Don't think you need an alarm to tell you theres an earthquake in progress. But i'm from the american midwest and we don't get earthquakes, so what do i know
The op wants an earth "quack" alarm anyway. Not sure what part of the world they have those in. Is that where the earth opens up and ducks come pouring out?
A quick google search yeids this circuit.
**broken link removed**
No clue how effective it is. I know you would need to filter out vibrations not caused by the earth moving. I would imagine computers are used nowadays to help decide if the vibration sensed was from the earth or from somthing else?
Recently I had a surgeon remove the foggy lenses in my eyes (cataracts) and replace them with synthetic implants. This doctor invented many of the methods that are used by him and other doctors today. The results are absolutely fantastic. My fairly near to distant vision is perfect! I use reading glasses for closeup like I did before my vision got bad.