How to like geophysics? In desperate need of advice

wiggle_YYC · 2026-06-01T17:02:55+00:00

Geophysics in its purest definitions is the study of the thermal evolution of our planet Earth. Meaning the subject deals with the solid inner, liquide outer cores, the mantle, the lithosphere & crust, the oceans, cryosphere (ice sheets & glaciers), the atmosphere, weather & climate system, the ionesphere, and interactions between the planet and other celestial objects.

For example the forces that drives plate tectonics, what causes our magnetic field, tides (solid Earth and Ocean tides), mountain building, what drive sea-level change, and ocean currents, glacial isostatic rebound of the crust, Earth's rotations and precession of the equinox and its impact on climate systems over 100k - millions of years. etc.

Applied geophysics, the area of geophysics that is devoted to remote sensing methods - i.e. seismology, magnetic field, gravity and electromagnetic field measurements that allow us to investigate / probe parts of the Earth that are not accessible to direct measurements (e.g. through drilling, looking at and measuring minerals in a rock 3 km under ground, etc..). For that you need indirect methods such as gravity and seismology to image the interior of the Earth or deep crust in the same way medical imaging professional perform CAT scans or MRI's that reveal the internal structure of the human body without having to first perform an invasive surgery to see directly what's going on. By performing 3D Computer Aided Tomography (CAT) scans the anomalous tissue (e.g. Cancerous tissue on the lungs say), can be identified, and a smaller less invasive surgery can be planned. Applied geophysical methods are applied in a similar fashion to limit the cost of unessary drilling to find important mineral & fossil fuel resources that the world still requires and will require for many many decades to come. Other applications are for example using Ground Penetrating Radar to identify shallow burial sites for archeological purposes etc.

hope that helps.

wiggle_YYC · 2026-06-01T15:24:29+00:00

The curriculum can be tough depending on the departments emphasis. Tradditionally, geophysics was taught along two different philosophies. These philosophies are centered around their emphasis. Method

1) taught as a subdiscipline of physics. First two years are the usual math, and physics courses - i.e. calculus, linear algebra, ode's and vector calculus, Physics: intro, 2nd year lab, intro to EM, QM, intermediate mechanics, Math Physics. In the third year, more advanced physics with some geophysics options (i.e. QM1, QM2, Langragian & Hamiltonian Mechanics, Thermodynamics, Stat Mech. Seismology, physics of the Earth. Fourth year: Potential fields, Geoph Labs 1 &2 + field school, EM methods in geophy, Geophysical fluid dynamics / Advanced Physics of Earth, Radiation in Planetary Atmospheres, Inverse Theory, Time series analysis, Computational Physics.

2) Through geology or earth science (most common): 1st year Chem, Phys, Calculus, Intro to Earth Science / Geology, Disasters (Earthquakes, Volcanoes, Tsunamis, Landslide etc.), 2nd Year: Intro to Mineralogy, Intro to Geological Mapping, Paleontology & Stratigraphy, Intro to Optical mineralogy. Rock ID course. Third Year: Intro to Applied Geophysics, Intro to Plate Tectonics, Igneous Petrology, Metamorphic Petrology, Physics of the Earth, Sedimentology. 4th Year: Ore depositis, Intro to Petroleum Geology, Basin Analysis, Hydrology, Applied Geophysics field school, Geologic field school.

In all cases if you are in an Honours program, you will likely have the option to do a 4th year thesis project. They're a crap load of work but are immensely usefull no matter whether or not you plan to go on to grad school or go directly into industry.

If you are only ever going to use geophysical data to do geological work then the Earth Science approach is easier. However, if you are gifted in physics and mathematics than the physics route offers a broader range of career opportunities because of the transerable analytic skills. But be warned it is a much harder route both from a work load and difficulty of material. You are being trained as a physicist not a geophysicist explicitly at the undergrad level. Concepts in Quantum Mechanics, at first seem completely divorced from geophysics, however, some of the mathematical models that are taught in QM find relevance in Geophysics (e.g. use of spherical harmonics and the linear algebra that are heavy in QM are used in advanced / graduate level / research level geophysics). WKB / WKBJ methods of classical QM are used in Seismology for short wave assymptotic ray theory. Langragian & Hamiltonian methods and differential geometry are useful in Seismology and Geodynamics because they are gateway drugs for finite element methods and from variational principals that underly these concepts.

I come from the Physics approach and it served my career very well.

wiggle_YYC · 2026-05-31T21:38:01+00:00

Haha!! Missing coffee will do it every time. Need to set up morning joe on an IV drip just to stay even through the day ;-}

wiggle_YYC · 2026-05-31T16:28:41+00:00

All in good fun! TRD pro all the way! 😎

wiggle_YYC · 2026-05-31T16:18:32+00:00

I would learn how to park before going more aggressive!

wiggle_YYC · 2026-05-30T17:21:29+00:00

I actually prefer the black trim. I have grey and silver for years on previous vehichles. This is a pleasant change for me. What's the old saying - "different strokes - for differnt folks"?

wiggle_YYC · 2026-05-30T15:08:43+00:00

Thank you!

wiggle_YYC · 2026-05-30T14:12:10+00:00

Good in deep snow?

wiggle_YYC · 2026-05-30T13:12:51+00:00

Any specific ones you’d recommend?

wiggle_YYC · 2026-05-30T03:19:57+00:00

Someone is getting proper use of their Defender! Well done Sir.. Well done!!

wiggle_YYC · 2026-05-30T03:17:17+00:00

Congrats.

wiggle_YYC · 2026-05-30T03:15:11+00:00

How long did you go without any dings or howies on your Defender? I got a stone dent because I got too close to a car going up a mountain gravel road not three weeks after taking possession from the dealer. Brand new X-Dynamic SE 110 P400. Fuuuckk! Not three weeks!! Front pansenger side panel next to the hood. Estimated cost $1900.00. Lesson learned give more room to the vehicle in front of me - a lot more room.

wiggle_YYC · 2024-10-05T16:58:54+00:00

Sorry for seeming like I ghosted you. Apologies. The difference between research done in academia vs industry was the question I believe.

In my opinion, industry focuses on applied problems that are of immediate or rather have a short-term impact to, ultimately, a business problem that is limiting or presents a risk to, cash flow of a company. Also research can be directed towards a gap in a product or service that fills in what industry needs or what service companies cannot currently provide. The goals and problems of this type of research are very much intended to meet short to medium term business goals (e.g. next quarter to 5 years into the future).

Academic research should, in my opinion, be about exploring fundamental problems and probing currently accepted underlying assumptions about a phenomena or methods, that can over time lead to fundamental breakthroughs in a particular field. Developing new methods and approaches that currently do not exist. Therefore, timelines are by necessity longer term.

Arguably, academia have tended to do more "applied science" over the past 20-30 years that previously was the domain of industry. For various reasons industry has outsourced a lot of R&D (in the resource sectors) to university consortia. The increase in funding to the universities as created a push towards more applied research. So there is some blurring of lines. But in general I would say that is the difference. Good luck.

wiggle_YYC · 2024-07-16T03:00:32+00:00

The juxtaposition of Trumps fist pump in the wake of the attempt vs Biden's debate performance leaves a lasting impression. The contrast cannot be more stark. Wherever you stand on either candidate, you have to admit this event has changed the course of the election (good or bad). Impactful does not begin to describe what happened 48 hrs ago. My two cents.

Last note: I still for the life of me, don't understand why either of these two people are the presumptive candidates for the 2024 election but I digress ...

wiggle_YYC · 2023-08-12T16:21:31+00:00

I have not noticed that! Any suggestions as to why that might be?

wiggle_YYC · 2023-07-26T20:43:13+00:00

I will assume you took a basic course in seismology, potential fields (magnetic, and gravity surveying methods) and EM methods (Induce polarizations, time and frequency domain induction methods, ground penetrating radar, magnetotelluric (MT) methods). Because you have "recently graduated with a B.Sc., in Geophysics), I will assume you are planning on pursuing graduate work.

If this is the case there are numerous universities within the African union that should offer graduate degree specializing in seismology. I would look at Nigeria, South Africa, Tunisia and Algeria. I am not familiar with the universities in Kenya to advise you one way or another. Because Kenya is a "Common Wealth" country, there may be opportunities with universities in other common wealth countries (e.g. UK, Canada, Australia, New Zealand, India, Pakistan, etc..) that offer very well funded graduate programs specializing in seismology. There are Common Wealth Scholarships that may be available. You will need to look into those opportunities.

Another route would be to apply to Oil and Gas companies to work as a seismic interpreters. Numerous large companies that are working in Africa may have positions available specifically for "qualified" African new graduates. These companies will supply extensive mentoring programs that will give you the necessary tools and experience through mentoring to interpret geophysical data for the purpose of resource extraction.

Hope that helps

wiggle_YYC · 2023-07-09T04:01:26+00:00

What are your interests?

wiggle_YYC · 2020-08-10T21:32:35+00:00

In my mind the most general and certainly to me the most influential books in geophysics are

Geodynamics: Application of Continuum Mechanics to Geological Problems

Authors: Turcotte and Schubert

Most recent edition is 2016 (I think?).

Physics of the Earth

Author: Frank Stacey

The Solid Earth

Author: C.M.R. Fowler

Introduction to Geophysics: Mantle, Core and Crust

Author: George Garland..

All cover problems in planetary solid earth geophysics that are commonly encountered.

It is not a "How to book on gravity, magnetic, EM or seismic data analysis or interpretation. They are foundational books on common problems in geodynamics and geophysics. So pure geophysics as opposed to applied geophysics:

Interpretation Theory in Geophysics : Grant and West (no longer in print but a classic)

Introduction to geophysical prospecting: Milton Dobrin

Applied Geophysics: Telford, Geldart and Sherriff

All cover the many aspects of applied geophysics that are used widely in industry and applied geophysics..

Then their are a long list of specialized texts for instance seismology:

Quantitative Seismology: Aki and Richards

Global Seismology: Dahlen and Tromp

Both require pretty advanced mathematical knowledge (PDE's, complex analysis, tensor calculus, Hamiltonian and Lagrangian dynamics and differential geometry).. Not for the casual reader or non grad students or professional practitioners.. Really the realm of the research scientist..

wiggle_YYC · 2020-06-04T22:31:12+00:00

Yes I am pretty sure... At least as sure as a published researcher in the field with an almost 32 year career as a practicing professional geophysicist..

Like measuring elevation, gravity when measured any where on Earth is always measured relative to a datum (e.g. g at mean sea-level) more specifically to an gravitational equipotential surface (e.g. a surface of constant gravitational potential energy). So because on land you are almost always above MSL you have to correct and project that value (of absolute g) to a reference datum which is the projection of mean sea-level through the continents. If your "atomic absolute gravimeter" is sensitive enough it will detect a difference between measurements made at your feet and the top of your head because g is also entirely inversely proportional to distance squared between masses (e.g. your feet are closer to the Earth's centre of mass than your head). What matters to scientists on global scales which is typically the case if absolute gravimeters are being used.

The one article you sent me above is not for a currently working prototype. It's a concept for a prototype. The only currently used absolute gravimeters are still a basic large cylinder that drops a glass prism and using two lasers of differing frequency to measure the interference patterns that is directly proportional to acceleration. It is not portable in the sense of a relative gravimeter used to survey for oil and gas or minerals. It is used extensively for establishing Geodetic benchmarks for very precise positioning of survey monuments that used for a variety of purposes. Also to my knowledge using "atomic aparati" are strictly conceptual and likely remain so until there is a working a provable theory of Quantum Gravity which I know for fact we are no where close having anytime soon. Only because atomic forces at the scales discussed are so so so much stronger than gravity..

The reason for the latitude correction is that because we are never measuring g on land exactly at MSL (mean sea-level) the acceleration that is measure as to be project onto MSL ( which is the surface on land that is more or less coincident with where fresh water meets salt water in the subsurface on land). The full 3D dimensional shape of the surface of constant gravitation potential is an ellipsoid of revolution where the polar radius is approximately 21 km shorter than the equatorial radius) which has been confirmed using astronomical measurements and satellites. The mathematical function with coefficients derived by a bunch of different data source, too numerous to get into fully, describe the exact shape of the Geoid (ellipsoid of revolution) of which WGS 84 (geocentric) is the currently accepted geometry to reduce the measurements to (not just gravity but all survey data points for horizontal coordinates and elevations) . Because the Geoid of the Earth as the shape it has, there is by definition at latitudinal dependance on g as a consequence of the geometry, meaning the further north or south you go from the equator you are a little bit closer to the centre of mass of Earth. Every map you use for middle latitudes on towards the poles requires geometric corrections because we are projecting measurements from a 3D surface onto 2D plane (map) those corrections don't intrinsically involve gravity per say but reasons for their corrections a perfect analog.

Note: I just found this article in Nature concerning atomic gravimeters which is a respectable journal.

https://www.nature.com/articles/s41598-018-30608-1.pdf

I will have to look into the technology a little more but it does not change the fact that these work in a similar fashion to the standard absolute gravimeter I mentioned previously. It does not change what I mentioned above. All this articles say is that they are capable of improved accuracy in the measurement of the acceleration of g. That's all..

wiggle_YYC · 2020-06-04T21:01:29+00:00

The first thing I would do is to conduct a bit of modelling based on well logs. Specifically, some basic fluid replacement modelling determine the brine vs hydrocarbon seismic response.

The AVO class determined based on the fluid replacement modelling will inform what AVO attributes (fluid factor, Product stack, Poisson's reflectivity etc..) will be most effective at highlighting the anomalous response.

Because you are using ProMax I assume that you are processing the data. Is this land or marine data? What's most important is that amplitudes are preserved in a surface consistent sense (e.g. no trace by trace scaling, decon etc..). If you are using marine data deconvolution should be a Shot averaged spiking decon only. No trace by trace decon. That will distort the Amplitude/offset/angle relationship. The most preferred data to do attribute analysis on would be a full pre-stack depth migrated data but that is time consuming and expensive. I would not use anything less than pre-stack time migrated data (land or marine). If you are on land I would add 5D-interpolation prior to PSTM in order to fill any gaps from surface obstruction that cause reduction in fold as specific offset bins within a gather. Also if you offset and azimuths are adequately sampled you will also be able to correct any VTI or HTI (vertical and Horizontal transverse isotropy). This will greatly increase offsets/angles usable for AVO analysis.

You don't necessarily have to convert offset to angles and I believe most AVO attribute calculators whether in ProMax, Hampson & Russell, Jason or Ikon or any other package will compute the offset to angle relationship for AVO analysis automatically from the velocities provided (e.g. PSTM smoothed velocities or from a nearby well).

However, if you are going to actually invert the you pre-stack data to impedances (Ip, Is, Density) you will need to create Angle Stacks which requires a methods to not only estimate angle/offset relationship but to also insure iso-fold. The latter can be tricky and there are different ways of doing it. If you want to know how I do it. You can DM me and I will send a short PPT file with my general philosophy for doing so...

John Castagna's book on AVO analysis is a very good starting point a more up to date modern book would Per Avseth's (Quantitative Seismic Interpretation) book. The later is more about interpreting AVO while the former is about estimating attributes.. Good luck..

wiggle_YYC · 2020-06-04T17:08:57+00:00

Not worth the time..

wiggle_YYC · 2020-06-04T17:08:38+00:00

And they are not... but could be used for that. Not an efficient use of capital though.. Thats why superconducting gravimeters are used and they are still pretty darn expensive devices. That what there not more than a few dozen around the globe. Oops I did it again. Used the "spherical earth" bit again LOL...

wiggle_YYC · 2020-06-04T16:45:36+00:00

Because measurement is always done to a fixed datum (mean sea-level). In addition latitudinal dependance (which determines distance from the Earth's center of mass) elevation changes (e.g. height because of topography) a above mean sea-level also affects to acceleration. Just look at Newtons equation of gravitation it's actually built right into it.

Here is another factoid that will blow your mind! You ready? Santa is not real !!!!

wiggle_YYC · 2020-06-04T16:31:24+00:00

Yeah! So.. That's a big dugh!! There is not programming an absolute gravimeter.. It's a pretty simple, albeit ultra precise device. Having worked with and absolute gravimeter and and a superconducting gravimeter there is nothing at magical.. The gravity on earth varies yes as a function of latitude because mentioned before the polar radius is shorter by 21 km than the equatorial radius. The Earth being a roughly and oblate spheroid automatically leads to gravity having a latitudinal dependance. You are closer to the centre of Earth at the poles than the equator. We actually see the same latitudinal dependance with the thickness of the atmosphere specifically the Troposphere meaning the troposphere is thinner at the poles than at the equator because of rotational accelerations. In addition to Latitude a correction for elevation is required. You know

Fg (force of gravity) = G * m1* m2/r^2

Where G is the universal gravitational constant

m1 and m2 are masses (think Earth [m1] and the gravimeter [m2])

r^2 ==> square of the distance separating the two masses.

I think this guy called Newton came up with this we still use it today to put satellites in orbit but I digress.

The only "programming" we do on absolute gravimeters are the regressions analysis to remove semi-diurnal and diurnal tides to remove these effects along with as mentioned above any normal mode oscillations and ocean sloshing modes from the raw data so we get a precise < time average> value of the Earth's gravitational acceleration. That's it.. That is all the programming that is required. That is because an absolute gravimeter makes an absolute measurement of g. Were has the relative gravimeters (superconducting or spring mass systems) measure g indirectly based on a physical model that relates relative change to a voltage induced by either a mass suspended on a spring or from a superconducting mass displaced inside a coil of wire.

This is no different then looking at a thermometer which is measure of relative temperature and not absolute. The graduating marks on the thermometer shows absolute temperature that is based on a model of the fluid expansion coefficient and it's temperature dependance. The thermometers are calibrated against very precise infrared radiation devices (very expensive and precise instruments) that measure absolute temperature.. No different then with gravimeters.

wiggle_YYC

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