# 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.

383 questions
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### How to calculate seismic moment from seismograms?

I was told that Seismic moment is determined by the observed spectral levels of the receiving waves. But I don't quite understand what it means. How is this done in practice? Do you need ...
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### What is seismic stretch in geophysical method?

What is seismic stretch in geophysical method ?
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### Forest rings shape regularity

In the answer to "Why is ground water rising on these forest rings?" it is written: these rings are too numerous and too regular in shape to be related to either kimberlites or (even more ...
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### Is there a high-temperature, non-magnetic glue that doesn't dissolve in water?

I have very small mineral samples, and I'm looking for a glue that can hold them through a sample preparation process that I'm doing: heating, polishing, and measuring magnetic moment. For that I want ...
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### Rossby radius as horizontal scale

In the introduction of "Geographical and monthly variability of the first baroclinic Rossby radius of deformation in the South China Sea", the authors states: In both theoretical and observational ...
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### How can this fountain of (hot?) water coming out of the Earth arise?

In this video from min. 7:00 is after digging in the Earth a fountain created of water. Is this due to the pressure of the water in the Earth, if so how did it get there and how did it get such a high ...
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### SEGD and SEGY recorded data

What is the difference between a segd recorded data and a segy recorded data and can we convert from segd to segy and vice versa?
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### Why is the Inner Core of the Earth solid in spite of being the deepest and the hottest layer of the Earth [duplicate]

I have been recently studying about the layers of the earth and I got stuck with the question that why is the inner core of the Earth solid in spite of being the deepest and the hottest layer. I hope ...
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### 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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### Calculating error in measuring geomagnetic Anomalies using IGRF

In textbooks it is mentioned that Magnetic anomaly = Observed Geomagnetic field - Theoretical Geomagnetic field observed value is measured using instruments like proton precession magnetometer or ...
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### 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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### What is trace-based seismic Inversion

Looking through different literature articles and books concerning seismic inversion - mostly post-stack - phrases like "trace-based" and "model-based" keep appearing. I know that model-based in when ...
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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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### How to calculate cumulative moment magnitude?

What is the proper way to calculate cumuluative moment magnitude if I know the moment magnitude of several earthquakes?
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### Why is the temperature between the earth core and surface not distributed linearly?

So I read somewhere that the inner core temperature of Earth might be as high as 7000 °C. Depending on the composition of the different layers towards the surface, the temperature should decline ...
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### measuring fracture length and width using PKN and KGD models for hydraulic fracturing?

I am trying to understand PKN and KGD models for hydraulic fracturing. I am wondering why equations for fracture width and length does not include 'breakdown pressure' (pressure at which fracture ...
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### Is winter hotter at the Equator?

I live in the Northern Emisphere. One of the things I have been taught when I was in high school is that winter is colder than summer because in that season we're at an unfavorable angle and nights ...
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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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### 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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### Is there any case that changed from earthquake safe zone to danger zone?

Is there any case that changed from earthquake safe zone to danger zone? As plates move, I think that earthquakes belt will change over time. But is there really a case in which the earthquake-safe ...
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### Cooling time of basalt flows?

In places like the Giant's causeway in Ireland (Antrim basalts) there are columnar basalt flows of 100 metres or more. I'm aware that the cooling mechanism is complex, but is there any rough and ready ...
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### Is the Earth heated up by the tides?

Reading about moons of other planets they often get heated up by the tides so for example Io and Europe of Jupiter get friction by which eruptions and liquid water can arise. But is there also an ...
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### 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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### What current evidence is there for a Glacial Hudson River Valley deluge?

Some have studied the Lake Missoula glacial dam breaking West and having created the Coulees of Eastern Washington. Who's studied the glacial dam breaking South and having cleared the Hudson River ...
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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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### 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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### Why do buoyantly rising mantle minerals melt, yet buoyantly rising atmospheric waters condense?

In the mantle, minerals contained in buoyant plumes of rock undergo phase changes from solid to liquid (decompression melting). In the atmosphere, waters contained in buoyant plumes of air undergo ...
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### How much water is the atmosphere losing to space?

Up until recently, I was under a (wrong) impression that the amount of planetary cumulative water resources was finite as I believed its escape from the atmosphere was impossible. I believed that, ...
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### Does the Earth receive a net charge from the aurorae?

The sun radiates a lot of charged particles to the Earth. When the magnetic field of the Earth lines up to the poles, we get the beautiful polar lights. But are there as many negative charged as ...
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### How much of the Earth's heat is caused by the hot centre?

What is the percentage of the Earth's warmth that the Earth's hot centre is responsible for? What would be the temperature of the atmosphere if the Earth's centre was 18° C (average temperature on the ...
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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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### 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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### In quasi-geostrophic frontogenesis, what happens if the potential vorticity is negative?

In particular, what happens if the Sawyer–Eliassen equation cannot be solved? I know that a condition for the Sawyer–Eliassen equation to have a solution is $F^2 N^2 - S^4 >0$, which means that the ...
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### Capillary rise experiment and obtainable information about the porous medium

I have access to rock core(s) and vacuum saturation chambers as seen in the image below. I can dry the rock core using an oven, measure its geometry and mass. I can place it into the vacuum ...
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### Could evidence of a signal from an exocivilization be found in the geologic record?

We know that the current SETI efforts have not found evidence for the existence of intelligent exo-civilizations (XCIV). There also has not been any evidence found of ancient non-human civilizations ...
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### What factors affect daily temperature range?

I was wondering if the difference between the low temp and the high temp depended on just the humidity content and the altitude of a place. Or are there more factors? What about the time of year? How ...
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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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### 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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### 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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### 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 causes the earth to be a good grounding system?

When working with electricity, rubber shoes are recommended because they prevent current from running through your body. But I've read that usually the earth is more negative charged than positive. ...
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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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### 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 to correct PSMSL data for GIA?

I have a PSMSL RLR (revised local reference) sea level dataset with records from various tide gauges. Can anyone explain how to correct them for GIA (glacial isostatic adjustment) using the ICE-5G ...
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### Earthquakes at plate boundaries

I was looking into tectonic plate boundaries and earthquakes with pictures like these One thing that is quite obvious is that some of the plate boundaries have very thin zones of earthquakes, ...
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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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### Why is the density of Earth higher at the core

If gravitation decreases as we approach the core and if density is a function of gravity we should expect a void core. Unless the accretion disk was formed starting with the objects of highest mass ...
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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 ...