Julie Schnurr, UH CVT Graduate Fellow FORENSIC ANALYSES OF UNSCHEDULED BLASTS: AUGUST 2015

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 Background

• Wednesday August 12th around 14:50 UTC a fire started in a warehouse in the • Warehouse was registered as a hazardous chemical storage facility for calcium carbide, sodium nitrate, and potassium nitrate • Sodium Cyanide (highly toxic) was also found nearby

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 2 • The warehouse was located within 1km of several residential areas.

Fig 1. Satellite view of blast area showing closeness of residential area. Satellite images captured some time before the explosions. http://www.bbc.com/news/world-asia-china-33844084

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 3 • Firefighters, unaware of the chemicals stored in the warehouse, attempted to fight the fire with • A reaction was set in motion causing two large explosions that could be felt kilometers away and were picked up by seismic and infrasound instruments

Fig 2. The aftermath of the explosions. Taken on August 15th. http://edition.cnn.com/2015/08/17/asia/china-tianjin-industrial-accidents/

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 4 Summary

• Two major explosions occurred in Tianjin • (39.0389°N 117.7371°E) • The First: ~15:34:01 UTC ~3 ton TNT [3] • The Second: ~15:34:33 UTC ~21 ton TNT [3] • We observed both explosions at one Fig 3. Stations with currently available data located near the Tianjin event. infrasound array and one seismic station

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 5 Seismic Detection

• Clear detection at station BJT located in Beijing • (40.0183°N 116.1679°E) • Source Distance: 173 km • BAZ: 128 degrees • Arrival times picked using STA/LTA function • Travel time for Primary (P) waves calculated using velocity model Fig 4. The 3-component seismogram produced by the iasp91 (speed ~6km/s) explosions, recorded by station BJT of the IC network ( New China Digital Seismograph Network). Frequency band 1.0 Hz to 35 Hz. Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 6 Spectral Representation

Fig 5. A spectrogram produced with the unfiltered Z component seismogram data, recorded by station BJT of the IC network ( New China Digital Seismograph Network). Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 7 1st

• Reported as a 2.3 magnitude earthquake according to the China Earthquake administration [3] • Measured P-arrival time is 15:34:30.9 +/- 0.1 • Expected Travel time 29.9 +/- 0.3 • Estimated time of blast is 15:34:01.0 +/- 0.3 Fig 6. The 3-component seismogram produced by the 1st blast, recorded by station BJT of the IC network. Times relative to 15:34:00. Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 8 2nd explosion

• Occurred 32.1+/-0.1 seconds after the first • Reported as a 2.9 Magnitude earthquake [3] • 7x greater intensity than the first explosion • Measured arrival time is 15:35:03.2+/-0.1 • Estimated time of blast is 15:34:33.1 +/- 0.3 Fig 7. The seismogram produced by the 2nd larger blast, recorded by station IC-BJT as well. Times relative to 15:34:55.000. Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 9 Infrasound Detection

• Detection at IMS array I34MN in Mongolia (47.8017°N 106.401°E) • BAZ is 133 degrees • Source distance is 1337 km • Expected arrival time is 16:39:32.1

Fig 8. Array processing for coherent acoustic arrivals.

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 10 Spectral Representation

Fig 9. The spectral representation of the beamform produced using the I34MN array. The top panel is the signal to noise ratio, the middle is the spectral representation and the bottom is the waveform. Frequency band 0.1-8HZ.

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 11 Future Analysis

• More local data is necessary for further analysis • Many Chinese stations likely picked up the explosions

Fig 10. Stations with currently available data located near the Tianjin event.

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 12 Aftermath of Blasts

• Fires continued to burn for several days after the explosions • August 15th several small explosions occurred • Possible Sodium Cyanide contamination

Casualties: 173 dead, 797 injured [2]

Consortium for Verification Technology: Workshop - October 15th & 16th, 2015 13 References

1. Richards and Kim report, Seismic analysis of BJT. 2. ISLA report on Tianjin blast 3. Chinese Seismic Network observations http://www.bbc.com/news/world-asia-china-33901206 4. The Guardian http://www.theguardian.com/world/2015/sep/12/tianjin-explosion-china-sets-final- death-toll-at-173-ending-search-for-survivors 5. CNN http://edition.cnn.com/2015/08/17/asia/china-tianjin-industrial-accidents/ 6. BBC http://www.bbc.com/news/world-asia-china-33844084

Data Sources 1. IRIS2. 2. US NDC

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