JEDDAH, 16 October 2007 — Following reports of seismic activity in the Harrat Lunayyir region about 200 km northwest of Madinah, the Saudi Geological Survey announced that it has opened a 24-hour-a-day control room to monitor these minor quakes — the strongest of which registering 2.3 on the Richter scale on Thursday.
Zuhair Nawab, president of the SGS, said in a statement published in the daily Al-Eqtisadiah yesterday that the station is located in Al-Aiss, which is roughly in the middle of the region about 75 km east of the Red Sea coast.
“The team did not observe any rapid variation in the natural thermal phenomenon, which confirms that the seismic activity is subsiding,” Nawab was quoted as saying.
He added that the tremors are centered deep inside the earth’s crust, further mitigating the risk to public safety.
Studies of earthquake precursory phenomena during the last several decades have found that significant geophysical and geochemical changes can occur prior to intermediate and large earthquakes.
The Arabian Peninsula is slowly breaking away from the African continent and a major fault line is located along the Red Sea off the west coast of the Kingdom. The peninsula is slowly drifting toward the Subcontinent.
However, the sandy soil that makes up most of Saudi Arabia acts as a kind of geologic mattress that absorbs most of the numerous tremors registered every year and few people actually feel them.
That is not to say Saudi Arabia is completely immune to potentially dangerous building-toppling earthquakes and the ensuing volcanic activity.
According to historical texts, Madinah was rocked with a staccato of tremors in 1256 (654 AH) strong enough to raise concerns among the locals.
The records document 18 tremors over a period of six days in June 1256, some of them strong enough to be felt by people attending Friday prayers in the Prophet’s Mosque. These quakes were followed by violent volcanic eruptions near Madinah; lava following from one volcanic eruption after these quakes came as close as 23 km from Madinah, threatening to consume the city with magma.
The land between Madinah and Makkah makes up the world’s largest expanse of volcanic rock. Lava fields are known in Arabic as “harraat” and the 180,000-square-mile Harrat Rahat between Makkah and Madinah covers an area twice the size of Lebanon.
The western region of Saudi Arabia contains a 40-km thick layer of volcanic rock beneath a soft layer of desert sand, known by geologists as the “Arabian Shield” which spans the entire west coast of Saudi Arabia. The main part of this geologic shield is so wide that it nearly reaches Riyadh, over 800 km from the west coast.
