# 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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### How do I derive the formula for lithostatic (overburden) pressure?

The title pretty much says it. I have the formula: $P = \rho g h$ where $\rho$ is the density, $h$ is how deep the pressure is in the Earth and $g$ is the gravitational acceleration(?). I don't get ...
4answers
4k views

### Are there any other earthquake magnitude scales other than Richter's?

There are sometimes confusion about the magnitude of Earthquakes. What scales, other than Richter's, are used to measure the magnitude of an earthquake? Is there a scale where magnitude 9.0 is ...
2answers
4k views

### Is the epicenter always directly above the hypocenter?

All the graphics I've seen showing epicenters with a hypocenter (labeled focus in the graph below) appear to show that epicenters are always directly above their related hypocenters. Is this correct?
2answers
181 views

### What ice phenomenon are we seeing in this video?

I don't know what this YouTube video shows, but it appears to be half glacier and half "the blob." It almost appears to be "growing" although I assume it's being pushed somehow. Can someone tell me ...
5answers
7k views

### Why is continental crust less dense than oceanic?

Why is it that continental crust is less dense than oceanic, where in fact continental crust is thicker than oceanic crust?
2answers
301 views

### Can rocks have pressure signatures?

Since rocks can have magnetic signatures, as is the case with paleomagnetism, can they store past pressures also? For example, when researchers are trying to determine past ocean levels, they ...
2answers
1k views

### Discrete Slant Stack on seismic data

In the formula for slant stacking (tau-p transform) a substitution t=tau+d/v is made. If we consider the substitution as a vector equation then how can vector d/v ...
1answer
442 views

### Is the Yellowstone National Park unique for its geysers?

The Yellowstone National Park in Wyoming is unique for its large number of "thermal occurrences, of which there are some 30 geysers. This, in turn, appears to be the result of the presence of large ...
1answer
416 views

### How long did it take for Earth's magnetic field to first appear?

Merely what the title states. My knowledge of geography/geology/*logy is limited to high-school, and some snippets, and snatches of conversation. As I understand Earth's magnetic field is attributed ...
1answer
241 views

### Generic pedo-transfer functions to compute field capacity and wilting point from sand/silt/clay?

I have a model (Miguez et al 2008) that defines wilting point as the soil water content below which there is no transpiration (from Johnson et al 1993). Field capacity is defined as the volume of ...
1answer
117 views

### Why is there a bend in the Lomonosov Ridge?

Why is there a bend in the Lomonosov Ridge? This is a supplementary question to that asked by Sabre Tooth in What is the tectonic explanation for parallel ridges in the Arctic ocean
1answer
330 views

### Relation between fault rupture aspect ratio and slip rate?

I am modeling a fault surface (which I consider to be a plane rectangle). I got the area of the surface, but the orientation is unknown, which can be found out if the aspect ratio of the rectangle is ...
1answer
169 views

### How do we determine subsurface composition?

Let's assume that a seismogram $s(t)$ is the convolution $s(t)=r(t)g(t)$ between a source signal $r(t)$ and propagation effects $g(t)$. If the source signal $r(t)$ is known, then we can obtain the ...
1answer
168 views

### What efforts have been made to separate the microseismic events related to wind-related ocean waves from the components of volcanic origin?

I have read the question What generates the microseism? and it's accompanying answer. In [#1, cited below], they use the azimuth values of seismographic activity on the flanks of the volcano ...
1answer
267 views

### What happens to the higher frequency content of the tremors associated with a volcanic eruption?

From [1]: The main characteristics of volcanic tremor depend strongly on whether a volcano is erupting explosively and on the intensity of the event. Long before an eruption, tremor is ‘narrow-band’ (...
2answers
23k views

### What is the difference between a geologist and a geophysicist?

What are the main differences between geologists and geophysicists?
3answers
2k views

### What geophysical instruments should I use to detect water without drilling?

How can one detect (preferably artesian) aquifers nowadays that a lot of sensors are available? Should I use ground-penetrating radars, neutron detectors, or any other advanced devices? Can seismic ...
1answer
376 views

### Carbonate reef not horizontal in seismic section?

Carbonate reefs usually appear as homogeneous bodies surrounded by sediment layers in seismic reflection data, but in the figure below the high amplitude reflection from the top of sediment (layer 2 ...
1answer
5k views

### Why is the South Pole colder than the North Pole?

This question popped into my head because I am designing a fictional world map, and I was wondering what factors influence the amount of ice at poles. I want to know why there is much more ice ...
2answers
299 views

### Is there a “submerged object” in Australia that causes a magnetic deviation of 20 degrees?

This answer quotes this blogpost as an example of a magnetic anomaly: Basalt formation, “Mt. Jim”, in remote north-east Victoria, Australia, has a magnetic anomaly -20 degree magnetic compass ...
1answer
1k views

### What are the challenges in predicting lithology directly from acoustic impedance?

Seismic inversion methods help to visualize the subsurface layers of the earth in terms of petrophysical properties (e.g. impedance). Still some geophysicists use the final inverted impedance model in ...
3answers
2k views

### Is it known what determines the rate with which plate tectonics occur?

When investigating the rate of the move of the Hawaii hotspot, from information provided here on Stack Exchange Earth Science, I cannot find a determination of cause for the rate, that does not point ...
2answers
209 views

### What is the geothermal potential of a volcano?

If there were lots of geothermal plants—even mobile ones—near a volcano, how much power could this provide? Could the sapping of some of the heat energy make the volcano less likely to erupt?
2answers
388 views

### 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 ...
1answer
2k views

### What tectonic structures exist on the Eurasian - North American plate boundary in eastern Siberia?

It is reasonably well known that the North American tectonic plate includes a portion of eastern Siberia. What is often typical in plate tectonic maps is that the actual plate boundary is often drawn ...
1answer
104 views

### What properties must a rocky body possess in order to exhibit the magnetic dynamo?

The magnetic field of the Earth is produced by the magnetic dynamo. What conditions must a rocky body possess in order to exhibit the dynamo? Clearly, the planet's interior must not be too cold. ...
1answer
4k views

### What is a massif and what differentiates it from other types of mountains?

Wikipedia says that a massif is "a section of a planet's crust that is demarcated by faults or flexures." It goes on to list mountain-like objects. Is it not true that most mountains are created by ...
1answer
2k views

### How does one determine the optimum offset in a seismic survey?

I was going through a report on MASW (Multi Station Analysis of Surface Wave) and found this "To avoid the aliasing in the space domain, geophone spacing (Δx) needs to be less than half of the ...
1answer
141 views

### How far from basalt bedrock can magnetometic survey find archaeological features?

Magnetometry is used to find archaeological features such as stone walls or ancient hearth. But it usually cannot be used for archaeological prospection in areas where the bedrock is strongly magnetic....
1answer
126 views

### 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 ...
1answer
601 views

### Stochastic seismic inversion

Could anyone recommend a free and reliable software capable of Stochastic seismic inversion for my project? am aware that Petrel is capable of Genetic inversion based on a non-linear multi-trace ...
1answer
202 views

### How quickly is the Earth shrinking?

Except for ice, acetic acid, bismuth and gallium and a few other things materials generally shrink when they cool and solidify, so I'm pretty sure Earth has as well. It probably wouldn't be ...
1answer
1k views

### What geological mechanisms result in the great depth of the Mariana Trench?

According to the Mariana Trench Oceanography page is at a maximum depth of is 11,033 meters (36,201 feet) The 'Challenger Deep' being the name of the deepest point. I understand that it is a ...
0answers
107 views

### Where did the energy released due to gravitational binding energy of the Earth go? [closed]

The gravitational binding energy of the Earth is $2×10^{32} J$, so the same amount of energy must have been released during the Earth's history. According to this and this, the current internal ...
5answers
4k views

### Why does New Zealand and cold countries have volcanoes?

I understand that volcanoes are caused by the heat that causes high intense pressure below the Earth's surface. This intense pressure gets released and causes magna which becomes hot lava to flow out ...
3answers
597 views

### How bad is geo-engineering?

It is just curiosity that forced me to ask this question. At some point in time, if we can't control global $\sf{CO_2}$ emissions, temperature will increase until a tipping point and it will be a ...
2answers
1k views

### How do Rossby Waves in the ocean form?

So on land, I believe that one factor in their formation is due to inhomogeneities in surface heating between land and ocean (and also inhomogeneities in surface heating due to terrain effects like ...
3answers
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### Why is the lithostatic pressure gradient 1 psi/ft? How is it derived from density?

Why is the geostatic (or is it the lithostatic?) gradient 1 psi/ft? How is that derived from g/cc? Thanks.
1answer
940 views

### How isotropic is the Earth's inner core boundary?

Often, in texts (particularly for schools etc) depict a smooth spherical isotropic boundary between the inner and outer core, as shown in the image from this USGS public education page: The inner ...
1answer
467 views

### Is the iron on Earth's crust a leftover of the Iron catastrophe, or it was brought back by volcanoes?

When pondering the hypothesis of the Iron catastrophe, that seem to be widely accepted nowadays. It surprises me that currently the crust still contain a significant amount of Iron (5.6% in weight). ...
1answer
3k views

### 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, ...
2answers
632 views

### What are the striations or ridges in the eastern Pacific Ocean?

Messing around on Google Earth recently I noticed a number of striations in the Eastern Pacific. These appear in an East-West orientation and seem to start on the North and South American continental ...
1answer
613 views

### Books for learning applied seismic geophysics

I am a software developer trying to learn applied geophysics. Specifically I am interested in seismic attributes. I have a strong background in mathematics and signal processing and therefore grasp ...
1answer
473 views

### Is altitude of everything decreasing due to sea level rise?

We know that sea level is rising, though some people say climate change is fake. Altitude is defined as the height of something measured from sea level. Since sea level is increasing, and the ...
1answer
235 views

### Does the global temperature vary daily (hotter and colder days)?

Earth's current average global temperature (i.e. including hot deserts and cold polar caps) is reported be somewhere between 14°C and 16°C (depending on sources and methods). This temperature varies ...
2answers
796 views

### Terrain correction for gravity data using Nagy, 1973

I am working with an algorithm for terrain correction of gravity data. I am using Nagy, 1973. However, I could not get the results I need. So, this is the problem. I have this function where x,y,z ...
1answer
206 views

### What is the current status of geophysical global cooling theory?

Plate tectonics effectively rubbished the theory of geophysical global cooling as a means of explaining many surface features on the Earth. However, this wiki says that the same process is responsible ...
1answer
160 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 ...
3answers
517 views

### Why is the elevation of the Iberian Peninsula so high?

The Iberian peninsula lies more than 600 m above sea level, on average, far above similar geological regions in western Europe. Even tectonically undeformed areas in the inner basins present a ...
1answer
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 ...