The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Bagus Jaya Santosa - One of the best experts on this subject based on the ideXlab platform.
-
Seismogram Analysis of the Earthquakes in Sumatra on WRAB Observation Station: S Wave Velocity Structure on Subduction Zone of Sumatra-Java.
2016Co-Authors: Bagus Jaya Santosa, Program Studi GeofisikaAbstract:Abstract. The S wave velocity structure at subduction zone under Sumatra-Java was investigated through Seismogram analysis in time domain and three Cartesian’s components simultaneously. The main data set was the comparison between the measured Seismogram and the Synthetic one, not the travel time data. The Synthetic Seismogram was calculated with the GEMINI method. The Seismogram comparison shows that the global earth mantle of PREMAN gives deviating Synthetic Seismogram and has later arrival times than the measured one. The gradient βh in the upper mantle is altered to positive from its negative slope as in the PREMAN model, and positive corrections are added to the zero order of polynomial’s coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, were obtained on the surface waves of Love and Rayleigh, the S and SS mantle and repetitive depth waves. The additional positive corrections were also confirmed by a well fitting on the repetitive depth waves. This result expresses that part of the earth mantle that due to tectonic processes has positive anomaly on S wave velocity and vertical anisotropy in all of the earth mantle layers
-
ANALYZING THE Seismogram OF EARTHQUAKES ON SUMATRA-JAVA SUBDUCTION PLANE AT CHTO OBSERVATION STATION
2012Co-Authors: Bagus Jaya SantosaAbstract:This research analyzes the earthquakes in subduction plane of Sumatra-Java to investigate the S speed structure under South-East Asia through Seismogram fitting, where the Seismogram data is recorded in CHTO observational station, Thailand. The observed Seismogram is compared to Synthetic Seismogram in time domain and three Cartesian components simultaneously. The Synthetic Seismogram is calculated with GEMINI program, where the input is initially the global earth model of SPREM. Both Seismograms are subjected to a low-pass filter with frequency of corner at 20 mHz. Seismogram comparison shows very strong deviation by observing the arrival time, oscillation number and is amplitude height, on surface wave of Love and Rayleigh, and S body wave. Therefore a correction to the S speed structure is needed. Corrections cover earth crust depth, gradient of speed’s polynomial that a negative for ;h in upper mantle and values of zero order coefficients for ; in the upper mantle, and a little change at S speed in earth layers under the upper mantle till the CMB depth. The obtained Seismogram fitting is excellent on waveform, as well as the time travel or the oscillation number. The research’s result shows that the South-East Asia zone between Sumatra Island and Thailand has a strong negative anomaly of S speed structure in upper mantle. This result differs from other seismological result. Keywords: Seismogram comparison, Negative anomaly, SE Asia
-
Seismogram ANALYSIS OF INDONESIA EARTHQUAKES AT DAV OBSERVATION STATION
2010Co-Authors: Bagus Jaya SantosaAbstract:The S-wave velocity across the earth structure under Indonesia for Indonesian earthquakes has been investigated through Seismogram analysis, simultaneously in the time domain and three Cartesian components. The data was recorded at DAV observational station, the Philippines. The main data set is the Seismogram comparison between the measured and Synthetic Seismogram, instead of travel time data, as commonly used in other seismological research. The Synthetic Seismogram is calculated using the GEMINI method, which is equivalent to Mode Summation. The above Seismogram comparison shows that the global earth mantle of PREMAN gives a deviating Synthetic Seismogram and has earlier arrival times than those of the measurement. The gradient of βh in the upper mantle layers is altered into a positive, rather than negative slope as stated in the PREMAN model, and negative corrections are imposed to the zero order of the polynomial’s coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, is obtained from the surface waves of Love and Rayleigh, surface wave to the S and SS mantle waves as well as the core reflected waves. This result expresses that part of the earth mantle, due to a collision between India and Asia tectonic released zones, has a negative anomaly in S-wave velocity and vertical anisotropy in all of the earth mantle layers.
Charles Lewis - One of the best experts on this subject based on the ideXlab platform.
-
Generation of Pseudo-Synthetic Seismograms from Gamma-Ray Well Logs of Highly Radioactive Formations
Pure and Applied Geophysics, 2018Co-Authors: Adnan Quadir, Charles Lewis, Ruey Juin RauAbstract:The conventional Synthetic Seismogram is created with a sonic and a density log; however, the sonic log can be replaced with the resistivity, neutron, gamma-ray or spontaneous potential log to produce a pseudo-sonic (PS) log. More recent techniques involve combining an SP log and a GR log to produce a PS log. In the past, a drawback in using GR logs for the PS is the presence of highly radioactive and often organic-rich layers possessing abnormally high GR readings. To improve the pseudo-sonic log produced from the gamma-ray log, a technique was developed to statistically treat the outliers from the wells in the Hugoton Embayment that encountered predominantly shale, sandstone, limestone, and dolomite and whose logged sections included both normal and abnormally high GR readings. To demonstrate a wider-range application of our method, the procedure was applied to wells from the Hugoton Embayment, Central Kansas Uplift, Sedgwick Basin, Salina Basin, Forest City Basin and Nemaha Uplift. The correlation coefficients between the PS and the conventional sonic for the six basins were 0.75, 0.92, 0.86, 0.91, 0.77, and 0.70, respectively. Also, the match between the resulting conventional Synthetic Seismogram and the pseudo-Synthetic Seismogram from a blind test well for each area was quite good. Provided the outliers have been properly treated, the GR log is a viable tool for creating pseudo-sonic logs and pseudo-Synthetic Seismograms for exploration in oil and gas basins where there are few wells with sonic logs or where sonic log quality is poor.
-
The Spontaneous Ray Log: A New Aid for Constructing Pseudo-Synthetic Seismograms
Pure and Applied Geophysics, 2018Co-Authors: Adnan Quadir, Charles LewisAbstract:Conventional Synthetic Seismograms for hydrocarbon exploration combine the sonic and density logs, whereas pseudo-Synthetic Seismograms are constructed with a density log plus a resistivity, neutron, gamma ray, or rarely a spontaneous potential log. Herein, we introduce a new technique for constructing a pseudo-Synthetic Seismogram by combining the gamma ray (GR) and self-potential (SP) logs to produce the spontaneous ray (SR) log. Three wells, each of which consisted of more than 1000 m of carbonates, sandstones, and shales, were investigated; each well was divided into 12 Groups based on formation tops, and the Pearson product–moment correlation coefficient (PCC) was calculated for each “Group” from each of the GR, SP, and SR logs. The highest PCC-valued log curves for each Group were then combined to produce a single log whose values were cross-plotted against the reference well’s sonic ITT values to determine a linear transform for producing a pseudo-sonic (PS) log and, ultimately, a pseudo-Synthetic Seismogram. The range for the Nash–Sutcliffe efficiency (NSE) acceptable value for the pseudo-sonic logs of three wells was 78–83%. This technique was tested on three wells, one of which was used as a blind test well, with satisfactory results. The PCC value between the composite PS (SR) log with low-density correction and the conventional sonic (CS) log was 86%. Because of the common occurrence of spontaneous potential and gamma ray logs in many of the hydrocarbon basins of the world, this inexpensive and straightforward technique could hold significant promise in areas that are in need of alternate ways to create pseudo-Synthetic Seismograms for seismic reflection interpretation.
-
A technique for improving pseudo-Synthetic Seismograms generated from neutron logs in gas-saturated clastic rocks
Journal of Geophysics and Engineering, 2013Co-Authors: Shih-ling Kung, Charles LewisAbstract:In clastic and carbonate rock sequences, the neutron and sonic log curves usually deflect in a similar fashion. Moreover, in some cases the two curves can be overlain and they generally appear to mimic each other, with variations between them only in the amplitudes of the two curves. This descriptive correlation is the basis of direct cross-plot techniques used to convert a neutron log into a pseudo-sonic log, which can then be combined with a density log to create a pseudo-Synthetic Seismogram. Unfortunately, the Seismograms produced in this way may not match the standard Synthetic Seismograms produced from the sonic and density logs if the ?gas effect? is not taken into account. In order to correct for the gas effect, the inter-log correlations between the compensated neutron log (CNL) and the borehole-compensated (BHC) sonic log curves from a well in Taiwan were carefully examined. Then, we developed a technique for transforming the CNL log into a pseudo-BHC log by splicing together several continuous sandstone intervals in which the gas effect could be identified from the scattered data on the cross-plot of neutron porosity versus sonic interval transit time. Based upon our results, application of the new composite transform method yields a pseudo-Synthetic Seismogram that better matches the standard Synthetic Seismogram (made from the sonic and density logs) according to frequency, amplitude and polarity. This gas correction technique may be particularly useful in oil and gas exploratory and development areas where neutron logs are more prevalent than sonic logs or where sonic logs are scarce.
Program Studi Geofisika - One of the best experts on this subject based on the ideXlab platform.
-
Seismogram Analysis of the Earthquakes in Sumatra on WRAB Observation Station: S Wave Velocity Structure on Subduction Zone of Sumatra-Java.
2016Co-Authors: Bagus Jaya Santosa, Program Studi GeofisikaAbstract:Abstract. The S wave velocity structure at subduction zone under Sumatra-Java was investigated through Seismogram analysis in time domain and three Cartesian’s components simultaneously. The main data set was the comparison between the measured Seismogram and the Synthetic one, not the travel time data. The Synthetic Seismogram was calculated with the GEMINI method. The Seismogram comparison shows that the global earth mantle of PREMAN gives deviating Synthetic Seismogram and has later arrival times than the measured one. The gradient βh in the upper mantle is altered to positive from its negative slope as in the PREMAN model, and positive corrections are added to the zero order of polynomial’s coefficients in all earth mantle layers. The excellent fitting, as well as travel time or waveform, were obtained on the surface waves of Love and Rayleigh, the S and SS mantle and repetitive depth waves. The additional positive corrections were also confirmed by a well fitting on the repetitive depth waves. This result expresses that part of the earth mantle that due to tectonic processes has positive anomaly on S wave velocity and vertical anisotropy in all of the earth mantle layers
Chen Zu-qing - One of the best experts on this subject based on the ideXlab platform.
-
APPLICATION OF TIME-WINDOW AND MULTI-WAVELET METHOD IN PRODUCING THE HIGH PRECISION Synthetic Seismogram
Computing Techniques for Geophysical and Geochemical Exploration, 2011Co-Authors: Chen Zu-qingAbstract:Synthetic Seismogram plays an important role in the seismic interpretation and reservoir prediction.Through analyzing the characteristics of the seismic wavelet which is time-varying and spatially variable,the paper explains the need for dividing the time window,then by combining the Synthetic Seismogram Principles with the methods,it is proposed that a general method using the divided time window to produce a high-precision Synthetic Seismogram,which utilizes the ricker wavelet and the extracted wavelet from the closest well seismic.Finally,this method is used on the actual well,the Synthetic Seismogram which is coincided not only with the seismic but also the higher resolution.
C Lewis - One of the best experts on this subject based on the ideXlab platform.
-
a resistivity log derived and gas corrected pseudo Synthetic Seismogram application to the fanpokeng gas field of northwestern taiwan
New Zealand Journal of Geology and Geophysics, 2014Co-Authors: Sl Kung, C LewisAbstract:Resistivity logs have been used by seismic interpreters for many years to construct Seismograms, particularly in hydrocarbon gas fields where sonic logs are scarce or absent. The correlation between the conventional Synthetic Seismogram made from density and sonic logs and the pseudo-Synthetic Seismogram made from density and resistivity logs has not been very satisfactory in the past because many of the pseudo-Synthetic Seismograms do not include the ‘gas effect’. Our research team has developed a method to correct for the gas effect, and thereby to improve the overall quality of the pseudo-Synthetic Seismogram. We apply this method to a well and then compare the improved results to a conventional Seismogram made from the same well. Our research should be of interest to researchers in New Zealand, Taiwan and other Pacific Rim countries because of the similarities in the tectonic setting of these nations.
