scholarly journals Analisa Persebaran Wetland Berdasarkan Metode Geolistrik di Kecamatan Pandak, Kab. Bantul, DIY

2021 ◽  
Vol 4 (2) ◽  
pp. 1
Author(s):  
Wrego Seno Giamboro ◽  
Puji Pratiknyo ◽  
Ardian Novianto ◽  
Lisna Tri Utami
Keyword(s):  
Field Data ◽  
Soft Water ◽  
Surrounding Area ◽  
Near Surface ◽  
Resistivity Sounding ◽  
Research Areas ◽  
Water Saturated ◽  
Geoelectrical Methods ◽  
Inversion Modelling

ABSTRAKWetland merupakan tanah lunak tersaturasi air yang berada di dekat permukaan yang menjadi permasalahan dalam pembangunan di sekitar daerah penelitian di Desa Gilangharjo, Kab. Bantul, DIY. Oleh karena itu dilakukan pengukuran metode geolistrik untuk mengetahui persebaran kedalaman wetland di sekitar daerah penelitian sebagai bahan kajian pendukung dalam program pembangunan desa. Dalam penelitian ini dilakukan pengukuran metode geolistrik sounding sebanyak lima titik sounding, kemudian data lapangan diproses menggunakan pemodelan inversi 1 Dimensi (1D) untuk mendapatkan kurva model 1D resistivitas batuan. Berdasarkan kurva model 1D resistivitas batuan didapatkan nilai resistivitas wetland berkisar antara 5.66 - 29.6 ohm.m dan kedalaman wetland berkisar antara 0.592 - 2.25 meter yang meningkat ke arah tenggara. kata kunci : Wet soils, resistivitas, geolistrik sounding ABSTRACTWetlands is a soft water saturated rocks in near surface which becomes a problems of developement in surrounding area of Gilangharjo Village, Bantul District, DIY. Therefore, the research with using geoelectrical methods has been conducted to delineating spreading of wetlands depth in surrounding research areas as a supporting data for village developing programs. In this research is conducted sounding geoelectrical methods measurements as much five sounding points, then  the field data is processes with using 1D inversion modelling to get 1D resistivity models curve of rocks. Based on 1D resistivity models curve of rocks is obtained wetlands resistivity value is between 5.66 - 29.6 ohm.m and the depth of wetlands is between 0.592 - 2.25 meters which increase to southwest.         keywords : Wet soils, resistivity, sounding geoelectric.

Joint inversion of TEM and distorted MT soundings: Some effective practical considerations

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 56-65 ◽  
Author(s):  
Maxwell A. Meju
Keyword(s):  
Data Processing ◽  
Field Data ◽  
Apparent Resistivity ◽  
Additional Data ◽  
Joint Inversion ◽  
Phase Information ◽  
Deep Basin ◽  
Near Surface ◽  
Resistivity Sounding ◽  
Joint Interpretation

Accurate layered‐earth interpretation of magnetotelluric (MT) apparent resistivity sounding curves distorted by the presence of near‐surface, 3-D bodies in an otherwise horizontally stratified ground requires that the curves be shifted to the level they would have assumed in the absence of these anomalous small‐size bodies. The most popular preinterpretation processing involves shifting the biased MT apparent resistivity curves to the levels determined by some additional data. This paper examines the nature of TEM field data, their relationship with MT data, and their usefulness in constraining the interpretation of MT data at locations affected by near‐surface 3-D effects. The MT apparent resistivity curves are neglected in a joint inversion scheme involving the (undistorted equivalent) phase information and TEM data, thus eliminating the need for preinterpretation data processing or correction of statically shifted curves. This approach is efficient and effective, and since an overlapping TEM observational bandwidth is not always required for a successful joint interpretation, simple inexpensive. TEM equipment can be deployed as a logical compliment to MT in deep basin exploration campaigns.

Computer Application in Geosciences: Imaging of the Subsurface by Structural Coupled Inversion of Potential Field Data

2014 ◽  
Vol 644-650 ◽  
pp. 2670-2673
Author(s):  
Jun Wang ◽  
Xiao Hong Meng ◽  
Fang Li ◽  
Jun Jie Zhou
Keyword(s):  
Potential Field ◽  
Field Data ◽  
Gravity Data ◽  
Computer Application ◽  
Magnetic Data ◽  
Imaging Method ◽  
Inversion Algorithm ◽  
Constant Property ◽  
Near Surface ◽  
Potential Field Data

With the continuing growth in influence of near surface geophysics, the research of the subsurface structure is of great significance. Geophysical imaging is one of the efficient computer tools that can be applied. This paper utilize the inversion of potential field data to do the subsurface imaging. Here, gravity data and magnetic data are inverted together with structural coupled inversion algorithm. The subspace (model space) is divided into a set of rectangular cells by an orthogonal 2D mesh and assume a constant property (density and magnetic susceptibility) value within each cell. The inversion matrix equation is solved as an unconstrained optimization problem with conjugate gradient method (CG). This imaging method is applied to synthetic data for typical models of gravity and magnetic anomalies and is tested on field data.

Textural and mineralogical controls on temperature dependent SIP behavior during freezing and thawing

2021 ◽  
Author(s):  
Jonas K. Limbrock ◽  
Maximilian Weigand ◽  
Andreas Kemna
Keyword(s):  
Freezing Point ◽  
Pore Space ◽  
Thermal Characterization ◽  
Complex Frequency ◽  
Freezing And Thawing ◽  
Temperature Dependent ◽  
Measured Resistance ◽  
Ice Content ◽  
Water Saturated ◽  
Geoelectrical Methods

<p>Geoelectrical methods are increasingly being used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties are sensitive to the phase change of liquid to frozen water. Here, electrical resistivity tomography (ERT) is most commonly applied, using resistivity as a proxy for various quantities, such as temperature or ice content. However, it is still challenging to distinguish between air and ice in the pore space of the rock based on resistivity alone due to their similarly low electrical conductivity. Meanwhile, geoelectrical methods that utilize electrical polarization effects to characterize permafrost are also being explored. For example, the usage of the spectral induced polarization (SIP) method, in which the complex, frequency-dependent impedance is measured, can reduce ambiguities in the subsurface conduction properties, considering the SIP signature of ice. These measurements seem to be suitable for the quantification of ice content (and thus the differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites. However, to improve the interpretation of SIP measurements, it is necessary to understand in more detail the electrical conduction and polarization properties as a function of temperature, ice content, texture, and mineralogy under frozen and partially frozen conditions.</p><p>In the study presented here, electrical impedance was measured continuously using SIP in the frequency range of 10 mHz to 45 kHz on various water-saturated solid rock and loose sediment samples during controlled freeze-thaw cycles (+20°C to -40°C). These measurements were performed on rock samples from different alpine permafrost sites with different mineralogical compositions and textures. For all samples, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperature. Also, hysteresis between freezing and thawing behavior is observed for all measurements. During freezing, a jump within the temperature-dependent resistance is observed, suggesting a lowering of the freezing point to a critical temperature where an abrupt transition from liquid water to ice occurs. During thawing, on the other hand, there is a continuous decrease in the measured resistance, suggesting a continuous thawing of the sample. The spectra of impedance phase, which is a measure for the polarization, exhibit the same qualitative, well-known temperature-dependent relaxation behaviour of ice at higher frequencies (1 kHz - 45 kHz), with variations in shape and strength for different rock texture and mineralogy. At lower frequencies (1 Hz - 1 kHz), a polarization with a weak frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, which likewise depends on the texture as well as on the mineralogy of the respective sample. This polarization response partially vanishes during freezing. Overall, the investigated SIP spectra do not only show a dependence on texture and mineralogy, but mainly a dependence on the presence of ice in the sample as well as temperature. This indicates the possibility of a thermal characterization, as well as a determination of the ice content, of permafrost rocks using SIP.</p>

scholarly journals Finite-difference modelling to evaluate seismic P-wave and shear-wave field data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 33-47 ◽  
Author(s):  
T. Burschil ◽  
T. Beilecke ◽  
C. M. Krawczyk
Keyword(s):  
Wave Field ◽  
Shear Wave ◽  
Field Data ◽  
P Wave ◽  
Sh Wave ◽  
Surface Shear ◽  
Near Surface ◽  
Reflection Seismic ◽  
Surface Shear Wave ◽  
Seismic Measurements

Abstract. High-resolution reflection seismic methods are an established non-destructive tool for engineering tasks. In the near surface, shear-wave reflection seismic measurements usually offer a higher spatial resolution in the same effective signal frequency spectrum than P-wave data, but data quality varies more strongly. To discuss the causes of these differences, we investigated a P-wave and a SH-wave seismic reflection profile measured at the same location on the island of Föhr, Germany and applied seismic reflection processing to the field data as well as finite-difference modelling of the seismic wave field. The simulations calculated were adapted to the acquisition field geometry, comprising 2 m receiver distance (1 m for SH wave) and 4 m shot distance along the 1.5 km long P-wave and 800 m long SH-wave profiles. A Ricker wavelet and the use of absorbing frames were first-order model parameters. The petrophysical parameters to populate the structural models down to 400 m depth were taken from borehole data, VSP (vertical seismic profile) measurements and cross-plot relations. The simulation of the P-wave wave-field was based on interpretation of the P-wave depth section that included a priori information from boreholes and airborne electromagnetics. Velocities for 14 layers in the model were derived from the analysis of five nearby VSPs (vP =1600–2300 m s-1). Synthetic shot data were compared with the field data and seismic sections were created. Major features like direct wave and reflections are imaged. We reproduce the mayor reflectors in the depth section of the field data, e.g. a prominent till layer and several deep reflectors. The SH-wave model was adapted accordingly but only led to minor correlation with the field data and produced a higher signal-to-noise ratio. Therefore, we suggest to consider for future simulations additional features like intrinsic damping, thin layering, or a near-surface weathering layer. These may lead to a better understanding of key parameters determining the data quality of near-surface shear-wave seismic measurements.

Surveying Batavia’s Graveyard: Geophysical controlled experiments and subsurface imaging of archaeological sites on an Indian Ocean coral island

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. B147-B163 ◽  
Author(s):  
Jeffrey Shragge ◽  
David Lumley ◽  
Nader Issa ◽  
Tom Hoskin ◽  
Alistair Paterson ◽  
...  
Keyword(s):  
Sea Water ◽  
Controlled Experiments ◽  
Near Surface ◽  
Survey Techniques ◽  
Geophysical Surveys ◽  
Archaeological Materials ◽  
Coral Island ◽  
Water Saturated ◽  
Ground Penetrating ◽  
Geophysical Anomalies

We conducted geophysical surveys on Beacon Island in the Houtman Abrolhos archipelago offshore Western Australia, to investigate areas of archaeological interest related to the 1629 Batavia shipwreck, mutiny, and massacre. We used three complementary near-surface geophysical survey techniques (total magnetic intensity, electromagnetic induction mapping, and ground-penetrating radar) to identify anomalous target zones for archaeological excavation. Interpreting near-surface geophysical anomalies is often complex and nonunique, although it can be significantly improved by achieving a better understanding of site-specific factors including background conditions, natural variability, detectability limits, and the geophysical response to, and spatial resolution of, buried targets. These factors were not well-understood for Beacon Island nor indeed for the Australian coastal environment. We have evaluated the results of controlled experiments in which we bury known targets at representative depths and analyze the geophysical responses in terms of an ability to detect and resolve targets from natural background variability. The maximum depth of detectability of calibration targets on Beacon Island is limited to approximately 0.5 m due to significant variations in background physical properties between a thin ([Formula: see text]) and highly unconsolidated dry sand, shell, and coral layer of variable thickness overlying a sea-water-saturated sandy half-space. Our controlled measurements have implications for calibrating and quantifying the interpretation of geophysical anomalies in areas of archaeological interest, particularly in coastal and sandy-coral island environments. Our geophysical analyzes contributed to the discovery of archaeological materials and five historical burials associated with the 1629 Batavia shipwreck.

3-D imaging of subsurface magnetic permeability/susceptibility with portable frequency domain electromagnetic sensors for near surface exploration

2019 ◽  
Vol 219 (3) ◽  
pp. 1773-1785 ◽  
Author(s):  
Julien Guillemoteau ◽  
François-Xavier Simon ◽  
Guillaume Hulin ◽  
Bertrand Dousteyssier ◽  
Marion Dacko ◽  
...  
Keyword(s):  
Magnetic Permeability ◽  
Field Data ◽  
Large Data ◽  
Archaeological Site ◽  
Phase Response ◽  
Magnetic Method ◽  
Data Sets ◽  
Near Surface ◽  
Inversion Procedure ◽  
Multichannel Deconvolution

SUMMARY The in-phase response collected by portable loop–loop electromagnetic induction (EMI) sensors operating at low and moderate induction numbers (≤1) is typically used for sensing the magnetic permeability (or susceptibility) of the subsurface. This is due to the fact that the in-phase response contains a small induction fraction and a preponderant induced magnetization fraction. The magnetization fraction follows the magneto-static equations similarly to the magnetic method but with an active magnetic source. The use of an active source offers the possibility to collect data with several loop–loop configurations, which illuminate the subsurface with different sensitivity patterns. Such multiconfiguration soundings thereby allows the imaging of subsurface magnetic permeability/susceptibility variations through an inversion procedure. This method is not affected by the remnant magnetization and theoretically overcomes the classical depth ambiguity generally encountered with passive geomagnetic data. To invert multiconfiguration in-phase data sets, we propose a novel methodology based on a full-grid 3-D multichannel deconvolution (MCD) procedure. This method allows us to invert large data sets (e.g. consisting of more than a hundred thousand of data points) for a dense voxel-based 3-D model of magnetic susceptibility subject to smoothness constraints. In this study, we first present and discuss synthetic examples of our imaging procedure, which aim at simulating realistic conditions. Finally, we demonstrate the applicability of our method to field data collected across an archaeological site in Auvergne (France) to image the foundations of a Gallo-Roman villa built with basalt rock material. Our synthetic and field data examples demonstrate the potential of the proposed inversion procedure offering new and complementary ways to interpret data sets collected with modern EMI instruments.

scholarly journals Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India

2019 ◽  
Vol 489 (1) ◽  
pp. 115-133 ◽  
Author(s):  
Gautier Nicoli
Keyword(s):  
Partial Melting ◽  
Water Budget ◽  
Critical Parameter ◽  
Bound Water ◽  
Dharwar Craton ◽  
Bulk Rock ◽  
Near Surface ◽  
Surface Conditions ◽  
Magma Compositions ◽  
Water Saturated

AbstractThe fluid budget of a composite crustal column is a critical parameter that influences many lithospheric processes. The amount of water introduced into the middle and lower crust can be quantified using phase equilibrium modelling. The Dharwar Craton, India, displays a now-exposed continuous crustal section from near-surface conditions to c. 30 km depth. This section records the different steps of a c. 15 myr-long high-temperature metamorphic event (60°C kbar−1) responsible for the formation of syn- to post-tectonic anatectic intrusions. The global water budget is assessed using thermodynamic modelling on bulk-rock compositions of an average early Proterozoic supracrustal unit and c. 3.0 Ga felsic basement, the Peninsular gneisses. Results show the fast burial of a water-saturated supracrustal package (1.6 wt%) will release c. 50% of its mineral-bound water, triggering water-fluxed partial melting of the basement. Modelled anatectic magma compositions match the observed granitoid chemistries, and distinction can be made between water-fluxed melting and water-absent melting in the origin of syn- to post-tectonic anatectic granites. Findings from this study show the importance of crustal pile heterogeneity in controlling the nature of partial melting reactions, the composition of the magmas and the rheology of the crust.

APPLICATION OF CONTINUOUS VELOCITY LOGS TO DETERMINATION OF FLUID SATURATION OF RESERVOIR ROCKS

Geophysics ◽  
1956 ◽  
Vol 21 (3) ◽  
pp. 739-754 ◽  
Author(s):  
Warren G. Hicks ◽  
James E. Berry
Keyword(s):  
Field Data ◽  
Acoustic Velocity ◽  
Gas Oil ◽  
Laboratory Measurements ◽  
Reservoir Rocks ◽  
Fluid Saturation ◽  
Saturated Sands ◽  
Similar Character ◽  
Water Saturated

Recent studies of continuous acoustic velocity logs indicate that these logs may provide important assistance in differentiating gas, oil, and water saturations in reservoir rocks. In general, velocities are appreciably lower in sands carrying oil or gas than in water‐saturated sands of otherwise similar character. Specific examples from field logs illustrate this application. Laboratory measurements have been made of acoustic velocity of synthetic and natural rocks. Published studies, both empirical and theoretical, of other workers concerned with the transmission of sound in porous media have been considered. All of these at least qualitatively confirm the conclusions drawn from field data.

The origin of resonance in the vertical component of earthquakes recorded on soft soil at Wainuiomata, New Zealand

2011 ◽  
Vol 44 (1) ◽  
pp. 19-30
Author(s):  
W. R. Stephenson
Keyword(s):  
New Zealand ◽  
Fundamental Mode ◽  
Rayleigh Waves ◽  
Soft Soil ◽  
Vertical Component ◽  
Soft Water ◽  
Saturated Layer ◽  
Water Saturated

Occasionally-observed resonances in the vertical components of earthquakes recorded at the Wainuiomata, New Zealand, soft site, are likely to be manifestations of the Airy phase of fundamental-mode Rayleigh waves which traverse the site. These packets of waves exist only when a soft, water-saturated layer of soil overlies a substrate with a much higher velocity. Other soft sites in Wellington also show the phenomenon, which may have implications for hazard estimates.

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