It's easy to tell when an earthquake hits an area full of Twitter users -- there's frequently a rush of panicked tweets within seconds of the ground shaking. If Twitter and Stanford University have their way, though, those posts could be useful for more than just alerting friends. They've conducted research showing that geotagged tweets can help model the effects of a quake while it's happening. When you combine geological data with the volume of related tweets within a given radius, it's easier to determine the intensity of tremors and accurately track how they spread.