSIS (PSHA) DI KABUPATEN KEPAHIANG PROVINSI BENGKULU Hadi, Arif Ismul; Brotopuspito, Kirbani Sri
BERKALA FISIKA 2015: Berkala Fisika Vol. 18 No. 3 Tahun 2015
Publisher : BERKALA FISIKA

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (639.376 KB)

Abstract

This study aims to analyze and map the peak ground acceleration using the approach of Probabilistic Seismic Hazard Analysis (PSHA) in the area. Earthquake catalog data obtained from BMKG, ISC and USGS began in 1914 until 2014. Declustering process using ZMAP ver.6 software. Identification and modeling of the seismic source uses three models of seismic sources: (1) to subduction earthquake source, (2) the source of the earthquake fault and (3) the source of the quake background. Parameters a-value and b-value is obtained by the Gutenberg-Richter recurrence law and maximum likelihood method, whereas the determination of the attenuation function and logic tree refers to the Revision Team of Indonesia Earthquake 2010. Peak ground acceleration values obtained using USGS-PSHA-07 software. The results showed that the value of the peak ground acceleration in the Kepahiang District for probability exceeded 10% and 2% in the 50 year design life of the building is 0.15 ? 0.8 g and 0.25 ? 1.3 g. Areas that are the red zone is the Ujan Mas Sub-district, Kepahiang Sub-district, Tebat Karai Sub-district, Seberang Musi Sub-district and Bermani Ilir Sub-district, while the regions are relatively safe from the red zone is the Merigi Sub-district, Kabawetan Sub-district and Muara Kemumu Sub-district. Red zone is an area adjacent to the Sumatran Fault of Musi Segment. Keywords: peak ground acceleration, PSHA, red zone and Sumatran Fault of Musi Segment.
Pre and post Mount Merapi eruption of free air anomaly in 2010 Indriana, Rina Dwi; Brotopuspito, Kirbani Sri; Setiawan, Ari; Soenantyo, Tarcisius Aris
International journal of physical sciences and engineering Vol 2 No 3: December 2018
Publisher : Universidad Tecnica de Manabi

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (987.047 KB) | DOI: 10.29332/ijpse.v2n3.231

Abstract

Mount Merapi eruption in 2010 was one type of eruption with large scale during the last 100 years. Eruptions that was occurred resulting topographic changes in the peak of Mount Merapi, and the possibility of changing the subsurface structure. The research was part of a large study that has been conducted to assess the subsurface changes of pre-and post-eruption of Mount Merapi in 2010. The study discussed observations of free air anomalies pre and after the 2010 eruption. There were grouped into three periods. Processing of air anomalies was free to use using the 2nd orde calculation method. The results obtained were the changes in the contours of the FAA Mount Merapi in 1988, 1998, and 2011 as a result of topographic changes that occurred in the peak area and the alleged dynamics of the surface. The dynamics at Mount Merapi in the 1988 to 2011 period occurred in the northwest, southeast, east, and northeast of the study area and southeast of the peak of Mount Merapi.