>Most of the phones have likely ran out of battery

I would suspect that a notable number of phones are still on. As long as you don't turn the screen on and don't use any battery-draining apps, modern smartphones can easily have a battery life of a week or longer (even outside airplane mode).

Using that big screen, the quad-core CPU and the high speed internet are the battery drains, all of those are mostly in low-power mode while the phone is just in your pocket.

If the issue is no cell coverage due to earthquake damage, and the victims do not enable airplane mode, those phones would likely die within a day searching for a signal; irregardless of the screen being off.

I don't think that false positives disqualify such approach.

You can easily combine techniques. Send rescue dogs and handlers wherever phone signals are traced.

Having worked for companies trying to detect mobile phones this would be about as useful as guessing. Triangulating a signal (if you could even get one from under 2 tons of rubble) is not an easy task in the real world, especially one that would need to be accurate to within 1m or so.

That's probably what they are doing. These people are not dummies that need to be lectured by some hacker news guys.

It would be a waste of resources to rescue an ownerless phone.

Use your imagination. No one is suggesting rescuers dig for ownerless phones. They would be just another signal used to determine where trapped people might be.

Which is why you'd correlate with lists of known missing and known not-missing people before digging in.

Missing people won't lose their phone in a disaster?

False dichotomy. You can do other things besides chasing a very high false positive-rate indicator and sitting still doing nothing.

It's one of many ways they are probably trying to find people. Seems worth a shot to me.

Not if it's so massively inefficient that the number of false positives mean that you waste time chasing air.

Massively inefficient meaning that 100x phones are not paired with people? That seems unlikely.

If people were at home when the quake struck it doesn't seem unlikely to me that only 1 in 100 would be in the immediate vicinity of their phone. (Maybe 1 in 100 is a strech, but 1 in 20?)

Who carries their phone in their pocket at home?

Smart phones.

I miss the time when I needed to charge my phone once per two weeks (I used it infrequently).