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Volcanic activity in Arabian Desert makes Case for Increased Monitoring



Volcanic activity in Arabian Desert makes Case for Increased Monitoring

VANCOUVER, Wash. – Underground magma movement was the trigger of a swarm of 30,000 earthquakes in Saudi Arabia last year, according to a new study published in Nature Geoscience Sunday.

The swarm occurred in the Harrat Lunayyir lava field near the Red Sea, prompting the Saudi government to evacuate 40,000 people from the region to avoid loss of life from a possible larger earthquake or volcanic eruption.

The seismic activity shook the region between April and June of 2009 and reached its peak on May 19 when 19 earthquakes with a magnitude greater than 4 produced a fault rupture 5 miles (8 km) long and 18 inches (45 cm) wide.

Last year’s event led to the immediate deployment of sophisticated seismic monitoring equipment by the Saudi Geological Survey and highlighted the need for additional monitoring of the Arabian lava fields.

“Although the Harrat Lunayyir lava field in Saudi Arabia is not near any large urban centers, encroachment by surrounding communities to other geologically active areas emphasizes the need to monitor the seismic and volcanic activity,” said John Pallister, U.S. Geological Survey volcanologist and chief of the Volcano Disaster Assistance Program.

Scientists with the USGS and the Saudi Geological Survey worked together and agreed that the seismicity was consistent with volcanic activity and used satellite imagery to confirm it. Satellite imagery revealed the earth’s surface was indeed being uplifted by magma moving underground.

The lava fields in Saudi Arabia are considered young on a geologic scale, with a notable eruption near Madinah in AD 1256; a recent event considering the 4.6 billion year age of the earth. Although humans haven’t witnessed volcanic activity in this area for hundreds of years, scientists say we shouldn’t be surprised.

“The Red Sea rift has a chain of underwater volcanoes along its axis,” said USGS volcano seismologist Wendy McCausland. “Since it is deep underwater, we are rarely reminded of this ongoing volcanism.”

Seismic readings from the swarm produced two distinct signals, a very low frequency rumble which the scientists believe is produced by magma rising underground and a higher frequency signal that indicates rocks fracturing under the pressure of the magma’s movement.

Pallister and McCausland, from the Cascade Volcano Observatory in Vancouver, Wash., were asked to assist the Saudi government under the authority of the Volcano Disaster Assistance Program, a joint program of USGS and U.S. Agency for International Development’s Office of Foreign Disaster Assistance. The program’s goal is to reduce the loss of life and minimize economic disruption by helping monitor volcanoes and forecast eruptions.

Pallister and McCausland were lead authors for an article published this week in the journal Nature Geoscience. Others assisting with the article included Sigurjón Jónsson of King Abdullah University of Science and Technology; Zhong Lu and Randal A. White of the USGS; Hani M. Zahran, Salah El Hadidy, Abdallah Aburukbah, Ian C. F. Stewart of the Saudi Geological Survey; Paul R. Lundgren of the Jet Propulsion Laboratory; and Mohammed R. H. Moufti of the King Abdul Aziz University.

USGS Newsroom



More information

Parameter Value Description
Magnitude mb The magnitude for the event.
Longitude ° East Decimal degrees longitude. Negative values for western longitudes.
Latitude ° North Decimal degrees latitude. Negative values for southern latitudes.
Depth km Depth of the event in kilometers.
Place Textual description of named geographic region near to the event. This may be a city name, or a Flinn-Engdahl Region name.
Time 1970-01-01 00:00:00 Time when the event occurred. UTC/GMT
Updated 1970-01-01 00:00:00 Time when the event was most recently updated. UTC/GMT
Timezone offset Timezone offset from UTC in minutes at the event epicenter.
Felt The total number of felt reports
CDI The maximum reported intensity for the event.
MMI The maximum estimated instrumental intensity for the event.
Alert Level The alert level from the PAGER earthquake impact scale. Green, Yellow, Orange or Red.
Review Status Indicates whether the event has been reviewed by a human.
Tsunami This flag is set to "1" for large events in oceanic regions and "0" otherwise. The existence or value of this flag does not indicate if a tsunami actually did or will exist.
SIG A number describing how significant the event is. Larger numbers indicate a more significant event.
Network The ID of a data contributor. Identifies the network considered to be the preferred source of information for this event.
Sources A comma-separated list of network contributors.
Number of Stations Used The total number of Number of seismic stations which reported P- and S-arrival times for this earthquake.
Horizontal Distance Horizontal distance from the epicenter to the nearest station (in degrees).
Root Mean Square sec The root-mean-square (RMS) travel time residual, in sec, using all weights.
Azimuthal Gap The largest azimuthal gap between azimuthally adjacent stations (in degrees).
Magnitude Type The method or algorithm used to calculate the preferred magnitude for the event.
Event Type Type of seismic event.
Event ID Id of event.
Event Code An identifying code assigned by, and unique from, the corresponding source for the event.
Event IDS A comma-separated list of event ids that are associated to an event.

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