What is Earthquake: Definition and 162 Discussions

An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to propel objects and people into the air, and wreak destruction across entire cities. The seismicity, or seismic activity, of an area is the frequency, type, and size of earthquakes experienced over a period of time. The word tremor is also used for non-earthquake seismic rumbling.
At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides and occasionally, volcanic activity.
In its most general sense, the word earthquake is used to describe any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake's point of initial rupture is called its hypocenter or focus. The epicenter is the point at ground level directly above the hypocenter.

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  1. Astronuc

    M7.5 Earthquake, near Anamizu, W Japan

    An earthquake struck at 4:10 p.m. local time at a depth of 10 kilometers (6 miles), around 42 kilometers (26 miles) northeast of Anamizu in Ishikawa prefecture, according to the United States Geological Survey (USGS). M 7.5 - 42 km NE of Anamizu, Japan...
  2. Astronuc

    2004 Indian Ocean earthquake and tsunami (19 years ago)

    I discovered a video in which various people discuss what they witnessed that day - including some survivors. At the time, the Pacific Tsunami Warning Center in Hawaii detected a large earthquake, but initially underestimated the magnitude (M 8.0). Furthermore, they had no instrumentation in...
  3. Astronuc

    M 5.9 - 37 km WNW of Linxia Chengguanzhen, China

    M 5.9 - 37 km WNW of Linxia Chengguanzhen, China https://earthquake.usgs.gov/earthquakes/eventpage/us7000ljvg/region-info 2023-12-18 15:59:30 (UTC) 35.743°N 102.827°E 10.0 km depth https://earthquake.usgs.gov/earthquakes/eventpage/us7000ljvg/executive News agencies report 100 or more people...
  4. Astronuc

    M7.6 Earthquake of coast of Mindinao, Philippines

    M 7.6 - Mindanao, Philippines https://earthquake.usgs.gov/earthquakes/eventpage/us7000lff4/executive 2023-12-02 14:37:03 (UTC) 8.527°N 126.449°E 32.8 km depth Numerous aftershocks in the Mag 4+ to 5+ range. M 6.4 - 47 km NE of Barcelona, Philippines...
  5. davenn

    M 6.7 - 98 km E of Port-Olry, Vanuatu

    M 6.7 - 98 km E of Port-Olry, Vanuatu ( northern Vanuatu ~ 100km E of Santo) 2023-11-22 04:47:33 (UTC) 14.985°S 167.983°E 22.5 km depth from my seismo .....
  6. Astronuc

    Mag 2.7 earthquake in Cornwall, 19 Nov 2023

    Cornwall shaken by 2.7 magnitude earthquake https://www.bbc.com/news/articles/c724le759lro That's not a significant earthquake, unless one's house is near the epicenter. Residents in Helston, Penzance and Camborne reported feeling the tremors. Some of my ancestors were from that area, and I...
  7. Astronuc

    M6.7 earthquake in Philippines off S coast of Mindinao

    M 6.7 - 26 km WSW of Burias, Philippines https://earthquake.usgs.gov/earthquakes/eventpage/us6000lp12/executive 2023-11-17 08:14:13 (UTC) 5.587°N 125.051°E 78.0 km depth https://apnews.com/article/philippines-earthquake-mindanao-688f1e3b08854f31e92eaf1fd12e0bcb The earthquake was reported as...
  8. Astronuc

    Rare 5.3 Mag earthquake jolts West Texas

    https://www.msn.com/en-us/weather/topstories/rare-5-3-magnitude-earthquake-jolts-west-texas/ar-AA1jBhJ8 M 5.2 - Coalson Draw, Texas https://earthquake.usgs.gov/earthquakes/eventpage/tx2023vxae/executive 2023-11-08 10:27:49 (UTC) 31.622°N 103.982°W 7.4 km depth There was an unusal set of...
  9. Astronuc

    M7.1 Earthquake, Banda Sea, Indonesia + aftershocks

    M 7.1 - Banda Sea - https://earthquake.usgs.gov/earthquakes/eventpage/us7000l9h4/executive 2023-11-08 04:53:51 (UTC) 6.456°S 129.513°E 10.0 km depth Fairly shallow Aftershocks in the 4-6 M range, but one at M 6.7 - Banda Sea 2023-11-08 13:02:06 (UTC) 6.146°S 129.914°E 10.0 km depth...
  10. Astronuc

    M 7.2 - 98 km S of Sand Point, Alaska; Shishaldin Volcano erupting

    https://earthquake.usgs.gov/earthquakes/eventpage/us7000kg30/executive M 7.2 - 98 km S of Sand Point, Alaska 2023-07-16 06:48:22 (UTC) 54.460°N 160.760°W 32.6 km depth There is some speculation that the Mag 7.2 earthquake may be indicative of an imminent eruption of the Shishaldin Volcano...
  11. Astronuc

    M5.5, Lake Almanor near Chester, California

    https://www.chicoer.com/2023/05/11/earthquake-shakes-north-state/ https://earthquake.usgs.gov/earthquakes/map/?extent=40.16313,-121.3076&extent=40.34393,-120.94368&listOnlyShown=true&baseLayer=terrain https://earthquake.usgs.gov/earthquakes/eventpage/nc73886731/executive M 5.5 - 4km SW of East...
  12. davenn

    M7.6 Earthquake Off Tonga - 2023-05-10

    M 7.6 - 95 km WNW of Hihifo, Tonga 2023-05-10 16:02:00 (UTC) 15.600°S 174.608°W 210.1 km depth A decent event that maxed out my seismo for some minutes https://www.sydneystormcity.com/seismograms.htm As it will disappear off my seismo in around 20 hours ( from time of writing this) a screen...
  13. hagopbul

    I Can Ground Penetrating Radar Help Locate Earthquake Survivors?

    Hello : As the news coming from Syria and Turkey about earthquake devastation, is it possible to use ground penetrative radar or sound identification and wave frequency spectrum analysis to locate survivours ? The human sound are in the range of 20 kHz shouldnt we be able to use microphones...
  14. Astronuc

    Java Mag 5.6 earthquake - Java, Indonesia

    https://earthquake.usgs.gov/earthquakes/eventpage/us7000ir9t/executive M 5.6 - 18 km WSW of Ciranjang-hilir, Indonesia 2022-11-21 06:21:10 (UTC) 6.853°S 107.095°E 10.0 km depth - relatively shallow https://earthquake.usgs.gov/earthquakes/eventpage/us7000ir9t/region-info City of Cianjur had...
  15. Astronuc

    Mag 5.3 earthquake - 39 km WSW of Mentone, Texas

    M 5.3 - 39 km WSW of Mentone, Texas 2022-11-16 21:32:44 (UTC) 31.634°N 104.005°W 8.3 km depth - relatively shallow https://earthquake.usgs.gov/earthquakes/eventpage/tx2022wmmd/executive Some 90 km (56 mi) SSE of Carlsbad, New Mexico - in an unpopulated area of the Llano Estacado (Staked...
  16. 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.
  17. Astronuc

    Mag 7.6 earthquake near Kainantu, Papua New Guinea

    M 7.6 - 66 km E of Kainantu, Papua New Guinea https://earthquake.usgs.gov/earthquakes/eventpage/us6000iitd/executive 2022-09-10 23:46:57 (UTC) 6.256°S 146.469°E 90.0 km depth https://www.msn.com/en-us/news/world/earthquake-of-magnitude-7-6-strikes-papua-new-guinea/ar-AA11GO6l
  18. Oldman too

    Dark fiber optic cables as Earthquake detectors

    Hello, Recently while familiarizing myself with the rodent menace affecting Fiber optic networks, I came across this rather novel use for the dark, or unused fibers in buried cables. The method apparently holds a lot of promise as well as significant advantages over many current Seismology...
  19. Astronuc

    M6.0 Earthquake and aftershocks, Island of Crete, Greece

    M 6.0 - 7 km NNW of Thrapsanón, Greece https://earthquake.usgs.gov/earthquakes/eventpage/us7000fes8/executive 2021-09-27 06:17:22 (UTC) 35.252°N 25.260°E 8.7 km depth https://earthquake.usgs.gov/earthquakes/eventpage/us7000fes8/region-info https://www.bbc.com/news/world-europe-58705376...
  20. Astronuc

    Mag 7.0 Earthquake - Acapulco, Mexico

    M 7.0 - Acapulco, Mexico https://earthquake.usgs.gov/earthquakes/eventpage/us7000f93v/executive 2021-09-08 01:47:47 (UTC) 16.982°N 99.773°W 20.0 km depth Waiting to see if it gets upgraded...
  21. mfb

    M 7.2 earthquake in Haiti August 14

    Wikipedia article (still rapidly evolving of course) USGS estimates 1000-10,000 deaths as most likely scenario, most likely the deadliest earthquake this year: https://earthquake.usgs.gov/earthquakes/eventpage/us6000f65h/executive Edit: An hour later the most likely scenario is now over 100,000...
  22. Astronuc

    Mag 8.2 Earthquake and aftershocks ~ 104 km SE of Perryville, Alaska

    https://earthquake.usgs.gov/earthquakes/eventpage/ak0219neiszm/executive https://earthquake.usgs.gov/earthquakes/eventpage/ak0219neiszm/region-info 2021-07-29 06:15:47 (UTC) 55.325°N 157.841°W 32.2 km depth A lot of aftershocks...
  23. Astronuc

    Earthquake swarm near Salton Sea, S. California

    M 4.9 - 4km NE of Westmorland, CA https://earthquake.usgs.gov/earthquakes/eventpage/ci39641528/executive 2020-10-01 00:31:27 (UTC) 33.056°N 115.590°W 11.5 km depth M 4.5 - 4km NE of Westmorland, CA https://earthquake.usgs.gov/earthquakes/eventpage/ci39643328/executive 2020-10-01 03:36:34...
  24. diogenesNY

    Earthquake; Sparta, NC; 5.1

    At approximately 8:07AM local time (EDT) there was a 5.1M earthquake centered near Sparta NC. It has been reported to have been felt all throughout the state (according to individual witness reports on reddit and news reports on broadcast media). I am in Durham, NC and managed to sleep right...
  25. gmax137

    Aftershock of Nevada Earthquake Felt in California

    https://www.usatoday.com/story/news/nation/2020/05/15/tonopah-nevada-earthquake-aftershocks-california/5196985002/ Woke me up at 4AM. I am 150 miles North West of the quake
  26. P

    What is the maximum depth to which a P-wave ray can travel?

    I've created an excel spreadsheet with the given model in addition to calculating radius of the layer by subtracting depth from 6371. I've calculated Zf. I've also found what I think is vs by doing alpha * (radius column/6371), but that could be wrong. I know I need to find where 20/6371 =...
  27. P

    Solving for earthquake transit time via Snell's Law

    I was told to solve the second equation above for x to get l2 and l2, but that only gets me those in terms of other unknowns. I'm assuming I just need to solve t for my knowns, but I keep getting caught up by my unknowns. i.e., solving for x gives x = (l2*L*v2)/(l1*v1+l2*v2). Please note "l" is...
  28. Astronuc

    Mag 6.5 Earthquake near Challis, Idaho

    M 6.5 - 72km W of Challis, Idaho, https://earthquake.usgs.gov/earthquakes/eventpage/us70008jr5/executive 2020-03-31 23:52:31 (UTC) 44.448°N 115.136°W 10.0 km depth followed by M 4.8 - 38km SW of Challis, Idaho, https://earthquake.usgs.gov/earthquakes/eventpage/ak020485mtmv/executive...
  29. Astronuc

    Mag 5.7 earthquake, Salt City, UT

    5.7 magnitude earthquake in Utah knocks out power to thousands and diverts flights https://www.cnn.com/2020/03/18/us/utah-earthquake/index.html M 5.7 - 6km NNE of Magna, Utah, 15.8 km (9.8 mi) E of Salt Lake City https://earthquake.usgs.gov/earthquakes/eventpage/uu60363602/executive 2020-03-18...
  30. E

    Is a 10.0 earthquake actually possible?

    Is a 10.0 magnitude earthquake theoretically possible? The most -powerful quake ever recorded was a 9.5, which occurred just off the coast of Chile on May 22nd, 1960.
  31. P

    Predicting tsunamis, what to measure from earthquake data?

    I have a project to create a program to predict tsunami possibility by gathering data and finding pattern from previous earthquakes. It would be using neural network. But I don't really know what I should consider from the data. Is it the magnitude that cause the tsunami? Or is it the depth...
  32. Astronuc

    Mag 6.1 Earthquake, Waitara, NZ - very deep 227.3 km

    https://earthquake.usgs.gov/earthquakes/eventpage/us1000hiup/executive M 6.1 - 64km ESE of Waitara, New Zealand 2018-10-30 02:13:39 (UTC) 39.054°S 174.977°E 227.3 km depth - every deep Yesterday, a Mag 6.3 in Drake Passage, south of Patagonia...
  33. Astronuc

    Mag 5.5 Earthquake, Romania and Earthquakes in Ionian Sea

    I noticed a relatively strong earthquake in SE Europe this weekend. https://earthquake.usgs.gov/earthquakes/eventpage/us1000hi43/executive M5.5 - 16km SE of Comandau, Romania 2018-10-28 00:38:11 (UTC) 45.652°N 26.403°E 151.0 km depth - very deep Then I noticed several earthquakes in the Ionian...
  34. Astronuc

    Mag 7.8 Earthquake, 101km ESE of Suva, Fiji

    M 7.8 - 101km ESE of Suva, Fiji 2018-09-06 15:49:14 UTC Location 18.494°S 179.332°E, 608.6 km depth https://earthquake.usgs.gov/earthquakes/eventpage/us2000h9e2#executive Very deep. A number of deep aftershocks have occurred. Potential for Mag 8 earthquakes in that region - along the Tonga...
  35. Astronuc

    Mag 6.7 earthquake near Tomakomai, Hokkaido, Japan

    USGS reports M 6.6 - 27km E of Tomakomai, Japan 2018-09-05 18:07:58 UTC 42.671°N, 141.933°E 33.4 km depth https://earthquake.usgs.gov/earthquakes/eventpage/us2000h8ty#executivePowerful M6.7 earthquake rocks Hokkaido, causing massive landslides; nine dead and 31 reported missing...
  36. StevieTNZ

    Mag. 7 Indonesia Earthquake - 5th August 2018

  37. berkeman

    Magnitude 6.9 Earthquake in Hawaii versus on the Hayward Fault -- What am I missing?

    How come I saw a video of a magnitude 6.9 earthquake on the island of Hawaii on the evening news just now, and the grocery store products were not even falling off the shelves (and no deaths or injuries), versus the same magnitude earthquake prediction here on top of the Hayward Fault (east of...
  38. BillTre

    5.5 Earthquake Associated with S. Korean Geothermal Plant

    Science magazine news article here.
  39. C

    Earthquake Predicted in Jakarta Tonight?

    So either we can now predict earthquakes or this news site has lost the plot...https://www.dailystar.co.uk/news/latest-news/685618/earthquake-jakarta-tonight-indonesia-megathrust-2004-tsunami
  40. davenn

    Earthquake Near Pinotepa de Don Luis, Mexico: M 7.2

    Hi everyone A M 7.2 quake in southern Mexico today M 7.2 - 37km NE of Pinotepa de Don Luis, Mexico Time: 2018-02-16 23:39:42 (UTC) Location: 16.646°N 97.653°W Depth: 24.7 km from my system It also shows a M 5.8 aftershock in the tail of the main shock location map cheers Dave
  41. StevieTNZ

    Taiwan Earthquake - 7 February 2018

    A fluid situation at the moment, as the news rolls in - https://www.stuff.co.nz/world/asia/101213618/taiwan-earthquake-topples-buildings Significant damage. EDIT: added later https://www.stuff.co.nz/world/asia/101213618/taiwan-earthquake-topples-buildings One hotel partially collapsed with...
  42. Evo

    5.8 Magnitude earthquake hits Montana

  43. BillTre

    Drilling into an Earthquake Fault

    Some Japanese scientists want to drill from the bottom of S. African mines into faults of recent earthquakes. Science news story here.
  44. StevieTNZ

    Christchurch Earthquake - February 2011

    http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/89668972/before-during-and-after-see-how-christchurch-has-changed Today we remember those who were lost. I was taking a nap at the time, but when I woke up and saw the headlines, I ran to the TV to watch the coverage...
  45. P

    Seismograms - Rayleigh Waves

    How can you tell where a dispersed Rayleigh wave train ends...? Is there a way to identify the end of a Rayleigh wave train on the following teleseismic records? The first shows the full surface wave train, the second is zoomed in but cuts off the final part of the original including the last...
  46. Shakir

    Can We Predict Earthquakes? | Hello PF

    Hello PF Why are scientists still unable to predict earthquake? Will it be possible to predict earthquake? Are there any promising research going on? If only we could know when earthquake was going to hit, how many lives could have been saved!
  47. K

    MHB Richter Scale Earthquake Magnitude Question?

    Hello. I am doing a review sheet for my Pre-Calculus final and one of the questions has me stumped. I'm going through our notes and we never did a problem like this in class. Any help would be greatly appreciated. Thank you. Find the Richter scale magnitude of an earthquake that releases energy...
  48. fresh_42

    Earthquake in South Pacific, NE of Australia

    They set a tsunami warning. Seems to be several. http://geofon.gfz-potsdam.de/eqinfo/seismon/globmon.php http://earthquake.usgs.gov/earthquakes/eventpage/us20007z8m#region-info
  49. StevieTNZ

    Japan Earthquake 22.11.2016

    Quite recent, so updates will follow. Over the radio in NZ, it is said a tsunami warning has been issued. Magnitude 7.3 at the moment, possibly be revised. http://www.stuff.co.nz/world/asia/86723022/big-earthquake-near-japan