Why can't earthquakes be predicted effectively?

I feel that the country has the ability to forecast, but it does not publish the forecast. For example, if the Sichuan earthquake is predicted nationwide, it will cause great riots, and people will worry that people will run around and go to other provinces. What about other provinces? With so many people running around at once, the social order has been seriously disturbed. After the earthquake, everyone read a lot of reports, and everyone sympathized and helped the people in the disaster area. If there were no earthquake, how many people would lend a helping hand and give their love when people from Sichuan came to your door? In many ways, some people say that family planning is not as fast as the earthquake. It's not nice, but it's possible. There are many more.