Articles
<![CDATA[Tomografi Waktu Tempuh Gelombang S dan Struktur 3-D Zona Penunjaman di Bawah Busur Sunda ]]>
<![CDATA[Sri Widiyantoro]]>;
<![CDATA[Nanang T. Puspito]]>
<![CDATA[ Jurnal Matematika & Sains Vol 3, No 2 (1998) ]]>
Publisher : <![CDATA[Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
<![CDATA[Tomographic imaging by using S-wave traveltime data to deliniate the three-dimensional subduction zone structure below the Sunda arc has been successfully conducted. Most of the resulting S-wave velocity model is in good agreement with the results of previous tomographic studies using P-wave traveltime data. The obtained tomographic images show that the lithospheric slab penetrates into the lower mantle beneath the Sunda arc, but there is an indication that the deep slab is detached from the seismogenic slab underneath Sumatra and the slab in the upper mantle is necking beneath Java. ]]>
<![CDATA[Analisis Hubungan Frekuensi-Magnitudo Gempa Bumi di Bali dan Sekitarnya ]]>
<![CDATA[Wandono Wandono]]>;
<![CDATA[Sri Widiyantoro]]>;
<![CDATA[Gunawan Ibrahim]]>;
<![CDATA[Edy Soewono]]>
<![CDATA[ Jurnal Matematika & Sains Vol 9, No 3 (2004) ]]>
Publisher : <![CDATA[Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
<![CDATA[We mapped the 3-D b-value variation in Bali and its vicinity through analyzing the frequency-magnitude relation. A high b-value anomaly is observed beneath the Lombok volcanic arc at 90-180 km depth interval. It is related to the zone of partial melting of basaltic magma on the subducted slab of Indian oceanic plate beneath the Eurasian plate in Nusa Tenggara Barat. This analysis supports the hypothesis about the existence of melting point on the slab.]]>
<![CDATA[Perbandingan Hasil Atenuasi Tomografi 3D Menggunakan Metoda Spectral Fitting & Spectral Ratio Dalam Usaha Pemetaan Bawah Permukaan (Studi Kasus Gunung Guntur) ]]>
<![CDATA[Awali Priyono]]>;
<![CDATA[Gede Suantika]]>;
<![CDATA[Sri Widiyantoro]]>
<![CDATA[ Jurnal Matematika & Sains Vol 15, No 3 (2010) ]]>
Publisher : <![CDATA[Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
<![CDATA[Spectral fitting and spectral ratio methods are tested to estimate the Q value or attenuation in the effort on imaging the subsurface structure using three-dimensional tomographic inversion techniques. In this study, we used microearthquakes data around Mount Guntur that was collected from 1995 until 2007 that consist of 4800 seismograms. Analyses using the spectral fitting and spectral ratio methods generally depict the same anomalous areas. Studies using P and S waves indicate that the area of high attenuation corresponds to the area of low velocity that extending from mount Guntur to Kamojang caldera. In terms of the image quality, it can be seen that the attenuation derived using the spectral ratio of S wave has the same pattern with the one derived using P wave. This is due to the attenuation of S wave, which was derived directly from the P-wave. The Q value in the spectral ratio method depends on the width of the frequency window taken and the effect of noise in the determination the slope of the linear relationship between the natural logarithm of spectral ratio with frequency. The result of the spectral fitting analysis shows that the pattern of S wave attenuation image is different from the pattern inferred from the P wave data, because each attenuation image has been determined separately and does not depend on each other. Since the sensitivity of the values of Qp and Qs are important in fluid rock identification, the determination of Qs should not depend directly on Qp. With the various reasons above and more influential factor in estimating the value of Q using spectral ratio, the spectral fitting method is more recommendable to be employed to determine the value of Q.]]>
<![CDATA[Complex Morphology of Subducted Lithosphere in the Mantle below the Molucca Collision Zone from Non-linear Seismic Tomography ]]>
<![CDATA[Widiyantoro, Sri]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol 35, No 1 (2003) ]]>
Publisher : <![CDATA[ITB Journal Publisher, LPPM ITB ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
Full PDF (771.494 KB)
|
DOI: 10.5614/itbj.eng.sci.2003.35.1.1
<![CDATA[Results of seismic studies presented in previous publications depict two opposing subducted oceanic lithospheric slabs under the Molucca region. This unique structure is related to the arc-arc collision between the Halmahera and Sangihe arcs. Recently, we have revisited the complex subduction zone structure by employing a non-linear tomographic imaging technique in which 3-D ray tracing has been implemented. We have used P- as well as S-wave arrival times from carefully reprocessed global data set. The results provide some improvements in the positioning of wave-speed anomalies. Consistent with earlier results, the new P-wave model depicts the two opposing subducted slabs of the Molucca Sea plate. The intriguing new observation is that the westward dipping slab appears to penetrate into the lower mantle by taking the form of folded slab. We envisage that the folding behavior may have been caused by the shift of the whole subduction system in the Molucca region toward the Eurasian continent due to the westward thrust of the Pacific plate combined with the large left-lateral movement of the Sorong fault. The inversion of traveltime residuals of direct S phases strongly confirms the new observation.]]>
<![CDATA[Estimation of Slip Distribution of the 2007 Bengkulu Earthquake from GPS Observations Using the LeastSquares Inversion Method ]]>
<![CDATA[Awaluddin, Moehammad]]>;
<![CDATA[Meilano, Irwan]]>;
<![CDATA[Widiyantoro, Sri]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol 44, No 2 (2012) ]]>
Publisher : <![CDATA[ITB Journal Publisher, LPPM ITB ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
Full PDF (579.484 KB)
|
DOI: 10.5614/itbj.eng.sci.2012.44.2.6
<![CDATA[Continuous Global Positioning System (GPS) observations showed significant crustal displacements as a result of the Bengkulu earthquake occurring on September 12, 2007. A maximum horizontal displacement of 2.11 m was observed at PRKB station, while the vertical component at BSAT station was lifted up with a maximum of 0.73 m, and the vertical component at LAIS station had subsided â0.97 m. Adding more constraints on the inversion for the Bengkulu earthquake slip distribution inferred from GPS observations can help solve the underdetermined least-squares inversion. Checkerboard tests were performed to help conduct the weighting for constraining the inversion. The inversion calculation yielded an optimal value for the slip distribution by giving the smoothing constraint a weight of 0.001 and the slip constraint a weight of = 0 at the edge of the earthquake rupture area. The maximum co-seismic slip of the optimal inversion calculation was 5.12 m at the lower area of PRKB station and BSAT station. The seismic moment calculated from the optimal slip distribution was 7.14 x 1021 Nm, which is equivalent to a magnitude of 8.5.]]>
<![CDATA[Borehole Microseismic Imaging of Hydraulic Fracturing: A Pilot Study on a Coal Bed Methane Reservoir in Indonesia ]]>
<![CDATA[Ry, Rexha Verdhora]]>;
<![CDATA[Septyana, Tepy]]>;
<![CDATA[Widiyantoro, Sri]]>;
<![CDATA[Nugraha, Andri Dian]]>;
<![CDATA[Ardjuna, Arii]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol 51, No 2 (2019) ]]>
Publisher : <![CDATA[ITB Journal Publisher, LPPM ITB ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
Full PDF (26.343 KB)
|
DOI: 10.5614/j.eng.technol.sci.2019.51.2.7
<![CDATA[Over the last decade, microseismic monitoring has emerged as a considerable and capable technology for imaging stimulated hydraulic fractures in the development of unconventional hydrocarbon resources. In this study, pilot hydraulic-fracturing treatments were operated at a coal-bed methane (CBM) field in Indonesia to stimulate the flow and increase the reservoir’s permeability while the monitoring system was set in a single near-vertical borehole. Locating event sources accurately is fundamental to investigating the induced fractures, but the geometry of a single downhole array is a challenging data processing task, especially to remove ambiguity of the source locations. The locating procedure was reviewed in 3 main steps: (i) accurate picking of P- and S-wave phases; (ii) inclusion of P-wave particle motion to estimate the back azimuth; (iii) guided inversion for hypocenter determination. Furthermore, the seismic-source moment magnitudes were calculated by employing Brune’s model. Reliable solutions of locations were obtained as shown statistically by uncertainty ellipsoids and a small misfit. Based on our results, both induced and triggered seismicity could be observed during the treatments and therefore conducting intensive monitoring is important. The triggered seismicity is an undesired activity so disaster precautions need to be taken, in particular for preventing reactivation of pre-existing faults.]]>
<![CDATA[Estimation of Slip Distribution of the 2007 Bengkulu Earthquake from GPS Observations Using the LeastSquares Inversion Method ]]>
<![CDATA[Moehammad Awaluddin]]>;
<![CDATA[Irwan Meilano]]>;
<![CDATA[Sri Widiyantoro]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol. 44 No. 2 (2012) ]]>
Publisher : <![CDATA[Institute for Research and Community Services, Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
DOI: 10.5614/itbj.eng.sci.2012.44.2.6
<![CDATA[Continuous Global Positioning System (GPS) observations showed significant crustal displacements as a result of the Bengkulu earthquake occurring on September 12, 2007. A maximum horizontal displacement of 2.11 m was observed at PRKB station, while the vertical component at BSAT station was lifted up with a maximum of 0.73 m, and the vertical component at LAIS station had subsided "“0.97 m. Adding more constraints on the inversion for the Bengkulu earthquake slip distribution inferred from GPS observations can help solve the underdetermined least-squares inversion. Checkerboard tests were performed to help conduct the weighting for constraining the inversion. The inversion calculation yielded an optimal value for the slip distribution by giving the smoothing constraint a weight of 0.001 and the slip constraint a weight of = 0 at the edge of the earthquake rupture area. The maximum co-seismic slip of the optimal inversion calculation was 5.12 m at the lower area of PRKB station and BSAT station. The seismic moment calculated from the optimal slip distribution was 7.14 x 1021 Nm, which is equivalent to a magnitude of 8.5.]]>
<![CDATA[Complex Morphology of Subducted Lithosphere in the Mantle below the Molucca Collision Zone from Non-linear Seismic Tomography ]]>
<![CDATA[Sri Widiyantoro]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol. 35 No. 1 (2003) ]]>
Publisher : <![CDATA[Institute for Research and Community Services, Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
DOI: 10.5614/itbj.eng.sci.2003.35.1.1
<![CDATA[Results of seismic studies presented in previous publications depict two opposing subducted oceanic lithospheric slabs under the Molucca region. This unique structure is related to the arc-arc collision between the Halmahera and Sangihe arcs. Recently, we have revisited the complex subduction zone structure by employing a non-linear tomographic imaging technique in which 3-D ray tracing has been implemented. We have used P- as well as S-wave arrival times from carefully reprocessed global data set. The results provide some improvements in the positioning of wave-speed anomalies. Consistent with earlier results, the new P-wave model depicts the two opposing subducted slabs of the Molucca Sea plate. The intriguing new observation is that the westward dipping slab appears to penetrate into the lower mantle by taking the form of folded slab. We envisage that the folding behavior may have been caused by the shift of the whole subduction system in the Molucca region toward the Eurasian continent due to the westward thrust of the Pacific plate combined with the large left-lateral movement of the Sorong fault. The inversion of traveltime residuals of direct S phases strongly confirms the new observation.]]>
<![CDATA[Borehole Microseismic Imaging of Hydraulic Fracturing: A Pilot Study on a Coal Bed Methane Reservoir in Indonesia ]]>
<![CDATA[Rexha Verdhora Ry]]>;
<![CDATA[Tepy Septyana]]>;
<![CDATA[Sri Widiyantoro]]>;
<![CDATA[Andri Dian Nugraha]]>;
<![CDATA[Arii Ardjuna]]>
<![CDATA[ Journal of Engineering and Technological Sciences Vol. 51 No. 2 (2019) ]]>
Publisher : <![CDATA[Institute for Research and Community Services, Institut Teknologi Bandung ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
DOI: 10.5614/j.eng.technol.sci.2019.51.2.7
<![CDATA[Over the last decade, microseismic monitoring has emerged as a considerable and capable technology for imaging stimulated hydraulic fractures in the development of unconventional hydrocarbon resources. In this study, pilot hydraulic-fracturing treatments were operated at a coal-bed methane (CBM) field in Indonesia to stimulate the flow and increase the reservoir's permeability while the monitoring system was set in a single near-vertical borehole. Locating event sources accurately is fundamental to investigating the induced fractures, but the geometry of a single downhole array is a challenging data processing task, especially to remove ambiguity of the source locations. The locating procedure was reviewed in 3 main steps: (i) accurate picking of P- and S-wave phases; (ii) inclusion of P-wave particle motion to estimate the back azimuth; (iii) guided inversion for hypocenter determination. Furthermore, the seismic-source moment magnitudes were calculated by employing Brune's model. Reliable solutions of locations were obtained as shown statistically by uncertainty ellipsoids and a small misfit. Based on our results, both induced and triggered seismicity could be observed during the treatments and therefore conducting intensive monitoring is important. The triggered seismicity is an undesired activity so disaster precautions need to be taken, in particular for preventing reactivation of pre-existing faults.]]>
<![CDATA[Estimation of S-wave Velocity Structures by Using Microtremor Array Measurements for Subsurface Modeling in Jakarta ]]>
<![CDATA[Mohamad Ridwan]]>;
<![CDATA[A. Afnimar]]>;
<![CDATA[Sri Widiyantoro]]>;
<![CDATA[Masyhur Irsyam]]>;
<![CDATA[Hiroaki Yamanaka]]>
<![CDATA[ Journal of Mathematical and Fundamental Sciences Vol. 46 No. 3 (2014) ]]>
Publisher : <![CDATA[Institute for Research and Community Services (LPPM) ITB ]]>
Show Abstract
|
Download Original
|
Original Source
|
Check in Google Scholar
|
DOI: 10.5614/j.math.fund.sci.2014.46.3.9
<![CDATA[Jakarta is located on a thick sedimentary layer that potentially has a very high seismic wave amplification. However, the available information concerning the subsurface model and bedrock depth is insufficient for a seismic hazard analysis. In this study, a microtremor array method was applied to estimate the geometry and S-wave velocity of the sedimentary layer. The spatial autocorrelation (SPAC) method was applied to estimate the dispersion curve, while the S-wave velocity was estimated using a genetic algorithm approach. The analysis of the 1D and 2D S-wave velocity profiles shows that along a north-south line, the sedimentary layer is thicker towards the north. It has a positive correlation with a geological cross section derived from a borehole down to a depth of about 300 m. The SPT data from the BMKG site were used to verify the 1D S-wave velocity profile. They show a good agreement. The microtremor analysis reached the engineering bedrock in a range from 359 to 608 m as depicted by a cross section in the north-south direction. The site class was also estimated at each site, based on the average S-wave velocity until 30 m depth. The sites UI to ISTN belong to class D (medium soil), while BMKG and ANCL belong to class E (soft soil).]]>
