Exploration Geophysics - Science topic

The Geometrics Geode User Manual: Once you have chosen a suitable record length, the sample interval that gets you closest to 2000 samples/trace will usually suffice. To determine the number of samples per trace, divide the sample interval into the total record length.

I will send you a drawing that shows the subvertical zone above the Muradkhanli oil field in Azerbaijan. And it shows generalized temperature data obtained from numerous wells, and data on the magnetic susceptibility of rocks taken from these wells, in the contour zone and beyond the contour part of the deposits. And the decrease in density in the contour part of the deposits is calculated using the formula obtained by me. I established a decrease in the magnetic susceptibility and density of rocks and an increase in temperature in the subvertical zone above the deposit (that is, in the contour part of the deposit).

Sincerely prof. V.G.Gadirov

in OasisMontaj, it is done using QCDIURNL GX or in exel also.

Dear Isaiah Adelere,

I understand that your question does not have a unique answer, and it is made in geographical units ("...I intend to use 4 half-degree aeromagnetic sheets for geothermal analysis with the intention of a 10' by 10' block size...."). I will try to help with the following explanation:

First of all, you must put in geological/structural/tectonic context, it means: if your scenario is related to a relatively high heat flow regime, the window size should be small enough to estimate the Curie point depth (CPD) because it is expected to be shallow. In contrast, if your geological scenario is considered a low heat flow, it should be large enough to estimate the deeper CPDs. It means several window sizes you must test, and the appropriate length must be selected based on the criteria of the minimal block size that does not cut off the spectral peak (Ravat et al., 2007).

On the other hand: if you have land, airborne, or satellite data, the filtering effect of anomalies could be critical, also the spectral answers. Therefore, the question is: Which is your data source for your research? Satellite magnetic data complement the existing local and regional data sets by providing a globally unified data set. It means: the local structures below the minimum wavelength content cannot be resolved in such a data set, therefore: you must choose the window size for FFT and CDPs estimation according to or in the function of your dataset.

The methodology that I recommend using to estimate Curie point depth is founded on the 2-D radial average power spectral (RAPS) analysis of magnetic anomaly data described basically by three foundational works:

The input dataset of a magnetic anomaly - the emphasis for land research - must reduce the influence:

The depth estimation from your RAPS advises you that the optimal square window dimension is about 10 times the estimated depth (Chiozzi et al., 2005). Thus, you should divide your work area/zone of interest (in km/m units) into square subareas of such as for example 300 km x 300 km to say you an accurate value, each of them overlapping with respect to each other in a step increment, for example, 100 km, and then applying the 2-D FFT RAPS method individually to get Zo and Zt. The computation requires an extensive dataset for estimating Curie point depth.

Best regards, Mario E. Sigismondi

Dear Saifur Rahman Khan and Al,

lI wish you Happy New Year: success in your spiritual achievement, good health and prosperity for it!

I found the next on the facbook (https://www.facebook.com/USGSVolcanoes):

'A volcanologist is a person who studies volcanoes, but there are many different specialties within the field of volcanology. Which interests you and what steps should you take to achieve your goal? Find out more in #VolcanoWatch.

Earthquakes are one primary tool used to study volcanoes. A volcano seismologist studies the earthquakes that are generated as magma moves through Earth’s crust.

A volcano geodesist studies the deformation, or change in shape, of a volcano caused by the movement of magma and gases beneath the surface. Many features of volcanoes can be studied from space, as well, using satellite sensors. Tools like these provide clues about the state of the volcano.

Geologists and geochemists study the composition of lavas and gases to understand the source and style of the eruption. Measuring gas emissions is especially important, as the vog (volcanic air pollution) caused by toxic volcanic gases can contribute to breathing problems, acid rain, and agricultural problems downwind, especially during long-lived eruptions.

If you are interested in becoming a volcanologist, you’ll need to work toward a bachelor’s degree, preferably in a STEM field (Science, Technology, Engineering, and Math). Volcanologists frequently pursue degrees in geology, chemistry, physics, and/or mathematics, but that is not always the case. Oceanography, computer science, engineering, environmental science are all potential pathways, and the list goes on. Explore different fields to find what interests you most.

After achieving a bachelor’s degree, consider options for advanced degrees like a Masters or Doctorate. Many advanced degree programs in the sciences are funded, meaning tuition may be waived, and you might get a stipend for doing the work. Basically, you get paid instead of having to pay for school, and you gain valuable work experience at the same time.

You might consider working for the USGS or other agencies and companies. You have seen many photos of HVO scientists working during the eruptions of Mauna Loa and Kīlauea. The National Park Service also offers a variety of positions for people with either bachelor’s or advanced degrees, such as park geologists, archaeologists, botanists, guides, interpretive rangers, and law enforcement rangers. Science writing and journalism are also excellent ways to explore the excitement of volcanology, natural disasters, and cutting-edge science, while encouraging those passions in others. Similarly, eco- and geo-tourism are great ways to get close to the action and work outdoors, while also meeting, educating, and inspiring people from all over the world. Careers in emergency management will have you helping people stay informed during crises.

Check out usajobs.gov for positions within the federal government. There is even a special section for students and recent grads.

Volcano Activity Updates

#MaunaLoa is not erupting. Webcam imagery shows weak, residual incandescence intermittently in the inactive Northeast Rift Zone fissure 3 lava flow at night. Seismicity remains low and ground deformation rates have decreased. Sulfur dioxide (SO2) emission rates are at background levels. For Mauna Loa monitoring data, see: https://www.usgs.gov/volcanoes/mauna-loa/monitoring-data.

#Kilauea is not erupting. Lava supply to the Halemaʻumaʻu lava lake in Hawai‘i Volcanoes National Park ceased on December 9. Sulfur dioxide emission rates have decreased to near pre-eruption background levels and were last measured at approximately 200 tonnes per day (t/d) on December 14. Seismicity is elevated but stable, with few earthquakes. Over the past week, summit tiltmeters recorded several deflation-inflation (DI) events. For Kīlauea monitoring data, see https://www.usgs.gov/.../past-week-monitoring-data-kilauea.

There were three earthquakes with 3 or more felt reports in the Hawaiian Islands during the past week: a M3.3 earthquake 14 km (8 mi) S of Fern Forest at 7 km (4 mi) depth on Dec. 27 at 4:33 a.m. HST, a M3.4 earthquake 7 km (4 mi) WSW of Volcano at 2 km (1 mi) depth on Dec. 24 at 8:31 p.m. HST, and a M2.5 earthquake 1 km (0 mi) S of Mountain View at 11 km (7 mi) depth on Dec. 24 at 9:57 a.m. HST.

In the photo, an HVO technician adjusts a volcanic gas analysis instrument that was specifically designed for this Unoccupied Aircraft System (UAS) unit, which carries three one-liter analysis bags. The instrument transmits gas concentration information in real-time during the flight at Kīlauea summit. USGS has special use permits from the National Park Service to conduct official UAS missions as part of HVO's mission to monitor active volcanoes in Hawaii, assess their hazards, issue warnings, and advance scientific understanding to reduce impacts of volcanic eruptions. Launching, landing, or operating an unoccupied aircraft from or on lands and waters administered by the National Park Service within the boundaries of Hawai‘i Volcanoes National Park is prohibited under 36 CFR § 1.5 - Closures and public use limits.

USGS image taken January 14, 2022 by M. Warren.

#USGS #HVO #HawaiianVolcanoObservatory'

Maybe it can help you!

Regards,

Laszlo

Many of the geophysical software companies are donating academic licenses to Universities. It is worthwhile contacting them directly. I strongly advise against downloading and installing pirated version of the software. Always go to the source.

Also consider programming rock-physics modules yourself. Especially during a PhD, this allows you to deeply understand what the rock-physics relationships are. Using commercial software allows you to be efficient, using your own code allows to understand deeply.

Best regards, Jorg

In general, for this area of land, you must first try to drill at least 10 boreholes. This is so that you can have parametric soundings to calibrate and validate electrical soundings.

Now, and given that the number of drilling is very limited, it seems judicious to me to carry out a grid of 500 m and to carry out a sounding (SEV) with AB/2 of 1000 m in each point of the grid.

The solicited depth of the SEV depends on the increase in the depth of the aquifers (according to geological data). It is therefore necessary to increase the length of electrical soundings in the areas of increase in P and to add SEVs with AB/2 between 3000 and 5000 m (for example).

The establishment of the geo-electrical profiles can be distributed, according to the configuration of the ground, in the following way:

Total number of SEV Number of profile Number of SEV/profile

Zone 1 24 04 06

Zone 2 18 03 06

Zone 3 20 05 04

Best regards

This is a good question.

Hi Ayaz, I hope this video tutorial can help you with voxi modeling using oasis montaj : https://youtu.be/DKTAkf-oCbI

Please Refer :

Engineering Geology Field Manual volume ii, 2nd Ed, Chapter 14.

Dear Moamen Ali:

You make two interrogations at once: A) one referring to time to depth conversion (“…is it acceptable to use constant…”), and further regarding B) the acceptance of your work in a magazine (“…If I do that and submit a paper…”).

A) There are several reasonable answers to your first question, there is enough material in the responses of colleagues, but let me share my point of view: to give to you a more useful answer, you must give us a little more description of your challenge, we're going on, for example, concern to:

There are a variety of time/depth conversion techniques, but in general, you must visualize in the geological/structural context, it means: You may require a greater effort to go from TWT to m, for more and more complex structure, the more and more complex velocity distribution. It means your time to depth conversion if you are not enough confidential, may be made more pitfalls than solutions, due to your limitations associated with velocity model building and depth imaging.

A key point for me, I suggest making a review of the sources of error in each time-depth estimation, e.g., if you are working in a structural complex zone, you must evaluate the anisotropy velocity distribution, a key limitation of seismic velocity estimation.

B) According to your second question “…If I do that and submit a paper in a journal…”, please let me say that if you have good research, even in TWT or depth, I understand that there are no problems to accept it to publish. I think you must know that depth conversion concerns the Seismic Interpreter because seismic measurements are made in time, and wells based on a seismic interpretation are drilled in depth. Historically, interpreters have trusted in TWT subsurface imaging, due to the sophisticated ray-trace techniques, but when the velocity distribution and structural complexity are such that the time-image of the subsurface does not permit the interpreter to understand the geology, your time to depth conversion if you are not enough confidential, maybe make more pitfalls than solutions.

Last idea or suggestion: thinking about a multidisciplinary workflow using - if you have - the gravity and magnetics together with seismic, answer first the primary question about the geometry and configuration of the basement, then the sedimentary column above.

Please, let me know if you need more help, best regards,

Mario E. Sigismondi

Dear Moamen, please, May you show us a picture of your seismic section, to try to understand your problem and give to you a better answer? Do you have a wide-azimuth -WAZ- and long-offset 3-D acquisitions? Do you have reverse time migration -RTM- PSDM seismic?

Salt has unusual physical properties, such as velocity and density, and therefore, it is relatively easier to map in seismic, even in cases of low SNR due to the strong acoustic/elastic contrast.

Best wishes, Mario

I actually wrote an article last year about how to get started with reading and performing low-level processing on log data from DLIS files in the Volve dataset. While the article focuses on acoustic well integrity log data, its principles are general and can be adapted to other types of well log data in DLIS files.

The full paper is linked below, and I also wrote a blog post summarising it here: https://erlend-viggen.no/well-log-data-tutorial/

Hi,

the SRME method usually do not require the application of the DMO. So it is advisable to perform it before DMO. Since SRME just remove the surface-related multiples, I suppose that the application of DMO after SRME do not affect the results you want to get.

Best Regards

one of methods is Normalized Full Gradient. it useful in detect source

Hi Moamen,

I am not sure if there are any sources of processed and gridded high resolution gravity data for the Red Sea region - this might exist in a national data archive or academic institutions?

Having said that, there are a few sources of raw and processed ship-bourne data available - but I always check the US ngdc/NOAA database first (https://maps.ngdc.noaa.gov/viewers/geophysics/), and tend to find this sufficient for most needs. The ngdc database tends to archive data from research cruises carried out by various research groups, and is the most comprehensive to my knowledge (you can get pretty much any marine geophysical data you could want). There is a user-friendly map browser, and you can normally extract data from research cruises in the region for free, as long as the data are not embargoed. You will then have to check if/how the data are processed, merge them, and grid them into a useable dataset. There may be regions where you can achieve a resolution that is sub-kilometer, but it really depends on the trackline spacing!

If you have access to other sources (airborne, land for the sea margins?) then you may be able to integrate the various datasets to improve the dataset resolution further.

Good luck with getting your hands on appropriate datasets, and with your research!

Dear Subhendu: please, let me share this landmark comments by Alan B. Reid and Jeffrey B. Thurston (The structural index in gravity and magnetic interpretation: Errors, uses, and abuses Alan B. Reid and Jeffrey B. Thurston, Geophysics, Vol. 79, No. 4 (July - August 2014):

Abstract:

"The structural index (SI) is based on the concept of Euler homogeneity, a description of scaling behavior. It has found wide use in potential-field depth estimation and is a constant integer for simple sources with single singularities (points, lines, thin-bed faults, sheet edges, infinite contacts). For these cases, the SI is identical to the index of a simple power-law field falloff with distance. The simple Euler formulation is only strictly correct for such simple sources and integer SI values. The widespread use of the simple Euler method on more complex structures, using fractional SI values is likely to produce misleading results because the SI is no longer a constant for any given source."....

Also, I attached "Comment on ‘A crustal thickness map of Africa derived from a global gravity field model using Euler deconvolution’ by Getachew E. Tedla, M. van der Meijde, A. A. Nyblade and F. D. van der Meer", article that was written by Reid, Ebbing and Webb in Geophys. J. Int. (2012) 189, 1217-1222. Please, read the point 3.3 Choice of structural index, and Conclusions "... The use of the Euler deconvolution method as applied by Tedla et al. (2011) does not provide new and useful results, but merely demonstrates that potential field data can produce misleading results, if used without proper understanding..." Learned lessons, that warn us to avoid the same mistakes.

Mario E. Sigismondi

Hello Larasati Pinanjar Putri

You may try to remove the well tops and use constant numbers for the top and bottom of the velocity model.

Hope it works.

Regards,

Ahmed

There are huge factors affecting to resistivities. Then this question has many answers based on the factors affecting resistivities in you area

To answer these questions you must first know the lecture of

Resistivity curves

1) Two-layer case (A & Q resistivity types)

2) Three Layer Case (AA, QQ, K & H resistivity types)

3) four Layer Case

4) Multilayer case

After that, with some training, you will be perfect in identification

First, you need to know the resistivity curve types.

Second: you must first know to interpret the data manually using master curves and auxiliary graphs.

Third: you can use after that software to reduce time and search for high quality data. Some software as Winsev, Risexp, Res2D ....etc based on your data is 1D, 2D or 3D

If one drill well with drilling fluid with mud weight under balanced then there are chances of formation damage due to imbalances of hydro static pressure and formation pressure. Caving may occur which is if not reduced may lead to stuck of drill strings.

Dear Haipeng Li, glad to meet you.

It is standard practice in land seismic data processing to correct for time delays caused by LVL (low-velocity layers / weathering) in the near surface. Therefore, the first stage is to pick the first arrival times of the refracting events. Nonetheless, first arrivals are often noisy due to, for example, windy during acquisition (it is a classical problem in Patagonia Argentina, where I live), causing automatic pickers to lead to unwanted results.

I understand, what you mean when you speak of FWI you are thinking about Tomographic FWI, TFWI, which combines FWI with wave-equation migration velocity analysis on the processing workflow. In the meantime, the extra cost on computation-time, you need to utilize a joint method combines FWI with TWFI: TFWI applied to the lower frequencies of the data, FWI applied to the higher frequencies starting from the velocity model estimated by TFWI. Through the test on synthetic datasets, the result show that the joint method converged to rather accurate models.

I attached the paper “FWI on land seismic datasets with topography variations: Do we still need to pick first arrivals?” by Lemaistre, Brunellière, Studer and Rivera © 2018 Society of Exploration Geophysicists - International Exposition and 88th Annual Meeting. The authors describe a velocity model building using FWI in complex land seismic scenario. I hope this article can help you.

Best regards,

Mario E. Sigismondi

When you import the data into ReflexW (that is when you convert it to the internally used format), use a Geometry file (e.g. "Geometry.1") in which you have described the geometry of the survey (see page 211 in the ReflexW manual for the format of the geometry file: https://www.sandmeier-geo.de/Download/reflexw_manual_a4.pdf ). In the import menu select "geometry file" under "ConversionMode". Then process the 2D profiles. Once you are happy with a representative profile, save the applied processing sequence as batch job and apply it through "Sequence Processing" to all profiles. Then exit the 2D mode and enter the 3D module. Here you have to specify for the X- and Y-Rasterincrement the crossline and inline sample spacing, so 2.5m and whatever your inline trace spacing was. The X- and YInterpolation are the horizontal dimensions of the generated and interpolated 3D volume. When ReflexW complains about too many data values, then increase the X- and YInterpolation values. It is not meaningful to interpolate to 10cm cell size when your profile spacing was 250cm. Maybe try 50cm and 10cm. for crossline and inline spacing?

Dear Subhendu Mondal, glad to meet you!

Your question is very useful to remember us some issues related with the gravity and magnetic interpretation.

First, it is tacit that gravity and magnetic data cannot be interpreted uniquely in terms of depth; even when the density or magnetic susceptibility contrast are strong or weak, a whole family of configurations can be found for the interface contrast, at various depths, and any one of which will satisfy the observed gravity / magnetic data.

I divide my answer in four parts, following your own words:

1) When you write: “…2D subsurface model…”. Please, you must remember that the real profiles from maps are not in 2D: they are 2.5D. This is an important concept. If you are working at GM-SYS modeling tool, you must to choice the gravity observation and / or magnetic observation profiles: the real data, and each one you change your model (density contrast, depth, shapes of the anomalies) the curves of your gravity model and / or magnetic model changes. The challenge is trying to do your best model for the convergence of the model with the observation data.

2) When you write: “…i am using residual anomaly…”. As a Geophysicist interpreter, I must say to you that nowadays, and in the past too, it is not possible to reach a whole discrimination of gravity / magnetic anomaly map / profile into the contribution of:

1- the regional

2- the residual

3- (plus, the noise)

because their power spectra overlapping.

If you are talking about residual data, therefore, you applied before an upward continuation, and also, a continuation distance of one grid cell is not uncommon, although you should be critical of how much resolution you are losing in the smoothed data when you choose the upward continuation distance. This is your choice, again, as a the better person who know the geology and target of your work.

3) When you write: “…which will be the maximum depth value for preparing the model with better accuracy?” As Interpreter, you can drive the maximum depth tolerance to allow (percentage) (default value is 15). Therefore, all depth-solutions with error estimate smaller than this tolerance will be accepted. A smaller tolerance will result in fewer but more reliable solutions.

I recommend trying to do before a spectral analysis (remember limitations that I said in point 2), and you will have an estimation of the shallower average sources of your zone of interest by measuring the slope of the energy spectrum and dividing it by 4pi. A typical energy spectrum for gravity / magnetic data may exhibit three parts – a deep source component, a shallow source component, and a noise component.

An additional argument: we do not escape the ambiguity: in fact, gravity and its derivatives are related by a result of Green’s theorem, that provides an analytical proof of ambiguity not only for gravity but also for magnetic as well.

Also, remember that there are a wide variety of gravity and magnetic surveys, as a function of the terrain clearances, sampling rates, line spacings … and your spectral analysis is reflecting not only these condition (acquisition) but also: the choice of your grid-cell-size (interpretation) e.g.: this should normally be ¼ to ½ the nominal data sample interval.

4) When you write: “…is there any thumb rule in this case?"

The best rule is trying to do

1- spectral analysis,

2- profiles in GM-SYS or similar;

3- inversion profiles, and

4- compare it with another solution, such as: Euler deconvolution, SPI, Werner, AS, and, of course, if you have: seismic and well-logs control.

It should be emphasized finally, that, regional - residual (local) separation that describe large-scale-deep structure and small-scale-shallow structure, respectively, you and me must be considered in terms of the scale of the survey; also, I recommend to you to define the regional as the effect in which you are not interested. Maybe for you the regional is different that my criteria.

Best regards, Mario E. Sigismondi

REQUEST:

Dear colleagues and friends, I need seismic reflection data for processing in a free software for master students. if there is someone who has some data, please send them.

Thank you for your helps

Sample of limestone with hydrocarbons together with Pb-Zn massive sulphides. Pine Point deposit.

Dear Ahmed,

I believe that a strong statement cannot be made regarding the limitations of gravimetry or magnetism without having evidence or data to endorse and verify them.

It happens many times that the comparison is not valid, because it is clear that seismic is a quintessential tool in reservoir characterization, especially in the case of loans in the domain of prestack elastic inversion, both, for fluid / lithology discrimination.

Such as Naeim said above, the integration of methods is the clue to solve the subsurface geometry.

But both, gravity and magnetic, are not only for Exploration stage (e.g., new frontier areas), but also it is very useful in Development or Reservoir Management: thinking about the case for instance of the 4-D Gravity Survey to characterize fluid contact in boreholes.

Even without this 4-D, gravity and magnetic aerial surveys are critical for example in areas with environmental restrictions, or logistical limitations in the stage of Reservoir Management. Thinking about the use of gravity and seismic for depth pre-salt imaging of complex hydrocarbon systems (Recóncavo Brazil / Gabon-Congo system; Santos-Campos Brazil / Kwanza – Benguela Angola).

Another example of the use of gravity anomalies in Reservoir Characterization is related with the construction of the low-frequency model to run seismic inversion. Remember that for potential method environment softwares, you can export a SEGY file with your gravity inversion, load in the seismic interpretation environment and go on with your low-frequency model previously to run the acoustic-elastic- seismic inversion workflow.

Let me show you two examples of my own experience that I compare the 3D seismic basement imaging with magnetic solutions and be careful of the sizes and the statistics that I show you, you take a better idea about the advantages.

I hope this answer will be useful for colleagues and you.

Mario E. Sigismondi

Dear colleagues and Vinicius:

My ideas about your questions:

Vinicius ask:

1. Could I calculate in Oasis Montaj the power spectrum for RTP-TMI grid or is it recommended to TMI grid only? Spector & Grant (1970) had calculated the power spectrum using total magnetic intensity maps.

Mario´s answer:

My answer is: you can use the RTP data, the result should be similar to TMI only, since the solution of sources is an average depth for the whole grid, and not a point solution of each source.

That is: each line segment you choose in your crossplot is an average depth´s solution for sources at deep, intermediate and shallow relative depth of your work area / grid.

In any case, the recommendation would be to know first, comparing the TMI and RTP outputs, how far the anomaly locations are displaced in one map and in the other, and of course it is according your region of research.

Vinicius ask:

2. In Spector & Grant (1970, p.295) it is written:

“The postulate states that the mathematical expectation of the value of the power density function is equal to the ensemble average of E. It is strictly valid only for large samples, but in fact works very well even if the number of bodies present is as small as 5 or 6.”

This means that the RAPS method cannot be used for studies of less than 5 bodies? I am asking this because I am pretending to use this method for 2 alkaline bodies close to each other.

Mario´s answer:

This question is related to the first in the sense that the most important thing to apply the solution of Spector and Grant is the size of your area of ​​work, and not the number of anomalies present. You should also be in mind that 50 years have passed since this breakthrough publication, and the authors did not have the computational tools that we have today. On the other hand: your RAPS solutions would be your first step in order to understand your research, in order to interpret your dataset. This solution is only one, maybe the first, maybe the most robust, maybe the most quickly for us, but it has limitations. You must be careful about the theory and assumptions of the Spector and Grant´s paper. If you are working with magnetic data, the first inspection is the RAPS, but you must try an extra step to get, e.g. the AS and SPI solutions, and compare to arrive a valid geological interpretation.

Vinicius ask:

3. Could I use the RAPS method for low magnetic latitudes or close to the geomagnetic equator?

In Spector & Grant 1970 work (p.295) it is written:

“...Care must be taken in low magnetic latitudes, however, and close to the geomagnetic equator.”

Mario´s answer:

Thinking about the first and second ideas. I am not original if I said that you are trying, such as Geophysicist Interpreter of Potential methods, to estimate parameters of the sources, but you must integrate geologic information, or seismic data, for a realistic solution.

Again: If you are working with magnetic data, the first inspection is the RAPS, but you must try an extra step to get, e.g. the AS and SPI solutions, and compare to arrive a valid geological interpretation.

I hope this words help to you, please, let me know if I can do anymore else.

Best wishes, Mario

Not so simple. It also depends on your "basement definition" , the nature of the rocks involved (metasedimentary rock, crystalline basement, weathered basement, ect...) and the deformation.

In many case the top often fits with a strong amplitude reflections and erosional surface above transparent/chaotic facies (or well layered if you are dealing with a basement shear zone).

In both cases, I suggest you to test your interpretation with potential field (gravity/magnetic) to be sure.

You can construct a 3D structural model using boreholes in Move software. Indeed, you can construct it in other free or cheaper-licenced programs. However, the most important thing to bear in mind or what you should ask yourself is: what is the purpose of this "3D structural model" and what really means for you a "3D structural model".

One thing is to construct a fence diagram (which usually is in 3D or quasi-3D) using formation tops or stratigraphic information (e.g., lithology, thickness, etc) from the boreholes, a fence diagram like that one suggested by Bayan Hussien, which is very useful to correlate stratigraphically. However, from a fence diagram, you will hardly construct a reliable structural model even a 2D structural model!. So, a reliable structural model must be at least balanced or geometrically consistent, in this way, you should have more structural data and a seismic line will be very useful to interpret structures.

Another important thing is the space between boreholes, you must consider that the greater spacing the greater unknown information in between (uncertainty increase dramatically).

Please consider the below examples (image) constructed from borehole data. In case #1, from the stratigraphic correlation in the fence diagram, you can infer a simple structural model with horst and graben structures related to planar normal faults. However, in case #2, from the same data/information you could interpret another structural model related to listric faults. So, the important point is, what is the detail or purpose of your work, depending on the latter, you can assess if move software is what really do you need or the advantages/disadvantages of constructing a (likely complex) "3D structural model" using only a limited borehole data.

Move software is very useful when you have a seismic line or very dense structural information.

Anyway, I hope I have understood your question correctly and be able to help a little.

Huber

It is not strictly true that there is no physical or geological meaning for negative values of magnetic susceptibility, as diamagnetic minerals have this property (quartz is one). However, the magnitude of this is invariably so low as to be insignificant for magnetic surveys. The one situation where negative apparent magnetic susceptibilities can be used in modelling is as a proxy for reversely magnetised material. This can be valid only if the remanent magnetisation vector is exactly opposed to the main Earth field.

It is a neat topic. Sure!

I am interested in exploring the inter-bed multiples which are generated due to the presence of thin coal beds.

Dear Mr. Hosseini,

The major ore minerals are chromite and PGM associated with the podiform Cr deposits. Chromite and the majority of PGM are heavy minerals (chromite, PGM, magnetite, Cr spinel) forming a clastic halo around the deposit denominated as alluvial-fluvial placers. Density and magnetic variation (magnetite, pyrrhotite) in the host rocks render geomagnetic and gravimetric geophysical methods applicable. Textural variation concerning the interlocking of ore and gangue minerals are a good basis for IP methods. Ultrabasic host rocks are outstanding with regard to their unbalanced element budget as they are depleted in K and Na and rife with Fe, Ca, Mg, Ni, Co, Cu, and Cr. This has some implications as to the vegetation and fosters botanical (geobotanical exploration marker plants) and bio-chemical methods in the field of applied geochemistry (biochemical exploration (sampling for chemical analyses) e.g. branches, needles, leaves, lichens, moss). Moreover common stream sediment sampling can be applied (stream sediments and water chemistry Ni, Co, As („pathfinder elements“)). Last but not least do not forget the good old geological methods (Geological methods, ultrabasic complexes, modern and ancient fold belts with ophiolite sequences). It has to be noted that podiform types pose more difficulties on exploration than stratiform type due to intensive structural deformation and disruption).

I wish you good luck

H.G.Dill

Depends what one plans to do with the PMSE data. For example, if goal is to investigate the wave activity in the summer mesopause region, probably Doppler velocity is the best to use. If one plans to do a statistical analysis about the phenomena itself, I do not expect big difference using SNR or volume reflectivity. Spectral width is used sometimes to highlight the turbulent areas in the observed region.

So, important is to define the interest of research whether assume PMSE as a tracer and use it to study dynamical processes or obtain background wind, or purpose is to investigate the PMSE morphology, micro-physics etc.

Geophysical technique is applied to study the physical parameters such as density; elasticity; resistivity; etc, using different methods. Using the electrical resistivity method one can study the resistivity of different sub-surface earth material. Geo-electric and geologic parameters may or may not be the same. Two / three geologic formations may be reflected with the same type of resistivity values. Hence it is always advised to conduct VESes initially at a place where sub-surface lithologic information is already available or known through bore-hole litho-logs and try to you calibrate the VES results.

Trying to Interpret the VES results only through soft-wares without the geologic knowledge of the study area is not at all recommended and this type of mechanical way of interpretation is expected to lead to erroneous results. Also it may be noted that there is no soft ware which will relate the resistivity to geologic formations. These soft wares give only the geo-electric sections in terms of number of layers and their respective thicknesses. At the end the researcher has to correlate the VES results with that of sub-surface geologic information/formations  

Do you have a 2D kirchhoff migration code?Thanks

Tomography and 4d Resistivity  methods are the best

Vindyan basin has low maturity and type II prone. It may be better for shale oil rather than shale gas.

Hi Nazeera, I underwent some of the links suggested above. Could please share the correct answer of your question ?  It is going to be helpful for me also. Though I am interest only with the porosity and permeability of the black shale in general. Thank you :)

VR=lamda*f (dispersion curve);  Vs=1.1*VR;  D=lamda/2 or Lamda/3 (depend on length of seismic source to first geophone)

We can use technique radar GPR

I wish you luck in your search

SIP from a ground based survey would require a very significant transmitting and receiving electrode spacing with a very large generator.  But it can be done. It's all about geometry and power. 

A relevant question has been raised. Modelling can be done.

There are a variety of commercially avaialble existing VLF-EM  processing algorithms, here's one that I have used previously:

Though it is reported to vary from zero to a few thousand ppm Re, and no generalizations are yet possible as to correlations of Re content with geological conditions of formation, .in our experience Rhenium invariably trends with porphyry Mo systems including the Hybrid Climax types that have some base metals such as with copper. . Perhaps it's so as molybdenum invariably breaches the hydrothermal spectrum into much hotter magmatic fancies evidenced by such things as molybdenum with rhenium in Unidirectional Solidification Textures (UST, rhenium having a high melting point, along with molybdenum, not occurring as the free metal but in varies oxidation states, rhenium itself having several) associated with super saturated convective melts brining the magmatic systems from very deep, magma-convectively hot, into the hydrothermal interface and depositions we call "plumes". Interestingly it has one stable isotope, Re185, shared with Indium and tellurium, which occur as rings about hybrid Climax molly porphyry such as the Unicorn deposit. Indium is an indicator of rift environments,  and by inference along with molybdenum and rhenium a direct mantle source into rhyolitic magmas evolved in thick crust of back arc rifts.  

Hi Anthony,

Beware of the precision and accuracy of Nb and Ta analyses. These elements are often close to the detection limit in mafic rocks, and what you see could be due to analytical error.

Otherwise, you might want to look at references such as:

Green, T. H. (1995) Significance of Nb/Ta as an indicator of geochemical processes in the crust-mantle system. Chemical Geology 120(3–4):347-359.

Baier, J., Audétat, A., and Keppler, H. (2008) The origin of the negative niobium tantalum anomaly in subduction zone magmas. Earth and Planetary Science Letters 267(1-2):290-300.

Good luck!

Antoine

The most useful technique is likely cross-borehole resistivity imaging, as electrical currents may flow horizontally through each layer. Attempting to resolve the mixed layers from surface resistivity data is likely to be problematic.

You might also employ time domain induced polarisation -- a simultaneous decrease of resistivity and IP may be taken as diagnostic of saline water (but expect some strange data!)

The attached paper gives information on relative fall in sea level due to intraplate deformation.  Similar criteria can also be used to estimate subsidence. Erosion and subsidence are two different processes.  Please make sure whether you want to know about subsidence or lowering of land due to erosion.  You can get back to be: krsubrahmanya@rediffmail.com

This is a nice paper you can use. However,  for surface water estimation microwave passive imager is a good source of data. You may use TMI, SSM/I etc. to retrieve the extent of water vapor. You will also require to a good Radiative transfer model to remove the atmospheric effect in the imager signal. For detail also check: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7061458

You are refering to the Chaerhan salt glacier if I am right.

The Chaerhan salt glacier (namakiers) is the largest surface salt flow in Kuqa depression which is remolded from a pre-existing salt diapir (Zhao and Wang, 2016, evidence of early passive diapirism and tectonic evolution in the western Kuqa depression; Tang, 2011, Doctoral thesis). In the field, components of the paleocene rock salt is completely recrystallized, dissovled and mixed up. The chemical measuring of field samples is hard to achieve certain aims, I'm afraid. However, I'm very willing to know a possible way to unravel the kinematics of a salt structure from surface samples.

Below could be some possible aims for your research:

a. Despite the common understanding of a passive early history, some researchers still suggest that the Quele salt nappe (from which the Chaerhan namaskier is fed) is formed during the Pliocene shortening of Kuqa depression, without an early stage;

b. What is the burial depth of present surface samples? Could we establish a satisfying equation between surface samples and deep source in lab? This could led to a new way to understand a few structural quenstions, such as the shortening rate (could be calculated from the burial depth), the early history (when is the salt extruded?)

Ps: the recent surface study by Cindy Colón et al., 2016 (The variety of subaerial active salt deformations in the Kuqa fold-thrust belt (China) constrained by InSAR) could be helpful if you wanna do some remote sensing work.

Best Regards

Dewow in Reflex acts on each trace in the profile in turn. For each point on each trace, it calculates the mean value of all the points either side of that point within the time range specified; and subtracts this mean value from the original point. It does this as a running average through all the points in the trace, moving the time window with the point, It does this on each trace independantly.

I don't use this function very often as there are more efficient methods. All depends what you are trying to achieve. In my experience the fewer processing steps you can get away with, the better. Each processing step adds its own artifacts to the mix and you need to be aware of this.  

Hi;

Below are some references I would like to share. Please check GPR radargrams included in the references, especially interpreted radargrams. I think they could give some ideas that will help in your work, Sir.

In addition to the basic data processing steps such as background removal, I would like to suggest you to apply de-convolution and migration to reduce your data. It seems to me both data processing steps would make your data more interpretable.

I hope the references given below could be helpful

Kind Regards

REFERENCES

 

Xu, X., Xia, T., Venkatachalam, A., 2012. Development of high-speed ultrawideband ground-penetrating radar for rebar detection. J. Eng. Mech. 139, 272–285. doi:http://dx.doi.org/10.1061/(ASCE)EM.1943-7889.0000458

Yehia, S., Abudayyeh, O., Abdel-Qader, I., Zalt, A., 2008. Ground-Penetrating Radar, Chain Drag, and Ground Truth: Correlation of Bridge Deck Assessment Data. Transp. Res. Rec. J. Transp. Res. Board 2044, 39–50. doi:10.3141/2044-05

URL 1 https://fhwaapps.fhwa.dot.gov/ndep/DisplayTechnology.aspx?tech_id=24

URL 2 http://www.ijser.org/paper/Thickness-evaluation-of-asphalt-and-base-layers-of-some-major-and-minor-arterial-roads-in-Kumasi-using-ground-penetrating-radar.html

URL 3 http://foundationperformance.org/pastpresentations/gehrig_paper_march2004.pdf

URL 4 http://ntl.bts.gov/lib/43000/43000/43073/134431_FR.pdf

URL 5 http://www.sciencedirect.com/science/article/pii/S0963869504001021

URL 6 http://www.mdpi.com/1424-8220/9/3/1454/htm

He was talking about a transient electromagnetic (TEM) sounding data interpretation software, for deriving a layered resistivity model of the subsurface. Not about satellite imagery.

Ivan, you can try:

"A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys"

M.H. Loke, Ian Acworth, Torleif Dahlin

Exploration Geophysics Sep 2003, Vol. 34, No. 3, pp. 182-187

Hi again Lukman, if you are using geophysics to interpret underground data you have to try Geosoft software, they have software and extensions for geophysics and they have academic licenses (Like the Advanced Research suite), reach them at www.geosoft.com.

 cheers

I did a fair bit of this over the years, and yes vitrinite reflectence does not help much with the timing of maximum burial but when combined with fission track dating and track length analysis and using that information to create a burial history plot you are on your way to getting to a Tt path.  Please try both forward models and inverse model to best understand the thermal history.

dear Simon,

You can find the detail answer by doing gassmann fluid substitution. You can play around with gas saturation to analysis bulk mod changes.

Here I want to give some analog.

Let say you have value 10 (analogue for 0 gas saturation or water saturated condition)

Then you add value 1 (analogue for let say 10% gas). You can calculate the average: 10+1 devided by 2 equal to 5.5. You can see, the value dramastically drop from 10 to 5.5.

Lets continue, imagine we add gas saturation per 10% or equal to value 1

10 + 1 + 1 devided by 3 equal to 4

10 + 1 + 1 + 1 devided by 4 equal to 3.25

10 + 1 + 1 + 1 + 1 devided by 5 equal to 2.8

So you can see the first gas adding makes original bulk mod drop dramatically to 5.5. Since the gas is adding more the bulk changes drop slighly become 4, then 3.25 then 2.8.

This is simple analogue why adding gas 10% results significant drop compare to 30% or even 80% of gas. It because there is significant different between bulk for quartz in sandstone filled by water compared to sandstone with gas.

I hope I can answer your question

IT depends entirely on the resistivity contrast at the boundary.  If the central geology is more conductive, the current will "pile up" in the central, conductive side.  (Currents propagate outward as well as downward with time.)   If the outside geology is more conductive, the currents will propagate quickly through the resistive geology, and concentrate across the conductive boundary, before continuing to propagate more slowly outward in the more conductive geology.  Where the conductive geology is only on one side, the current ring will definitely distort - moving out faster on the resistive side.

.

Addition to previous answer, If you are interested in equivalence of MT and TEM recordings Pellerin and Hohmann (1990), Meju (2005) and references therein may help you.  

Emin

The Mw=7.4,1999 Izmit Earthquake in Turkey started contained two earthquakes whose epicenters were about 80 kms apart along the North Anatolian Fault Zone. Please see the reference below.

Çemen, I., Gokten, E.,  Varol., B., Kilic, R.,  Ozaksoy, V., Emre, C., and Pinar, A., 2000, Turkish Earthquakes Reveal Dynamics of Fracturing along a Major Strike-Slip Fault Zone;  EOS, Transactions, American Geophysical Union, v. 81, No. 28, p. 309 and 313

Its actually not possible to achieve a complete separation of observed gravity into regional, local and noise value by any mathematical filter, because their power spectra overlap. So all such attempts (and there are very many variations on the theme) are doomed to failure. It can only ever be an approximation, often a poor one. The best you can do is remove the things you understand (which is what the standard corrections do), then realise that even the Bouguer correction is an interpretive step, because you're assuming constant density between ground surface and datum, and any modelling you do MUST take that into account. 

The concept of regional-residual separation arose in more qualitative times, when people just wanted to get an approximate "picture" of shallower vs deeper geology. You MUST NOT try to model data that have been subjected to this kind of filtering, unless you apply the same filters to the models. You are much better off modelling the "whole earth" and not trying to filter to separate. These days any decent PC has the power to do that.

I would look to MLA or advanced SEM techniques.

There are two different questions: (1) the number of data locations (as well as the spatial pattern) used to estimate/model the variogram  (2) the number of data locations (as well as the spatial pattern) used in the kriging equations. There is no minimum number for the first question that is always sufficient although you will find various statements in the literature that claim there is. There are two different aspects of estimating/modeling the variogram, one is to select the variogram model (e.g spherical) and secondly to determine the parameter values in the model. It is common practice to compute and plot empirical variograms but for a given data set these are not unique. The number of data location pairs is completely determined by the number of data locations however this number does not determine the numbers of pairs for each distance class/angle window. Those numbers are affected by the width of the distance classes and the angle window tolerance, it will always be a compromise. The question you are asking is far more complicated than you recognize and does not have a simple answer.

The variogram model is a function satisfying certain conditions, e.g conditionally negative definite. The kriging equations will have a unique solution for any function satisfying these conditions but there is still the question of whether to use  a moving search neighborhood or a unique neighborhood. If you are using a moving search neighborhood then 20-25 data locations in the neighborhood is sufficient and may be too many but note the phrase "in the neighborhood".

There is no such thing as an "accurate" variogram and you can not determine the "accuracy of kriging" The kriging variance does not depend on the data values, only on the variogram model and its parameters, numbers of data locations in the search neighborhoods and the spatial patterns of those data locations.

You should begin with asking what you know about the phenomenon that generates the data, e.g is the spatial correlation likely to have a directional dependence,  is there a plausible guess as to the range of the spatial correlation. Is the data cheap or expensive, is it easy or difficult to get. Is it "point" data or does it have non-point support? Once you have some data you will want to use various exploratory statistics to gain some insight into the data. You may want to experiment with different variogram models, different search neighborhood parameters and look at the cross validation statistics

I don't think 2D will give a better picture, because the data clearly indicates 1D structure.

Here you have something focused on broadband surface wave dispersion measurements http://ciei.colorado.edu/pubs/2007/2.pdf

but your question does not specify or detail your needs. Processing techniques or pre-processing of (I suppose seismic ?) ambient noise is different if you want to calculate Horizontal to Vertical spectral ratios (Nakamura measurements) or e.g. the Green's function or a pseudo-spectral density with time.

Recording well the ambient noise with a 24-bit sensor and over a broad frequency range, the coupling of the sensor with the ground, insulation from pressure variations, the wind and other industrial/human-generated noise are key points of paramount importance.

Good data will allow you to apply as you prefer your codes, but it depends on what you are looking for. As an example, if you are looking to mine microcracks, it's important to have a seismic network but sensors must be borehole sensors, and processing should include match filter cross-correlation methods and stacking techniques if the target is M<0 earthquakes.

What is the most suitable distance between 2 continuous radon monitoring in soil gas sites?

Dear Aftab Alan,

I think it is very important to do frequent (or, better, continuous) radon monitoring in sites where gas emission from the soil occurs, with a capillary distribution of research centers on the territory, for a reason of  health prevention, but there can be economical problems in many country, so it is at least desirable that a frequent radon monitoring is undertaken in schools, hospitals and underground working places of every town, city, … and  it is right to do a continuous radon monitoring in every working place in mines, in tunnels and in caves…, independently from the distance between 2 continuous radon monitoring stations.

What is the most suitable distance between 2 continuous radon in soil gas monitoring stations?

This is an issue of research on seismic forecast: we must consider the seismic classification of different places and the different geological structures, for example if an area is rich in minerals with uranium, radon is indeed a very good seismic precursor, so a continuous radon monitoring can give important information about earthquakes forecast. We must always consider the whole seismic precursors in their synergic complexity , not only radon emission, for a forecast always more and more precise.

I can answer to your question, but let me tell you that we can individuate only a good and suitable distance between 2 continuous radon monitoring studies in research centers and not “the most suitable”, in relation to the seismic classification of diverse areas and in relation to the actual spatial and temporal earthquake forecast that the radon monitoring can give us. It is necessary to consider also the different geological structure in relation to the depth of the future earthquake and its magnitude, because the radon emission can change. It is also important to take into account the classification of earthquakes: tectonic earthquakes, earthquakes originated by volcanic activity and earthquakes originated by balances in underground caves.

So I can only answer you on the basis of my experimental researches that I conduct with my “Seismic Precursors Study Center” (SPSC, a no-profit association), whose operative centre is in Torre Pellice. I do not know what cat be “the most suitable distance between 2 continuous radon in soil gas monitoring stations” in other areas with a different geological structure and with a different seismic classification. We must always be prudent if we would like to give an ideal model of prevention and forecast planning.

So I can sum the following, based on my observations:

- increase in radon emission over mean values is significantly higher 2-3 days before earthquakes with magnitude M ≤ 1, with a distance from SPSC of the future epicentrum d ≤ 20 km;

- increase in radon emission over mean values is significantly higher 2-3 days before earthquakes with magnitude 1 < M ≤ 2, with a distance of SPSC from future epicentrum d ≤ 50 km;

- increase in radon emission over mean values is significantly higher 2-4 days before earthquakes with magnitude 2 < M ≤ 3, with a distance of SPSC from future epicentrum d ≤ 90 km;

- increase in radon emission over mean values is significantly higher 3-7 days before earthquakes with magnitude 3 < M ≤ 4, with a distance of SPSC from future epicentrum d ≤ 130 km;

- increase in radon emission over mean values is significantly higher 3-15 days before earthquakes with magnitude 4 < M ≤ 5, with a distance of SPSC from future epicentrum d ≤ 280 km.

So, considering an earthquake with a magnitude 2 < M ≤ 3, we can propose the following model for a forecast planning, about a good and suitable distance between 2 research centers undertaking a continuous radon monitoring: 180 km.

 In the attached image:

- the circle with radium of 90 km shows the area in which the future earthquake can occur with a magnitude 2< M≤ 3.

- the circle with radium of 20 km shows the area in which the future earthquake can occur with a magnitude M ≤ 1.

The future magnitude is deduced by the difference between the maximum and minimum of radon values in a temporal period Δt comprised between a rapid increasing and a rapid decreasing, in relation to means values.

This is valid if the differences between maximum and minimum radon values are only considered as relative values for every research center.

I would like to note that, for greater magnitudes, the radon emission rises too much and the radius of the area where a possible earthquake can occur is bigger. An integration of data from different research centers and the eventual discussion about radon anomalies give good information about the future earthquakes, under the point of view of the temporal and the spatial forecast, but this study is now at the beginning, we must experimentally prove.

I don’t know if this model of mine could be good for other regions of Italy or other countries, with a different seismic classification, but it is good for the Piedmont region, in Italy. It is necessary to share the same research.

Best regards

Giovanna de Liso

Dear Inna:

REESA uses 14 rules with default threshold values to help flag anomalous data.  Petroleum systems modelling software, such as Platte River's BasinMod, uses REESA, along with maturity modelling, to identify potential source rocks.

Dear Mr. Rurui.

the answer is simply yes. It is only a question of time which lies between the formation  of these very contrasting geodynamic settings. There are numerous crustal sections where you can find interlocked with each other lithologies indicative of both settings.

Best regards

H.G.Dill

A basoc but important test is the dessorption measurement, using canisters. This is an onsite test and needs to be done ASAP at the mine or at the rig, in the case of a drilling site.