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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

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.

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

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 Julianâ€™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.

Locating Tremor Source with Polarization and Semblance Methods During the 2014 Crisis Period of Raung Volcano Ipmawan, Vico Luthfi; Brotopuspito, Kirbani Sri; Triastuty, Hetty
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

DOI:10.17014/ijog.7.1.41-49Raung is a basaltic-andesitic volcano with strombolian-type eruptive activity located in East Java Province, Indonesia. The seismic activity of this volcano increased on 11th November 2014 which was dominated by tremors. Due to the difficulty to distinguish the onset of body waves of tremor waveform, polarization and semblance methods were proposed and applied to locate the tremor source. The tremors recorded during November to December 2014 were analyzed. The results showed that the back-azimuth values obtained by the polarization method were around N 288o - 324o E in accordance with the direction of Raung summit, while the incidence angle ranged around N 81o - 89.3o E. The semblance method was performed on 2 x 2 km area around the summit. The result of the tremor source showed the distribution of epicentre extending N52o E to the northeast direction about Â±2.1 km away from the Raung summit.

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 | DOI: 10.17014/ijog.5.1.13-21

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 Julianâ€™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.

Locating Tremor Source with Polarization and Semblance Methods During the 2014 Crisis Period of Raung Volcano Ipmawan, Vico Luthfi; Brotopuspito, Kirbani Sri; Triastuty, Hetty
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.1.41-49

DOI:10.17014/ijog.7.1.41-49Raung is a basaltic-andesitic volcano with strombolian-type eruptive activity located in East Java Province, Indonesia. The seismic activity of this volcano increased on 11th November 2014 which was dominated by tremors. Due to the difficulty to distinguish the onset of body waves of tremor waveform, polarization and semblance methods were proposed and applied to locate the tremor source. The tremors recorded during November to December 2014 were analyzed. The results showed that the back-azimuth values obtained by the polarization method were around N 288o - 324o E in accordance with the direction of Raung summit, while the incidence angle ranged around N 81o - 89.3o E. The semblance method was performed on 2 x 2 km area around the summit. The result of the tremor source showed the distribution of epicentre extending N52o E to the northeast direction about Â±2.1 km away from the Raung summit.

Gliding and Quasi-harmonic Tremor Behaviour of Raung Volcano: November 2014 Crisis Period Case Study Vico Luthfi Ipmawan; Kirbani Sri Brotopuspito; Hetty Triastuty
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

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.

Locating Tremor Source with Polarization and Semblance Methods During the 2014 Crisis Period of Raung Volcano Vico Luthfi Ipmawan; Kirbani Sri Brotopuspito; Hetty Triastuty
Indonesian Journal on Geoscience Vol 7, No 1 (2020)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.7.1.41-49

DOI:10.17014/ijog.7.1.41-49Raung is a basaltic-andesitic volcano with strombolian-type eruptive activity located in East Java Province, Indonesia. The seismic activity of this volcano increased on 11th November 2014 which was dominated by tremors. Due to the difficulty to distinguish the onset of body waves of tremor waveform, polarization and semblance methods were proposed and applied to locate the tremor source. The tremors recorded during November to December 2014 were analyzed. The results showed that the back-azimuth values obtained by the polarization method were around N 288o - 324o E in accordance with the direction of Raung summit, while the incidence angle ranged around N 81o - 89.3o E. The semblance method was performed on 2 x 2 km area around the summit. The result of the tremor source showed the distribution of epicentre extending N52o E to the northeast direction about ±2.1 km away from the Raung summit.

Geophysical Analysis Using Proton Precession Magnetometer GSM-19T as Information on Fault Presence in Medana, North Lombok, Indonesia Haerul Anwar; Haerul Anwar; Vico Luthfi Ipmawan; Thanaporn Sriyakul
International Journal of Hydrological and Environmental for Sustainability Vol 1, No 1 (2022): International Journal of Hydrological and Environmental for Sustainability
Publisher : Foundation of Advanced Education

Lombok island is included in one of the areas prone to earthquakes due to the existence of a subduction zone resulting from the meeting of the Indian-Australian Plate. In this study, the magnetic method was used to determine the subsurface structure of the fault as a research objective. The instrument used in this study consisted of a Proton Precession Magnetometer GSM-19T v7.0 Geomagnet measuring instrument with an accuracy of 0.1 nT to measure the total magnetic field strength. Garmin 60CSx GPS to determine position (latitude and longitude), elevation, time and point of measurement location. The geological compass determines the position and direction of the north-south fault which includes the dip/strike. Some software is also used in processing this geomagnetic data, namely Software (Numeri, Mag2DC, Surfer 9.0) and MS Excel 2013. Based on the results of data processing with 2D and Mag2DC forward modeling, the subsurface structure is obtained in the form of a normal fault, with the average susceptibility value is 0.00605 in Susceptibility (SI) which is a type of limestone. The depth of this normal fault is estimated to be at a depth of 31.5 meters to 74.0 meters.

Determining Soft Layer Thickness Using Ambient Seismic Noise Record Analysis in Kota Baru, South Lampung Ipmawan, Vico Luthfi; Permanasari, Ikah N. P.; Siregar, Rahmat Nawi
Makara Journal of Science Vol. 23, No. 1
Publisher : UI Scholars Hub

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The local site effect of an earthquake can be calculated through an analysis of short period ambient noise, known as microtremors. The fundamental frequency and amplification factors can be identified by analyzing microtremors using the Horizontal to Vertical Spectral Ratio (HVSR) method. This information can then be used to determine the thickness of the soft layers of sediment. This study analyzed microtremor recordings made in Kota Baru, South Lampung. The amplification factor range according to the HVSR method was 2.3 to 6.17, and the fundamental frequency range was 0.56 Hz to 1.46 Hz. Some spectrums exhibit two peaks with f0 > f1. We suggest that these locations have two layers with significant impedance contrast, which aligns with the geological conditions. The center of the Kota Baru area, especially the region around T11 and T15, has a thicker soft layer than the outskirts; in the central area, the soft layer is approximately 85 to 102 meters thick. The western part of the analyzed area has a shallower soft layer of about 32 to 46 meters. The analysis indicates that the western part has less amplification because it is shallower than the other parts of the analyzed region.

Ambient Noise-Based Mapping of Bedrock Morphology and Potential Fissure Zone in East Tanjung Karang, Bandar Lampung, Lampung, Indonesia Ipmawan, Vico Luthfi; Permanasari, Ikah Ning Prasetiowati; Suhendi, Cahli
Makara Journal of Science
Publisher : UI Scholars Hub

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As a business center and the most populous subdistrict, East Tanjung Karang in Bandar Lampung, Lampung, Indonesia, is considered an area with excessive groundwater exploitation. This activity can trigger ground fissures that can consequently cause damage to buildings and roads. In this study, microtremor recordings from 17 sites were collected and analyzed by using the horizontal to vertical spectral ratio and ellipticity curve method. Results showed that the ground profiles of shear wave velocity from 17 sites ranged from 143.5 m/s to 1752.46 m/s, and they could be used to determine sediment layer and its thickness based on the SNI 1726-2012 criteria. The thickness of the bedrock varied from 8.18 m to 117.18 m. Bedrock morphology was obtained by subtracting the sediment thickness from the altitude value. The bedrock morphology and slope were then used to construct a potential fissure map of the area between Y16 and Y17 and between Y26 and Y27, which had high bedrock slopes (more than 45°). The ground fissure potential in these areas was higher than that in other areas. Such areas also had a geological hazard potential from ground fissures caused by excessive groundwater exploitation. Our study could be used by authorities as a basis for preventing subsidence-related disasters in this subdistrict.

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