That would eradicate life on Earth.

it would destroy that city and things around it for a good number of miles... say - 40. the earth, no... it's not that big. now one like that scaled up to 4-5 miles... yeah, bye bye earth as we know it.

It would make a huge crater, world wide shock wave and nuclear winter equivalent for years. Much of the higher level life, perhaps most, would perish.

still looking through this myself... but appears 40 miles for impact might not be enough,....


Your Inputs:
Distance from Impact: 64.40 km ( = 40.00 miles ) Projectile diameter: 3.22 km ( = 2.00 miles ) Projectile Density: 1500 kg/m3 Impact Velocity: 33.80 km per second ( = 21.00 miles per second ) Impact Angle: 90 degrees Target Density: 2500 kg/m3 Target Type: Sedimentary Rock
Energy:
Energy before atmospheric entry: 1.50 x 1022 Joules = 3.58 x 106 MegaTons TNTThe average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.2 x 107years
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 tilt of Earth's axis (< 5 hundreths of a degree).The impact does not shift the Earth's orbit noticeably.
Crater Dimensions:
What does this mean?


Transient Crater Diameter: 31.7 km ( = 19.7 miles )Transient Crater Depth: 11.2 km ( = 6.96 miles )
Final Crater Diameter: 50 km ( = 31 miles )Final Crater Depth: 961 meters ( = 3150 feet ) The crater formed is a complex crater. The volume of the target melted or vaporized is 133 km3 = 31.8 miles3 Roughly half the melt remains in the crater, where its average thickness is 168 meters ( = 550 feet ).
Thermal Radiation:
What does this mean?


Time for maximum radiation: 1.46 seconds after impact
Visible fireball radius: 48.9 km ( = 30.4 miles ) The fireball appears 173 times larger than the sunThermal Exposure: 1.70 x 109 Joules/m2Duration of Irradiation: 10.7 minutesRadiant flux (relative to the sun): 2660
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:
What does this mean?


The major seismic shaking will arrive approximately 12.9 seconds after impact.Richter Scale Magnitude: 9.0Mercalli Scale Intensity at a distance of 64.4 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:
What does this mean?


The ejecta will arrive approximately 1.92 minutes after the impact.Your position is beneath the continuous ejecta deposit.Average Ejecta Thickness: 33.8 meters ( = 111 feet ) Mean Fragment Diameter: 1.06 meters ( = 3.49 feet )

Air Blast:
What does this mean?


The air blast will arrive approximately 3.25 minutes after impact.Peak Overpressure: 4.87e+06 Pa = 48.7 bars = 691 psiMax wind velocity: 1760 m/s = 3930 mphSound Intensity: 134 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.

at 80 miles away... with the comet hitting at a 45 degree angle... makes a difference


Air Blast:
What does this mean?


The air blast will arrive approximately 7.32 minutes after impact.Peak Overpressure: 790000 Pa = 7.9 bars = 112 psiMax wind velocity: 668 m/s = 1490 mphSound Intensity: 118 dB (May cause ear pain)Damage Description:

just 112 psi... you would if in a bunker.

site - http://impact.ese.ic.ac.uk/ImpactEffects/