What is Seismic: Definition and 49 Discussions

Seismology (; from Ancient Greek σεισμός (seismós) meaning "earthquake" and -λογία (-logía) meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology.

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  1. Astronuc

    Major Earthquakes - 7.4 (7.2) Mag and 6.4 Mag near Hualien, Taiwan

    M 7.4 - 18 km SSW of Hualien City, Taiwan https://earthquake.usgs.gov/earthquakes/eventpage/us7000m9g4/executive 2024-04-02 23:58:11 (UTC) 23.819°N 121.562°E 34.8 km depth M 6.4 - 11 km NE of Hualien City, Taiwan https://earthquake.usgs.gov/earthquakes/eventpage/us7000m9gc/executive...
  2. Astronuc

    Alaska's Trident Volcano has increased seismic activity

    Andrew Wulfeck (FOX Weather) - Alaska officials raise alert level for volcano after increase in earthquake activity Wed, February 22, 2023 at 6:47 PM EST https://www.yahoo.com/news/alaska-officials-raise-alert-level-234711944.html https://www.avo.alaska.edu/activity/Trident.php...
  3. Ira_anabelle

    Using Seismic Waves detected at 4 Seismometers to determine the Epicenter

    My first attempt was to work with the the difference in arrival times, but that didnt account for the focus to be under the epicenter. So I tried again in combination with the angle between the stations but have not arrived at a clear solution.
  4. Remixex

    Estimating the velocity of seismic waves through an idealized Earth

    Hello, this is a repost from a much less-clear question I posted before (link to question: https://www.physicsforums.com/threads/triangles-inside-a-circle-to-represent-raypaths-inside-an-ideal-earth.1011998/#post-6596165). It's kind of a loaded question, however it can be expressed as triangles...
  5. Twigg

    Seismic ray-tracing, when does a spherical Earth matter in practice?

    I'm taking a geophysics class and the math makes sense but the context is lost on me. My understanding is that the primary use of seismic ray-tracing is to locate disturbances that cause waves to propagate radially. I also understand that 35km is the depth at which the Earth's spherical shape...
  6. N

    Silence of Canadian Cities: COVID19 Lockdown and Seismic Vibrations

    On 11 March 2020, the World Health Organization (WHO) declared Coronavirus disease (COVID-19) as a pandemic. By then it had spread to at least 110 countries. The announcement made by WHO had a cascading effect. Cities, territories, and countries around the world ended up declaring states of...
  7. P

    Ratio of the Earth's core radius to total radius via seismic turning point

    I've attached a figure I've made; I know I'm to assume the Earth is a perfect sphere in this case. Assuming the 103 degrees is measured as latitude, I've calculated the distance in kilometers (Xp in the second equation above) to be 1.1453e4 km. I know I need u = p at the turning point, but not...
  8. N

    How does Quadruple Pendulum isolate LIGO from Seismic Vibrations?

    On 28 November 2018, a lecture was given by Dr. Rainer Weiss (2017 Nobel Prize Winner for Physics) at the Ontario Science Centre, Toronto. The lecture was about his work with the Laser Interferometer Gravitational-Wave Observatory (LIGO). In his lecture talked about quadruple pendulums or...
  9. Remixex

    Stress and Strain tensors in cylindrical coordinates

    Homework Statement I am following a textbook "Seismic Wave Propagation in Stratified Media" by Kennet, I was greeted by the fact that he decided to use cylindrical coordinates to compute the Stress and Strain tensor, so given these two relations, that I believed to be constitutive given an...
  10. B

    I Effect of impedance changes less than a wavelength

    I am interested to know what is the impact of various length scales of impedance changes on wave propagation. From undergraduate physics (a few years ago for me) I roughly remember how to derive reflection and transmission coefficients for a wave traveling from one medium to another with a...
  11. CapnGranite

    Nocturnal seismic activity at Mt. Vesuvius

    https://www.researchgate.net/publication/301759171_Evidences_for_higher_nocturnal_seismic_activity_at_the_Mt_Vesuvius abstract We analyze hourly seismic data measured at the Osservatorio Vesuviano Ovest (OVO, 1972–2014) and at the Bunker Est (BKE, 1999–2014) stations on the Mt. Vesuvius. The...
  12. Astronuc

    Mount Teide, Tenerife Island, seismic activity

    http://www.ibtimes.co.uk/volcanologists-fear-infamous-tenerife-volcano-will-erupt-after-100-earthquakes-are-recorded-1584962 Keep an eye on that one.
  13. 1oldman2

    Exploring Earth's Interior with Seismic Tomography and Weather Bombs

    This could open a new frontier on seismic study of the Earth's interior. http://www.bbc.com/news/science-environment-37177575 From, http://science.sciencemag.org/content/353/6302/919 Seismic tomography is like an x-ray of Earth's interior, except that it uses earthquakes for the illumination...
  14. jeisson botache

    Seismic isolator based on magnetic forces

    Hi, i am an student of civil engineering and i am doing my graduate thesis. so sorry if i misspell, english is not my native languaje. so, here we go :D Homework Statement Before entering in details you (whoever you are) most know: The system is scaled for obvious reasons. The system consists...
  15. Astronuc

    Low level seismic (swarm) activity at Mt Hood, Oregon

    A journalist reported a 'New Earthquake Swarm is Rocking Oregon's Mt Hood. http://www.wired.com/2016/05/new-earthquake-swarm-rocking-mt-hood I wouldn't say rocking. I checked USGS, and didn't find anything over Mag 2.5, so I refined the search in the range of Mag 1 to 2.5, and found a number...
  16. H

    Seismic Ground Response Parameters

    Hey guys, recently I have do some self-study on the ground response parameters on cohesive and cohesionless soil.. I made some deduction but I cannot confirm if it is correct or not, thus needing the help from the PF community. The deduction is as follows; I need explanation for the occurrence...
  17. xpell

    Antipodal seismic focusing after an impact: real or not?

    Reading about meteorites, I have found this idea of "antipodal earthquakes" or "antipodal vulcanism" after a major impact several times. There seems to be perfectly good papers for and against, together with the usual crankish "information." There also was a thread here about the issue almost 4...
  18. C

    P wave and S wave Seismic velocity

    Homework Statement I need to calculate the P wave velocity (VP[mantle]) and S wave velocity (VS[mantle]) in the mantle just above the core-mantle boundary? All the data is found in the diagram. I know the equation to find compressional wave (P waves) velocity but you need to find the...
  19. Astronuc

    News North Korea - Suspicious Seismic Activity

    Breaking News: North Korea claims it has conducted a successful hydrogen bomb test South Korea says "artificial earthquake" detected near North Korean nuclear testing site http://news.yahoo.com/earthquake-detected-north-korea-not-clear-nuke-test-020439757.html That will certainly stir...
  20. Farah AbdlGhany

    Numerical course in geophysics

    I am studying numerical and programming course in this semester, I was asked to know the applications of this course (numerical methods like Bisection, Newton Raphson, Secant, Simpson, Euler and Lagrange) in geophysics and how can I exploit these methods in seismic or in geophysics in general...
  21. RJLiberator

    Do Seismic Reflections Reveal Velocity Information in Layer 3?

    Homework Statement The question is set up by a diagram. It has: Layer 1 velocity = 6km/s Layer 2 = calculated velocity of 7.58 km.s Layer 3 = reflection The angle of the source in layer 1 is 34 degrees, the angle in layer two is then 52.33 degrees The source then reflects off of layer...
  22. RJLiberator

    How Do You Calculate Seismic Moment for Major Earthquakes?

    Homework Statement The great Sumatra earthquake of late 2004 had a main shock with an M_w magnitude of 9.1 and a large aftershock in early 2005 had an M_w of 8.6. Calculate the seismic moment, M_o (energy release) of each earthquake. Homework Equations M_w = 2/3*log(M_o)-6.0 Where log = log...
  23. Peter Jackson

    Computer simulation of seismic waves

    Hello, I am working in Papua New Guinea where there is a great deal of seismic activity. I am interested in using MS Excel for simulation of SHM due to seismic waves. To investigate the how frequency and wavelength of the waves affects buildings. Does anyone have any experience of this type of...
  24. P

    Seismic Wave Movement: Calculating Distance w/ Density & Force

    Is there a formula I could use to determine how far in a medium a seismic wave would move if I hit one end of it with a hammer? I know the density of the rock and the force of the hammer.
  25. B

    Seismic Scattering: Topography, Faulting, Fluid/Melt

    How do the following affect seismic scattering ? 1) topography 2) faulting 3) fluid and melt Any scientific sources are appreciated, thanks
  26. davenn

    First seismic T-Phase events for 2015

    hi everyone, Well we are into a new year and into new discoveries and observations Yesterday morning, Jan 6th, 0548NZST ( 05 Jan 1748UT) there was a reasonable quake in the mountains of the central South Island of New Zealand M 6.0 GNZ ( M 5.6 USGS). Now the quake itself isn't unusual, NZ is...
  27. davenn

    Exploring Seismic T-Waves off the SW Tip of NZ

    a year ago ( 18 Dec 2013) I started a thread on the first observed/confirmed recording I did of a seismic T wave from a quake off the SW tip of the South Island of New Zealand. https://www.physicsforums.com/threads/seismic-t-waves.729045/ Since then I have recorded them on 3 other quakes from...
  28. A

    Absorption of energy in a seismic pulse

    Hey, Just doing some reading on this and I'm a little confused as to why absorption produces a progressive lengthening of a seismic pulse. Quote from the textbook "In general, the effect of absorption is to produce a progressive lengthening of the seismic pulse". I understand how the...
  29. S

    Surface seismic waves and amplitude with distance

    OK so we all know that seismic waves decrease in amplitude at about 1/r, the decay is slower than P and S-waves but it's there. So how do you explain that when I see examples of seismograms of the same earthquake from stations at different distance you can sometimes notice that surface waves...
  30. davenn

    Exploring Seismic Waves: Uncovering a New Phenomenon

    Greetings all Over the last couple of days I have been delving into a new personal discovery about seismic waves. And with the talk recently in several threads in the general and classic physics sections about sound wave propagation in water, I thought this was appropriate to share. Many of...
  31. F

    Tracing seismic rays - possible intersection

    This problem is about seismic wave propagation in a non-homogeneous layer over a halfspace. I'm not asking you to solve anything, I've already solved the problem both algebraically and in Matlab. However, the graph that I've gotten mildy surprises me. According to the graph, the seismic rays...
  32. M

    Seismic sensor and accelerometer

    Both Seismic sensors and accelerometers are used for sensing vibration. Then what is the difference between them?
  33. A

    Can You Determine an Epicenter in a Classroom Seismic Activity Simulation?

    Seismic Activity Project! Please help me! So, I have to find the location of the epicenter of seismic activity. Of course, our project does not intend to find that of real seismic activity. This is a school project, in which my teacher will drop an object at some unknown location in a large...
  34. L

    Seismic Prospecting: What is It? Find Info Here

    Does somebody know what is seismic prospecting? and where can I find more info about it
  35. A

    What seismic design codes should I consider for my subsea structures?

    Hi I am looking for a "Western" seismic analysis design code? So something by BS, ISO, API, etc... If there is one specific to the oil & gas industry and subsea strucutures, then great, but as this may not be available, any code on structural seismic design would do. I essentially...
  36. S

    Seismic activity on the east coast

    I have been searching online trying to find information about any unusual/unexpected seismic activity on the east coast of U.S. before the earthquake struck on August 23rd. So far, I've not been able to find any articles about that subject. Has anyone seen any information on that topic...
  37. L

    Japan's Seismic Activity Altered the Earth's Axis

    http://photoblog.msnbc.msn.com/_news/2011/03/12/6256280-how-the-quake-shifted-japan?chromedomain=cosmiclog I thought this was pretty fascinating. According to this, the Earth's rotation has increased in speed as well, by 1.8 microseconds.
  38. I

    Solar flares triggering seismic events

    Well I'm sure a lot of us have seen websites predicting the end of the world from solar flares causing earthquakes. I'm a physics grad student and with my limited knowledge I have the impression that all such theories are pseudo scientific. But still I want to ask the question. It is...
  39. A

    Seismic Waves: How Are They Produced?

    HI, I want to know how seismic waves are produced?. I cannot find any information on it on google. Any help will be helpful. Thanks.
  40. B

    Seismic displacement ofr a plane wave

    Homework Statement phi(x,y,z,t)= cos(wt- the dot product of K and x) k= kx i hat + ky j hat + kz k hat units are m^-1 x= x i hat + y j hat + z k hat units are m t is time and w is the angular velocity w/ units of sec^-1 show that abs. value of k = w/alpha by plugging the...
  41. F

    How Far Away Was the Earthquake if S Waves Arrived 2 Minutes After P Waves?

    Homework Statement Earthquakes are essentially sound waves traveling through the earth. They are called seismic waves. Because the Earth is solid, it can support both longitudinal and transverse seismic waves. These travel at different speeds. The speed of longitudinal waves, called P waves...
  42. M

    Difference between GPR from seismic

    (1) What would you consider to be the qualitative difference between GPR (Ground Penitrating Radar) and Seismic? (2) How is the GRP similar and different from seismic
  43. Ivan Seeking

    Unusual Seismic Activity in the Pacific NW US

    We have been rockin and rollin here in the NW. http://www.sciencedaily.com/releases/2008/04/080413184801.htm
  44. Orion1

    Acoustic vs. seismic waveforms

    Is it possible to correlate the atmospheric acoustic vs. ground seismic waveforms from a charge detonation? Are there any physicists on this forum that recognise the acoustic and seismic waveform signatures from a charge detonation? Acoustic, Seismic wave function equation: \psi (x,t) = A...
  45. kat

    News Typically Dem voting populace: seismic shift

    This is BIG IMHO Analysis: 'Seismic' Catholic shift to Bush *snip*
  46. zoobyshoe

    Seismic Scare At The Zooby Brush Shelter

    Earlier today I was briefly scared out of my wits when a seismic wave passed beneath the Zooby brush shelter here in San Diego, and seemed to toss the whole place up unto the air a couple feet as it passed underneath. Apparently the epicenter was about 50 miles away, out in the ocean to the...
  47. Atrayo

    Seismic Global Activity & Nuclear Underground Testing, Bad Combo.

    Hello All, I've always been curious about historical seismic activity prior to the 20th century. Then the advent of the last century until now, i have heard that seismic activity has increased dramatically. Then i got to conceptualizing how many underground nuclear test's have been...
  48. T

    Solving a Seismic Mystery: Calculating Epicenter Distance

    It seems to me that this is just a simple algebra problem, that doesn't have much to do with waves, but it's the only problem on the homework that I can't figure out. :-/ I know there's an easy solution to it, but I keep getting the wrong answer. Anyway, here it goes: A seismographic station...
  49. Ivan Seeking

    Volcanic and Seismic Threats to Northwest U. S.

    " http://www.earthfiles.com/news/news.cfm?ID=571&category=Science