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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17
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0answers
218 views

How much heat is transported from the interior to the surface in the form of hydration enthalpy?

Heat is transferred from the interior to the surface through several methods. One is simply the conduction of sensible heat through the crust - I would guess this accounts for most of it. But some is ...
14
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153 views

What are the ground motion prediction equations for 3-D ruptures?

Ground motion prediction equations (GMPEs) estimate ground motion at any given site due to an earthquake at a distance. There are many such equations, each with different parameters. Can somebody ...
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109 views

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 ...
6
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1answer
109 views

Where can I find an anisotropic PREM-like model for Earth's interior?

So, I just discovered PREM (the Preliminary reference Earth model) which models the density distribution of matter inside the Earth to any depth. The PREM is very convenient but since it only depends ...
6
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71 views

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 ...
5
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65 views

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 ...
4
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41 views

Range of frequencies of the Schumann resonance?

Crossposted at Physics SE As the surface-ionospheric gap acts as a resonator for electromagnetic waves, it should have several harmonic values from the base, fundamental frequency of 7.83 Hz. These ...
4
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0answers
110 views

How do the Andes get so high?

I'm interested in the limiting factors on the height of mountains. There is a very good explanation at https://www.quora.com/How-tall-can-a-mountain-become-on-Earth-Neil-deGrasse-Tyson-says-Mount-...
4
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98 views

Did the Three Gorges Dam shift the North Pole by 2 cm?

Numerous sources repeat that, apart from slowing down the rotation of the globe, the Three Gorges Dam caused the geographic pole to shift by 2 cm. For example: https://blog.prv-engineering.co.uk/...
4
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78 views

How do you choose appropriate parameters for a lowpass filter when filtering a Bouguer anomaly?

I am trying to filter my Bouguer anomaly data to remove the short wavelength features. I have created a lowpass filter to achieve this, but I am wondering how I can more objectively choose my cutoff ...
4
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2answers
161 views

Can an igneous rock have a Vp of less than 1000 m/s and need blasting to excavate?

I have run a 60 m refraction seismic line on a mountain summit. The environment was noisy (wind would be the principal agent) and quite difficult to pick first arrivals. It resulted in 800 m/s. A ...
4
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49 views

How do I generate a Moho depth model from seismic refraction data?

There are several permanent seismograph stations in Eastern Canada that have been recording arrival times for over 25 years. Using refracted Pn arrival times from natural earthquakes I would like to ...
4
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48 views

Over what scales can we begin to apply fluid dynamics to accurately model properties of the mantle?

Over what size temporal/spatial scales do geophysicists and geodynamicists begin to apply fluid dynamics to model the mantle rather than elastic/plastic deformation theory?
3
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44 views

Coriolis parameter approximations

When solving equations involving the Coriolis parameter $f = 2\Omega\sin{\varphi}$, I often see the $f$-plane (constant) or the $\beta$-plane (Taylor expansion) approximations. If I'm solving ...
3
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37 views

What is the electrical conductivity of a liquid Komatiite?

I am searching for previous work that has determined the electrical conductivity range for komatiites at the surface. Does anyone have some values or references?
3
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45 views

How hot would days get if it were always the solstice in the northern hemisphere?

Imagine the Earth's axis of rotation were to precess in synch with the orbit of earth around the sun so the north pole always pointed towards the sun (same current axial tilt of about 23 degrees). ...
3
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66 views

How much would the ground be displaced in a magnitude 11 earthquake?

In a magnitude 5 earthquake, the ground shakes violently and it's often impossible to stay upright. This is caused by about 50-120 cm of displacement of the ground. But how much would the ground move ...
3
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53 views

Hypothetically, in the near future, could gas hydrate pingos erupt?

Could gas hydrate pingos erupt? If so, how quickly? And how much CH4 could they release? I'm sorry if the questions sounds silly. I'm new here and I don't know much about gas hydrates and oceanography....
3
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39 views

How long for tectonic plates to develop from a planetary, molten planetary surface?

On Earth or an Earth-like planet, how long does it take for a molten surface to solidify into planetary crust, and how long does it take for that crust to develop into tectonic plates?
3
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213 views

Cratonization - how did the Archean cratons form?

Before the onset of modern style plate tectonics and the Wilson cycles in the late Archean, it is thought that smaller units of continental crust, called cratons, roamed the oceanic crust over a more ...
3
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41 views

What is the minimum temperature difference to drive mantle convection?

The condition for convection to cease is that the Rayleigh number $$\mathrm{Ra}=\frac{g\rho\alpha L^3\Delta T}{\kappa\nu}\lessapprox 10^3.$$ For the Earth's mantle I have seen estimates of $\mathrm{Ra}...
3
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50 views

Why an inertial gyro has a frequency and a geostrophic gyro does not?

Inertial flow is given by the balance between Coriolis and centrifugal forces. A geostrophic flow is given by a balance between Coriolis and the gradients of pressure. The frequency of the inertial ...
3
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73 views

Seismic data acquisition: reliability of high-bandwidth data

In my research, finding and understanding info relating to the lower end of (conventional) surface seismic data acquisition (i.e. 15 - 1 Hz) is relatively simple. However, when I look at specs for a ...
3
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34 views

How do people determine initial ratio of the parent nuclide and daughter product in radiometric dating?

I understand that we have zircon crystals that prevent entering or leaving of nuclide or lead after forming. But how cand we understand what was the initial ratio?
3
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79 views

What gravitational evidence do we have to counter the idea that oceans are formed when continents sink?

Is there some evidence for this based on gravity anomalies? I think I know how to tell if a mountain or structure is compensated based on bougeur and free air anomalies, but this really has me ...
3
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0answers
70 views

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 ...
2
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0answers
35 views

Do greenhouse gases absorb and re-emit photons or reflect them diffusely? Or both? (CO2, CH4, H2O, N20, HFC-134a, etc.)

Also, would it matter if a particular type of greenhouse gas molecule reflected rather than absorbed and then re-emitted light? Would its GWP be higher or lower? Perhaps this is more of a pure ...
2
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0answers
38 views

How long do geostrophic currents last?

My professor posed this question, without any relevant material. I suppose the currents last until the density gradient is neutralized, but I can't find any literature nor articles on this, regarding ...
2
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1answer
98 views

IGRF -13 Geomagnetic field, Calculating Partial Derivatives of Legendre Polynomials

I have been trying to implement the IGRF-13 geomagnetic model on my own in C code. I have followed the equations from the website below and I am getting correct results for the B$_{\phi}$ and Br ...
2
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0answers
52 views

Is it possible for Mexico to have a magnitude 9 earthquake?

Everyone has heard of the Cascadia Subduction Zone and the potential threat it poses. However, I have heard nothing about The Cocos Subduction Zone, even though it caused a devastating earthquake over ...
2
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0answers
112 views

Construction of a drift curve in the well tie calibration and how to interpret it?. Sonic calibration vs checkshot calibration

Good afternoon. Inside the creation of the synthetic seismogram some softwares have the option to run what is called "sonic calibration" or "checkshot calibration". I have some questions: 1)why some ...
2
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77 views

Do northern lights (aurora borealis) show the same visual activity all along their visible latitude range?

Probability aside regarding their visibility (I did read on Neil Davies Aurora watcher's handbook that probability is highest in the middle of their latitude range called aurora oval, lowering both ...
2
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0answers
15 views

transition elastic deformation to flow

Let's assume a small (and smooth) vertical deformation of the seabed. If done quickly, I can consider it a vertical force generating an acoustic wave in the water, where every particle of water ...
2
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0answers
62 views

Difference between landslide waves and earth quake waves

I am new to this field, recently started working on landslide monitoring mainly in signal processing part. I have the following questions? 1.Will each land slide and every vibration have p wave, s ...
2
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0answers
259 views

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 ...
2
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0answers
305 views

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 ...
2
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0answers
41 views

Phase of S2 constituent in tidal prediction

I ran the ETERNA code for the prediction of tidal gravity at some station. Then I use Fourier analysis to recover the amplitude and phase of the S2 constituent. As I understand, the phase of the S2 ...
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0answers
26 views

How can you find the seismic intensity at a given point?

Given the distance, material, and seismic intensity at the epicenter, can you calculate the seismic intensity at a given point?
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37 views

What are the boundary conditions for Navier's Equations of motion in seismic?

Navier's equations of motion in seismic have 3 solutions, according to how it is resolved (boundary conditions): for Vp (compression waves) for Vs (shear waves) for Vr (Rayleigh waves) I know the ...
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0answers
48 views

Understanding the EM survey results

I have contour maps showing conductivity and in-phase data from an electromagnetic survey done on a ground, where, supposedly, an underground sewer system is running horizontally across the survey ...
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0answers
25 views

Quality control in Seismic Acquisition - shot offset shift

I have a problem with seismic data where the minimum offset of the shot is not centered at the nearest receiver, this shift can be for 3 traces 2 or one and maybe more in the two sides !! So is there ...
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0answers
19 views

Conversion of SEG-Y relative to MSL

I am working on the conversion of CSF file from SonarWiz into SEG-Y data. However, it comes back always related to the Sensor depth/altitude and never to the MSL. I have tried changing the bytes from ...
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0answers
812 views

Is there a way to convert from Dip direction to Strike direction?

I have some set of recorded data in dip direction/dip format. I wish to transform then to strike/dip. I am currently having a hard time imagining how to convert from dip direction to strike direction. ...
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36 views

Broadband Albedo Conversion Scheme

I had this albedo conversion written down: $$\alpha = 0.53\alpha_{VIS}+0.47\alpha_{NIR}$$ I had on my notes that this equation was form Collins et al (2002). However, I cannot find where this came ...
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0answers
139 views

Equatorial Bulge and its implications on the climate

How much of the variance in the climate is due to the equatorial bulge and how much sun radiation do we lose due to the equatorial bulge? I am interested in the variance both through time and ...
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0answers
71 views

Finding out actual dip and dip direction of refractor

We have two traveltive curves for first arrivals (direct and refracted) from a dipping refractor in the forward and reverse directions along a profile line. my question is: Is there a logical way (non-...
1
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0answers
24 views

Determining the spatial orientation of a fault given ground acceleration magnitude in different directions

Accelerographs measure ground acceleration in three different components of motion: east-west, north-south, and vertically (up-down). I know that fault orientation is important here, so let's say we ...
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0answers
95 views

Which is naturally more radioactive: a tertiary or cretaceous sandstone? Why?

I've come across this question in a Petrophysics exercise regarding the Gamma Ray well logging. And I don't know how to solve it. This is the "believed" AFAIK session Natural radioactivity ...
1
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0answers
28 views

Which wavelengths is limestone most transparent to?

I think of the non-ionizing range, e.g. Terahertz or Radio. Limestone clearly is transparent to x-ray or gamma but thats not what i am asking for. Natural to low ranges of porosity/water content ...
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0answers
21 views

Do living things have a magnetic field capable of any level of solar protection?

I understand how anything with an electrical current have a magnetic field including living things. Would a densely populated rain forest or jungle have enough combined magnetic field among the living ...