I am currently working on the backstory to a story I'm writing as a means of world-building. However, I'm not quite as physics-literate as everyone else, so rather than winging it and coming off like an idiot, I came here. http://sta.sh/0126svntmin Exhibit A. The red marks the range of the crater, the black dot is ground zero. Southern California was destroyed several decades before the story proper. The cataclysmic Salton Sea Event wiped out various cities, reaching into Nevada and Arizona. The Baja California peninsula was also separated from the land, becoming an island through the formation of the Gulf of California. The official report claims an asteroid did this. What size, speed, and amount of force would be enough to generate a crater that large? What sort of effects would the blast have on the region? I can be certain about wildfires and Las Vegas would be affected by the aftershock.