:::::Those Google hits you mention could lead to coverage of the 1906 quake or the 1989 quake, or any of the many other quakes that have hit Northern California in the past few centuries. "South Napa earthquake" describes the area impacted concisely while "Northern California Earthquake" describes a vastly larger area, and it would be foolish to give that title to this article. Any reliable source describing the quake in any detail would use much more targeted descriptions, though they may include the phrase "Northern California" in their coverage if writing for an international audience. I challenge you to produce a single reliable source that calls this quake "The Northern California Earthquake" as if that is its accepted name.