Concern over the safety of the public in the region spiked in February 2007 when the SGS recorded a cluster of 400 small seismic disruptions. From April to June 2009, scientists recorded approximately 40,000 small tremors, including a larger quake that registered 4.8 on the Richter scale on May 17.
Two days later a quake measuring 5.4 on the Richter scale caused panic among local residents.
Both of the larger quakes were sizable enough to create fissures on the surface and damage structures, spurring an evacuation of residents in Al-Ais and surrounding communities up to 40 km away from the epicenter in Harrat Al-Shaqah (also known as Harrat Lunayyir). Residents as far away as northern Madinah felt the tremors. Geologists also measured a rise in underground temperatures and an increase in radon gas emissions associated with volcanic activity.
After the May 17 earthquake, the SGS classified the region as “code orange” on a threat-level system, meaning there was a significant threat of a sizable earthquake or volcanic eruption. Locals were panicked, forcing the Civil Defense to evacuate several communities. Nearly 1,000 people were provided temporary shelter in Yanbu and Madinah.
Since then the region has been reduced to guarded code yellow, which means the risk of another sizable earthquake is unlikely although low-level tremors are still relatively frequent. The tremors are largely attributed to the magma (superheated liquefied rock) activity beneath the numerous dormant volcanoes in the area.
