Asteroid impact risks 'underappreciated' (BBC) {new data from infrasound detectors}

[eppur_se_muova]

A visualisation showing where sizeable asteroids have hit the Earth in recent years has been released by the B612 Foundation.

The US-based group, which includes a number of former Nasa astronauts, campaigns on the issue of space protection.

It hopes the visualisation will press home the idea that impacts are more common than we think.

The presentation leans on data collected by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

The CTBTO operates a network of sensors that listens out for clandestine atom bomb detonations.
***
more: http://www.bbc.com/news/science-environment-27039285
video: https://b612foundation.org/
more: http://www.neoshield.net/en/index.htm (an EU-based organization)




Worth a read. Apparently there have been several strikes larger than the Chelyabinsk meteor in the last several years, all over the open ocean, where they were unobserved, except for seismic signals.

[jakeXT]

1. I thought they gave a min. value for some impacts and used an estimate for Chelyabinsk,

or where is the 600 kt number coming from? That would make Chelyabinsk the biggest one in the last 14 years.

The team used a variety of other models to estimate airburst damage including the bolide period – yield (E) relation of log E = 3.28log(P) + 0.71 (virtually identical to the widely used nuclear weapons data testing as given by the Air Force Application Centre) which gives a best estimate of 600 kt, however the standard error allows for values of equivalent energy of 350-990 kt.

http://alpha-lyrae.co.uk/2013/11/09/analysis-of-chelyabinsk-meteorite-yields-size-energy-source-and-concludes-large-asteroid-impact-risk-underestimated/

Between 2000 and 2013, a network of sensors that monitors Earth around the clock listening for the infrasound signature of nuclear detonations detected 26 explosions on Earth ranging in energy from 1-600 kilotons – all caused not by nuclear explosions, but rather by asteroid impacts.

...
8/25/2000 (1-10 kilotons) NORTH PACIFIC OCEAN

4/23/2001 (1-10 kilotons) NORTH PACIFIC OCEAN

3/9/2002 (1-10 kilotons) NORTH PACIFIC OCEAN

8/9/2006 (1-10 kilotons) INDIAN OCEAN

9/2/2006 (1-10 kilotons) INDIAN OCEAN

10/2/2006 (1-10 kilotons) ARABIAN SEA

12/9/2006 (10-20 kilotons) EGYPT

9/22/2007 (1-10 kilotons) INDIAN OCEAN

12/26/2007 (1-10 kilotons) SOUTH PACIFIC OCEAN

10/7/2008 (1-10 kilotons) SUDAN

10/8/2009 (>20 kilotons) SOUTH SULAWESI, INDONESIA

9/3/2010 (10-20 kilotons) SOUTH PACIFIC OCEAN

12/25/2010 (1-10 kilotons) TASMAN SEA

4/22/2012 (1-10 kilotons) CALIFORNIA, USA

2/15/2013 (>20 kilotons) CHELYABINSK, OBLAST, RUSSIA

4/21/2013 (1-10 kilotons) SANTIAGO DEL ESTERO, ARGENTINA

4/30/2013 (10-20 kilotons) NORTH ATLANTIC OCEAN
https://b612foundation.org/list-of-impacts-from-impact-video/

[eppur_se_muova]

2. The 600 kt estimate appears to be due to a different group, published Nov 2013 ...

I don't know if that conclusion was subsequently revised, or the B612 group used estimates from other sources.

[jakeXT]

3. They only list CHELYABINSK and SOUTH SULAWESI as >20kt, all the others in the list are smaller

Tunguska 1908 with 10-15Mt was definitely bigger than Chelyabinsk, but there isn't much more in the last 100 years.
South Sulawesi is listed on Wikipedia as 31–50kt.

http://en.wikipedia.org/wiki/List_of_meteor_air_bursts