DDM Explanation Of Seismic Activity
By DDM, BVI
Tue, 15 Aug 2006, 08:53
Tortola, BVI, August 15, 2006 (Department of Disaster Management)–The recent earthquakes that were felt throughout the British Virgin Islands originated in the Sombrero Seismic Zone, which is located between 18.5–19.0 north latitude, according to reports issued by the Puerto Rico Seismic Network.
The Sombrero Seismic zone is one of the most active seismic zones in the region. All earthquakes that occur within the parameters of this zone share similar characteristics; they are usually shallow at 25 kilometers or less and have similar magnitudes. Currently studies are being conducted to determine if a fault is located in the Sombrero Seismic Zone.
The frequency of earthquakes that the BVI experienced yesterday can be identified as a seismic swarm. A seismic swarm is a group of earthquakes that occurs in the same place, share similar characteristics such as depth and magnitude, and occur in a determined period of time. For example, in 2006 between January 12th & 13th a seismic swarm, which consisted of 39 earthquake events, took place in the Sombrero Seismic zone. In 2005 between January 2nd and 7th a seismic swarm, which consisted of 33 seismic events took place in the same zone.
These statistics demonstrates the level of the high seismic activity in the Puerto Rico & Virgin Islands area.
The reason why the earthquake activities experienced yesterday seem abnormal is because of the magnitude and the depth. Usually when earthquakes occur in this zone the magnitudes are not high enough to be felt. Even though the recent earthquakes were felt widely throughout the BVI, there intensity were still considered to be light. The reason why they were so widely felt is because they occurred at shallow depths. The last earthquake that took place last night had a depth of 6.9 kilometers.
The Puerto Rico Seismic Network will issue a Tsunami Warning if an earthquake occurs in a shallow depth and has a magnitude of 6.5 or more.
Over the next four weeks the DDM will be conducting an Earthquake & Tsunami Campaign. The public is advised to take heed to the awareness and preparedness information that will be disseminated through the local media.
Department of Disaster Management
#3 Wailing Road MacNamara
Tortola, British Virgin Islands
Ph. 284-494-4499 Fax: 284-494-2024
E-Mail: bviodp@candwbvi.net