U.S. Earthquake Faults is an iPhoneŽ/iPad 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 (see below):

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 15,000 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" (15,000 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 (1.18) is available on the App Store (here) for $1.99. It requires IOS 12.0 or later and an 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).

The current version (1.18) works with iPhone SE, 5s, 6-8, X, 11 and iPad mini 2-4, Air 1-2, 5th Gen, 9.7" Pro, 10.5" Pro and 12.9" Pro.

NOTES:
(1) We developed another app called California Earthquake Faults. It's described here and available on the App Store here.
(2) Under certain conditions, Location Services doesn't work properly. You can work around this problem by: (a) turning Location Services off and back on (Settings, Privacy, Location Services), and/or (b) setting Location Services, U.S. Faults to "Ask Next Time" (Settings, Privacy, Location Services, U.S. Faults).
(3) This app currently has 2 reviews in the App Store - a 5 star and a 2 star. The 2 star review states: "As of this review, faults are limited to the western USA. No faults in Alaska." The App Store description and this website have always clearly stated in the first sentence that this app covers the continental United States. The continental United States includes the "lower 48". It does not include Alaska and Hawaii. There is a good reason for this limitation. If the map covered the entire United States, it would have to be zoomed out considerably to show Hawaii and Alaska and that would come at the expense of clearly showing the "lower 48" and its faults.

FAULT MAPS

Shows faults near the current/found location 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.

DISTANCES, FIND, INFO & SETTINGS

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.

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.

DRIVING OVER FAULTS

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

SUPPORT

Comments and questions are welcome. Contact us at dpasadis@icloud.com. You will get a response.