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2013 Seddon earthquake: Difference between revisions

Coordinates: 41°37′S 174°20′E / 41.61°S 174.33°E / -41.61; 174.33
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The earthquake swarm may have occurred on an unmapped fault line. The source fault of the quake is under investigation but potential candidates are the Needles fault, London Hill fault, and/or extensions of the larger faults in the [[Marlborough Fault System]], the [[Awatere Fault|Awatere]], [[Clarence Fault|Clarence]], [[Hope Fault|Hope]], and [[Wairau Fault]]s. The geologic (and tectonic) complexity increases as the system moves off the South Island and into Cook Strait. The locations/interactions of the individual faults are not fully understood. There were about 24 known active faults in the Cook Strait and five in the area where the earthquakes occurred. However, the weekend's quakes could have occurred on a new fault yet to be mapped. The faults in Cook Strait are not large enough to generate magnitude-8 earthquakes, but are capable of magnitude 7-7.5 size earthquakes. The weekend's Cook Strait earthquakes would have needed to be at least a magnitude 7.5 to generate a [[tsunami]]. However, some coastline around Cook Strait had areas identified as potential landslide risk, and a smaller earthquake could cause a landslide which could then generate a tsunami. This type of tsunami could be quite devastating to the south coast of the North Island and north coast of the South Island.<ref name=nisi>{{cite web | url=http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10901958 | title= Wellington earthquakes may have occurred on unmapped fault line | work= The New Zealand Herald | accessdate=23 July 2013}}</ref>
The earthquake swarm may have occurred on an unmapped fault line. The source fault of the quake is under investigation but potential candidates are the Needles fault, London Hill fault, and/or extensions of the larger faults in the [[Marlborough Fault System]], the [[Awatere Fault|Awatere]], [[Clarence Fault|Clarence]], [[Hope Fault|Hope]], and [[Wairau Fault]]s. The geologic (and tectonic) complexity increases as the system moves off the South Island and into Cook Strait. The locations/interactions of the individual faults are not fully understood. There were about 24 known active faults in the Cook Strait and five in the area where the earthquakes occurred. However, the weekend's quakes could have occurred on a new fault yet to be mapped. The faults in Cook Strait are not large enough to generate magnitude-8 earthquakes, but are capable of magnitude 7-7.5 size earthquakes. The weekend's Cook Strait earthquakes would have needed to be at least a magnitude 7.5 to generate a [[tsunami]]. However, some coastline around Cook Strait had areas identified as potential landslide risk, and a smaller earthquake could cause a landslide which could then generate a tsunami. This type of tsunami could be quite devastating to the south coast of the North Island and north coast of the South Island.<ref name=nisi>{{cite web | url=http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10901958 | title= Wellington earthquakes may have occurred on unmapped fault line | work= The New Zealand Herald | accessdate=23 July 2013}}</ref> i like sheep


==Damage==
==Damage==

Revision as of 05:19, 18 March 2014

For the 16 August 2013 earthquake, see 2013 Lake Grassmere earthquake.

2013 Cook Strait earthquakes
2013 Seddon earthquake is located in New Zealand
2013 Seddon earthquake
UTC time??
Magnitude6.5 Mw
Depth17 kilometres (11 mi)
Epicenter41°37′S 174°20′E / 41.61°S 174.33°E / -41.61; 174.33
Areas affected New Zealand
TsunamiNone
Casualties4 people injured[1]

The 2013 Seddon earthquake was an earthquake measuring 6.5 on the moment magnitude scale 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 21–26 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

A ShakeMap is a representation of ground shaking produced by an earthquake. The information it presents is different from the earthquake magnitude and epicentre that are released after an earthquake because ShakeMap focuses on the ground shaking produced by the earthquake, rather than the parameters describing the earthquake source. So, while an earthquake has one magnitude and one epicentre, it produces a range of ground shaking levels at sites throughout the region depending on distance from the earthquake, the rock and soil conditions at sites, and variations in the propagation of seismic waves from the earthquake due to complexities in the structure of the Earth's crust
A "ShakeMap" showing the shaking intensity as determined by GeoNet instruments and modelled against ground conditions[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

The earthquake swarm may have occurred on an unmapped fault line. The source fault of the quake is under investigation but potential candidates are the Needles fault, London Hill fault, and/or extensions of the larger faults in the Marlborough Fault System, the Awatere, Clarence, Hope, and Wairau Faults. The geologic (and tectonic) complexity increases as the system moves off the South Island and into Cook Strait. The locations/interactions of the individual faults are not fully understood. There were about 24 known active faults in the Cook Strait and five in the area where the earthquakes occurred. However, the weekend's quakes could have occurred on a new fault yet to be mapped. The faults in Cook Strait are not large enough to generate magnitude-8 earthquakes, but are capable of magnitude 7-7.5 size earthquakes. The weekend's Cook Strait earthquakes would have needed to be at least a magnitude 7.5 to generate a tsunami. However, some coastline around Cook Strait had areas identified as potential landslide risk, and a smaller earthquake could cause a landslide which could then generate a tsunami. This type of tsunami could be quite devastating to the south coast of the North Island and north coast of the South Island.[6] i like sheep

Damage

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][7]

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.[8]

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

See also

References

  1. ^ a b "Wellington earthquake: We can afford new quake damage - PM". The New Zealand Herald. 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. Retrieved 23 July 2013. Cite error: The named reference "nisi" was defined multiple times with different content (see the help page).
  7. ^ Quilliam, Rebecca (22 July 2013). "Wellington earthquake: 35 buildings damaged in CBD". www.nzherald.co.nz. Retrieved 23 July 2013.
  8. ^ "Wellington earthquake: What you need to know". The New Zealand Herald. Retrieved 22 July 2013.
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