2013 Seddon earthquake

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For the earthquake of 16 August 2013, see 2013 Lake Grassmere earthquake.
2013 Cook Strait earthquakes
2013 Seddon earthquake is located in New Zealand
2013 Seddon earthquake
Date 21 July 2013 (2013-07-21)
Origin time 5:09:30 pm NZST
Magnitude 6.5 Mw
Depth 17 kilometres (11 mi)
Epicenter 41°37′S 174°20′E / 41.61°S 174.33°E / -41.61; 174.33Coordinates: 41°37′S 174°20′E / 41.61°S 174.33°E / -41.61; 174.33
Areas affected New Zealand
Tsunami None
Casualties 4 people injured[1]

The 2013 Seddon earthquake measured 6.5 on the moment magnitude scale and was centred in New Zealand's Cook Strait, around 20 kilometres (12 mi) east of the town of Seddon in Marlborough. The earthquake struck at 5:09:30 pm on 21 July 2013 (05:09 UTC) at a depth of 17 kilometres (11 mi), according to Geonet.[2] The United States Geological Survey also measured the quake at 6.5, at an even shallower depth of 14 kilometres (8.7 mi).[3] The quake caused moderate damage in the wider Marlborough area and Wellington, the nation's capital city 55 kilometres (34 mi) north of the epicentre. Only minor injuries were reported. Several aftershocks occurred during 21–29 July.

The Seddon earthquake is considered the first of an earthquake doublet, with a second earthquake of similar magnitude occurred on 16 August 2013.

Quake[edit]

Shakemap[4]

The mainshock followed a series of gradually increasing magnitude earthquakes from a sequence which began two days earlier:[5]

  1. Magnitude 5.7, 16 km depth, 19/07/2013
  2. Magnitude, 6.5 17 km depth, 21/07/2013
  3. Magnitude 5.8, 19 km depth, 21/07/2013
  4. Magnitude 5.3, 16 km depth, 21/07/2013
  5. Magnitude 5.0, 16 km depth, 21/07/2013
  6. Magnitude 4.9, 16 km depth, 21/07/2013
  7. Magnitude 4.9, 18 km depth, 21/07/2013
  8. Magnitude 4.8, 10 km depth, 22/07/2013
  9. Magnitude 4.8, 17m depth, 21/07/2013
  10. Magnitude 4.9, 10 km depth, 22/07/2013

[6]

Main aftershocks since 21 July 2013[edit]

Below is a list of all aftershocks of Richter,Moment & Body-wave Magnitudes 5.0 and above that have hit the Cook Strait since 16 August 2013 earthquake.[7]

Date Time Richter Magnitude Earthquake Epicentre Depth (km) Depth (miles)
21 July 2013 5:13 pm 5.2 30 km northeast of Seddon 13 km 8.1 miles
22 July 2013 10:47 am 5.0 15 km east of Seddon 16 km 9.9 miles
29 July 2013 1:07 am 5.4 20 km east of Seddon 12 km 7.5 miles
16 August 2013 2:37 pm 5.4 5 km southeast of Seddon 9 km 5.6 miles
16 August 2013 2:45 pm 5.4 10 km southeast of Seddon 6 km 3.7 miles
16 August 2013 2:56 pm 205 km east of Seddon 5 km 4.1 miles
16 August 2013 3:09 pm 5.5 10 km south of Seddon 8 km 5.0 miles
16 August 2013 3:51 pm 5.6 10 km east of Seddon 19 km 11.8 miles
16 August 2013 5:31 pm 6.0 15 km east of Seddon 14 km 8.7 miles
16 August 2013 5:56 pm 5.0 5 km northwest of Seddon 10 km 6.2 miles
16 August 2013 6:42 pm 5.2 20 km east of Seddon 20 km 12.4 miles
16 August 2013 8:38 pm 5.2 10 km southeast of Seddon 22 km 13.7 miles
17 August 2013 4:13 pm 5.0 15 km southwest of Seddon 20 km 12.4 miles
17 August 2013 8:58 pm 5.5 10 km south of Seddon 20 km 12.4 miles
18 August 2013 4:07 am 5.0 5 km southeast of Seddon 20 km 12.4 miles

Damage[edit]

The quake resulted in varying degrees of damage to thirty-five buildings within the Wellington CBD with glass from broken windows falling onto the main thoroughfare of Lambton Quay. Damage was also caused in Paraparaumu, Wainuiomata, Porirua and the Hutt Valley in the North Island.[6][8]

The Wellington Region emergency management office was activated on the evening of 21 July, as were those in the lower part of the North Island.[6] On 22 July parts of Wellington's central business district were closed to the public to allow for inspections to buildings with damaged and potentially dangerous façades.[9]

Four people were injured in the quake, which lasted for 20 seconds, blowing out windows, cracking concrete and swaying buildings.[1]

See also[edit]

References[edit]

  1. ^ a b "Wellington earthquake: We can afford new quake damage - PM". The New Zealand Herald. 22 July 2013. Retrieved 22 July 2013. 
  2. ^ "Quakes". GeoNet. Retrieved 21 July 2013. 
  3. ^ "M6.5 - 46km ESE of Blenheim, New Zealand". USGS. Retrieved 21 July 2013. 
  4. ^ "M6.5 Cook Strait earthquake ShakeMap". GNS Science. Retrieved 23 July 2013. 
  5. ^ "Cook Strait aftershocks and forecast probabilities". GeoNet. Retrieved 23 July 2013. 
  6. ^ a b c "Wellington earthquakes may have occurred on unmapped fault line". The New Zealand Herald. 23 July 2013. Retrieved 23 July 2013. 
  7. ^ "Canterbury quakes: Aftershocks". Geonet. GNS Science. 26 December 2011. Retrieved 26 December 2011. 
  8. ^ Quilliam, Rebecca (22 July 2013). "Wellington earthquake: 35 buildings damaged in CBD". www.nzherald.co.nz. Retrieved 23 July 2013. 
  9. ^ "Wellington earthquake: What you need to know". The New Zealand Herald. 22 July 2013. Retrieved 22 July 2013.