Big Shock Shakes Big City!

Almost 100 years ago, a big shock made the ground shake and that made houses fall down in a big city where people make movies and there are (now) too many cars. It was a bad ground shake. A lot of houses fell down. A lot of schools fell down, too. More than 100 people died. In one place, the big ground shake even made some things fly into the air. People have studied this ground shake before, but for the first time, we looked at exactly which houses fell down and which houses did not fall down. All ground shakes happen under the ground on things called faults. If a ground shake happens today, people can find out exactly how the fault moved because we have ground-shake boxes with computers inside that tell us exactly how the ground shook. One hundred years ago, there were no ground-shake boxes with computers inside. But by looking at which houses fell down and which houses did not fall down, we could use a big computer to find out how the fault moved to cause the big ground shake. We found the reasons why a lot of houses fell down in some places, but in other places, the windows in houses did not even break, even though they were not far from the fault. Our study tells us some important things about what could happen the next time a big ground shake happens in the same city.