[Baron von Richthofen (Vaclav)]

Originally Posted by DavidU

Vaclav, recalc it with a more likely 25kms.

Your Inputs:

Distance from Impact: 12000.00 km = 7452.00 miles
Projectile Diameter: 1000000.00 m = 3280000.00 ft = 621.00 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 25.00 km/s = 15.53 miles/s
Impact Angle: 90 degrees
Target Density: 1000 kg/m3
Target Type: Liquid Water of depth 1000.00 meters, over typical rock.
Energy:

Energy before atmospheric entry: 4.91 x 1029 Joules = 1.17 x 1014 MegaTons TNT
The average interval between impacts of this size is longer than the Earth's age.
Such impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion years ago.
Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
Crater Dimensions:

The crater opened in the water has a diameter of 4910 km = 3050 miles

For the crater formed in the seafloor:
Transient Crater Diameter: 3000 km = 1860 miles
Transient Crater Depth: 1060 km = 659 miles

Final Crater Diameter: 8540 km = 5310 miles
Final Crater Depth: 4.51 km = 2.8 miles
The final crater is replaced by a large, circular melt province.
The volume of the target melted or vaporized is 4.36e+09 km3 = 1.05e+09 miles3
Melt volume = 1.23 times the crater volume
At this size, the crater forms in its own melt pool.
Thermal Radiation:

Time for maximum radiation: 631 seconds after impact

Your position is inside the fireball.
The fireball appears 141 times larger than the sun
Thermal Exposure: 5.86 x 1011 Joules/m2
Duration of Irradiation: 205000 seconds
Radiant flux (relative to the sun): 2860

Effects of Thermal Radiation:

Clothing ignites

Much of the body suffers third degree burns

Newspaper ignites

Plywood flames

Deciduous trees ignite

Grass ignites

Seismic Effects:

The major seismic shaking will arrive at approximately 2400 seconds.
Richter Scale Magnitude: 14.0 (This is greater than any earthquake in recorded history)
Mercalli Scale Intensity at a distance of 12000 km:
IX. General panic. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluviated areas sand and mud ejected, earthquake fountains, sand craters.

X. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly.

Ejecta:

Little rocky ejecta reaches this site; fallout is dominated by condensed vapor from the projectile.

Air Blast:

The air blast will arrive at approximately 36400 seconds.
Peak Overpressure: 1.67e+07 Pa = 167 bars = 2380 psi
Max wind velocity: 3280 m/s = 7340 mph
Sound Intensity: 144 dB (Dangerously Loud)
Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Highway girder bridges will collapse.

Glass windows will shatter.

Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.