The explosion they describe is in the kiloton range. To get megatons the main body would have to strike the ground in the 60,000 miles per hour range, not 2,000.
Table 1 - Risk of direct impact for a given location
Diameter | Kinetic Energy | Area Devastated |
|
||
(m) | Mt TNT | sq km | Earth | "City" | Inhabited Region & Expected Death toll |
50
|
10
|
1900
|
100 yr
|
30 million yr
|
900 yr
1 million
|
100
|
75
|
7200
|
1000 yr
|
70 million yr
|
8000 yr
3 million
|
200
|
600
|
29 000
|
5000 yr
|
90 million yr
|
30 000 yr
14 million
|
500
|
10 000
|
70 000
|
40 000 yr
|
290 million yr
|
180 000 yr
30 million
|
1 km
|
75 000
|
200 000
|
100 000 yr
|
260 million yr
|
290 000 yr
60 million
|
2 km
|
1 million MT
|
-
|
1 million yr
|
-
|
1 million yr
1.5 billion
|
All*
|
90 yr
|
14 million yr
|
800 yr
|