Scientists have detected previously unknown movement along the San Andreas Fault, although the discovery doesn't change the two most important facts: There will be a major quake along the California fault at some point, and nobody knows just when it will happen. The analysis of GPS data found that large areas of land along the fault, including the Los Angeles Basin, are rising by 2mm to 3mm a year—which NBC San Francisco notes counts as major movement in seismic terms—while other areas, including Santa Barbara and San Luis Obispo counties, are sinking. The motion makes it seem like the huge 125-mile lobes of land along the fault are "doing the wave in slow motion," reports Live Science.
Lead study author Sam Howell of the University of Hawaii tells the Los Angeles Times that the movement is the result of a buildup of seismic energy, which will eventually be released in an earthquake. He says they happen along the fault roughly every 150 years, and while the last major one was 159 years ago, stress has been building up in some areas for centuries longer. The movement will help researchers "understand more about how the fault is behaving and the effect it's going to have in the surrounding region," he says, though it won't be any help in predicting an exact date for the next quake. "It's pretty much impossible to say when the next one will happen." (The director of the Southern California Earthquake Center says the southern part of the fault "looks like it's locked, loaded, and ready to go.")