Strong and deep earthquake M 7.4 struck Tonga

Strong and deep earthquake M 7.4 struck Tonga

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A strong and deep earthquake M 7.4 struck south of Tonga on May 23, 2013 at 17:19 UTC. By preliminary reports USGS measured depth at 171 km, EMSC is reporting 179 km. Epicenter was located at the sea, 255km (158mi) SW of Vaini, Tonga and 753km (468mi) SE of Suva, Fiji at coordinates 23.100°S 176.600°W.

There are no people living in 100 km radius. 

This earthquake was near the Tonga trench, a convergent plate boundary, in the region well known for seismic activity. The trench lies at the northern end of the Kermadec-Tonga Subduction Zone, an active subduction zone where the Pacific Plate is being subducted below the Tonga Plate and the Indo-Australian Plate.

This seismicity maps have been generated by concatenating the ISC catalogue (since 1964), the EMSC Euro-Med Bulletin catalogue and the EMSC Real Time catalogue. Therefore, they show the seismicity from 1964 until the earthquake occurrence. Credit: EMSC

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 sesimically 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: USGS/Leaflet

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Tags: tonga

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