Eruptions


Fissures formed by seismicity in the Al-Ais region of Saudi Arabia. Image courtesy of Ahmed Al-Hussaini.

Although it seemed last week that the earthquakes in western Saudi Arabia were subsiding last week, there have been a number of reports that there was still significant seismicity in the area over the weekend. Earthquakes in the M2.5-3.5 range occurred on Saturday – both of which the SGS are attributing to “subterranean volcanic activity.” This has prevented the evacuees from the Al-Ais region to return to their homes. The Saudi government has begun to assess how much effect this activity could have on industrialized cities like Yanbu if it continues.

I have yet to run across any thorough analysis of the seismicity beyond the vague statements made by the SGS in the limited news articles. The connection with the Harrat Lunayyir volcanic field still seems fairly clear, but what exactly might be going on – volcanically or not – is just not being clearly reported. Likely, it is because no one is really sure. This region has seen a lot of activity before, some of which lead to eruptions, some of which didn’t. Also, the results of this seismicity are rather impressive (above and below). It is obvious that the SGS is concerned, however, I feel uneasy about how quickly they want to declare that events are winding down (but I’m not there, so it is just speculation on my part). Looks like there is still a lot to be learned from the ongoing activity.

{Hat tip to Eruptions readers Robert Somerville and Thomas Donlon for links to some of these stories.}


More effects of the western Saudi Arabian seismicity. Image courtesy of Ahmed Al-Hussaini.

Comments

  1. #1 mike don
    June 1, 2009

    WOW! and again WOW! The top picture in particular shows a fissure which would be impressive for a Magnitude 7 quake, let alone the M 3-5 shocks reported. Wondering what rock types make up the fissure walls, might give an idea of the energy required..and it’s a pity there don’t seem to have been any measurements of ground deformation (I’m open to correction on that)

  2. #2 albalawi
    June 1, 2009

    hi

    do you remember earth quake M 5.5?

    these faults have been discovered after it

    and this is another image http://www.burnews.com/infimages/myuppic/4a1b1592cdeb6.jpg

  3. #3 rocky
    June 1, 2009

    hi im from umlujj saudi arabia just beside red sea, we are 90km frm al ais place but i personally felt the tremors last saturday. Im confused about harrat lunayyir and al qider volcano?are they the same?because i’ve read lunayir is 50km frm umlujj seaport? any advantage or disadvantage having the red sea?please enligthen me. Thank u.

  4. #4 theroachman
    June 2, 2009

    From Halemaʻumaʻu Overlook Vent, Kīlauea Volcano

    http://i35.photobucket.com/albums/d166/tie-dyelady383/M.jpg

    Not clear if that silvery stuff is lava but it sure is a major change from weeks past

    http://hvo.wr.usgs.gov/cams/HMcam/

  5. #5 Boris Behncke
    June 2, 2009

    Mike, the fissures we see in these images are not necessarily to be correlated to the magnitude of the earthquakes – they are, in my view, a clear expression of extensional movement, or rifting. I say this because we have seen similar cracks on a number of occasions at Etna, when magma was pushing toward the surface (or travelling underneath the surface, which is not necessarily the same thing). These are the first images I come to see of the recent ongoings in Saudi Arabia, and they are impressive. The prolonged seismicity and this sort of ground fracturing look strikingly like an expression of magma movement – although there is no way to say whether the magma will ever reach the surface. Recent rifting episodes in Ethiopia and Iceland have shown that eruptions accompanying such rifting events deliver only a small portion of the magma involved to the surface, whereas most of the magma remains below the surface. Furthermore, rifting often comes in sequences of short episodes – such as in 1975-1985 in the Krafla system in Iceland, with no less than nine eruptive episodes.
    And yes, Halema’uma’u looks quite intense …

  6. #6 GregR
    June 2, 2009

    I’m having a devil of a time finding pictures of these Saudi volcanos. Can anyone point me in a direction to find images?

  7. #7 robert somerville
    June 2, 2009

    Eris and Boris:
    any reason this type of event would be expected to show up more strongly on the horizontal components ( N ,E )of a seismogram (versus the Z component) ?

    thanks;
    Robert Somerville

  8. #8 Albalawi
    June 2, 2009

    hi gregR

    go through this page and you will find images for Harrat Alsakah(lunayyer).
    http://www.mekshat.com/vb/showthread.php?t=206249
    another thing .
    images are above and images in that page ,they have been taken by Doctor Khalid Alzaak.

  9. #9 Thomas Donlon
    June 2, 2009

    From:

    http://www.a1saudiarabia.com/No-discrimination-in-evacuee-aid-Officials/

    “… According to Al-Aboudi, the latest statistics show that 1,812 families, consisting of 12,564 individuals, have been relocated in Madina, while 933 families of 6,127 individuals have gone to Yanbu and 139 families of 315 persons have been accommodated in Al-Aula.

    Meanwhile, security checkpoints at the entrances of Al-Eis region have intensified their procedures to prevent residents from entering as groups started to arrive Monday morning after rumors on the Internet stating authorities had allowed them to return.

    The Presidency of Meteorology and Environment said Monday in its daily statement that seismic activity at Harrat Al-Shaqa is declining and the strongest tremor was recorded at 2.8 degrees on the Richter scale. No volcanic vapors and no expansion of the ground cracks associated with the tremors, and the thermal measurements are normal, it said. – Okaz/SG – With reports from Khaled Al-Shalalhi and Ali Al-Harbi”

  10. #10 mike don
    June 2, 2009

    Point taken Boris about the fissures. Maybe I phrased it badly; if a tectonic quake had opened something that size it would be news. Makes me wonder if any ground deformation measurements have been taken? And echoing Robert’s point to an extent; are there details of the type of quakes as well as just the magnitude? Anything like harmonic tremor for instance? The SGS conviction that ‘magma movement’ is involved makes me wonder.

  11. #11 Philip Mulholland
    June 5, 2009

    Doctor Khalid Alzaak.

    Thank you for posting your photographs of the ground fractures caused by the recent earthquakes in Harrat Alsakah

    I believe that this picture in particular is very important.

    http://www.burnews.com/infimages/myuppic/4a1b112cba315.jpg

    The surface trace of the foreground fracture climbs upslope to the right towards the skyline; however the ground surface on the skyline shows that the land to the left has been broken by the line of the fracture and that this ground is uplifted. This photograph is evidence of a thrust fault breaking the surface. As thrust faulting can be associated with magma emplacement forming a sill in the deep subsurface. I suggest that a map of the pattern of the ground fractures and their lateral extent will be very informative in establishing the extent of this possible sill.

    Kind Regards
    فيليب

  12. #12 mike don
    June 5, 2009

    Philip: interesting comment on faulting/uplift on the fissure -check out the photo on Erik’s latest post (Quick Update…etc) if you haven’t already done so. Hard to tell for certain, but it looks very much from the pic as if the right-hand side of the fissure there has been visibly uplifted

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