A strong earthquake near the instrument will usually displace the reading off scale or may even damage the instrument.
如果在这类仪器的附近发生一次强烈的地震，一般就会使记录出格，甚至可能损坏仪器。
2
Focusing eyepiece provides a sharp, easy-to-read scale, which is designed with semi-transparent blue background so you don't have to point the instrument in a certain direction to get your reading.