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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6
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1answer
274 views

Unwarranted claim of higher degree of accuracy in zircon geochronology

The uncertainty in the half life of uranium-238 is stated at 0.05% [1]. The same paper gives the date 251.941 myr ± 31 kyr. 251.941 $\times$ 0.05% = 125 kyr. How are the authors justified in ...
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Why are pole reversals not more detrimental to life?

This question is linked to the following question, and has two parts. Mars interdicts approximately 40% of the radiation (per square meter) of the sun that Earth does. It has been claimed that Mars ...
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181 views

How high do you need to be to see Los Angeles from Washington DC?

If you were to stand on a tall building in Washington, DC and looked west, how tall would the building need to be to see Los Angeles? I would like answers based on if the world was flat and if the ...
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194 views

Can the crust be compared to an arch?

Since tectonic plates are held together by lateral stress, friction, and gravity, and the Earth is a sphere, they work just like a full-circle arch or full-sphere dome. So can the crust be compared to ...
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Why is it necessary in seismic imaging to calculate an image of reflection coefficients when one of the inputs is the velocity model?

Note: I'm not at all an expert in this field. I read in the first few pages of Robein (2010; Seismic Imaging, A Review of the Techniques, their Principles, Merits and Limitations, EAGE) that both ...
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184 views

Why do we measure eustatic sea-level from the center of earth?

Earth is rotating so it has a ellipsoidal shape. The measurement will therefore be different from equator and pole. So why do we measure eustatic sea-level from the center of earth?
6
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294 views

Hydrocarbon potential in Ganges Brahmaputra delta

According to Curray (1991): Total sediment thickness beneath the [Ganges–Brahmaputra delta] southeast of the hingezone exceeds 16 km... Considering a normal geothermal gradient and data for oil ...
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413 views

Is the Cameroon Line still an active rift zone?

The Cameroon Line is described by the Oregon State University's Volcano World webpage What is known about the volcanoes of Cameroon? as a a chain of volcanoes extending from Annobon Island in the ...
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Would it be wise to monitor real time human activity to anticipate earthquakes?

Documented strange behaviors of animals before an earthquake could invite us to believe that some of them anticipate tectonic activity. We also know that human complex organization makes it difficult ...
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Time standard for IERS Bulletin A

IERS Bulletin A and Bulletin B contains Earth orientation parameters. These include the time difference between UT1 and UTC and pole position. The values for these parameters are listed once per day, ...
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73 views

What theories exist connecting volcano temperatures to eruption probabilities?

Wikipedia names thermal monitoring as one of the methods for predicting volcanic eruptions. I was able to find some papers (First, Second) on such thermometry and while they are challenging (I retired ...
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170 views

Why is ground water rising on these forest rings?

I am seeking a physical explanation for this; There is huge amount of such a Forest rings in Earth; (Link to Google Maps to one ~400 m Ring) They range in diameter from 30 metres to 2 kilometres, ...
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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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Does dirt compact itself over time? If so, how does this happen?

If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against ...
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98 views

Querying Seismic Databases

I'm trying to find 3-component records of the P-wave arrivals of a variety of earthquakes at seismic stations (specific earthquakes or stations aren't important, I just want a small library of these ...
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201 views

Seismic migration concepts

In Dr Hua-Wei Zhou's book Practical Seismic Data Analysis (2014), he includes and explains figures from previous classic works (i.e. Schneider, 1971) in order to describe migration from a fundamental ...
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How do seismic charges help to investigate the subsurface?

In the film Kong: Skull Island, scientists investigate an island's structure by dropping explosive charges from helicopters: Source: YouTube trailer In reality, geophysicists do something similar ...
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360 views

How much does the electric current within the Earth' core depend on the axis of the Earth's orbit?

I always thought that the movement of the iron core was caused by the axis of orbit of the Earth. Probably that isn't quite as true as I read, because in the core the iron material undergoes types of ...
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155 views

How did the intensity of Earth's magnetic field change through geological time?

Looking at the wikipedia article on the Earth's magnetic field, I see that its strength varies through time. How did Earth's magnetic field change throughout its history, from the beginning of the ...
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226 views

What is the mass of our planet's atmosphere, hydrosphere, and cryosphere combined?

What is the mass of our planet's atmosphere, hydrosphere, and cryosphere combined? How accurate can our estimates be?
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How to define the force at the base of an oceanic crust

In the book of Turcotte and Schubert, Geodynamics I'm trying to solve problem 2.8. The pressure in the water, in the oceanic crust, and in the mantle beneath the oceanic crust are (from equation 2.19,...
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222 views

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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74 views

Mars maar craters explosive style formation gravitational effect

"Maars usually form when magma rises within a fissure and interacts with groundwater. If groundwater ceases to interact with magma at times during the eruption, continued magma ascent to the surface ...
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How are the ZNE, ZRT and LQT coordinate systems defined?

I'm confused about the direction of Z (upward or downward?), R (outward or toward the source?) and T.
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High-resolution laterolog array tool

Does anybody know if it is necessary to apply corrections to the reading given by this logging tool? Corrections such as bed thickness, borehole diameter, invasion, etc.? If so, is there anywhere I ...
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Why did the carboniferous period have so much atmospheric oxygen?

Even if all the carbon dioxide (which makes up less than 1% of the atmosphere) in the air were sequestered by plants, would the atmosphere not remain about 21% oxygen? Why did the carboniferous period ...
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Megathrust earthquakes on subduction zones

I am a beginner in geology and earthquake studies, and learning about subduction zones recently. Question is: do large earthquakes (sometimes referred to as megathrust quakes) occur on any point in ...
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Why can Thomsen's parameter $\epsilon$ be negative in VTI media?

I just got several well log curves, some of which are Thomsen's parameters. They are a result of interpretation of Sonic Scanner tool measurements (Schlumberger). Negative epsilon values appear quite ...
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Does the Coriolis Effect affect a wind from East to West?

I'm studying meteorology for a pilot license and there I was taught as a rule of thumb that wind at higher altitudes is approximately turned 30° clockwise to the wind on the surface due to the ...
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What would change if our earth lacks mountains?

I just asked myself what is the role of the mountains on our planet earth? Well there's a well known role for the climate and weather. But is there a kind of physical or geological role? What would ...
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281 views

Is an underground mine collapse or a tunnel collapse called a sinkhole?

Imagine there's an underground man made structure e.g. a tunnel or an underground train station that collapses creating a depression in the surface. Would that technically be called a sinkhole? What ...
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393 views

What is the tectonic explanation for parallel ridges in the Arctic Ocean?

Looking at a map of the underwater features of the Arctic Ocean reveals three roughly parallel ridges, separated by basins (see image below): Image source The three ridges, as labelled are the Alpha ...
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What percentage of the earth's surface is covered by 2D or 3D reflection seismic data?

It was recently asserted to me that we have no idea what Planet Earth really looks like below our feet. I responded that (mainly oil-industry) seismic data covers a vast area and so actually we have a ...
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What is difference between divergent boundary and hot spot?

As I know, both divergent boundary and hot spot are formed by rise of magma of convention, but divergent boundary is a line and hot spot is a point, is there difference between 2 kinds of rising magma?...
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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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582 views

Is there evidence to delineate where a southern extension of the East African Rift 'plate boundary' is developing?

The East African Rift system is described by James Wood and Alex Guth of Michigan Technological University in the Geology.com web-article East Africa's Great Rift Valley: A Complex Rift System as ...
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What is (negative) wind stress curl?

I'm currently doing research for a paper in school where we need to research on a university-like level. When I read the paper Causes and impacts of the 2014 warm anomaly in the NE Pacific, I found ...
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502 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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194 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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726 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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101 views

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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394 views

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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104 views

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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Is “seismic energy released” a regionalized variable and can be analyzed using geostatistics?

In geostatistics, we can assess and analyze regionalized variables. Tectonic stresses releases in seismically active regions by occurring earthquakes. We can calculate and estimate the seismic energy ...
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114 views

Does subduction of continental crust happen at continental-continental convergent boundaries?

What exactly happens at a continental-continental (cc) convergent boundary? I read myself through the web for the last few days and what I came up with is that such a boundary will start as an oceanic-...
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862 views

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 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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169 views

How can I calculate the sensitivity of a seismometer?

I would like to know if a specific seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but I'm not a seismologist and am trying to figure out how to relate the specs ...
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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.