Interpolation artifacts as a result of spatial aliasing: A case study of the airborne magnetic data set of southeastern Minas Gerais, Brazil

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. B193-B205
Author(s):  
Tobias Maia Rabelo Fonte-Boa ◽  
Aline Tavares Melo ◽  
Tiago Amâncio Novo
Keyword(s):  
High Frequency ◽  
Interpolation Method ◽  
Acute Angle ◽  
Magnetic Data ◽  
Aeromagnetic Survey ◽  
Data Set ◽  
Linear Pattern ◽  
Spatial Aliasing ◽  
Geologic Interpretation ◽  
Airborne Magnetic

Linear features at an acute angle with the flight direction are imaged as a series of aligned circular anomalies in the images of Area 15 aeromagnetic survey, which covered part of the Brazilian southeastern region. These features are interpolation artifacts, a recurring problem found in airborne magnetic images that cause problems for qualitative and quantitative geophysical-geologic interpretation. This imaging problem is attributed to spatial aliasing. By running simulations of magnetic data on a synthetic model, we have physically demonstrated that the interpolation artifacts from Area 15 are due to inappropriate survey design. Besides the most common expression of artifacts, we described a geologically noncoherent linear pattern as a new type of artifact. Supported by spectral analyses, we found that the Area 15 aliased spectrum is similar to geologic high-frequency magnetic features, which constitutes a motive for unearthing the correct geophysical signal. Thus, we made use of four techniques for removing the artifacts. The trend enforcement method partially improved the images, whereas the inverse interpolation method was ineffective, apparently because Area 15 data are severely aliased. The constrained coherence diffusion and multitrend gridding methods were able to significantly reduce the presence of artifacts. Despite the high-frequency attenuation, these tools adequately enhanced the magnetic trends and minimized the artifacts. Therefore, the improved images are better suited for reliable geologic interpretation.

Interpolation of potential‐field data by equivalent layer and minimum curvature: A comparative analysis

Geophysics ◽  
1995 ◽  
Vol 60 (2) ◽  
pp. 399-407 ◽  
Author(s):  
Carlos A. Mendonça ◽  
João B. C. Silva
Keyword(s):  
Potential Field ◽  
Interpolation Method ◽  
Mineral Exploration ◽  
A Priori ◽  
Magnetic Data ◽  
Aeromagnetic Survey ◽  
Potential Field Data ◽  
Linear Pattern ◽  
Equivalent Layer ◽  
Minimum Curvature

Interpolation using only the observations at discrete points is an ill‐posed problem because it admits infinite solutions. Usually, to reduce ambiguity, a priori information about the sample function is introduced. Current interpolation methods in mineral exploration introduce only the constraints of continuity and smoothness of the interpolating function. In interpolating potential‐field anomalies, the constraint that the sampled function is harmonic may be introduced by the equivalent‐layer method (ELM). We compare the performance of the ELM and the minimum curvature method (MCM) in interpolating potential‐field anomalies by applying these methods to synthetic magnetic data simulating an aeromagnetic survey. In the case the anomaly flanks and peak are undersampled, the ELM performs better than the MCM in recovering the anomaly gradients and peak. In the case of elongated linear anomalies, the ELM recovers the exact linear pattern, but the MCM introduces spurious oscillations in the linear pattern. Also, the ELM is able to reduce the data from a survey flown at different heights to a common level. In contrast, the MCM, being a 2-D interpolation method, cannot account for variations in the vertical coordinates of the observation points.

Interpretation of airborne magnetic survey of Gabel Um Tineidba area, south eastern desert, Egypt

2015 ◽  
Vol 12 (6) ◽  
pp. 563-576
Author(s):  
Tharwat H. Abdel Hafeez
Keyword(s):  
Analytical Signal ◽  
Eastern Desert ◽  
Structural Features ◽  
Geological Mapping ◽  
Magnetic Data ◽  
Magnetic Survey ◽  
Aeromagnetic Survey ◽  
Reasonable Proportion ◽  
The Cost ◽  
Airborne Magnetic

The study area is regionally covered by rock exposures ranging in age from the Precambrian to Quaternary. The aeromagnetic survey is a useful tool that help in geological mapping, providing information at a reasonable proportion of the cost of ground mapping. The reduced to the northern magnetic pole (RTP) map was separated into regional and residual magnetic component maps by the computed power spectrum of the magnetic data. The estimated mean depths of both regional and residual magnetic sources were found to be 2510 m and 383 m respectively. Also, two advanced techniques were used to analyze the depth magnetic data. These methods are analytical signal (AS) and source parameter imaging (SPI). The results of average depth estimates both methods (–950 m). These depth values were helped -to great extent- for define the direction of throw for the interpreted faults in the basement tectonic map. The statistical analysis shows that, most of the welldeveloped structural features are oriented mostly in the N-S, NNE-SSW, NW-SE and NNWSSE trending faults are considered the main trends affecting the distribution of the radioactive minerals.

Connecting onshore-offshore Campos Basin structures: Interpretation of high-resolution airborne magnetic data

2014 ◽  
Vol 2 (4) ◽  
pp. SJ35-SJ45 ◽  
Author(s):  
Juarez Lourenço ◽  
Paulo T. L. Menezes ◽  
Valeria C. F. Barbosa
Keyword(s):  
Source Rocks ◽  
Magnetic Data ◽  
Data Sets ◽  
Hydrocarbon Migration ◽  
Data Set ◽  
Campos Basin ◽  
Turbidite Sedimentation ◽  
Edge Detection Method ◽  
Transfer Faults ◽  
Airborne Magnetic

We interpreted northwest-trending transfer faults whose extensions are not entirely mapped in the Precambrian basement of the onshore and offshore Campos Basin. To enhance the subtle northwest–southeast lineaments not clearly seen in the total-field data, we reprocessed and merged two airborne magnetic data sets aiming at producing a single merged magnetic data set. Next, we applied a directional filter to these integrated magnetic data. Finally, we applied a multiscale edge detection method to these filtered data. This combination allowed the detection of edges and ridges that are used to produce several northwest–southeast lineations. We interpreted these northwest-trending lineations as magnetic expressions of transfer faults that cut across the onshore adjacent basement of the Campos Basin to the shallow and deep Campos Basin waters. These interpreted northwest-trending faults suggested the continuity of the known northwest-striking transfer faults in the deep Campos Basin waters toward the shallow Campos Basin waters and the adjacent continent. Moreover, our interpreted northwest-trending faults revealed the control of several known oilfields in the Campos Basin. This result supported the hypothesis of the influence of the northwest–southeast-trending transfer faults on the petroleum system of Campos Basin, which were reactivated in the Tertiary providing a pathway for the turbidite sedimentation, reworking, and redistribution of several deepwater reservoirs. In addition, it was hypothesized that this faulting system controlled the hydrocarbon migration paths from the presalt source rocks through salt windows into basal suprasalt layers.

Aeromagnetic survey over lower palaeozoic andesites in the Parkes-Daroobalgie area N.S.W.

1972 ◽  
Vol 3 (2) ◽  
pp. 1
Author(s):  
D.W. Emerson ◽  
M.J. Smith ◽  
R.J. Templeton
Keyword(s):  
Magnetic Data ◽  
Magnetic Response ◽  
Aeromagnetic Survey ◽  
Lower Palaeozoic ◽  
Airborne Magnetic

Detailed and reconnaissance airborne magnetic data over a 150 square mile tract in the Parkes area N.S.W. have been compared and used to investigate the magnetic response and distribution of Ordovician volcanics and metasediments which occur in the area.

scholarly journals Aeromagnetic survey in Kusatsu-Shirane volcano, central Japan, by using an unmanned helicopter

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takao Koyama ◽  
Wataru Kanda ◽  
Mitsuru Utsugi ◽  
Takayuki Kaneko ◽  
Takao Ohminato ◽  
...  
Keyword(s):  
Hydrothermal Systems ◽  
Magnetic Data ◽  
Unmanned Helicopter ◽  
Quaternary Period ◽  
Aeromagnetic Survey ◽  
Magnetization Intensity ◽  
Line Spacing ◽  
Normal Polarity ◽  
The Cost ◽  
Measurement Line

AbstractKusatsu-Shirane volcano is one of the active volcanoes in Japan. Phreatic explosions occurred in Mt. Shirane in 1983 and most recently, in 2018, in Mt. Motoshirane. Information on the subsurface structure is crucial for understanding the activity of volcanoes with well-developed hydrothermal systems where phreatic eruptions occur. Here, we report aeromagnetic surveys conducted at low altitudes using an unmanned helicopter. The survey aimed to obtain magnetic data at a high spatial resolution to map the magnetic anomaly and infer the magnetization intensity distribution in the region immediately after the 2018 Mt. Motoshirane eruption. The helicopter used in the survey was YAMAHA FAZER R G2, an autonomously driven model which can fly along a precisely programmed course. The flight height above the ground and a measurement line spacing were set to ~ 150 m and ~ 100 m, respectively, and the total flight distance was 191 km. The measured geomagnetic total intensity was found to vary by ~ 1000 nT peak-to-peak. The estimated magnetization intensity derived from measured data showed a 100 m thick magnetized surface layer with normal polarity, composed of volcanic deposits of recent activities. Underneath, a reverse-polarity magnetization was found, probably corresponding to the Takai lava flow in the Early Quaternary period (~ 1 Ma) mapped in the region. Our results demonstrate the cost-effectiveness and accuracy of using drone magnetometers for mapping the rugged terrain of volcanoes.

scholarly journals Prediction of Wide Range Two-Dimensional Refractivity Using an IDW Interpolation Method from High-Altitude Refractivity Data of Multiple Meteorological Observatories

2021 ◽  
Vol 11 (4) ◽  
pp. 1431
Author(s):  
Sungsik Wang ◽  
Tae Heung Lim ◽  
Kyoungsoo Oh ◽  
Chulhun Seo ◽  
Hosung Choo
Keyword(s):  
High Altitude ◽  
Korean Peninsula ◽  
Interpolation Method ◽  
Atmospheric Condition ◽  
Propagation Path ◽  
Two Dimensional ◽  
Data Set ◽  
Wide Range ◽  
Atmospheric Data ◽  
Terrain Surface

This article proposes a method for the prediction of wide range two-dimensional refractivity for synthetic aperture radar (SAR) applications, using an inverse distance weighted (IDW) interpolation of high-altitude radio refractivity data from multiple meteorological observatories. The radio refractivity is extracted from an atmospheric data set of twenty meteorological observatories around the Korean Peninsula along a given altitude. Then, from the sparse refractive data, the two-dimensional regional radio refractivity of the entire Korean Peninsula is derived using the IDW interpolation, in consideration of the curvature of the Earth. The refractivities of the four seasons in 2019 are derived at the locations of seven meteorological observatories within the Korean Peninsula, using the refractivity data from the other nineteen observatories. The atmospheric refractivities on 15 February 2019 are then evaluated across the entire Korean Peninsula, using the atmospheric data collected from the twenty meteorological observatories. We found that the proposed IDW interpolation has the lowest average, the lowest average root-mean-square error (RMSE) of ∇M (gradient of M), and more continuous results than other methods. To compare the resulting IDW refractivity interpolation for airborne SAR applications, all the propagation path losses across Pohang and Heuksando are obtained using the standard atmospheric condition of ∇M = 118 and the observation-based interpolated atmospheric conditions on 15 February 2019. On the terrain surface ranging from 90 km to 190 km, the average path losses in the standard and derived conditions are 179.7 dB and 182.1 dB, respectively. Finally, based on the air-to-ground scenario in the SAR application, two-dimensional illuminated field intensities on the terrain surface are illustrated.

scholarly journals Statistical analysis of Stromboli VLP tremor in the band [0.1–0.5] Hz: some consequences for vibrating structures

2006 ◽  
Vol 13 (4) ◽  
pp. 393-400 ◽  
Author(s):  
E. De Lauro ◽  
S. De Martino ◽  
M. Falanga ◽  
M. Palo
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Noise Source ◽  
Volcanic Tremor ◽  
Large Data ◽  
Musical Instruments ◽  
Data Set ◽  
Long Period ◽  
Vibrating Structures ◽  
Analyze Time Series

Abstract. We analyze time series of Strombolian volcanic tremor, focusing our attention on the frequency band [0.1–0.5] Hz (very long period (VLP) tremor). Although this frequency band is largely affected by noise, we evidence two significant components by using Independent Component Analysis with the frequencies, respectively, of ~0.2 and ~0.4 Hz. We show that these components display wavefield features similar to those of the high frequency Strombolian signals (>0.5 Hz). In fact, they are radially polarised and located within the crater area. This characterization is lost when an enhancement of energy appears. In this case, the presence of microseismic noise becomes relevant. Investigating the entire large data set available, we determine how microseismic noise influences the signals. We ascribe the microseismic noise source to Scirocco wind. Moreover, our analysis allows one to evidence that the Strombolian conduit vibrates like the asymmetric cavity associated with musical instruments generating self-sustained tones.

Adaptive sampling of potential-field data: A direct approach to compressive inversion

Geophysics ◽  
2014 ◽  
Vol 79 (1) ◽  
pp. IM1-IM9 ◽  
Author(s):  
Nathan Leon Foks ◽  
Richard Krahenbuhl ◽  
Yaoguo Li
Keyword(s):  
Potential Field ◽  
Adaptive Sampling ◽  
Field Data ◽  
Computational Cost ◽  
Large Field ◽  
Magnetic Data ◽  
Data Sampling ◽  
Data Types ◽  
Data Set ◽  
Potential Field Data

Compressive inversion uses computational algorithms that decrease the time and storage needs of a traditional inverse problem. Most compression approaches focus on the model domain, and very few, other than traditional downsampling focus on the data domain for potential-field applications. To further the compression in the data domain, a direct and practical approach to the adaptive downsampling of potential-field data for large inversion problems has been developed. The approach is formulated to significantly reduce the quantity of data in relatively smooth or quiet regions of the data set, while preserving the signal anomalies that contain the relevant target information. Two major benefits arise from this form of compressive inversion. First, because the approach compresses the problem in the data domain, it can be applied immediately without the addition of, or modification to, existing inversion software. Second, as most industry software use some form of model or sensitivity compression, the addition of this adaptive data sampling creates a complete compressive inversion methodology whereby the reduction of computational cost is achieved simultaneously in the model and data domains. We applied the method to a synthetic magnetic data set and two large field magnetic data sets; however, the method is also applicable to other data types. Our results showed that the relevant model information is maintained after inversion despite using 1%–5% of the data.

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