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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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Catching up: Mayon, Redoubt, Poás, Saudi Arabia… 31 December 2009

Posted by admin in activity reports, Alaska, Costa Rica, Mayon, Philippines, Poás, Redoubt.
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The Volcanism Blog Christmas Break lasted a little longer than intended, as round here the internet celebrated the holiday season by breaking down and we’ve only just got it back. Here’s a summary of what’s been going on in the meantime.

Mayon has so far stopped short of the big explosive eruption that everyone has been expecting (although the full moon might do it). Some 50,000 people have spent Christmas as evacuees in temporary shelters, and it does not look as if they will be returning to their homes any time soon. Meanwhile the authorities are losing patience with people who refuse to quit the danger zone: power and water supplies to evacuated areas are to be cut off, and the Philippine Commission on Human Rights has okayed ‘forcible evacuation’ measures. The latest Phivolcs bulletin (no. 18, 31 December 2009) reports continuing ‘extrusion of lava and rolling down of incandescent lava fragments’. Poor visibility has hampered observations of the volcano, but no ash explosions have been observed during clear periods. The last significant explosion (to 9,000 feet/2,740 metres) was reported by Tokyo VAAC at 00:17 UTC on 30 December. The alert status for Mayon remains at the second-highest level of 4; the level of activity has declined somewhat over the last few days, but Phivolcs warns that the threat remains.

In Alaska, Redoubt stirred for the first time in five months or so, altering its usual seismic behaviour to produce a series of small repetitive earthquakes near its summit. The Alaska Volcano Observatory raised the alert level for Redoubt to Yellow/Advisory on 28 December 2009. The latest AVO bulletin (30 December 2009, 21:46 UTC) reports that the earthquake activity has declined markedly.

Poás in Costa Rica revealed itself to have a great sense of occasion, putting on a fine display of phreatic activity on Christmas morning. A mixture of sediments and water from the crater lake and volcanic blocks was ejected to a height of more than 500 metres at 09:50 on Christmas Day, startling visiting parties of festive tourists.

Remember the earthquakes in the Al-Ais region of Saudi Arabia earlier this year? The last tremors were reported in June. It seems that there were some more earthquakes on 18 December, causing alarm among local residents who have only recently returned to their homes after being evacuated in May and June. The Saudi Geological Service has said that the tremors are normal for this volcanic region of the country, no eruption is imminent, and that there is no need for new evacuations.

The Global Volcanism Program has published two weekly volcanic activity reports over the holiday period, one covering 16-22 December 2009 and one for 23-29 December 2009. Full posts for both of these will be published here next week.

Happy New Year!

The Volcanism Blog

Saudi tremors continue: return of evacuees delayed 25 June 2009

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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

Saudi earthquakes update 21 May 2009 21 May 2009

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There are some new reports tonight from the English-language Saudi media on the earthquakes (possibly with some volcanic connection) that have been affecting the west of the country. The indications that some kind of volcanic activity is under way are mounting up, albeit many are as yet unconfirmed.

The Business Maktoob headline says ‘Saudi volcanic eruption “imminent”‘, a dramatic claim derived from actually rather cautious comments from UK seismologist Roger Musson: ‘Looking at this recent activity it does seem that an eruption is imminent. We cannot say for definite. But the combination of the earthquakes and the release of hot gasses does suggest something is about to happen. The region has experienced volcanic activity in the past so this is possible’.

Meanwhile a report from the Saudi Press Agency, quoted by the Malaysian National News Agency BERNAMA, says that an overflight by the Saudi Geological Survey has revealed the existence of ‘ground groves’ (fissures?) at the seismic activity area, and that ‘The SGS reassured the variables associated with this activity in terms of the rise in temperature and concentration of radon gas in some regions of volcanic area of “Al Harrat AS-Shaqqah”‘. Possibly the translation here is not all it might be. There is a discussion of the significance of Radon measurement in the latest Saudi update at the Eruptions blog.

The particular Saudi Press Agency news release quoted by BERNAMA is unfindable at the SPA’s horrible website, but an apparently more recent report is available which says that:

The Saudi Geological Survey Commission, Saudi Arabia’s authority in charge of monitoring and controlling seismological activity in the country, said today that the volcanic activity at Harrat Al-Shaqa, which showed unprecedented activity over the last 30 days, registered recent remarkable fall in terms of number and strength. In a press statement, the authority said only six minor quakes were registered during the last 24 hours measuring about 3 points on the Richter scale. The statement said nobody felt or reported the shocks neither of which exposed in volcanic vapor.

Only time will tell if things really are quietening down, or if any lull is just temporary.

UPDATE 22 May 2009. The latest story in Arab News quotes the Saudi Geological Survey as reporting no further gas emissions since Wednesday (which is probably also what is meant by ‘neither of which exposed in volcanic vapor’ in the SPA report above):

The Saudi Geological Survey (SGS) said no emission of volcanic gases has been observed since Wednesday in Harrah Al-Shaqah, the epicenter of the earthquake and the location of extinct volcanoes. It said six minor tremors were recorded at Harrah Al-Shaqah in the 24 hours until 2 p.m. yesterday.

‘Our tracking devices did not detect on Wednesday any gas emissions indicating the eruption of lava. However, we are closely observing the extinct volcanoes in the region for any sign of renewed activities’, said Ahmad Al-Attas, acting head of the SGS.

N.B. Whatever the SGS says, the volcanoes in this area cannot be regarded as extinct.

News
Saudi volcanic eruption ‘imminent’Business Maktoob, 21 May 2009
Saudi Geological Survey explains Al-Ais tremors – BERNAMA, 21 May 2009
Volcanic activity is in the fall, reports Saudi Seismological Authority – Saudi Press Agency, 21 May 2009
Madinah governor tours quake-prone Al-AisArab News, 22 May 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
Volcanic Arabia – a detailed and well illustrated article from Saudi Aramco World, 2006, on Arabian volcanism

The Volcanism Blog

Earthquakes in Saudi Arabia – rumbles and rumours 19 May 2009

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There have been various reports over the past couple of weeks of earthquakes in western Saudi Arabia, possibly with some volcanic component. Some of the news reports are listed below. Significant earthquakes are clearly taking place: there are reports of structural damage, people fleeing their homes, and confusing references to ‘magma moving’.

Dr Erik Klemetti at Eruptions is doing a superb job of putting together all the information he can (including reports, via his comments columns, from people who are on the spot) and trying to make sense of it. Check out his posts: An eruption brewing in Saudi Arabia? and the more recent Updates on the Saudi Arabian earthquakes.

UPDATE 20 May 2009: Dr Erik Klemetti’s latest post on the Saudi Arabian earthquakes is here. This morning (this post is published at 07:38 UTC) the USGS is listing six earthquakes in the area occurring between 19:50 UTC on 17 May and 20:35 UTC on 19 May: the largest is a magnitude 5.7 event at 17:35 UTC on 19 May. There are reports of large-scale evacuations and of aftershocks and ‘a large crack in the earth’, and unconfirmed accounts of gas emissions, ‘smoke’, and changes in well water – all very suggestive, but there is a lack of hard evidence. Dr Klemetti notes:

So, we don’t really know much else about what is going on that we didn’t know a few days ago. Earthquake appear to be continuing. Rumors of smoke, pungent odors, changes in well water. Evacuations. These items, taken at face value, would suggest an eruption is imminent, however, right now, all I can do is say that things are definitely getting interesting in Saudi Arabia right now.

More news links have been added to the list below, which I will keep updating as new information comes in. Knowing no Arabic, however, I’m limited to English-language sources.

Google Earth users can find the earthquake locations using KML files available from the USGS Earthquake Hazards Program site. The Saudi earthquakes are listed on this USGS page: clicking on the date for a particular event will take you to a range of tabs giving further information. The ‘maps’ tab includes a link labelled ‘Google Earth KML’ which will open Google Earth and take you to the location for that earthquake. Over at Eruptions Dr Klemetti has published a Google Earth map of the earthquakes so far, and has interesting observations on the Harrat Lunayyir lava field where they are located.

P.S. An American blogger in Saudi Arabia samples local opinion on the earthquakes here. Another Saudi-focused blog covering the earthquakes is here (most recent post here). And CNN notices something is happening here.

UPDATE 21 May 2009. A report in Arab News says that a total of 2,289 people have been evacuated from villages in Al-Ais:

The evacuations took place as 30 tremors of varying magnitudes — measuring between 3 and 5.4 on the Richter scale — were registered at Harrah Al-Shaqah in the Al-Ais area during the 24 hours ending 2 p.m. yesterday, the Saudi Geological Survey reported. … The Civil Defense has warned people living within a radius of 40 km of Harrah Al-Shaqah, the quake’s epicenter, to keep away. The warning was issued following the discovery of dangerous gases and unusually hot air and water in wells as the frequency of tremors increased in Al-Ais. A Civil Defense source said the discoveries suggested a volcanic eruption was likely.

The USGS and Centre Sismologique Euro-Méditerranéen report no new quakes since the magnitude 4.6 event at 20:35 UTC on 19 May, but smaller quakes since then will not have been reported on these sites.

More recent updates here (The Volcanism Blog) and here (Eruptions).

News
1,200 mild tremors felt in MedinaKhaleej Times Online, 4 May 2009
Tremors continue to shake Al-Eis regionSaudi Gazette, 14 May 2009
Evacuation begins as tremors continueSaudi Gazette, 15 May 2009
Rumblings from Al-Ais volcanoes send villagers into a state of panicArab News, 15 May 2009
More tremors jolt Al-AisArab News, 16 May 2009
Saudi Arabia evacuates 5 villages in volcano scare – Reuters India, 19 May 2009
40% of Al-Eis residents flee from earth tremorsSaudi Gazette, 19 May 2009
Residents told to leave Al-Eis amid stronger tremorsSaudi Gazette, 20 May 2009
Aftershocks rock Al-AisArab News, 20 May 2009
Evacuation called as another quake hits SaudiBusiness Maktoob, 20 May 2009
Two tremors hit Saudi volcano region, no injuries – Reuters India, 21 May 2009
Earthquake hits Saudi villagesTimes of India, 20 May 2009
Saudi prepares fresh evacuation from volcano zone – Reuters AlertNet, 20 May 2009
Earthquake hits Saudi villages – PR-inside.com, 20 May 2009
Saudi earthquake zone evacuated after spate of strong tremors – Dow Jones Newswires, 20 May 2009
Volcanic tremors recorded in Saudi Arabia – Radio New Zealand, 21 May 2009
Villagers flee Saudi quake zone after spate of tremors – Inside the Gulf, 21 May 2009
Saudi volcanic eruption ‘imminent’Business Maktoob, 21 May 2009
Saudi Geological Survey explains Al-Ais tremors – BERNAMA, 21 May 2009
Madinah governor tours quake-prone Al-AisArab News, 22 May 2009

Information
Global Volcanism Program: Arabia – information from the GVP about the volcanoes of Arabia
Volcanic Arabia – a detailed and well illustrated article from Saudi Aramco World, 2006, on Arabian volcanism

The Volcanism Blog

Rumbles in Saudi Arabia? 14 May 2009

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There have been some strange reports out of Saudi Arabia, of earthquake swarms around Medina and magma apparently being ‘pushed by some force from a depth of 8 km to a depth of 4 km below the surface’. Leaving aside the question of how one would know that is happening, is something volcanic going on? Eruptions has the facts, such as they are, so far: ‘An eruption brewing in Saudi Arabia?’

The Volcanism Blog