This app was mentioned in 4 comments, with an average of 1.75 upvotes
If you live anywhere in Japan, you should have something that gets the live data from NIED seismic stations (I recommend 強震モニタEx but there are many). You can set it to alert for anything down to shindo 1 which is usually ~M3.5.
I've tried a number of earthquake apps and had by far the best experience with 強震モニタEx (there are a bunch of others that pull the same data from NIED but this one delivers it in the nicest package IMO).
Not to say I've tried every single monitor out there - I've seen videos of feeds from people running tons of them on a single system, including ones I don't recognize - but this is the one I keep coming back to.
I wish the scale were in shindo instead of gals, but every now and then I try out alternative apps that use the same data feed and I keep coming back to this one because I have bigger complaints about the others.
I wish the scale were in shindo instead of gals, but every now and then I try out alternative apps that use the same data feed and I keep coming back to this one because I have bigger complaints about the others.