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Magmatic dyke intrusion behind Saudi quakes of 2009, says US/Saudi study 26 September 2010

Posted by admin in Middle East.
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Back in the late spring and summer of 2009 western Saudi Arabia was shaken by significant earthquake swarms: 30,000 quakes happened between April and June, prompting large-scale evacuations. The earthquakes happened in the Harrat Lunayyir volcanic field and were clearly related to active volcanism in some way, but the details remained unknown.

Now, however, a new study of the Harrat Lunayyir earthquake swarms by a joint United States/Saudi Arabian team of geologists has been published which concludes that ‘the earthquake swarm resulted from magmatic dyke intrusion’. The paper, ‘Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia’, is available as an advanced online publication at Nature Geoscience (available to subscribers, that is). There’s also a news report of the study at AFP.

  • John S. Pallister, Wendy A. McCausland, Sigurjón Jónsson, Zhong Lu, Hani M. Zahran, Salah El Hadidy, Abdallah Aburukbah, Ian C. F. Stewart, Paul R. Lundgren, Randal A. White & Mohammed R. H. Moufti, ‘Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia’, Nature Geoscience, Published online 26 September 2010, doi:10.1038/ngeo966. [abstract]

P.S. Nature News reports on the study here, calling the Harrat Lunayyir event a ‘failed eruption’, which is a curious way of describing it. One might as well say it was a ‘successful magmatic intrusion’. Volcanism and related processes take many forms, and assuming that some forms are ‘successful’ (lava fountaining! extensive lava flows! success!) and others are ‘failed’ (nearly there, just arriving at the surface … no, not quite, a mere intrusion, oh what a failure) is not particularly relevant or helpful. It’s also notable that the term ‘failed eruption’ nowhere appears in the Pallister et al paper itself.

[Apologies for giving a duff link to the paper in the initial version of this post. I’ve now corrected the link.]

News
New study sheds light on Saudi volcano risk – AFP, 26 September 2010
Northwest Saudi Arabia vulnerable to volcanoes – ABC News, 26 September 2010
Failed eruption shook Saudi ArabiaNature News, 26 September 2010

Information
Global Volcanism Program: Harrat Lunayyir – information from the GVP on the area where the seismic activity has been located
Global Volcanism Program: Arabia – information from the GVP about the volcanoes of Arabia

The Volcanism Blog

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Saudi tremors continue: return of evacuees delayed 25 June 2009

Posted by admin in activity reports.
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The earthquakes in Saudi Arabia may have dropped out of the news recently, but the activity has been continuing. The return of residents evacuated from the Al Ais area of western Saudi Arabia has been indefinitely postponed following the occurrence of significant tremors over the past few days, reports the English-language Saudi daily Arab News:

The decision follows the relatively high intensity of tremors registered over the past two days, he said. According to an SGS bulletin issued yesterday, the National Network for Seismic Monitoring, a subsidiary of SGS, registered two tremors measuring 4.55 and 3.2 on the Richter scale in addition to several lesser tremors during the 24 hours ending noon yesterday.

Meanwhile an intriguing (if rather vague) story from the Saudi Gazette quotes a Saudi Geological Survey report that ‘geologists discovered the detachment of a large chunk of a mountain in Harrat Al-Shaqqah from the main mountain mass as the result of the widening of the faults in its base’, and gives the explanation of geology professor Dr Abdul Aziz Bin La’boon for the Al-Ais activity: ‘molten rocks under the ground tried to push their way to the surface through the channels used by old volcanoes that erupted earlier, but due to their old age the rocks had solidified, so the current molten rocks are trying to find a new way out’.

News
Earthquake threat persists in Al-AisArab News, 31 May 2009
SGS issues statement on Harrat Al-Shaqqah tremorsSaudi Gazette, 12 June 2009
Return of Al-Ais dwellers delayedArab News, 24 June 2009

Information
Global Volcanism Program: Harrat Lunayyir – information from the GVP on the area where the seismic activity has been located
Global Volcanism Program: Arabia – information from the GVP about the volcanoes of Arabia

The Volcanism Blog