Magnitude 6.1 shallow earthquake hit Tonga region

Magnitude 6.1 shallow earthquake hit Tonga region

Shallow earthquake with recorded Magnitude 6.1 hit Tonga region on November 17, 2012 at 05:12 UTC according to USGS. Epicenter was located 174 km (108 miles) ENE of Neiafu, Tonga and 473 km (293 miles) SSW of Tafuna, American Samoa at coordinates 18.311°S, 172.374°W. Recorded depth by USGS was only 9.8 km (6.1 miles). EMSC recorded magnitude 5.9.

No people are living within 100 km.

Magnitude 6.1
  • Saturday, November 17, 2012 at 05:12:56 UTC
  • Friday, November 16, 2012 at 06:12:56 PM at epicenter
Location 18.311°S, 172.374°W
Depth 9.8 km (6.1 miles)
Distances 174 km (108 miles) ENE of Neiafu, Tonga
430 km (267 miles) NE of Nuku`alofa, Tonga
473 km (293 miles) SSW of Tafuna, American Samoa
480 km (298 miles) SSW of Pago Pago, American Samoa
Location Uncertainty horizontal +/- 14.6 km (9.1 miles); depth +/- 2.7 km (1.7 miles)
Parameters NST=479, Nph=491, Dmin=490.9 km, Rmss=0.62 sec, Gp= 32°,
M-type=regional moment magnitude (Mw), Version=A
  • Magnitude: USGS NEIC (WDCS-D)
    Location: USGS NEIC (WDCS-D)
Event ID usc000du43

Tectonic summary by USGS

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most seismically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again. (Read the rest here)

Featured image: EMSC + Google Earth

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