# 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.

427 questions
Filter by
Sorted by
Tagged with
2k views

### Why Vp/Vs and not Vs/Vp?

The relation between shear wave velocity (Vs) and pressure wave velocity (Vp) is often expressed as Vp/Vs. Wouldn't the opposite be more logic? Vs/Vp would never lead to division with zero and the ...
116 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
343 views

### What is this strange feature on Mars in Valles Marineris

While I was browsing Mars on Google Earth, I stumbled upon an interesting feature on one of the slopes of Valles Marineris. The feature seems unique in the sense that I couldn't find any similar ...
2k views

### 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 ...
420 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 ...
5k views

### What would be the first thing which will render the Earth uninhabitable?

There are quite a few things which can make an otherwise habitable planet uninhabitable, and some of these will eventually happen, sooner or later: engulfed by its star when it becomes a red giant ...
931 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 ...
113 views

### What geophysical knowledge have we learned by the construction of IceCube?

The IceCube is a particle detector at the South Pole that records neutrino interactions. It has lead to many fascinating new discoveries in the field of astrophysics (e.g., 1, 2) and it was awarded "...
553 views

### 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. ...
1k views

### What do the derivative or the integral of amplitude of a seismogram mean?

I'm doing a project in which I'm analyzing earthquake seismogram waves. I used a program to graph the exact amplitudes and how they changed over the course of a single earthquake. For the project I ...
2k views

### Can impact events cause widespread volcanic activity on the other side of the planet?

The currently accepted theory for P-T mass extinction is environmental change triggered by the Siberian Traps volcanic activity. A paper(1) suggests that the Siberian Traps were caused by a hotspot ...
773 views

### What are the non-anthropogenic causes of The Netherlands' low elevation?

A large area of The Netherlands is below sea level. There are two non-anthropogenic reasons that I can think of: Compaction of delta sediments that lie below the country, A side effect of the ...
1k views

### Why is ocean surface velocity around 3% of wind velocity?

Many introductory level textbooks suggest that, as a rule of thumb, the velocity of the ocean surface is around 3% the wind velocity at 10 meters above the sea surface. For instance, Ocean ...
798 views

### 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 ...
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 ...
106 views

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

The gravitational binding energy of the Earth is $2Ć10^{32} J$, so the same amount of energy must have been released during the Earth's history. According to this and this, the current internal ...
1k views

### What fraction of dry land is below sea level?

Someone just asked me if it would be practical to counter the rise of sea level by pumping water into storage on land. It struck me that if there is enough land below sea level, this would require ...
12k views

### 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.
186 views

### How are Richter magnitudes of past earthquakes estimated?

In reading about historical major earthquakes, in particular, the Great Shaanxi Earthquake that killed approximately 830,000 people in July, 1556, there is a claim made about the approximate Richter ...
204 views

### Is angular momentum preserved in a gastropod fossil?

In the Northern hemisphere the rotation of the Earth determines a counter-clockwise spin on matter. Weather, ocean currents all are related in that spin. I wonder if my snail fossils preserve the ...
458 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 ...
1k views

### Does the climate have any effect on plate tectonics?

After reading the question and answer Is there any correlation between La NiĆ±a/El NiĆ±o and seismic activity?, I am wondering if there is any evidence (case studies) to suggest that longer term ...
319 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 ...
208 views

### Why does seismic activity shed light on the inner core rigidity?

Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that: Earth was discovered to have a solid inner core distinct from its liquid outer ...
1k views

### Has an entire plate ever subducted?

We know that plates can subduct, causing one plate to be pushed into the core by another. As the plates move, the subduction continues, pushing one plate under the other. If this process continues, ...
2k views

### At what point does plate tectonics stop?

As the core and mantle of the earth cools, it will reach a point where new crust cannot be produced. How can this point be calculated? If we can, has anyone done such calculations? Thanks!
2k views

### converting SU file to ASCII format in seismic unix using OpenSeaSeis

I have tried to convert a Seismic SU file to ASCII format in seismic unix using openseaseis module named "sutoascii". I have already tested the SU file by opening it in SeaView Seismic Viewer and ...
402 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 ...
823 views

### Why are minerals found in “large” quantities and not scattered throughout the earth as individual atoms?

Heavier elements are created in stars. After stars die they scatter these heavier elements throughout the universe. These elements eventually gather to form planets. But why do we find "chunks" of ...
6k views

### Farthest point from the center of the Earth

At first glance, this seems like such a simple question of "What's the highest point on Earth". However, I also know that the Earth isn't perfectly round. So that "highest point" may be in a ...
637 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 ...
114 views

### 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 ...
698 views

### Successful Earthquake predictions

Have there been any instances where seismologists have successfully predicted the occurrence of earthquakes? If so, then why has the number of scientists working on this area has declined (as ...
1k views

### Temporal Resolution of Seismic data

Radius of the Fresnel zone is given by $$Rf=(v/2)(t_0/f_\mathrm{dom})^{1/2}$$ where $v$: velocity of layer $t_0$: two way travel time $f_\mathrm{dom}$ :dominant frequency in the spectrum This shows ...
355 views

### How much silicon is in the Earth's core, and how did it get there?

With some informal conversation with a peer of mine, he had suggested that there is evidence (which he couldn't find,but had remembered reading) that there was Silicon in the Earth's core. I referred ...
413 views

### To what accuracy and precision do we know the volume of the Earth?

Satellites such as GOCE and GRACE measure the geoid with unprecedented accuracy. Altimeters can determine local surface elevation with millimetre-precision. This makes me wonder: to what precision ...
103 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. ...
758 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 ...
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 ...
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 ...
343 views

### How accurately can explosions be triangulated from the IRIS seismogram data?

There's a bunch of armed conflicts going on right now. What are the lower boundaries on accuracy of triangulating and timing man-made events from the IRIS datasets (accessible, for instance, with the ...
343 views

### How are Earth's rotational changes due to large earthquakes calculated?

According to NASA (and many other sources), Japan Quake May Have Shortened Earth Days, Moved Axis and in the answers to the question here What geophysical events can (temporarily) increase the Earth's ...
50k views

### How long until Earth's core solidifies?

How much longer does Earth have until the core turns solid? Does global warming change these estimates at all?
2k views

### How do you calculate the depth of penetration in a Schlumberger array?

In a resistivity survey, how do we calculate the depth of penetration for a Schlumberger array?
165 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 ...
142 views

### 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 ...
148 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 ...
86 views

### 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 ...
1k views

### Interpretation of a seismogram (three components)

In most cases (as shown in the figure below), a seismogram shows data from three components: North-South East-West Vertical/depth(z) However, if these components are not marked and all we have are ...