[BenLurkin]

This composite of 30 images of asteroid 2014 JO25 was generated with radar data collected,
using NASA’s Goldstone Solar System Radar in California’s Mojave Desert on Tuesday April 18.
Credit: NASA/JPL-Caltech/GSSR

[Godebert]

Arecibo Observatory Planetary Radar System observations on 17 April reveal that peanut-shaped asteroid 2014 JO25 is twice as large as previously thought. This looping movie of the 1.3-kilometre-long body was produced by combining several delay-Doppler images. The movie spans two hours of observations. Vertical resolution is 7.5 metres/pixel. Movie credit: Arecibo Observatory/NASA/NSF.An asteroid discovered three years ago by the Catalina Sky Survey in Arizona as part of NASA’s Near-Earth Object (NEO) Observations Program passes within five lunar distances of Earth on 19 April — the closest any known space rock of this size has approached our planet since September 2004. Previously believed to be 650 metres in diameter, data gathered by the Arecibo Observatory Planetary Radar System in Puerto Rico on 17 April reveals that the peanut-shaped asteroid is double that size.

[Godebert]

I recalculated the impact for the increased size of 1.3 km. Calculations were for an impact off the east coast in 2,000 ft. feet depth at 1,000 miles from the coast. Impact assumes a dense rock type impact.

Energy before atmospheric entry: 2.9 x 10^21 Joules = 6.93 x 10^5 MegaTons TNT

The crater opened in the water has a diameter of 30.4 km ( = 18.9 miles ). For the crater formed in the seafloor: Transient Crater Diameter: 16.4 km ( = 10.2 miles ) Transient Crater Depth: 5.79 km ( = 3.59 miles ) Final Crater Diameter: 23.7 km ( = 14.7 miles ) Final Crater Depth: 767 meters ( = 2520 feet ) The crater formed is a complex crater. The volume of the target melted or vaporized is 10.1 km^3 ( = 2.42 miles^3 ) Roughly half the melt remains in the crater, where its average thickness is 48 meters ( = 158 feet ).

The major seismic shaking will arrive approximately 3.33 minutes after impact. Richter Scale Magnitude: 8.3 Mercalli Scale Intensity at a distance of 1000 km:

• Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.

• Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

TSUNAMI

The impact-generated tsunami wave arrives approximately 3.6 hours after impact. Tsunami wave amplitude is between: 9.28 meters ( = 30.4 feet) and 18.6 meters ( = 60.9 feet).