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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9
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1answer
162 views

How should I choose the block size in constrained model-based inversion?

In constrained model based inversion, block size (in ms) is one of the inversion parameters. Specifying the block size value in the software divides the pseudo-velocity log into that number of layers ...
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153 views

What makes the conditions at the core/mantle boundary ideal for aluminum to combine with other elements besides oxygen?

Recently, steinhardite was accepted as a new mineral by the International Mineralogical Association. It's quite an interesting story in its own right. There's an interesting article in New Scientist ...
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Impact craters vs volcanic explosions on Mars

A maar is a shallow volcanic crater with steep sides that is surrounded by tephra deposits. The tephra deposits are thickest near the crater and decrease with distance from the crater. Source: http://...
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What tectonic structures delineate the split between the Australian and Indian tectonic plates?

Growing up, when looking in textbooks and other references about plate tectonics, there was always the Indo-Australian (or Indian-Australian) plate, such as shown below: Image source: The Geologic ...
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What are the factors that dictate a given topology for seismometer placement around a volcano?

The image below (borrowed from [#1]) shows the topology of the seismometers around the volcano Stromboli. In the text, they explain the following: The seimometers were set on the flanks of the ...
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Dependence of solar irradiation through the atmosphere on Sun's altitude

I want to show that the higher the Sun's altitude, the higher the solar irradiation through the atmosphere, through simple experiments. However, I don't have the instrument that measures irradiation. ...
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3answers
424 views

How do archaeologists address time dilation when analyzing carbon dating results?

It is a proven fact that the gravitational force exerted upon an object directly affects that objects experience of time; the greater the gravity, the slower time passes, and visa versa. While the ...
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Does the climate have any effect on plate tectonics?

After reading the question and answer Is there any correlation between La Niña/El Niño and seismic activity?, I am wondering if there is any evidence (case studies) to suggest that longer term ...
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7answers
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Does a mountain top have higher gravity than a nearby sea-level surface?

Regardless the latitude and centrifugial 'force' is the gravity on mountains higher or lower than at sealevel? Gravity is depending on the radius to the centre and the mass. Now if you are on a ...
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How did the Ural mountains form?

A nice picture for "how mountains formed" on Earth is due to the motion of tectonic plates. As the plates crash together, mountains may get "pushed upwards". However, a quick look at a map of the ...
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Why do deviated wells show poor correlation to seismic data?

Well correlation and calibration is an important step in any type of seismic inversion. In order to obtain a good broadband frequency model, the synthetics should be correlated with original seismic ...
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822 views

What is the total Earth's interior energy budget?

What is the total Earth's interior energy budget? What is the heat flux per m2 that warms the Earth surface because of the Earthy's internal heat. How much of that heat is replenished from the ...
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Changes in Earth's orbital and rotation speeds

What are the Earth's maximum and minimum orbital speeds around the Sun? Is there any way to calculate orbital speed at any point of Earth's orbit? Is there a way to relate this to the calendar? Does ...
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How fast does the Earth's inner-core spin?

How fast does the Earth's inner-core rotate compared to the Earth's daily rotation? The inner core is always described as a spinning/rotating solid core while the Earth has a single revolution per ...
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How viscous is the Earth's mantle?

I'm posting here to get some more expert information based on this question. If the Earth were to stop rotating, removing the centrifugal force causing the equatorial bulge, how long would it take ...
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What is meant by phase-change in mantle?

Phase transition usually means changing from liquid to solid phase. But in geology literature we come across transitions from one mineral to other mineral. For example olivine-spinel transition at 410 ...
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142 views

Regarding velocity of P/S-waves

I feel like I am missing something blindingly simple, but I am curious about something. We are given the velocity of a P-wave as $v_{p} = \sqrt{(K+\frac{4}{3}μ)/ρ}$. So I am to understand ...
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How do we convert the seismic trace wavelet to zero phase which is in mixed phase?

As we know the mixed phase data would not give the "real TWTT" through the medium. We need a zero-phase wavelet that can directly correspond to the time taken to travel in a given media. So my ...
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328 views

Laboratory simulation of the Earth's magnetic field

I remember reading an article where a scientist was able to make a spinning iron tube with liquid nickel inside and it created a magnetic field, providing a laboratory-scale simulation of the ...
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128 views

Magma resultant from group 1 and group 2 elements?

I was recently speaking with a geology professor over lunch at a university who has a theory that I've never heard before. His postulation was quite compelling and I was hoping to do a little digging ...
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Why does the wind periodically change direction?

Image Subtitle: Wind going across the page - and changing direction To clarify, imagine you were sat in a boat in the middle of a lake recording the wind direction every minute. You notice that the ...
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How do I extract seismic amplitude on an interpreted horizon?

It seems that seismic amplitude extracted on an interpreted horizon is good for showing channels. E.g.:http://seismicatlas.org/entity?id=98a83c60-ea81-47cc-9304-6041f6ec5277. It seems that often the ...
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334 views

What causes the entrainment of atmospheric gases towards a volcanic ash/tephra plume?

I understand that volcanic ash plumes can only rise to great heights (e.g. 50km) with the help of some other processes, as the velocity of the material ejected isn't great enough to send it high into ...
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What is the long term impact of large scale removal of material from subterraneal caches on the structural integrity of the soil?

For example, sinkholes can be human induced: New sinkholes have been correlated to land-use practices, especially from groundwater pumping and from construction and development practices. ...
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Are there measurement techniques that can help determine the exact geometry of a volcanic vent?

In a previous question What happens to the higher frequency content of the tremors associated with a volcanic eruption?, I asked about the high(er) frequency content of a volcanic eruption. In the ...
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Checking the bedrock with radiowaves - how does it work?

I've heard long ago that the rock material deeply below surface are checked by a device that acts like radar - it sends radiowaves into the ground, and geologists find out from reflections that what ...
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254 views

Seeming correlation between time of day and earthquakes

I live in a generally geographically active area (Southern California, near the San Andreas fault, if that matters), that has had two relatively minor earthquakes that I have felt in the last week (in ...
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Cross-line fold of a towed-streamer survey

On page 29 of the book 3D Seismic Survey Design by Gijs O. Vermeer, Vermeer says that the equation for a maximum fold in a 3D survey is the following: $M = M_i \times M_c$ where $M_i$ is the inline ...
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151 views

Flexure of a viscous lithosphere - derivation

I have been trying to figure out solution for the fourth order differential equation of flexure for a viscous plate. The fourth order differential equation for a viscous plate is given as $$Dv*\...
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681 views

What is a Geophysical Model Function (GMF)?

I have heard the term mentioned many times in seminars, and in papers on remote sensing. What does it mean? References would be helpful if available.
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Calculating the displacement of a fault

In the calculation of scalar moment magnitude of an earthquake we have the formula $$M_0=\mu AD$$ where: $\mu$ is the shear modulus of the rocks involved in the earthquake (in Pa) $A$ is the area ...
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Distance to epicenter vs distance to focus

I am not really a "budding seismologist." I am a chemistry/physics teacher teaching an Earth science class (low academic level) in a small-town high school. (My college coursework in earth sciences = ...
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186 views

Geometrical differences of subduction zones

I am looking for geometrical differences in subduction zones. What are the differences, in dip, curvature of the interface, thickness of the plates etc.? There are differences between the Chile and ...
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Are there any signs on the Earth's surface that indicate a shrinking iron core? [duplicate]

It appears that Mercury shows some cracks on its surface that were not caused by moving tectonic plates but by shrinking due to the inner metal core cooling. The Earth is also cooling down, but are ...
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Are old geophysics textbooks useful?

I have had much success with old textbooks in mathematics. Generally, for any branch of mathematics that I (as a non-mathematician) would like to learn or re-learn, I can buy a classic textbook from ...
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5answers
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Are the oceans rising or the continents going down? How can we know?

The century old sustained rising of oceans, at a rate of 2-4 mm/y, remains a unexplained phenomenon; there is no correlation with temperature variations, so it is not due to the thermal variation of ...
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2answers
926 views

How did Great-Britain separate from France?

Looking at continental plates both France and GB lie on the Earasian plate. Now those plates moves and created our continents of today out of Pangea. But a lot of pictures shows that France and GB ...
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692 views

Why do most seismic inversion methods ignore high frequencies?

Different post-stack inversion methods such as model based, sparse spike, colored and recursive inversion methods use high cut frequency impedance logs (low frequency) and mid-frequency seismic trace ...
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278 views

Incised valleys and hydrocarbon potential

The Wikipedia page on sequence stratigraphy states: Sandstone bodies associated with incised valleys are good hydrocarbon reservoirs. Can anyone elaborate on this statement and the reason behind ...
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2answers
267 views

Predicting earthquakes using disturbances in DTH TV transmission

It is said that before an earthquake happens, a viewer experiences disturbances in DTH TV transmission in the form of distorted images on the screen which automatically correct after a few seconds. ...
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4answers
523 views

In the oil field, when a vertical cylinder coring sample is taken, how is the core severed at the bottom and removed from the formation?

I would like to know how the core is cut off at the bottom of the drill. I also would like to know how the core is brought up to the surface without slipping out and falling back down.
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Should RTM amplitudes (pre- and post-stack) be related to rock physics properties?

There is as huge uplift in the image quality near and under salt bodies (e.g. the Middle Miocene of the deepwater Gulf of Mexico) by using reverse time migration or RTM. We can now make accurate ...
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516 views

What “g” would be needed to keep helium on Earth?

I know that helium is a very light and rare gas on Earth because Earths gravity is not strong enough to keep it. Instead, helium and hydrogen are rising through the atmosphere and escape into outer ...
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656 views

petrophysical crossplots

I recently developed a computer program that generates some petrophysical and elastic parameters from well logs such as water saturation and hydrocarbon saturation, bulk volume, irreducible water ...
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142 views

What is a fault?

Curious if to what degree it is possible to cluster epicentres as originating from a single formation/fault? Seems like it is possible that apart of the issue might being able to map the hypocentre of ...
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Why do tectonic plates have a tendency to drift closer to the equator?

There are many factors that drive the movement of tectonic plates on the surface of asthenosphere, and some of these factors have a larger contribution than others (e.g. slab suction). One driving ...
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What physical measurement / elevation is used to define Earth's radius?

Earth's radius is usually given as 6378137 meters (equatorial radius), its flattening is defined as 1/298.257223 (WGS84), and thus its polar radius is calculated as 6356752 meters. However, the ...
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Compute direction of gravity vector

As I understand to compute vector of gravity not saficient to compute normal to elipsoid, but we need to computer normal to geoid (by definition geoid is a surface to which the force of gravity is ...
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Available Matlab code to design Seismic Colored Inversion Operator?

I want to apply seismic colored inversion technique to my datasets. Is there a Matlab code available that I can easily use? Are there any other recommended codes to apply seismic colored inversion?
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What is the meaning of seismic spectral blueing?

What is the meaning of seismic spectral blueing? Please cite any good introductory materials if possible.

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