Yesterday, a M4.9 earthquake struck South Australia, and was felt by potentially millions of people including in Adelaide. While harmless as the October 27th 2026 earthquake caused no damage, its origin is quite interesting. It seems to have originated via a reactivated 500 million year old shear zone which is buried deep in the crust. Thumbnail Photo Credit: Google Earth, Data SIO, NOAA, U.S. Navy, NGA, GEBCO, Image Landsat / Copernicus. This image was overlaid with text, and then overlaid with GeologyHub made graphics (the image border & the GeologyHub logo). The MMI 2 and 3 contours in this video's thumbnail image (outer 2 contours) are traced from 0.1% g & 0.5% g respectively contours provided at from the © Commonwealth of Australia (Geoscience Australia) 2026, CC BY 4.0. https://earthquakes.ga.gov.au/. Only those contours also fall under that license in the thumbnail image, and nothing else. If you would like to support this channel, consider using one of the following links: (Patreon: http://patreon.com/geologyhub) (YouTube membership: https://www.youtube.com/channel/UCYeGh5VML5XPr5jYnzh3J6g/join) (Gemstone & Mineral Etsy store: http://prospectingarizona.etsy.com) (GeologyHub Merch Etsy store: http://geologyhub.etsy.com) Google Earth imagery used in this video: ©Google & Data Providers This video is protected under "fair use". If you see an image and/or video which is your own in this video, and/or think my discussion of a scientific paper (and/or discussion/mentioning of the data/information within a scientific paper) does not fall under the fair use doctrine, and wish for it to be censored or removed, contact me by email at [email protected] and I will make the necessary changes. Various licenses used in sections of this video (not the entire video, this video as a whole does not completely fall under one of these licenses) and/or in this video's thumbnail image (and this list does not include every license used in this video and/or thumbnail image): Public Domain: https://creativecommons.org/publicdomain/mark/1.0/ CC BY 3.0: https://creativecommons.org/licenses/by/3.0/legalcode CC BY 4.0: https://creativecommons.org/licenses/by/4.0/legalcode Sources/Citations: [1] The locations, magnitudes, depths, MMI contours (MMI 2 & 3 specifically), and dates of earthquakes mentioned in this video were sourced from © Commonwealth of Australia (Geoscience Australia) 2026, CC BY 4.0. https://earthquakes.ga.gov.au/ [2] U.S. Geological Survey 0:00 South Australia Earthquake 1:19 Strike-Slip Fault 2:29 Orogeny 2:54 Ancient Tectonics 3:21 George V Fracture Zone