Embarrassed and frustrated to note that apparently a lot of New Zealanders still just don't get tsunami's or tsunami warnings, as evidenced here (from the NZ Herald), and here (from Stuff, also using any excuse to publish pictures of naked people). It's not the height of the surge, its the force behind it (there is footage of a 30cm ish surge happily relocating a 4x4 from last year's Samoan tsunami). Tsunami's on shore are less waves than they are instant and recurring turbulent rivers or floods, with a habit of dragging things out to sea when they recede. We got off very lucky yesterday in only being mildly inconvenienced, with some dramatic looking surges around the place to lead the news. Regardless of actual event / non-event status, the potential danger is quite real, and the warnings were justified. Previous tsunami related facepalming/headdesking here.
I noticed a figure in the paper concerning the amount of energy released in Saturday's 8.8 Richter Scale Chilean earthquake that got me thinking about comparisons.
Mostly off the top of my head, with some looking up here and there to clarify numbers.
Hiroshima Atomic Bomb : Energy release is estimated, but generally agreed to be arond 10-15 kilotons (kiloton = 1000 tons of TNT).
Largest nuclear weapon deployed during the cold war : 25 megatons (megaton 1,000,000 tons of TNT). The sort of thing you would use to lay waste to a city the size of say, New York, Tokyo or Los Angeles and the surrounding districts, or turn small mountains into lakes should the need arise.
Largest nuclear device ever tested (and largest man-made explosion in history) : 50 Megatons and generally considered to be too powerful to be a practical weapon. It was designed to be 100 megatons, but there was no way to safely test it so it was scaled down.
Thats where the human numbers run out. Get nature involved and the numbers go crazy.
1883 Krakatoa volcanic eruption : The cataclysmic explosion event that destroyed the volcano itself is estimated at 200 megatons. Made half an island disappear, and being heard 5,000 km away, one of the loudest sounds in recorded history. Generated tsunamis 30m or more high locally.
2008 Sichuan earthquake : 8.0 on the richter scale, and equivalent to 1 gigaton (1000 megatons, or 1,000,000,000 tons of TNT)
75,000 years BP (Before Present) Toba eruption : 8.5 on the richter scale, equivalent to 5.6 gigatons, and the largest known volcanic eruption. The eruption that created Lake Taupo 26,000 years ago is on a similar scale. This sort of power easily exceeds that of every nuclear weapon ever built combined.
2010 Chilean earthquake : 8.8 on the richter scale, equivalent to nearly 16 gigatons.
2004 Indian ocean earthquake : 9.1, 67 gigatons, and responsible for the Boxing Day Tsunami.
1960 Chilean earthquake : 9.5, 178 gigatons, and the most powerful earthquake ever recorded.
65,000,000 years BP Yucatan asteroid impact : Estimated at 13 on the richter scale (which is logarithmic remember), and an apocalyptic in every sense 100 teratons (1,000,000,000 megatons). Generally held to be the event that caused the final extinction of dinosaurs, allowing the rise of mammals and eventually, us.