Questions tagged [geophysics]

Geophysics is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment.

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657 views

How does Vertical Electrical Sounding Work?

I recently conducted a brief training exercise with VES equipment, although it had to be called off due to rain. I can't help but wonder about the basic physics of it, why is it that increased ...
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221 views

Glossary of oil and gas industry geophysical terms

Reviewing market regulatory standards I came across the problem of finding a source that I could cite of concise, worldwide accepted industry geophysical terms. So far I know Schlumberger Oilfield ...
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808 views

Calculating magnetic declination for a non-axial dipole field

I'm trying to answer the following question: Compute the inclination and declination of the magnetic field that would be observed in Boulder, Colorado (40°N, 105°W) if the Earth’s field ...
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Utah rock pattern identification - looks like small craters

This formation was found in the Capital Reef area of Southern Utah (38.2970546, -111.2979319). There wasn't just one, but several of these small crater formations all over the area. All of them had ...
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Global scale seismology experiments / observations disproving flat earth conspiracy?

Recently I've taken an exceptionally unwise interest in the beliefs on conspiracy theorists, in particular flat earthers. Flat earthism has been trending heavily lately and indeed is undergoing some ...
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Wobbly Tire Theory — Is there an existing theory that fits the following description?

I am not an earth scientist but for many years I have wondered about the following. I am curious if this has already been explored by scientists? If so, what is the theory formally called? and what is ...
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Does the extension of the absorption line of $\text{CO}_2$ with temperature play a role in the climate change?

I've read not long ago that the absorption line of the $\text{CO}_2$ becomes larger with temperature thanks to Doppler effect (if it's false it would be great to tell me). My question is the following:...
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275 views

Surface temperature in early hadean period

I am considering earth's internal heat budget for a project in university. For this I need an estimate on the temperature of the earth shortly after it had formed. In Kelvin's On the Secular cooling ...
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120 views

Performing time-frequency analysis (FTAN)

I am trying to do ambient noise tomography and I am quite confused on how to perform time-frequency analysis (FTAN) as shown in figure 13b and 13d of this paper by Bensen et al.. I am using Python and ...
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where are the poles of rotation of the tectonic plates located?

Euler's "fixed point" theorem ... can be stated as: The most general displacement of a rigid body over the surface of a sphere can be regarded as a rotation about a suitable axis which passes ...
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Open source seismic refraction processing

What I am in search of is an open source tool to pick first arrivals, plot travel-time curves, and perform simple velocity modeling. I am experimenting with seismic refraction to identify shallow ...
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How do you choose appropriate parameters for a lowpass filter when filtering a Bouguer anomaly?

I am trying to filter my Bouguer anomaly data to remove the short wavelength features. I have created a lowpass filter to achieve this, but I am wondering how I can more objectively choose my cutoff ...
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Relationship Between Ratio of Atmospheric Gases and Ocean Gases

A version of this question was posted in Chemistry SE and Worldbuilding SE but I've been told it wasn't appropriate to either SE. I was told to give this SE a chance. If you think it doesn't belong on ...
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How much does the Earth's center of mass move around?

How much does the Earth's center of mass move around relative to the most stationary objects on the surface? I'm wondering whether the molten outer core has enough asymmetry to move the center of ...
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How can we measure the thickness of the Earth's mantle? [duplicate]

According to Wikipedia the earth's mantle is approximately 2900 km (1,800 miles) thick. How is it possible to achieve such measurements? Obviously we haven't sent anything down that far to check.
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Is there a risk with putting out smouldering underground coal reserves? [closed]

According to this Discovery News video about Centralia Pennsylvania and other underground coal fires, there are many smouldering underground coal reserves making the land above it uninhabitable to ...
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Why do clouds have ceilings and bases?

What is the point called when water can not rise above or visually seem to have a ceiling in the atmosphere? What makes that point ideal?
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Why doesn't subducted earth crust melt?

If you take a look at a typical picture tectonic plate subducting under another plate, the subducting plate is always drawn as deep (seemingly tens of km) into molten rock, but the subducted part of ...
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Winter in the Northern Hemisphere in July? Can anyone explain it?

The July 2007 issue of the National Geographic Magazine dedicates several pages to "Climate Change" and "Global Warming". The author explains in detail the Earth's movements and how they provoke ...
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How many days has it been since the Cambrian explosion?

I want to know how to calculate the number of days since an event in Earth's past, and am using the Cambrian explosion as an example. I define a day to be one rotation of Earth with respect to the ...
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77 views

Waves in very thin layer

Elastic waves in the earth are described by the elastodynamic equations \begin{align} \rho \frac{\partial^2 u}{\partial t^2} &= (2 \mu + \lambda) \frac{\partial^2 u}{\partial x^2} + \mu \left( ...
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If all the world's ice were to melt, would this shift the earth's centre of gravity with consequential effects on sea levels?

This question on Maths SE asked how we might calculate the effect on sea level if all the world's ice (ie including the whole Antarctic ice sheet) were to melt. I posted an answer containing ...
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What causes ringing effect when using corner filter?

I used the corner filter (band pass) with this frequency values (8,10,45,50). I get ringing effect on the data. my questions are: what is the name of this effect and the cause? should be removed and ...
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540 views

Using the Born approximation in seismic inversion

In physics, the Born approximation allows us to separate the wave-function in terms of electronic and nuclear components. Why is this concept relevant in seismic inversion? For example in Colombi et ...
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What will be the temperature on Earth when Sun finishes its main sequence?

We know that presently Sun is 4.5 billion years into its main sequence. It has another 5 billion years before it enters the Red Giant phase. We also know that Sun's luminosity increases by 10% every ...
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Is it possible to create ice in poles? [closed]

Is it possible that human can built under the poles a controlled system to create again artificial icebergs? In order keep tight the melting ice and reduce the sea level? Can this system impact the ...
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508 views

Temperature differences in sand

Sand is granular in nature, which allows air columns to trap in between them. As we know that air is an insulator of heat. So here are my questions: Does sand maintain its temperatures close to its ...
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What is the relationship between raw seismic data, CMP Stacking, NMO & Machine Learning

I recently joined a geophysics project to assist with some of their machine learning modeling but am trying to gather the domain knowledge required to participate. Something I don't quite understand ...
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Acoustic impedance in geophysical context

What is the intuition behind acoustic impedance? Yes, I know that it is the opposition to a seismic wave travelling in the medium. But why it is defined as density × velocity? The velocity of a ...
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229 views

Is there a differential angular rotation on Earth?

I asked a question about solar day difference between two latitudes on the same longitude here on the Earth surface. The answer was clear due to constant angular rotation time is the same. Tangential ...
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181 views

Thermal expansion of Earth

Matter tends to change its volume in response to changes in temperature--or, hot things tend to be expanded. Is the thermal expansion of Earth significant? That is, is it significant when compared ...
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What factors explain mountain glacier retreat variability?

It is well known that the majority of the world's mountain glaciers are retreating, but looking at a few LANDSAT images from the 1980s and today I am able to see glaciers that have retreated ...
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230 views

Gravitational Anomaly of a subsurface body

How does the gravitational anomaly measured at the Earth's surface and produced by a subsurface body depend on its depth and on the density contrast of the body relative to its surroundings?
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Plate boundary lon/lat data

I'm working on a map in GMT and am having trouble finding lon/lat data for the minor plate boundaries (specifically the adriatic). Is there a database I can refer to?
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What's up with the “jelly sandwich” analogy of the lithosphere, asthenosphere and mesosphere?

Here's what I know: The lithosphere is hard because it is cold and low-pressure. The asthenosphere is more deformable because of higher temperatures and pressures. The mesosphere is below the ...
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436 views

Why is fluid pressure in a fractured rock reservoir only dependent on hydrostatic pressure?

Why does lithostatic pressure not play a role? (or does it?)
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Is it dangerous to live in Seattle due to the earthquakes?

I'm considering a move/vacation to Seattle, and I'm concerned it may be dangerous due to the risk of an earthquake?
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Why do we consider hydrostatic pressure and lithostatic pressure separately?

In petroleum geology, why do we consider hydrostatic pressure and lithostatic pressure separately? Surely the pressure at any point, whether fluid or rock, at depth is simply equal the weight of all ...
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How do the different densities of the oceanic and continental crust affect earth's outer shape?

I am currently reading a textbook and I am slightly confused at a paragraph that deals with some general facts about earth's outer shape. It mentions that the density of the continental crust is ...
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Where to start with P190s Seismic Navigation Files?

I have a few P190s navigation files from a 2D reflection seismic acquisition shoot and wondering what the best way was to extract UTM's (or latitude and longitude) and depth. I am reading through the ...
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61 views

State of Stress in rotated 2D system

I'm working on the rotation of the state of stress using the book Geodynamics of Turcotte page 101. The 2D coordinate system $x'$ and $y'$ is inclined at an angle $\phi$ with respect to the $x$, $y$ ...
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Did the Three Gorges Dam shift the North Pole by 2 cm?

Numerous sources repeat that, apart from slowing down the rotation of the globe, the Three Gorges Dam caused the geographic pole to shift by 2 cm. For example: https://blog.prv-engineering.co.uk/...
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61 views

How to measure global temperature?

people always talk about global temperature (such as the global temperature goal of 1,5 K) - but how is this value achieved? It seems to me that it clearly depends on where the measuring stations are, ...
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Seismic data acquisition: reliability of high-bandwidth data

In my research, finding and understanding info relating to the lower end of (conventional) surface seismic data acquisition (i.e. 15 - 1 Hz) is relatively simple. However, when I look at specs for a ...
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How do I generate a Moho depth model from seismic refraction data?

There are several permanent seismograph stations in Eastern Canada that have been recording arrival times for over 25 years. Using refracted Pn arrival times from natural earthquakes I would like to ...
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Over what scales can we begin to apply fluid dynamics to accurately model properties of the mantle?

Over what size temporal/spatial scales do geophysicists and geodynamicists begin to apply fluid dynamics to model the mantle rather than elastic/plastic deformation theory?
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How accurate are the resistivity values from the electrical resistivity tomography (ERT)?

Modern ERT methods/devices can provide 2D resistivity profiles for some terrain. How accurate are the resistivity values in those profiles? Are these some sorts of apparent resistivities and one ...
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meaning of Grid resolution [duplicate]

I have some queries regarding grid. What does this mean. The grid has spatial resolution of 1/2 degrees latitude × 2/3 degrees longitude.?
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What is the origin of oil?

Most people may believe that oil comes from dead plants and animals, but there are alternative theories that are known as Abiogenic Petroleum Origin. If oil in generated in this manner it could mean ...
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How to graph gravity as a function of depth, given radius and density?

I need to do this for a planet that has uniform density, and a planet that has two layers. For the first part, I was given that the density was 550 kg/m³, so I made one column in an Excel spreadsheet ...

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