I’ve always been an amateur geology buff, and I’ve read about the most vulnerable areas of the the United States for years. The following list is entirely subjective, in no particular order, and does not take terrorism into account. If it did, a nuke/bioweapon/whatever smuggled into New York or Los Angeles harbor would become the instant #1.
#1: Everything from Memphis, Tennessee to Saint Louis, Missouri. These cities sit on top of the New Madrid fault, which, in 1811, produced a quake strong enough to ring church bells in Boston (!!!). Estimates of its magnitude range from 8.0 on up to 9+. Damage will be massively increased by the water saturated ground (which will undergo liquifaction) and the fact that this region has almost no quake-proofing in its buildings. Only the fact that almost no one lived there at the time prevented this from being the worst disaster in US history. As it was, several very small towns were completely engulfed by liquid earth.
#2: Seattle, Washington and its southeastern suburbs. All kinds of fun are possible here. There’s a major subduction zone off the coast capable of producing enormous tsunamis, as evidenced by dead forests and meters-thick mud deposits. Mt. Ranier, to the southeast, has been dismantling itself via explosive eruptions for tens of thousands of years now, producing lahars that underlie many current bedroom communities.
#3: The Oakland to San Jose corridor. The Hayward fault, a little known but powerful quake-maker, runs under the densely populated East Bay, most of which is built on loosely consolidated soils prone to liquifaction. Quake building codes are good here, but the proximity of the fault would create enormous ground shaking that would test the strongest of structures.
#4: The Los Angeles metro area, of course. The last major quake along the infamous southern stretch of the San Andreas was in 1859, the huge 8.0 to 8.5 Tejon rupture. As much as 250 miles of the fault let go at the same time, with ground displacements of 30 feet or more. The average span between quakes of this magnitude is 150 to 200 years. You do the math. I currently live in the area, but not for long. My wife and I are moving to the far more stable region just north of San Diego in a matter of months. The fact that the “Big One” could fire before I get out of here terrifies me as much as living in New Orleans in the late 80’s during hurricane season did.
Who’d like to add to this list?