Earth Impact Effects Program

Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current (limited) understanding of the impact process and come with large uncertainties; they should be used with caution, particularly in the case of peculiar input parameters. All values are given to three significant figures but this does not reflect the precision of the estimate. For more information about the uncertainty associated with our calculations and a full discussion of this program, please refer to this article

Your Inputs:

Distance from Impact: 48.30 km ( = 30.00 miles )

Projectile diameter: 1.61 km ( = 1.00 miles )

Projectile Density: 8000 kg/m³

Impact Velocity: 48.30 km per second ( = 30.00 miles per second )

Impact Angle: 90 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 30.5 meters ( = 100.0 feet ), over crystalline rock.

Energy:

Energy before atmospheric entry: 2.04 x 10²² Joules = 4.87 x 10⁶ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.6 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?

The crater opened in the water has a diameter of 60.2 km ( = 37.4 miles ).

For the crater formed in the seafloor:

Transient Crater Diameter: 36.8 km ( = 22.8 miles )

Transient Crater Depth: 13 km ( = 8.07 miles )

Final Crater Diameter: 59.1 km ( = 36.7 miles )

Final Crater Depth: 1.01 km ( = 0.627 miles )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 180 km³ = 43.1 miles³

Roughly half the melt remains in the crater, where its average thickness is 169 meters ( = 555 feet ).

Thermal Radiation:

What does this mean?

Time for maximum radiation: 1.13 seconds after impact

Your position is inside the fireball.

The fireball appears 256 times larger than the sun

Thermal Exposure: 4.14 x 10⁹ Joules/m²

Duration of Irradiation: 11.8 minutes

Radiant flux (relative to the sun): 5840

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 9.66 seconds after impact.

Richter Scale Magnitude: 9.1

Mercalli Scale Intensity at a distance of 48.3 km:

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.

XI. As X. Rails bent greatly. Underground pipelines completely out of service.

XII. As X. Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into the air.

Ejecta:

What does this mean?


The ejecta will arrive approximately 1.66 minutes after the impact.

Your position is beneath the continuous ejecta deposit.

Average Ejecta Thickness: 145 meters ( = 475 feet )

Mean Fragment Diameter: 2.71 meters ( = 8.88 feet )

Air Blast:

What does this mean?


The air blast will arrive approximately 2.44 minutes after impact.

Peak Overpressure: 1.19e+07 Pa = 119 bars = 1680 psi

Max wind velocity: 2760 m/s = 6170 mph

Sound Intensity: 141 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.

Tsunami Wave:

What does this mean?

Your location is within the crater formed in the water layer. This is where the impact tsunami wave is generated.

Click here for a pdf document that details the observations, assumptions, and equations upon which this program is based. It describes our approach to quantifying the important impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The processes included are: atmospheric entry, impact crater formation, fireball expansion and thermal radiation, ejecta deposition, seismic shaking, and the propagation of the atmospheric blast wave.

Recent improvements in the airblast calculation are described here.