Types of Earthquakes Explained: 8 Ways the Ground Breaks, Slips and Shakes

Some earthquakes stronger than magnitude 8 begin about 600 km underground, where rock should be too hot and squeezed to break. Others shake almost no one: every 14 months or so, a fault beneath the Pacific Northwest slides for weeks and quietly releases the energy of a strong quake. And in Oklahoma, earthquakes above magnitude 3 went from one or two a year to about nine hundred. This video sorts earthquakes by the hidden force that drives them, with a cutaway or a map for each: how a locked fault bends and snaps back, why the biggest quakes come from subduction megathrusts, how an old scar wakes up in the middle of a continent, why deep-focus earthquakes shouldn't exist, what volcanoes do to the rock around them, how pumped water triggers quakes, how a fault can slip in slow motion, and why a foreshock is only a foreshock in hindsight. Along the way we check a popular claim: do small earthquakes let off pressure and prevent the big one? What you'll learn: Fault slip: elastic rebound, and the three basic fault motions (normal, reverse or thrust, and strike-slip). Megathrusts: why magnitude grows with fault area and slip; the 2004 Sumatra-Andaman rupture, about 1,300 km long and roughly 8 minutes in duration; why each magnitude step releases about 30 times more energy; and why small quakes can never add up to "pay off" a big one. Intraplate earthquakes: the New Madrid sequence of 1811-1812 in the middle of North America, the buried Reelfoot rift, and why central US quakes are felt far wider than western ones. Deep-focus earthquakes: Bolivia 1994 (magnitude 8.2, about 630 km deep) and the Sea of Okhotsk 2013 (magnitude 8.3), magnitude versus intensity, and the unsolved puzzle of how rock breaks that deep. Volcanic earthquakes: volcano-tectonic quakes, low-frequency quakes from resonating cracks, volcanic tremor, and the 62 summit collapses of Kilauea in 2018. Induced earthquakes: Oklahoma's wastewater disposal wells (not mainly fracking), pore pressure on stressed faults, the 2016 Pawnee magnitude 5.8, and the 1967 Koyna reservoir earthquake in India. Slow slip: Cascadia's episodic tremor and slip, a few centimetres over weeks with the energy of about a magnitude 6.7, deeper than the locked part of the fault. Foreshocks: Ridgecrest 2019, a magnitude 6.4 followed by a 7.1 about 34 hours later, and why only about 5 to 10 percent of quakes turn out to be foreshocks. How the ground shakes and what an earthquake damages (waves, soft ground, liquefaction, landslides, aftershocks, fire) has its own episode on this channel: "Earthquake Hazards Explained: 8 Ways a Quake Does Damage". Where each fault type dominates is in "Plate Boundaries Explained", and how megathrusts launch tsunamis is in "What Triggers a Tsunami? 8 Causes Explained". Chapters: 0:00 Earthquake Types 0:32 Fault Slip 1:51 Megathrust 3:35 Intraplate 5:05 Deep-focus 6:25 Volcanic 7:33 Induced 8:51 Slow Slip 9:43 Foreshocks 10:28 Earthquake Types Main sources: USGS: Earthquake Facts & Earthquake Fantasy; Earthquake Magnitude, Energy Release, and Shaking Intensity; What is a fault and what are the different types?; Myths and misconceptions about induced earthquakes; The New Madrid Seismic Zone; 1811-1812 New Madrid earthquakes (Nuttli overview and sequence summary); Kilauea 2018 lower East Rift Zone eruption and summit collapse; Monitoring volcano seismicity; ANSS Comprehensive Catalog event records British Geological Survey: What causes earthquakes? IRIS / EarthScope: How often do earthquakes occur?; Foreshock, mainshock, aftershock; EarthScope Consortium: Volcanoes Pacific Northwest Seismic Network: Volcanic earthquakes Berkeley Science Review (2019): The mystery of deep earthquakes Earth Observatory of Singapore: What are the biggest historical earthquakes? Ishii et al. (2005), Nature; Ammon et al. (2005) and Lay et al. (2005), Science: the 2004 Sumatra-Andaman earthquake Central US Earthquake Consortium: New Madrid Seismic Zone; S. Stein, Northwestern University US Energy Information Administration (2017); Seismological Society of America (2024): Oklahoma induced earthquakes Rao et al. (2017), Journal of the Geological Society of India: Koyna-Warna seismicity Hulbert et al. (2020), Nature Communications; N. Bartlow (2020); OPB (2019): Cascadia slow slip Tepp et al. (2020), Earth and Planetary Science Letters; Neal et al. (2019), Science: Kilauea caldera collapse Ross et al. (2019), Science: the Ridgecrest earthquake sequence; Stanford Earth (2021): What causes earthquake foreshocks? Illustrations are AI-generated; narration is synthetic. Maps and diagrams are simplified and not to scale; realistic scenes are illustrations, not photographs of any real place or event. #Earthquake #TypesOfEarthquakes #EarthquakesExplained #Seismology #Geology #PlateTectonics #Megathrust #DeepEarthquake #InducedSeismicity #NewMadrid #SlowSlip #Foreshock #Volcano #EarthScience #ScienceExplained