Yes, fault lines on Earth can be seen from space with the naked eye.

The crews of the ISS ( and other manned missions ) regularly take photos with handheld cameras ( "Gateway to Astronaut Photography of Earth at https://eol.jsc.nasa.gov/ ), and obviously, they need to point the camera at the subject of interest. ( https://eol.jsc.nasa.gov/FAQ/#nakedEye ).

These are incredibly valuable to geologists, especially for very emergent events, or acquisitions needing very specific orientations and other conditions which are impossible for standard satellite sensors. You can even ask for your own: https://eol.jsc.nasa.gov/RequestNewImagery/

For example ISS030-E-35487 East African Rift Valley Features, Kenya at https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=ISS030&roll=E&frame=35487

"The most striking features in this view are the numerous, nearly parallel, linear fault lines that occupy the floor of the valley (most of the image). Shadows cast by the late afternoon sun make the fault scarps (steps in the landscape caused by slip motion along individual faults) more prominent. The faults are aligned with the north-south axis of the valley (image lower left to top right). A secondary trend of less linear faults cuts the main fault trend at an acute angle, the fault steps throwing large shadows."

Şeyda Bostancı

Yes, some fault lines on Earth can be seen from space, especially from satellites and spacecraft. The largest and most active faults often leave clear geological traces that can be observed from orbit.

Examples of visible fault lines:

🌍 San Andreas Fault (USA) – One of the most famous faults in the world, stretching through California. It is visible from space as a long crack in the landscape.

🌍 North Anatolian Fault (Turkey) – Clearly noticeable in satellite images due to terrain deformations caused by frequent earthquakes.

🌍 East African Rift – A massive tectonic rift that is splitting the African plate. Its width and depth make it highly visible from space.

🌍 Alpine Fault (New Zealand) – Partially visible from satellites due to distinct changes in the terrain.

Although some smaller faults may not be easily detectable, large fault lines that cause significant topographic changes are well visible from orbit. Satellite radar, LiDAR, and other technologies further enhance the ability to map them from space

Faults can be mapped under the surface by taking seismic data from oil and gas surveys. Not all seismic datasets of this kind are available but some are available through universities. Using the seismic data to produce a subsurface fault and then projecting a plane up to the surface can produce a virtual previously unseen fault lines on the surface. One other method that can be used is taking earthquake data from a region over time (years). Most earthquakes occur along a fault. By taking all the the earthquake foci across a region over time and fitting a plane to the surface will produce a virtual fault line on the surface. The accuracy, detail, and resolution of using a series of earthquake foci mapped to a plane may not be as accurate as seismic data from oil and gas but in some regions this may be the only data available. The data for earthquakes going back to the 1900s is free from USGS and other centers. The last method is radar interferometry also know as SAR. This can map differences some very subtle as a few centimeters. This is depended on data sets taken before and after an earthquake that has caused the area of the fault line to move in order to detect the differences. The resolution is also dependent on the frequency band of the radar, strength of signal, and the 3D delta on the surface. Hope this helps you and others in the discussion.