Overblog
Suivre ce blog
Editer l'article Administration Créer mon blog

Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Sismologie

.A strong earthquake followed by numerous aftershocks hit this February 14 Christchurch on the South Island in New Zealand. The main tremor of magnitude 5.7, occurred at 1:13 p.m. local, northeast of the coast of Christchurch in Pegasus Bay, and a depth of about 15 km.

Described as severe, it was felt to Wellington. The replicas include an earthquake of magnitude 3.6 to 5:44 p.m. ET an earthquake of magnitude 4.2 at 6:27 p.m..

For now, it only reports of minor injuries and damage.


 

Christchurch earthquake of 02.14.2016 - the main earthquake in peach, replicas (at 16:15 loc) in orange - doc. GeoNet

Christchurch earthquake of 02.14.2016 - the main earthquake in peach, replicas (at 16:15 loc) in orange - doc. GeoNet

Description of the earthquake 02.14.2016 by Anna Keiser, GNS seismologist

Description of the earthquake 02.14.2016 by Anna Keiser, GNS seismologist

This earthquake would be part of the "Canterbury earthquake sequence", which began in 2010 with the 7.1-magnitude earthquake in Darfield and is still ongoing.

In September 2010, the earthquake was caused by movements along the fault, west of Christchurch in the Canterbury Plains.

The earthquake of 22 February 2011, 6.3 magnitude, that devastated the center of Christchurch, was caused by movements along a fault which does not appear on the surface; it is located by measuring devices - GPS, seismographs and radar satellite images - six kilometers from the city center. It is 14 km long and runs east to the northeast from Cashmere to the estuary of Avon-Heathcote. The top of the fault git one kilometer below the surface, and it delves deeper at an angle of 65 °.

Location of the epicenter of the earthquake of 02/14/2016 and seismicity at April 11, 2014 - Doc. GNS Science

Location of the epicenter of the earthquake of 02/14/2016 and seismicity at April 11, 2014 - Doc. GNS Science

In addition to the damage in populated areas, including increased damage already caused to the Christchurch Cathedral in previous shocks, one notes a collapse of cliffs in Sumner beach area.

Earthquake of 02.14.2016 has caused further damage to the Christchurch Cathedral - photo David Walker Fairfax / Stuff.nz

Earthquake of 02.14.2016 has caused further damage to the Christchurch Cathedral - photo David Walker Fairfax / Stuff.nz

Collapse of the cliffs in the area of ​​Sumner beach, following the earthquake of 02.14.2016 - top photo: Graeme Jolliffe - photo below: Thomas Wieberneit - via Stuff.nz:
Collapse of the cliffs in the area of ​​Sumner beach, following the earthquake of 02.14.2016 - top photo: Graeme Jolliffe - photo below: Thomas Wieberneit - via Stuff.nz:

Collapse of the cliffs in the area of ​​Sumner beach, following the earthquake of 02.14.2016 - top photo: Graeme Jolliffe - photo below: Thomas Wieberneit - via Stuff.nz:

Video Christchurch earthquake - the area of ​​Sumner beach, Scarborough Hill and Taylor's Mistake after the earthquake of M5,7; collapse of part of the cliffs - taken by a drone DJI Phantom

Compared to 2010-2011, the liquefaction phenomena (*) associated are lower this time. This  liquefaction appears in the Christchurch area when the PGA / Peak of Ground Acceleration (**) is greater than 0.1. This Feb. 14, 2016, the maximum acceleration of soil observed is 0.4 g compared to 2.2 g measured in the 2011 earthquake, of M 6.3.

(*) Liquefaction of soil: geological phenomenon, generally brutal and temporary, by which a water-saturated soil loses part or all of its lift, allowing the penetration of heavy objects on the surface.

(**) PGA: Peak Ground Acceleration is a parameter that characterizes the movement of soils under seismic wave. Added to the soil displacing speed in those circumstances, these two parameters depend on the intensity of the earthquake and the geological nature of the soil.

 

Christchurch - 02/14/2016 - liquefaction in Bower Avenue - photo Sally Murphy / Twitter

Christchurch - 02/14/2016 - liquefaction in Bower Avenue - photo Sally Murphy / Twitter

Sources :

- Stuff- nz - Christchurch hit by a 5,7 M earthquake – link

- GeoNet - Large quake off the coast of Christchurch – link

- GNS Science - Canterbury earthquake – link

Commenter cet article

Articles récents

Hébergé par Overblog