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.
Physical Science
Environment
Comments (62)
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)
Posted by: mike don | June 1, 2009 5:17 PM