Detection & Prediction
Most earthquakes are detected using a machine called a seismograph. A seismograph is a machine that makes little waves when there is an earthquake. There's two versions of the machine - a computer versions and a machine paper chart version. They do the same things, but the computer prints it.
The sheets of paper from the seismograph get the information from these metal transmitters that sends the information from one place to the place they have the seismograph like at an earthquake observatory, or university. The seismograph shows the magnitude during an earthquake. Loma Prieta measured at 7.1 on the Richter scale.
There is some proof that animals act strange before an earthquake. Dogs bark more, caged birds become crazy, and animals run away from home before an earthquake. The Indiana Times newspaper said cats can predict earthquakes, but they don't know how or why.
One site we went to was The United States Geological Service called the USGS. The USGS says some animals act weird before earthquakes, but you can't use that to predict an earthquake. The USGS also says there is no such thing as earthquake weather. Some people say if it's hot, it's earthquake weather. The USGC says since the things that control an earthquake are deep in the earth, the weather doesn't matter. There is also no time of year when more earthquakes happen. The best the USGS can do is guess that a big earthquake will probably happen in the next 30 years in Northern California.