A 8.0 magnitude earthquake hit the town of Lata, on Santa Cruz in Temotu, the eastern-most province in the Solomons last thursday. There have been many many aftershocks, the largest of which had magnitude 7.0 and quite many earthquakes stronger than magnitude 6. The 8.0 quake caused a Tsunami which caused the death of 13 persons ( other sources speak of 9 or 10) and some people went missing. So i thought i d try to collect as many links and hints i could find on this event. Most of them were provided by readers. This is not a pretty or amusing post, just a summary of links and information:
The Stana Cruz Islands are a group of islands to be found in the South Pacific 250 km south of the Solomon Islands, and are located close to a tectonic plate boundary. Vanatu can be found south of them, but the tropical rain forest covering the islands is the same type as can be found on Vanatu. They are composed of limestone which is covered with volcanic ash and are surrounded by coral reefs.
The islands are considered rather young on geological terms, being only about 5 million years old. The largest island is Nendo, which is also known as Santa Cruz Island. Wikipedia Quote:” The term Santa Cruz Islands is sometimes used to encompass all of the islands of the present-day Solomon Islands province of Temotu.”
From Wiki “The Santa Cruz Islands are less than five million years old, and were pushed upward by the tectonic subduction of the northward-moving Indo-Australian Plate under the Pacific Plate.
We often look at the volcanoes in the area, especially after a strong earthquake happened. This earthquake was clearly a tectonic one and not volcano related.
John Seach relates Tinakula, but if some or any volcano really starts erupting, remains to be seen. Talla found an artcile about worries of a possible increased activity at Tinakula, an uninhabited island of the Solomons. ( Remember The Solomons lie farther north! )
List of the volcanoes in this area. http://en.wikipedia.org/wiki/List_of_volcanoes_in_the_Solomon_Islands
KarenZ also mentioned that Tinakula seems to be a little bit north of the earthquakes and that the Pacific Plate is subducting under the Indo-Australian plate.
USGS analysed the 8.0 magnitude earthquake http://earthquake.usgs.gov/earthquakes/eventpage/usc000f1s0#summary and additional information about the tectonic plates can be found in this article. http://pubs.usgs.gov/of/2010/1083/i/
Earthquake Report started a list of the earthquakes in the Solomon Islands.
http://earthquake-report.com/2012/02/14/solomon-islands-real-time-earthquake-list/ and has an article last updated February 9th: http://earthquake-report.com/2013/02/06/very-strong-earthquake-santa-cruz-islands-on-february-6-2013/
We are still looking for a list or map which displays small earthquakes. These would be important to crate plots shwoing what is really going on.
The plate boundary near the Solomon Islands is a combination of a subduction zone and a transform fault:
This map provides the latest earthquakes but the faultlines are clearly visible also.
http://hisz.rsoe.hu/alertmap/index2.php Worldwide Emergency and Risk Map pointed out by KarenZ.
A german site was mentioned by Renato who found it on FB. Some information is doubtful but there are earthquake lists to be found and aslo 2 videos.
This is Chris Rowan’s take on Solomon Islands earthquakes:
KarenZ started a list of the recent earthquakes: http://oi50.tinypic.com/15q2b8o.jpg
and plots of the Solomon Island EQs for 2013:
Depth v lat and depth v lon plots for the area from 1964:
Updated 2d plot of number of eqs by mag for Santa Cruz Islands Area:
Some reports were mentioned saying steam comes out of cracks on Santa Cruz Island. It is not clear to me, if this is just fear mongering or if something is really happening.
And i dont want to miss pasting GeoLurking´s take on the situation:
“Well, some of the loon theorists think that part of the plate is going snap off…. but these are the same guys that claim a basin wide crack is going to form on the pacific plate. The actual liklihood of that happening are about as good as me hitting the powerball lottery and getting struck by lightning at the same time… as well as winning the triple crown (on foot)
I’ve yammered at them to no end about the dynamics of tectonics and the lunacy of the claim.
In fact… that region is littered with old plate / plate fragment boundaries. Remains of ancient back-arc basins, etc. If anything is going to happen, one of those
boundaries will re-activate to accomedate the prevailing stress if the active boundaries can’t handle it.
It will be unique, someone will write a paper about it, and that will be it.
Volcano wise…. I don’t know how long decompression melting takes to occur (under the extensional areas). Some of one subducting plate has had a greater extent thrust just a bit deeper and into hotter material than it was sitting at before this all started. Hydrated material (rock) will pass into the area where it can more easily melt, so fresh magma is a possibility. how long that will take, or if it will then percolate up is anybodies guess.
I second KarenZ’s lament about the lack of data on small quakes. You can tell a lot from them. They can point to moving magma or stucture that we didn’t even know that was there. (like when we were watching the sill emplacements under El Hierro.)
Right now… it’s wait and see.
The system as a whole, is capable of generating tsunami, so anyone living there needs to be ready to high tail it if a large quake occurs.”
Maybe this article by Highly Allochtonous helps understanding the beach balls. http://all-geo.org/highlyallochthonous/2009/12/5-focal-mechanisms/
And the IRIS maps of seismic sations: http://www.iris.edu/hq/programs/gsn/maps
Thanks for the contribution: Newby, Renato, Talla, KarenZ GeoLurking and Chyphria.
And as latest update: El Nathan mentioned this: Interesting to see what others make of the activity in the Solomon Islands, also using the info from this blog. In some way I find it amusing….
http://lunaticoutpost.com/Topic-New-Supervolcano-Possibly-Being-Born-South-Pacific-Near-Solomon-Islands?page=1 ( VC mentioned and quoted on page 2)