U.S. Earthquake Faults is an iPhoneŽ/iPadŽ app that shows your current location or a location you specify, the closest faults in the continental United States and approximate distances to those faults.  There are 5 main screens (shown below):

Fault Maps Current or found location, faults in the selected area and names/distances to the closest 4 faults.
Distances Names, distances and color coding of the closest 50 (iPhone) or 70 (iPad) closest faults.
Find Find the nearest faults to a location you specify.
Info Basic information about the app.
Settings View and adjust app settings.

U.S. Earthquake Faults shows the vast majority of faults the USGS classifies as "Historic" (active in the last 150 years) and "Holocene to Latest Pleistocene" (active in the last 1500 years). That includes over 300 faults and over 700 fault lines (some faults have multiple fault lines). It does not include all faults or faults classified as "Quaternary" (1,500 to 1,600,000 years) by the USGS. All fault lines and distances are approximations. For more information, go the the USGS web site (here).

The current version (1.04) is available on the App Store (here) for $1.99. It requires IOS 10.x and runs on the iPhoneŽ 5s/6/6+/6s/6s+/SE/7/7+, iPadŽ Air 1/2, iPad miniŽ 2/3/4 and iPad Pro 9.7/12.9. It also requires active WiFi or cellular services (preferably both) that allow secure connections to the Internet. Some public WiFi networks do not allow secure connections, in which case, you can turn off WiFi and use a cellular network (if you have one).


Shows faults near the current/found location, faults in that state, faults in that region of the country or faults in the United States. Shows distances to the 4 closest faults and allows zooming into them (like San Andreas below). Tapping a fault with show its name.

Current Location
United States
Zoom into San Andreas
San Francisco


Distances shows distances to closest 50 (iPhone) or 70 (iPad) faults.
Find allows searches for specific locations.
Info shows basic app information.
Settings shows and adjusts app settings.

San Francisco
San Francisco
San Francisco
San Francisco

A few settings require explanation:

- "Update Map Region" controls whether or not the map display is adjusted automatically when you are moving.
- "Describe Selected Fault" controls whether or not a fault name is displayed when you select one of the 4 closest faults.
- "Describe Found Location" controls whether or not a location name is displayed when you use the Find function.


If you live near faults included in this app, you can locate faults by driving over them.

Approach fault
Drive up to fault
San Francisco
San Francisco


Comments and questions are welcome. Contact us at You will get a response.

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